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Vegetation establishment on the southern Israeli coastal sand dunes between the years 1965 and 1999
Landscape and Urban Planning 67 (2004) 141–156
Vegetation establishment on the southern Israeli coastal sand dunes between the years 1965 and 1999 Pua Kutiel a,∗ , Oded Cohen a , Maxim Shoshany b , Merav Shub b a
Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel b Department of Geography, Bar-Ilan University, Ramat Gan 52900, Israel
Abstract Since 1960, the Israeli coastal dunes have undergone a stabilization process that is manifested in the increase of vegetation cover and in a decrease in the abundance of sand-living flora and fauna species. The objective of the study was to quantify, using remote sensing and GIS, the rate and extent of vegetation expansion and their resultant temporal changes on Israel’s southern coastal dunes between the years 1965 and 1999. The results indicate that during the entire study period, the vegetation-covered area grew by 82% at an annual average growth rate of 1.75%. Concurrently, the bare shifting dune area decreased by 37% at an annual average growth rate of 1.34%. The conspicuous trend over the period studied, despite regressive processes, is a transition from bare shifting dunes to stabilized, vegetation-covered dunes. The extrapolation of the results, assuming continuation of processes and no destruction effects, indicates that with the decrease in the bare shifting dunes, the ratio of bare shifting dunes and sparse vegetation coverage landscape will equalize by between 2007 and 2010. According to this extrapolation, between 2012 and 2015, no bare shifting dune landscape will remain, and the study area will be covered with sparse- and dense-level vegetation cover. Beginning in 2035, the entire study area will be covered in vegetation whose density will be between 60 and 100%. Meso-climate and land use changes are among the factors that might explain this phenomenon. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Coastal sand dunes; Landscape changes; GIS
1. Introduction An increase in the human population, a rise in use of resources utilization, and expansion of urban spaces are some of the factors affecting the environment and ultimately causing significant changes in the landscape over short periods of time. The coastal regions, where approximately 60% of the world’s population lives, are considered areas where human interference in the landscape is at its highest level ∗ Corresponding author. Fax: +972-8-6472821. E-mail address: [email protected] (P. Kutiel).
0169-2046/$20.00 © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0169-2046(03)00035-5
compared to other areas (Holdgate, 1993). For example, 75% of dune spaces around the Mediterranean Basin have been disturbed or destroyed in the past 30 years due to extensive urbanization, industrialization and recreation- and tourism-based development (van der Meulen and Salman, 1996). In various places in the world, great efforts have been made to stabilize coastal dunes in particular and foredunes in general. In an effort to stabilize the shifting dunes or to expand the beach for recreational needs (Nordstrom and Lotstein, 1989), in most cases exotic species were used, such as the Australian acacia (Acacia saligna and A. cyclop), various species of
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Fig. 1. Aerial photograph of Nitzanim Sand Park in 1965 (below) and 1999 (above).
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tamarisk, pine, and perennial grasses, such as maritime grass (Ammophilla arenaria). These plants are rapid growers, have low demands on their habitats, and are able to cope with high-speed wind regimes and seawater spray close to the coast, as well as the harsh conditions typical of sand. Over time, some of these plants have expanded and covered broad areas, thereby, stabilizing the sand and modifying the landscape in both geomorphic and biological sense. In many cases this has caused nature conservation problems (McManus, 1988; Avis, 1989; Witkowski, 1991; Barrere, 1992; Isermann and Cordes, 1992; Sanjaume and Pardo, 1992; Vestergaard and Hansen, 1992; Heikkinen, 1994; Pluis, 1994; Muhs and Holiday, 1995; Bate and Ferguson, 1996; Hellstrom, 1996; Danin et al., 1998; Gadgil and Ede, 1998). In contrast, in other places, vegetation was removed from dunes as a result of over-grazing and cutting. In these cases, the reverse of the stabilization process took place, in which sand-shifting increased. There are researchers who understand this destruction process as part of the desertification process (Kumar and Bhandary, 1993; Barth, 1999). This process too causes changes in the natural landscape. Discernible, conspicuous changes in landscape have occurred along Israel’s coast. Seventy percent of the population of Israel’s large urban centers (with population over 100,000) lives on the coastal plain at an average density of 272.8 persons/km2 (Israel Central Bureau of Statistics, 1998). In the past, the coastal sands covered an area of 462 km2 (Tsoar and Blumberg, 1990). Since the establishment of the state of Israel in 1948, the dune areas have been reduced to half of their former area as a result of accelerated building and development along the length of the coastal plain (Kutiel and Sharon, 1996). Unfortunately, only about 51 km2 , (20%) of the remaining dune areas are protected today by any of the various designations: reserves, parks, and national parks (Nature Protection and National Parks Authority statistics). Paralleling the reduction in dune areas, bare shifting dunes have likewise been reduced as a result of vegetation coverage (Fig. 1), which caused their stabilization (Barzilay et al., 1998; Kutiel et al., 2000). The stabilization process has in turn caused significant changes in the morphology of the dunes, the floral and faunal composition typical of bare shifting dunes, and overall changes in the general dune landscape along the
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coast (Barzilay et al., 1998; Kutiel, 2001; Kutiel et al., 2000). In light of pressures on the world’s coastal systems, international awareness in recent years has risen regarding the protection and management of the natural resources and landscape of these systems (Charlier and de Mayer, 1995; Charlier and Charlier, 1995). GIS and remote sensing tools enable the quantification and understanding of spatial and temporal processes that accompany spatial dynamics and changes as well as the presentation of how extensive the phenomenon is on a spatial scale. Dune areas are ideal places to monitor the sand-vegetation relationship using these tools, thanks to the high color contrast (light-colored sand with dark-colored vegetation) and pixel reflection of sand as compared with that of vegetation. The objective of the study was to quantify, using remote sensing and GIS, the rate and extent of vegetation expansion and corresponding temporal changes in Israel’s southern coastal between the years 1965 and 1999. The results of the study are meant for use as a basis for predicting future vegetation expansion, understanding the causes of the process, and understanding the ecological significance of the future existence of shifting coastal dunes as a part of the landscape. All of this information is essential to the development and advancement of policies for the preservation and management of coastal dune areas.
2. The study area Nitzanim Park is situated on Israel’s southern coast, covering an area of 13 km2 (Fig. 2). The park is located on the northern portion of a preserved strip of dunes whose entire area covers 20 km2 . Until about 50 years ago, Israel’s coastal strip was continuously linked to the dune sands of the Sahara and the Sinai Peninsula, and was characterized by a shifting dune landscape (Kutiel and Sharon, 1996; Barzilay et al., 1998). This continuity was fragmented by urban, industrial, and recreational development, and today, only a few remaining sand dune “islands” represent the coastal dune landscape, among the largest of which is Nitzanim Park. The area studied stretches over 7 km2 , and is situated in the western portion of the dune park, adjacent to the coastline (Fig. 2). The boundaries of the area
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Fig. 2. The study area.
studied are the access road to the sea on the south, the city of Ashdod to the north, the Mediterranean Sea to the west, and to the east, a demarcation line roughly 2.5 km from the sea. The climate is Mediterranean. The annual average temperature is 19–21 ◦ C, where the temperature in the hottest month (July) is 26–28 ◦ C and the temperature in the coldest month (January) is 12–14 ◦ C. The annual average rainfall ranges from 400 to 500 mm (Israel Atlas), all of which occurs during the winter months (October–March). The geological infrastructure of the study area is formed from two Kurkar (coastal sandstone) ridges that run parallel to the coast. The Kurkar ridges are covered by the sand dunes at various depths and stabilization levels; the dunes in turn are covered with varying levels of vegetation density, from bare shifting dunes to dunes densely covered with vegetation. In recent decades,
the study area was given over to quarrying and sand mining activity. Since the 1950s and as of today, we have been witness to a stabilization process of the dunes manifested among other ways in the covering of bare shifting dunes by vegetation. This vegetation is composed of dwarf shrubs, shrubs, and herbaceous species excepting the alien tree Acacia saligna, and single trees of common date palm and sycamore ficus (Phoenix cadtylifera and Ficus sycomorus) that were planted in the dunes before the establishment of Israel in 1948 (hereinafter: “ancient trees”). As far as we know, the origin of the acacias in the study area is a copse planted by the Jewish National Fund in 1962 on the dunes at the eastern edge of the park and the red loam boundary for stabilization and protection of the citrus orchards.
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3. Methods 3.1. Mapping of vegetation density from aerial photographs The study followed five series of black-and-white aerial photographs taken between the years 1965 and 1999 (1965, 1974, 1982, 1990, and 1999). The photographs were chosen from those found in the archives of the Israel Mapping Center. To ensure consistency in interpretation, the photos chosen were taken at similar times of the year, have similar resolutions, elevations from which they were taken, and an equal division of years on the time axis (differences of about 8 years between photo series). The total area studied is 7 km2 , and includes diverse coastal landscape components designated for preservation. The scale of the photos is 1:12,000–1:15,000. The aerial photos underwent geometric adjustment. Such an adjustment in a sandy environment is problematic compared to that in other habitats because in a sandy environment, there are usually no natural reference points (such as cliffs, ridges, or cisterns) or artificial reference points (such as roads, structures, or cultivated fields). In addition, the environment is dynamic and entails changes as a result of natural geomorphic processes or due to human interference, such as sand mining. In our case, we were forced to use “ancient” trees as permanent reference points in the field. These trees were planted in the dunes through the first-half of the 20th century and have remained in place ever since. The 1999 airphoto was georectified at a precision level of 2.65–2.76 m using the New Israel Grid as a base map reference. However, the earlier sets of photographs increasingly differed from the New Israel Grid due to the rapid rate of development, particularly in the northern portion where the city of Ashdod has lately encroached on much of the open dune land. It was therefore necessary to use the georectified 1999 images as the references for correcting those of 1990 and 1982. The georectified 1982 images were in turn used to correct the 1974 and 1965 sets (Shoshany and Degani, 1992; Shoshany et al., 1996). The photo-to-photo accuracy in corresponding photo series from different periods ranges from 2.5 to 3.2 m. In order to create a uniform basis for measuring changes in vegetation densities, the photos were ad-
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justed using the relative normalization technique. A detailed explanation of the technique appears in Shoshany (2000). The technique is based on identifying permanent features of the landscape with a different spectral return that constitute a reference level for determining a ranking of shades of gray that represent vegetation densities for our purposes. These features were located in quarrying areas, dense vegetation areas, and deep sea areas, all of which are found in all of the photo series. The plants appear in the photos as dark pixels, while the sand appears light. The vegetation patches were mapped on this basis after shady areas and artificial features (roads, trails, quarrying areas) that were identified in a visual analysis were taken out of the processed aerial photos. The relative vegetation density, were calculated based on the average shades in a 5 × 5 pixel unit, around each pixel. Based on the mapping comparison with the existing situation in the field, the study area was divided up into four main landscape units: 1. Dunes bare of vegetation and areas characterized by very thin vegetation coverage (up to 20%); mostly presenting with a surface exposed to the wind, including a relatively low percentage of perennials, with the main portion of the coverage being annuals. Among the typical perennials that appear mostly at the dune crests or on their windward slopes: maritime grass (Ammophila arenaria), Artemisia monosperma, Cyprus conglomeratus, and Asthenatherium forsskalii. Among the characteristic annuals: Rumex pictus, Ifloga spicata, Senecio joppensis, a species endemic to Israel’s coastal plain, and Lotus halophilus. 2. Sparsely covered vegetation (20–60%) characterized mainly by coverage of perennials with some annuals. Among the perennials: Desert broom (Retama raetam), Artemisia monosperma, Polygonum palaestinum, Silene succulenta. Among the characteristic annuals, it is also possible to find species that are characteristic of bare shifting dunes as well as those that are not, among them: Cornyephorus divaricatus, Urospermun picroides, and Trisetaria linearis. 3. Dense vegetation coverage (60–100%). These mostly present on the leeward slopes and the depressions between the dunes. The group typical of
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these areas is the desert broom and the Artemisia monosperma. In the particularly wide and deep depressions where traditional agriculture existed prior to the establishment of Israel, the proportion of the area covered by vegetation is over 100% (according to the relative coverage of every species). In these depressions, mountainous Mediterranean shrubs, such as the Calicotome villosa and creepers, such as the Prasium majus predominate. 4. Copses (two or more trees) of Acacia saligna. To all appearances, the origin of the acacia copses is a copse planted in 1962 at the eastern edge of the park. Since then and up until now, the acacias have spread in a disorderly fashion in areas where sand mining, quarrying, and pre-construction earthworks have taken place. In addition, the acacia has spread into the wider depressions where the groundwater is relatively close to the surface, and where the proportion of coverage and the species richness and species diversity is high compared to other habitats in the coastal system. 3.2. Landscape change analysis using GIS Mapping four landscape units at each of the photographs’ acquisition dates yields 16 possible types of landscape change. The distribution of relative area cover between these 16 different types represents the diversity of processes. Theoretically high diversity represents either cyclic change, where processes might be reversed, such as in disturbance and recovery cycles, or where there is a continuous introduction and expansion of new landscape types. In some cases those two types could be combined. Landscape transition matrix is a GIS technique allowing the determination of the relative area cover for each of the transition type. Measuring the transitions’ diversity is important for analyzing landscape stability (Goldschlager and Shoshany, 2000) by assessing sequences of changes. The Information index (Ii ) introduced by Shannon and Wiener represents one of the frequently used for measuring diversity in of distributions, it takes the following form: l Ii = − Pi ln Pi i=1
where Pi is the proportional coverage of the landscape unit of the entire area and i the number of landscape transition types (from 1 to 16 in our case). In order to build an estimated scenario of the continuation of the dune vegetation coverage process, we chose a five square kilometer sub-area of the study area. This sub-area has been minimally affected by humans throughout the period studied compared to other parts of the study area. We related to this sub-area as a “natural” area. Because from 1995, the sand park has acquired legal status as a protected area, from 1995 it must be related to as a “natural” area in which vegetation establishment processes take place undisturbed. For the purposes of describing the future scenario, we related only to natural vegetation units and to bare shifting dunes. The scenario was based on an examination of the time variables of each of the landscape units: bare shifting dunes, medium-coverage dunes, and dense-coverage dunes. In addition, we evaluated the continuation of the vegetation establishment in the entire study area without relating to human impact or the effect of the invasion of alien species.
4. Results The changes between various landscape units in the time periods studied. 4.1. 1965–1974 The relationship of bare shifting dunes to vegetation in 1965 was 69% bare shifting dunes to 31% sand covered by vegetation (Fig. 3). In 1974, the relationship decreased to 64.6% bare shifting dunes to 35.4% sand covered by vegetation. The total change intensity (Ii index) between all of the landscape units during this period was 1.59, the lowest of all the periods during the 34-year period studied (Fig. 4). 75% of all of the landscape units retained their landscape stabilization, 9.5% of the landscape units were given to regressive processes of decrease of vegetation coverage due to sand cover, and 15.4% of the landscape units were in progressive processes of establishment and coverage by vegetation. An area of <1% of all of the landscape transformations included combinations of the Acacia saligna and natural vegetation species.
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Fig. 3. Temporal changes in bare sand and vegetation cover between the years 1965 and 1999.
4.2. 1974–1982
4.3. 1982–1990
During this period, the relationship between bare shifting dunes (64.3%) and dunes covered by vegetation (35.7%) continued to decrease (Fig. 3). In addition, the intensity of landscape changes increased compared to the previous period (Ii 1.72, Fig. 4). During this period, 71.1% of all of the landscape units retained their landscape stability, 14.2% of the landscape units were given to regression processes (re-coverage by sand), and 13.5% of the landscape units were undergoing progressive processes (coverage by vegetation).
The bare shifting dunes/vegetation-covered sand relationship continued to decrease in this period to 53.2% bare shifting dunes versus 35.7% vegetation-covered dunes (Fig. 3). The change intensity in this period increased compared to the previous period (Ii 1.81, Fig. 4). 68.9% of all of the landscape units in this period retained their landscape stability, 5.7% of all of the landscape transformations were in a regressive trend, 23.6% of the transformations were in a progressive trend, the remainder of the area (<2%) included a combination of an acacia copse and
Fig. 4. Trend of change transition diversity (information index): empirical data (upper line) and uni-directional model (lower line).
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indigenous species. In this period, the vegetation establishment and intensity processes are conspicuous. 4.4. 1990–1999 In this period, the reversion point begins in the bare shifting dunes/vegetation-covered dunes relationship: the area of bare shifting dunes is smaller (43.6%) than the vegetation-covered dunes (56.4%, Fig. 3). The change intensity between the various landscape units in this period is highest (Ii = 2.00, Fig. 4). In this period, 67.1% of all of the landscape units retained landscape stability. And 8.4% of all of the landscape transformations were in a regressive trend and 20.3% of the transformations were in a progressive trend. The total number of transformations between natural vegetation units and acacia copses increased significantly in this period compared to the previous period (over 4%). During the entire study period (34 years), the vegetation-covered area grew by 82% at an annual average growth rate of 1.75%. Concurrently, the bare shifting dune area decreased by 37% at an annual average growth rate of 1.34%. The relationship between bare shifting dunes areas and vegetation-covered areas changed over this period from 7:3 in favor of bare shifting dunes areas in 1965 to a ratio of 5.6:4.4 in favor of vegetation-covered areas in 1999. The intensity of change between landscape units increased over the years, reaching its zenith during the 1990–1999 period. The majority of the area in this period is
vegetation-covered (Fig. 5). The conspicuous trend over the period studied, despite regressive processes, is a transition from bare shifting dunes to stabilized, vegetation-covered dunes. The transition of one landscape unit to the other does not happen at the same area proportions nor does it take place mono-directionally. The area covered for 34 years by natural vegetation at a medium density doubled in size (to 2.273 km2 ) from an area that went from thin coverage to dense coverage (1.141 km2 ), and areas that were covered by vegetation became covered by sand (0.62 km2 of dense vegetation and 1.206 km2 of thin vegetation (Table 1)). The transition from vegetation-covered dunes to bare shifting dunes is smaller as compared to bare shifting dunes area that becomes covered with vegetation, and it decreases over the years. If in the period 1965–1974 an area of 0.765 km2 was covered by sand, then in the period 1990–1999, only half of this area was covered by sand. The contribution of the Acacia saligna to the depletion of bare shifting dunes is relatively negligible. A relatively small area of 0.21 km2 of bare shifting dunes was covered over the 34 years by acacias, in contrast to 3.41 km2 of bare shifting dunes that got covered by indigenous vegetation. Of the natural vegetation that covered the bare shifting dunes, the proportion of dense coverage was one-third, as opposed to two-thirds medium coverage. That is, the invasion of sandy areas by medium vegetation coverage is double the increase in landscape units covered by dense
Fig. 5. Decrease in the landscape area of bare shifting dunes over the years.
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Table 1 The changes in the area size (%) of the landscape units within four periods between the years 1965 and 1999
Dense vegetation to dense vegetation Dense vegetation to sparse vegetation Dense vegetation to bare sand Dense vegetation to Acacia Sparse vegetation to dense vegetation Sparse vegetation to sparse vegetation Sparse vegetation to bare sand Sparse vegetation to Acacia Bare sand to dense vegetation Bare sand to sparse vegetation Bare sand to bare sand Bare sand to Acacia Acacia to dense vegetation Acacia to sparse vegetation Acacia to bare sand Acacia to Acacia
1965–1974 (%)
1974–1982 (%)
1982–1990 (%)
1990–1999 (%)
8.52 2.92 2.08 0.16 3.87 3.36 4.47 0.14 3.52 7.32 58.05 0.33 0.11 0.02 0.02 5.10
7.46 4.07 3.82 0.65 3.12 4.03 6.19 0.27 2.41 7.41 54.25 0.57 0.15 0.10 0.15 5.34
10.75 1.10 0.83 0.54 7.90 3.70 3.60 0.45 6.18 8.58 48.59 0.93 0.64 0.20 0.18 5.83
18.38 2.89 2.22 2.00 5.38 3.86 3.11 1.23 4.34 9.39 38.15 1.31 0.65 0.20 0.15 6.75
vegetation. This increase is at the expense of those same areas of bare shifting dunes.
5. Discussion An increase in vegetation cover in the southern coastal dunes of Israel drives a process of their stabilization. It is most important to understand how complex is this process, and for that purpose a reference simple process should be established representing possible simple landscape change scenario. In our case a simplified Uni-Direction Change Model was established (Fig. 6). The main two components of landscape changes are the extension of dense vegetation and the contraction of bare dunes. Trends of change in these two landscape components within the time frames of the data collection seems to be significantly described by linear trends (except for a relatively low figure of dense vegetation cover in 1982 that might be attributed to confusion with sparse vegetation). According to the linear regression (Fig. 7) bare sand will decrease by 0.74% a year and dense vegetation will increase by 0.46% a year. Applying the Uni-Directional Model has resulted in cover type distributions that are very similar to those determined empirically (Table 2), and thus allows us its assessment relative to the real changes. This assessment is facilitated by calculating the landscape transitions us-
ing the Uni-Direction Model, and then calculating the transition information index (Ii ). Temporal changes in the transition information between the model and the empirical results indicate parallel evolution with a significant phase shift of higher diversity in the empirical data (Fig. 4). This higher diversity is attributed mainly to the inverse processes of expansion of the shifting sand into units of sparse and dense vegetation cover. The magnitude of these inverse processes is between 5.5 and 14% of the area, while their effect on the transitions index is generally twice these figures as the existence of inverse processes also reduces the area characterized by other transformation processes. It is the action of the inverse processes that probably forces the only linear rather exponential growth of the dense vegetation cover unit. This result is highly significant Table 2 Total percent cover according to the airphotographs’ retrieval (E) and according to the uni-directional model (M)
Dense vegetation (E) Sparse vegetation (E) Bare sand (E) Acacia saligna (E) Dense vegetation (M) Sparse vegetation (M) Bare sand (M) Acacia saligna (M)
1965
1974
1982
1990
1999
13.85 11.83 69.08 5.24
16.02 13.62 64.61 5.74 15.24 12.21 64.90 7.01
13.22 15.65 64.28 6.85 18.97 13.21 58.93 8.11
25.49 13.58 53.18 7.75 22.70 14.32 53.20 9.22
28.74 16.34 43.63 11.28 27.35 27.35 45.32 10.60
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Fig. 6. The flowchart of the uni-directional model and the calculation of the corresponding elements of the landscape transition matrix. ) Flow of landscape transition calculations. ( ) Feedback loop: updating the cover proportion for each cover type. ( ) ( Updating the landscape transition matrix.
in terms of management planning as there could be an equilibrium reached by local intervention in limiting the vegetation expansion in areas of high potential of continuing dunes migration. The optimal relative cover that may maintain such equilibrium depends on the assessment of sand availability changes due to the reported changes in the sediment transport along the coast of Israel (Golik, 1997; Shoshany et al., 1996). However, such planning needs assessment of the spatial processes, which is beyond the scope of this paper. If the annual average rate of increase of total vegetation (naturally occurring as well as alien acacia) that characterized the 34 years between 1965 and 1999 also characterizes the upcoming years, this means that by 2035, the entire sand dune area will be vegetation-covered (Fig. 8a). A similar scenario arises from the natural landscape units that we chose. According to this scenario, by 2000, the dense
vegetation-bare shifting dunes ratio will be equal, henceforth, the densely covered unit will be the larger of the two. With the shrinkage of the bare shifting dunes, the ratio of bare shifting dunes and medium-coverage vegetation will equalize by 2007; beginning with this year (2001), the medium-coverage vegetation unit is the second largest. According to this forecast, in 2012, no bare shifting dune landscape will remain, and the study area will be covered with medium- and dense-level vegetation. Beginning in 2035, the entire study area will be covered in vegetation whose density is predicted to reach 60–100% (Fig. 8b). According to this forecast, the trend is an increasing density of vegetation. Medium-density vegetation increased as long as the bare shifting dune landscape existed, and concurrently, the landscape unit covered by dense vegetation also increased in size with the
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Fig. 7. Trend of temporal change in vegetation and bare sand cover.
total disappearance of the bare shifting dune landscape, indicating the shrinkage of the medium-density covered area up until its total eventual disappearance in 2035. The expansion of the vegetation cover on the sand dunes and their stabilization during the last four decades was also observed and documented for the northern coastal dunes of Israel (Kutiel, 2001; Kutiel and Sharon, 1996). There is disagreement among the researchers regarding the dominant causes of landscape changes in the dunes of the Israeli coastal plain in the last half of the 20th century. There are those who link global or local climatic change processes that go beyond the direct human impact factor (Alpert and Mandel, 1986; Issar, 1990; Lancaster, 1994; Gvirtzman and Vider, 2000). Others point to causes
related to intensive human interference in these areas (Kumar and Bhandary, 1993; Barth, 1999), and in contrast, there are those who actually link the process to the cessation of human activity in the area as a result of the defining of the statutory status of the areas that came about along with the establishment of Israel, as well as changes in management policies (Tsoar, 2000). Studies around the world based on the luminescence and dedrochronology methods prove that the movement of dunes is dependent upon climatic changes, even the most minor ones. Lancaster (1994) and Gvirtzman and Vider (2000) described a consecutive series of climate-linked events that took place on the eastern coast of the Mediterranean during the past 50 years. Studies show that a high correlation exists
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Fig. 8. A scenario of the continuation of coverage of the dunes by vegetation: (a) scenario based on an average annual growth rate of the general vegetation, both natural and alien invasive acacia in the 34-year study period. The data was collected from the entire study area. (b) Scenario based on a change in landscape units over time in a relatively undisturbed area. The data was collected from landscape units containing natural vegetation.
between the invasion of sand inland during dry periods, as well as the opposite: the stabilization of dunes by vegetation during humid periods and development of red loam soil or sandstone ridges. The development of moist conditions induces the establishment of vegetation that is also seen in other habitats in the world (Gundy et al., 1999). According to Stohlgren et al. (2000), climate is the main factor that determines vegetation structure and species richness and diversity. There are those who indicated that a climatic change can take place even during a short period of a few decades. Issar (1990), for example, pointed out that during the mere 40 years from 600–640 AD, a significant climatic upheaval took place in our area in
which the transition from a moist period to a dry period took place. Such an upheaval left its mark in the drying processes of the area that manifest themselves, among others, in the abandonment of settlements and cultivated land on the coastal plain. An account of sand penetrating the coastal plain from the Hadera Configuration (a top layer of sand in the geological cross-section today covered by vegetation) beginning from the end of the Byzantine era (Netzer, 1994) fits chronologically with Issar’s findings, thus reinforcing his assumptions. Local climatic changes in our area have been reported by several researchers, and have been summarized by Goldreich (1998) and Paz et al. (2000). Alpert
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and Mandel (1986) reported on a decrease in the wind speed and an increase in the rainfall in the southern coastal plain since 1964. In their opinions, this change stems from changes in land use, such as building, agricultural development, and afforestation that began in recent decades all over the coastal plain. These changes in turn caused an increase in soil surface roughness as well as a decrease in its albedo. These phenomena lessened the wind speed and increased the convective rainfall, or “October rains”, in the area. Batz (1996) points out the upward trend of the numbers of synoptic depressions (or “Gaza depressions”) and of events connected to the coastline, that to all appearances stem from exchanges that began in the Nile with the completion of the Aswan Dam. Another explanation for the extensive covering of the dunes by vegetation and their stabilization is connected to essential changes of land use in the area and its management policies. For hundreds of years, a traditional agriculture existed on the coastal dunes, which among others was based on grazing and the cutting down of the woody vegetation in the area. The removal of vegetation by these means prevented the stabilization of the dunes. The shifting of the sands as a result of intensive cutting and grazing activity is known in various places throughout the world (Kumar and Bhandary, 1993; Barth, 1999). With the establishment of Israel in 1948, some of the dunes were declared protected areas that it was forbidden to disturb. This declaration entailed a halt to grazing and cutting. As a result, vegetation returned to cover the dunes. Hester et al. (1994) indicated that protection from grazing was sufficient to bring about the establishment of vegetation in the aeolian system. The rapid establishment of the Nitzanim vegetation is also made possible thanks to the relatively low wind speed that characterizes the area compared to other areas in the world. According to Tsoar (2000), the rate of movement of the sand over the period in question dropped from 3.3 m per year in 1944 to 1.9 m per year during the years 1980–1999. According to Provolotzky (1996), shrubs like the desert broom and the Artemesia monosperma that cover most of the study area are unpalatable to goats and sheep, and therefore it would be difficult to presume that the bulk of the removal of the vegetation came about due to grazing. From a perusal of reports from the British Department of Agriculture
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and Forests for the years 1927–1946, it emerges that only during drought years, when there was a shortage of food for livestock, did Bedouin (nomadic Arab tribes)-owned herds invade the bulk of the dunes despite the sparse vegetation offered there. It might be that the invasion of the dunes by these flocks was enough to break the biogenic and mechanical crusts once every few years in order to stimulate the shifting of the sand and to suppress the successional process that in turn leads to the stabilization of the dunes. The relationship between grazing and the removal of vegetation in the area in question is riddled with disagreement, but the impact of cutting on vegetation is on more solid ground. In the southern coastal plain (Gaza-Rafiah) traditional agriculture dependent upon a high groundwater level in the low depressions between dunes is still practiced. Additionally, those who live on the dunes are still using local woody vegetation for building trenches and for firewood. It is quite possible that even at Nitzanim such a culture existed, in which cutting had a strong impact on the morphology and mobility of the dunes. A comparison of satellite images of the Egypt–Israel border reveals that on the Egyptian side, where intensive human activity takes place, the dunes have remained free of vegetation, whereas on the Israeli side, where law has restricted human activity, the dunes are densely covered with vegetation. Likewise, the convective rain events, and thus the total annual amount of rain, are significantly higher on the Israeli part than that on the Egyptian side (Katz and Kadmon, 2000). In addition to the opinion that links the establishment of vegetation to the halting of human activity (grazing and cutting), the causes of dune stabilization can actually be considered based on intensive human activity of dune afforestration. The movement of sand can be a nuisance to man when the sand covers settled land, agricultural land, airports, and transportation arteries. In order to overcome this nuisance, methods were developed for stabilization of the sand, one of which is the use of suitable plants (Isermann and Cordes, 1992; Barrere, 1992; Sanjaume and Pardo, 1992; Vestergaard and Hansen, 1992; Danin et al., 1998). Nordstrom and Lotstein (1989) point out that part of the degeneration of the aeolian landscape all over the world is related to the extensive human labor invested in limiting the shifting of sand, which they also perceive as ecological and aesthetic spoilage.
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In Mandatory Palestine too, British policy-makers and the first Jewish settlers related to the sand as an environmental defect, a strange and alien landscape in contrast to the European forest, which was perceived as the ideal landscape for the Holy Land (Reuveny, 1993; Lifschitz and Biger, 1994, 1997). The planning-based need for the stabilization of the sand took shape by means of two actions aimed at this objective: Planting and anti-cutting of vegetation legislation, and restrictions on grazing. During this period, a variety of indigenous plants were planted on the dunes, which were collected and acquired from the proximate area, such as maritime grass and Artemisia monosperma, as well as many exotic shrubs and trees, among them eucalyptus (Eucalyptus cornuta, E. lehmany, E. robusta), pine, tamarisk, and various acacias (Acacia arabica, A. cyanophylla, A. cyclopis, A. pycnantha), which were imported from other countries. In order to enable the continuation of the stabilization of the shifting dunes, the British enacted legislation and regulations restricting cutting and grazing activity in the area of the coastal dunes. These laws and restrictions were designed to enable the establishment of the vegetation that was planted. These plantings, the remains of which can still be seen today, and the protection of the area from harm to the plantings, accelerated the establishment processes of vegetation that ultimately caused the stabilization of the dunes and the landscape transformations characteristic of the area prior to the stabilization. In addition, an analysis of the British Department of Agriculture and Forests shows that the total scope of coping with dune stabilization during the Mandatory period did not take on the nature of a sweeping activity throughout the coastal plain. At the beginning of this period, stabilization activity took on a research quality (experiments and observation), and over time, became more hands-on. The main part of the plantings was focused around a few locations along the length of the coastline. The planting strategy was focused on protecting the transportation arteries and preventing sand from moving inland by planting along the coast, which created foredunes, and planting around worn away sites on the sandstone ridge, used as a natural causeway for sand to move inland. Intensive human involvement in coastal areas influenced and still influences even the quantity of sand
washed up onto the shore, as well as the inland balance of sand. The reduction in the supply of sand on Israel’s shores is connected to the building of dams, such as the Aswan Dam on the Nile, the building of ports and power plants all along the coast, which act as sand traps along the length of Israel’s coastal current, and sand quarrying for construction purposes (Nir, 1989; Shoshany et al., 1996; Golik, 1997). A limited supply of sand and low wind speeds can stimulate the establishment of vegetation and the stabilization of the dunes. It is also possible that the simultaneous effects of part or all factors caused the dense cover of woody vegetation. Whatever the reason, it is clear that the aeolian landscape of Israel’s coastal dunes is disappearing, making way for a landscape of dense vegetation. In light of the rate of the process during the 34-year study period, we estimate that by 2030, the dunes will be 100% covered by vegetation of over 60% density. Regarding the uniqueness and the importance of the aeolian sand system in the various relevant scientific spheres, there is no dispute (Fromkin, 1998; Kutiel, 2001; Netzer, 1994; Tsoar, 2000; Malul, 2000). These, now stable areas require effective management for the conservation of this ecosystem. A study that was conducted in a coastal dune nature reserve north of Nitzanim Park aimed to analyze the hypothesis that removal of the above-ground vegetation will encourage repopulation and increase of the existing sand-living herbaceous annual species and rodents (some of which are endemic to Israel). The results of the research demonstrated that removal of perennial vegetation reduces the field mouse (Mus musculus praetextus) population and encourages the endemic gerbil (Gerbillus andersoni allenbyi) dominance. In addition, the annual plant coverage increased significantly in the treated sites, when the species that characterize the sand, such as Rumex pictus, Daucus glaber, Crepis aculeata, Brassica toumefortii, Cutandia philistaea and Corynephorus divaricatus were dominant. This situation persisted for at least 5 years after the removal of the vegetation (Kutiel et al., 2000). The practical conclusion that resulted from this work is that deliberate removal of dense woody vegetation can serve as a management tool for areas that are designated for the conservation of species diversity that characterize the region. Today, after five consecutive years of research, the removal of woody
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vegetation in a patchy form from the crest of the stabilized sand dunes is part of the Nature Reserve and National Authority management in this area.
Acknowledgements This study was carried out thanks to the financial support of the Jewish National Fund. Thanks also to Yair Farjun, principal of Shikmim Field School, for his help, support, and knowledge of everything related to Nitzanim Park. References Alpert, P., Mandel, M., 1986. Wind as an indicator for a mesoclimatic changes in Israel. J. Climate Appl. Meteor. 25, 1568–1576. Avis, A.M., 1989. A review of coastal dune stabilization in the Cape Province of South Africa. Landscape Urban Plann. 18, 55–68. Barrere, P., 1992. Dynamics and management of the coastal dunes of the Landes, Gascony, France. In: Carter, R.W.G., Curtis, T.G.F., Skeffington, M.J.S. (Eds.), Coastal Dunes. Balkema, Rotterdam, Brookfield, pp. 25–33. Barth, H.J., 1999. Desertification in the eastern province of Saudi Arabia. Arid Environ. 43, 399–410. Barzilay, E., Tsoar, H., Blumberg, D., 1998. Dynamics and morphological changes that occurred in the Ashdod Sand over the past fifty years. In: Proceedings of the Israel Geographic Society Conference, 16–18 December 1998. Bar-Ilan University, Ramat Gan, Israel (in Hebrew). Bate, G., Ferguson, M., 1996. Blowouts in coastal foredunes. Landscape Urban Plann. 34, 215–224. Batz, A., 1996. Does the Aswan Dam affect the quantity and distribution of rainfall in Israel? Meteor. Israel 4, 17–18. Charlier, R.H., Charlier, C.P., 1995. Sustainable multiple-use and management of the coastal zone. Environ. Manag. Health 6, 14–24. Charlier, R.H., de Mayer, C.P., 1995. Beach nourishment as efficient coastal protection. Environ. Manag. Health 6, 26–34. Danin, A., Stephen, R., Barbour, M., Jurjavcic, N., Connors, P., Uhllinger, E., 1998. Early succession on Budega Head. California. Madrono 45, 101–109. Fromkin, S., 1998. Botany, Zoology, and Archaeology. From the Master Plan for the Rehabilitation and Development of Nahal Lachish, Interim Report no. 1 (in Hebrew). Gadgil, R.L., Ede, F.J., 1998. Application of scientific principles to sand dune stabilization in New Zealand: past progress and future needs. Land Degrad. Develop. 9, 131–142. Goldschlager and Shoshany, 2000. Use of GIS for Analysis of Landscape Stability in the Carmel Region. In: Eshel, Y. (Ed.), Judean and Samaria Research Institute, Kedumim Ariel. Eretz Publication, (in Hebrew, with English abstract) pp. 347–358.
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Goldreich, Y., 1998. The Climate in Israel: Observations, Research, and Applications. Bar-Ilan Press, Ramat Gan (in Hebrew), pp. 181–183. Golik, A., 1997. Dynamic and management of sand along the Israeli coastline. CIESM Science Series no 3: Transformation and Evolution of the Mediterranean Coastline, pp. 97–110. Gundy, A.H., Brenner, M., Hodell, D.A., Curtis, J.H., Leyden, B.W., Binford, M.W., 1999. A 10,300 14C year record of climate and vegetation change from Haiti. Q. Res. 52, 159–170. Gvirtzman G., Vider, M., 2000. Climatic exchanges during the past 50,000 years as recorded by stratigraphy of sedimentary and soil layers in Israel’s central coastal plain. In: Proceedings of the Workshop on Conservation and Management of the Coastal Sand Dunes of Israel Nitzanim Park, May 2000 (in Hebrew). Heikkinen, O., 1994. The Pacific Northwest coastal dunes: human influence and natural changes. Terra 106, 267–276. Hellstrom, G.B., 1996. Preliminary investigations into recent changes of Goukamma Nature Reserve Frontal Dune System, South Africa, with management implication. Landscape Urban Plann. 34, 225–235. Hester, M.W., Wilsey, B.J., Mendelssohn, I.A., 1994. Grazing of Panicum amarum in a Louisiana Barrier Island dune plant community: management implications for a dune restoration project. Ocean Coastal Manag. 23, 213–224. Holdgate, M.W., 1993. The sustainable use of tourism: a key conservation issue. Ambio 22, 481–482. Issar, A., 1990. Climatic changes and the abandonment of the desert edges. Environments 24, 133 (in Hebrew). Isermann, M., Cordes, H., 1992. Changes in dune vegetation on Spiekroog (East Friesian Islands) over a 30-year period. In: Carter, R.W.G., Curtis, T.G.F., Skeffington, M.J.S. (Eds.), Coastal Dunes. Balkema, Rotterdam, Brookfield, pp. 201–209. Kumar, M., Bhandary, M.M., 1993. Impact of human activities on the pattern and process of sand dune vegetation in the Rajasthan desert. Desertification Bullet. 22, 45–54. Kutiel, P., 2001. Conservation and management of the Mediterranean coastal sand dunes in Israel. J. Coastal Conserv. 7, 183–192. Kutiel, P., Sharon, H., 1996. Landscape changes in the last 50 years in the area of HaSharon Park. Israel. Ecol. Environ. 3, 167–176 (in Hebrew, English abstract). Kutiel, P., Peled, Y., Gefen, E., 2000. The effect of removing shrub cover on annual plants and small mammals in coastal sand dune ecosystems. Biol. Conserv. 94, 235–242. Katz, M., Kadmon, R., 2000. The impact of grazing and topography on accelerated Vegetation coverage of the Nitzana dunes, Israel. In: Proceedings of the Workshop on Conservation and Management of the Coastal Sand Dunes of Israel Nitzanim Park, May 2000 (in Hebrew). Lancaster, N., 1994. Controls on aeolian activity: some new perspectives from the Kelso Dunes, Mojave Desert. California. Arid Environ. 27, 113–125 (In Hebrew, English abstract). Lifschitz, N., Biger, G., 1994. British afforestation policy in Mandatory Palestine. Horizons Geog. 40/41, 5–16 (in Hebrew, English abstract). Lifschitz, N., Biger, G., 1997. The stabilization of bare shifting dunes using vegetation in Mandatory Palestine. Horizons Geog. 46/47, 21–38 (in Hebrew, English abstract).
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Malul, A., 2000. The hydrology of the sand areas. In: Proceedings of the workshop on Conservation and Management of the Coastal Sand Dunes of Israel Nitzanim Park, May 2000 (in Hebrew). McManus, D., 1988. Plant community dynamics on sand dunes at Murlough National Nature Reserve, Dundrum, County Down, Northern Ireland. M.Phill. Thesis. Department of Environmental Studies, University of Ulster at Jordenstown, 377 pp. Muhs, D.R., Holiday, V.T., 1995. Evidence of dune sand on the great plains in the 19th century from account of early explorers. Q. Res. 43, 198–208. Netzer, M., 1994. The Climatic Changes During the Holocene Stage and their Effect in the Formation of the Landscape in Gush Dan and the Human Settlement in this Region. Ph.D. Thesis. Department of Geography, Bar-Ilan University, Israel, pp. 127 (in Hebrew, English abstract). Nir, Y., 1989. The Mediterranean coast of Israel and Northern Sinai: Sedimentological aspects. Infrastructure Ministry report—The Geological Institute (in Hebrew). Nordstrom, K.F., Lotstein, E.L., 1989. Perspectives on resource use of dynamic coastal dunes. Geo. Rev. 79, 1–12. Paz, S., Steinberger, H., Kutiel, H., 2000. Spatial correlations, trends, and movements in the rains of the Eastern Mediterranean Basin in the years 1951–1999. Horizons Geog. 52, 37–53 (in Hebrew, English abstract). Pluis, J.L.A., 1994. Algal crust formation in the inland dune area, Laarder Wasmeer, The Netherlands. Vegetatio 113, 41–51. Provolotzky, A., 1996. The relationship between grazing and nature conservation in Israel. Ecol. Environ. 3, 245–248 (in Hebrew, English abstract). Reuveny, Y., 1993. Mandatory Rule in Palestine, 1920–1948: A Historical-Policy Analysis. Bar-Ilan University Press, Ramat Gan. (in Hebrew), 245 pp. Sanjaume, E., Pardo, J., 1992. The dunes of Valencia Coast (Spain): Past and present. In: Carter, R.W.G., Curtis, T.G.F., Skeffington, M.J.S. (Eds.), Coastal Dunes. Balkema, Rotterdam, Brookfield, pp. 475–486. Shoshany, M., 2000. Detection and analysis of soil erodibility patterns using air photographs of the Avisur Highlands, Israel. IAHS 261, 127–139. Shoshany, M., Degani, A., 1992. Shoreline detection by digital image processing of aerial photography. J. Coastal Res. 8, 29–34. Shoshany, M., Golik, A., Degani, A., Lavee, H., Gvirtzman, G., 1996. New evidence for sand transport direction along the coastline of Israel. J. Coast. Res. 12, 311–325. Stohlgren, T.J., Owen, A.J., Lee, M., 2000. Monitoring shifts in plant diversity in response to climate change: a method for landscapes. Biodive. Conserv. 9, 65–86. Tsoar, H., 2000. The dynamics of the Southern Coastal Sands. In: Proceedings of the Workshop on Conservation and Management of the Coastal Sand Dunes of Israel Nitzanim Park, May 2000 (in Hebrew). Tsoar, H., Blumberg, D., 1990. The impact of the coastal cliff on aeolian sand in Israel’s southern coastal strip. Horizons Geog. 31, 155–168 (in Hebrew, English abstract). van der Meulen, F., Salman, A.H.P.M., 1996. Management of Mediterranean coastal dunes. Ocean Coastal Manag. 30, 177– 195.
Vestergaard, P., Hansen, K., 1992. Changes in the morphology and vegetation of a man-made beach-dune system by natural processes. In: Carter, R.W.G., Curtis, T.G.F., Skeffington, M.J.S. (Eds.), Coastal Dunes. Balkema, Rotterdam, Brookfield, pp. 165–176. Witkowski, E.T.F., 1991. Growth and competition between seedlings of Protea repens (L.) L. and the alien invasive, Acacia saligna (Labill.) Wendle. in relation to nutrient availability. Function. Ecol. 5, 101–110. Pua Kutiel specializes in the dynamics and management of natural and artificial Mediterranean ecosystems. For 10 years, beginning 1985, she was involved with impacts and behavior of prescribed and wildfires in Israel (15 articles in refereed journals. 23 oral presentations at scientific meetings and editing a special issue of Horizons in Geography on forest fires). During this period she acted as the Forest Service Department (Jewish National Fund, JNF) counselor for prescribed fires and management of protected burned ecosystems. Since 1995, after spending a year in the Faculty of Environmental Studies and the Institute of Nature Reserve at the University of Waterloo, Canada (financed by the Canadian Foundation to further the study and research of Canadian subjects), she is involved with the development of sustainable management of open spaces that combine conservation, recreation and ecotourism (20 articles in refereed journals; a book in Hebrew published by “Eretz” publication, more than 20 oral presentations at scientific conferences). She has also acted as an Ecological counselor of the National Parks Board in this field. To this day she is a counselor to the Nature Reserve and National Park Authority (NRNPA) on all subjects involving the development and restoration research and management policies in protected areas for conservation of biodiversity and landscape heterogeneity. In 1997, together with Dr. Gefen of Tel-Aviv University, she was awarded first prize for preserving natural areas in the Henry Ford European Conservation Awards (National Award). Since 1999 she has begun to study, together with graduate and undergraduate students, the urban social and ecological outlook as a basis for developing sustainable eco-urban systems (two articles in preparation and two oral presentations at scientific meetings). Maxim Shoshany, an associate professor, did his BA in physical geography, MA in computerized mapping, GIS and PhD in remote sensing, from the Geodetic Engineering Division, Faculty of Civil Engineering, Techno, Israel Institute of Technology, Haifa, Israel. His fields of interest are remote sensing, GIS, landscape ecology. His research interests include landscape fragmentation and patch dynamics, spatial and contextual knowledge conceptualization, shoreline change monitoring and modelling, environment change detection. Oded Cohen and Merav Shub are students of the Geography Department in Bar-Ilan University. Cohen finished his MA with a thesis on landscape changes in the vegetation coverage in the southern coastal plain of Israel in the years 1965–1999. He is now PhD student in the Department of Geography and Environmental Development, and working on various aspects on the biological invasion of Acacia saligna in the coastal dunes of Israel.
Vegetation establishment on the southern Israeli coastal sand dunes between the years 1965 and 1999 Pua Kutiel a,∗ , Oded Cohen a , Maxim Shoshany b , Merav Shub b a
Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel b Department of Geography, Bar-Ilan University, Ramat Gan 52900, Israel
Abstract Since 1960, the Israeli coastal dunes have undergone a stabilization process that is manifested in the increase of vegetation cover and in a decrease in the abundance of sand-living flora and fauna species. The objective of the study was to quantify, using remote sensing and GIS, the rate and extent of vegetation expansion and their resultant temporal changes on Israel’s southern coastal dunes between the years 1965 and 1999. The results indicate that during the entire study period, the vegetation-covered area grew by 82% at an annual average growth rate of 1.75%. Concurrently, the bare shifting dune area decreased by 37% at an annual average growth rate of 1.34%. The conspicuous trend over the period studied, despite regressive processes, is a transition from bare shifting dunes to stabilized, vegetation-covered dunes. The extrapolation of the results, assuming continuation of processes and no destruction effects, indicates that with the decrease in the bare shifting dunes, the ratio of bare shifting dunes and sparse vegetation coverage landscape will equalize by between 2007 and 2010. According to this extrapolation, between 2012 and 2015, no bare shifting dune landscape will remain, and the study area will be covered with sparse- and dense-level vegetation cover. Beginning in 2035, the entire study area will be covered in vegetation whose density will be between 60 and 100%. Meso-climate and land use changes are among the factors that might explain this phenomenon. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Coastal sand dunes; Landscape changes; GIS
1. Introduction An increase in the human population, a rise in use of resources utilization, and expansion of urban spaces are some of the factors affecting the environment and ultimately causing significant changes in the landscape over short periods of time. The coastal regions, where approximately 60% of the world’s population lives, are considered areas where human interference in the landscape is at its highest level ∗ Corresponding author. Fax: +972-8-6472821. E-mail address: [email protected] (P. Kutiel).
0169-2046/$20.00 © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0169-2046(03)00035-5
compared to other areas (Holdgate, 1993). For example, 75% of dune spaces around the Mediterranean Basin have been disturbed or destroyed in the past 30 years due to extensive urbanization, industrialization and recreation- and tourism-based development (van der Meulen and Salman, 1996). In various places in the world, great efforts have been made to stabilize coastal dunes in particular and foredunes in general. In an effort to stabilize the shifting dunes or to expand the beach for recreational needs (Nordstrom and Lotstein, 1989), in most cases exotic species were used, such as the Australian acacia (Acacia saligna and A. cyclop), various species of
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Fig. 1. Aerial photograph of Nitzanim Sand Park in 1965 (below) and 1999 (above).
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tamarisk, pine, and perennial grasses, such as maritime grass (Ammophilla arenaria). These plants are rapid growers, have low demands on their habitats, and are able to cope with high-speed wind regimes and seawater spray close to the coast, as well as the harsh conditions typical of sand. Over time, some of these plants have expanded and covered broad areas, thereby, stabilizing the sand and modifying the landscape in both geomorphic and biological sense. In many cases this has caused nature conservation problems (McManus, 1988; Avis, 1989; Witkowski, 1991; Barrere, 1992; Isermann and Cordes, 1992; Sanjaume and Pardo, 1992; Vestergaard and Hansen, 1992; Heikkinen, 1994; Pluis, 1994; Muhs and Holiday, 1995; Bate and Ferguson, 1996; Hellstrom, 1996; Danin et al., 1998; Gadgil and Ede, 1998). In contrast, in other places, vegetation was removed from dunes as a result of over-grazing and cutting. In these cases, the reverse of the stabilization process took place, in which sand-shifting increased. There are researchers who understand this destruction process as part of the desertification process (Kumar and Bhandary, 1993; Barth, 1999). This process too causes changes in the natural landscape. Discernible, conspicuous changes in landscape have occurred along Israel’s coast. Seventy percent of the population of Israel’s large urban centers (with population over 100,000) lives on the coastal plain at an average density of 272.8 persons/km2 (Israel Central Bureau of Statistics, 1998). In the past, the coastal sands covered an area of 462 km2 (Tsoar and Blumberg, 1990). Since the establishment of the state of Israel in 1948, the dune areas have been reduced to half of their former area as a result of accelerated building and development along the length of the coastal plain (Kutiel and Sharon, 1996). Unfortunately, only about 51 km2 , (20%) of the remaining dune areas are protected today by any of the various designations: reserves, parks, and national parks (Nature Protection and National Parks Authority statistics). Paralleling the reduction in dune areas, bare shifting dunes have likewise been reduced as a result of vegetation coverage (Fig. 1), which caused their stabilization (Barzilay et al., 1998; Kutiel et al., 2000). The stabilization process has in turn caused significant changes in the morphology of the dunes, the floral and faunal composition typical of bare shifting dunes, and overall changes in the general dune landscape along the
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coast (Barzilay et al., 1998; Kutiel, 2001; Kutiel et al., 2000). In light of pressures on the world’s coastal systems, international awareness in recent years has risen regarding the protection and management of the natural resources and landscape of these systems (Charlier and de Mayer, 1995; Charlier and Charlier, 1995). GIS and remote sensing tools enable the quantification and understanding of spatial and temporal processes that accompany spatial dynamics and changes as well as the presentation of how extensive the phenomenon is on a spatial scale. Dune areas are ideal places to monitor the sand-vegetation relationship using these tools, thanks to the high color contrast (light-colored sand with dark-colored vegetation) and pixel reflection of sand as compared with that of vegetation. The objective of the study was to quantify, using remote sensing and GIS, the rate and extent of vegetation expansion and corresponding temporal changes in Israel’s southern coastal between the years 1965 and 1999. The results of the study are meant for use as a basis for predicting future vegetation expansion, understanding the causes of the process, and understanding the ecological significance of the future existence of shifting coastal dunes as a part of the landscape. All of this information is essential to the development and advancement of policies for the preservation and management of coastal dune areas.
2. The study area Nitzanim Park is situated on Israel’s southern coast, covering an area of 13 km2 (Fig. 2). The park is located on the northern portion of a preserved strip of dunes whose entire area covers 20 km2 . Until about 50 years ago, Israel’s coastal strip was continuously linked to the dune sands of the Sahara and the Sinai Peninsula, and was characterized by a shifting dune landscape (Kutiel and Sharon, 1996; Barzilay et al., 1998). This continuity was fragmented by urban, industrial, and recreational development, and today, only a few remaining sand dune “islands” represent the coastal dune landscape, among the largest of which is Nitzanim Park. The area studied stretches over 7 km2 , and is situated in the western portion of the dune park, adjacent to the coastline (Fig. 2). The boundaries of the area
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Fig. 2. The study area.
studied are the access road to the sea on the south, the city of Ashdod to the north, the Mediterranean Sea to the west, and to the east, a demarcation line roughly 2.5 km from the sea. The climate is Mediterranean. The annual average temperature is 19–21 ◦ C, where the temperature in the hottest month (July) is 26–28 ◦ C and the temperature in the coldest month (January) is 12–14 ◦ C. The annual average rainfall ranges from 400 to 500 mm (Israel Atlas), all of which occurs during the winter months (October–March). The geological infrastructure of the study area is formed from two Kurkar (coastal sandstone) ridges that run parallel to the coast. The Kurkar ridges are covered by the sand dunes at various depths and stabilization levels; the dunes in turn are covered with varying levels of vegetation density, from bare shifting dunes to dunes densely covered with vegetation. In recent decades,
the study area was given over to quarrying and sand mining activity. Since the 1950s and as of today, we have been witness to a stabilization process of the dunes manifested among other ways in the covering of bare shifting dunes by vegetation. This vegetation is composed of dwarf shrubs, shrubs, and herbaceous species excepting the alien tree Acacia saligna, and single trees of common date palm and sycamore ficus (Phoenix cadtylifera and Ficus sycomorus) that were planted in the dunes before the establishment of Israel in 1948 (hereinafter: “ancient trees”). As far as we know, the origin of the acacias in the study area is a copse planted by the Jewish National Fund in 1962 on the dunes at the eastern edge of the park and the red loam boundary for stabilization and protection of the citrus orchards.
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3. Methods 3.1. Mapping of vegetation density from aerial photographs The study followed five series of black-and-white aerial photographs taken between the years 1965 and 1999 (1965, 1974, 1982, 1990, and 1999). The photographs were chosen from those found in the archives of the Israel Mapping Center. To ensure consistency in interpretation, the photos chosen were taken at similar times of the year, have similar resolutions, elevations from which they were taken, and an equal division of years on the time axis (differences of about 8 years between photo series). The total area studied is 7 km2 , and includes diverse coastal landscape components designated for preservation. The scale of the photos is 1:12,000–1:15,000. The aerial photos underwent geometric adjustment. Such an adjustment in a sandy environment is problematic compared to that in other habitats because in a sandy environment, there are usually no natural reference points (such as cliffs, ridges, or cisterns) or artificial reference points (such as roads, structures, or cultivated fields). In addition, the environment is dynamic and entails changes as a result of natural geomorphic processes or due to human interference, such as sand mining. In our case, we were forced to use “ancient” trees as permanent reference points in the field. These trees were planted in the dunes through the first-half of the 20th century and have remained in place ever since. The 1999 airphoto was georectified at a precision level of 2.65–2.76 m using the New Israel Grid as a base map reference. However, the earlier sets of photographs increasingly differed from the New Israel Grid due to the rapid rate of development, particularly in the northern portion where the city of Ashdod has lately encroached on much of the open dune land. It was therefore necessary to use the georectified 1999 images as the references for correcting those of 1990 and 1982. The georectified 1982 images were in turn used to correct the 1974 and 1965 sets (Shoshany and Degani, 1992; Shoshany et al., 1996). The photo-to-photo accuracy in corresponding photo series from different periods ranges from 2.5 to 3.2 m. In order to create a uniform basis for measuring changes in vegetation densities, the photos were ad-
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justed using the relative normalization technique. A detailed explanation of the technique appears in Shoshany (2000). The technique is based on identifying permanent features of the landscape with a different spectral return that constitute a reference level for determining a ranking of shades of gray that represent vegetation densities for our purposes. These features were located in quarrying areas, dense vegetation areas, and deep sea areas, all of which are found in all of the photo series. The plants appear in the photos as dark pixels, while the sand appears light. The vegetation patches were mapped on this basis after shady areas and artificial features (roads, trails, quarrying areas) that were identified in a visual analysis were taken out of the processed aerial photos. The relative vegetation density, were calculated based on the average shades in a 5 × 5 pixel unit, around each pixel. Based on the mapping comparison with the existing situation in the field, the study area was divided up into four main landscape units: 1. Dunes bare of vegetation and areas characterized by very thin vegetation coverage (up to 20%); mostly presenting with a surface exposed to the wind, including a relatively low percentage of perennials, with the main portion of the coverage being annuals. Among the typical perennials that appear mostly at the dune crests or on their windward slopes: maritime grass (Ammophila arenaria), Artemisia monosperma, Cyprus conglomeratus, and Asthenatherium forsskalii. Among the characteristic annuals: Rumex pictus, Ifloga spicata, Senecio joppensis, a species endemic to Israel’s coastal plain, and Lotus halophilus. 2. Sparsely covered vegetation (20–60%) characterized mainly by coverage of perennials with some annuals. Among the perennials: Desert broom (Retama raetam), Artemisia monosperma, Polygonum palaestinum, Silene succulenta. Among the characteristic annuals, it is also possible to find species that are characteristic of bare shifting dunes as well as those that are not, among them: Cornyephorus divaricatus, Urospermun picroides, and Trisetaria linearis. 3. Dense vegetation coverage (60–100%). These mostly present on the leeward slopes and the depressions between the dunes. The group typical of
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these areas is the desert broom and the Artemisia monosperma. In the particularly wide and deep depressions where traditional agriculture existed prior to the establishment of Israel, the proportion of the area covered by vegetation is over 100% (according to the relative coverage of every species). In these depressions, mountainous Mediterranean shrubs, such as the Calicotome villosa and creepers, such as the Prasium majus predominate. 4. Copses (two or more trees) of Acacia saligna. To all appearances, the origin of the acacia copses is a copse planted in 1962 at the eastern edge of the park. Since then and up until now, the acacias have spread in a disorderly fashion in areas where sand mining, quarrying, and pre-construction earthworks have taken place. In addition, the acacia has spread into the wider depressions where the groundwater is relatively close to the surface, and where the proportion of coverage and the species richness and species diversity is high compared to other habitats in the coastal system. 3.2. Landscape change analysis using GIS Mapping four landscape units at each of the photographs’ acquisition dates yields 16 possible types of landscape change. The distribution of relative area cover between these 16 different types represents the diversity of processes. Theoretically high diversity represents either cyclic change, where processes might be reversed, such as in disturbance and recovery cycles, or where there is a continuous introduction and expansion of new landscape types. In some cases those two types could be combined. Landscape transition matrix is a GIS technique allowing the determination of the relative area cover for each of the transition type. Measuring the transitions’ diversity is important for analyzing landscape stability (Goldschlager and Shoshany, 2000) by assessing sequences of changes. The Information index (Ii ) introduced by Shannon and Wiener represents one of the frequently used for measuring diversity in of distributions, it takes the following form: l Ii = − Pi ln Pi i=1
where Pi is the proportional coverage of the landscape unit of the entire area and i the number of landscape transition types (from 1 to 16 in our case). In order to build an estimated scenario of the continuation of the dune vegetation coverage process, we chose a five square kilometer sub-area of the study area. This sub-area has been minimally affected by humans throughout the period studied compared to other parts of the study area. We related to this sub-area as a “natural” area. Because from 1995, the sand park has acquired legal status as a protected area, from 1995 it must be related to as a “natural” area in which vegetation establishment processes take place undisturbed. For the purposes of describing the future scenario, we related only to natural vegetation units and to bare shifting dunes. The scenario was based on an examination of the time variables of each of the landscape units: bare shifting dunes, medium-coverage dunes, and dense-coverage dunes. In addition, we evaluated the continuation of the vegetation establishment in the entire study area without relating to human impact or the effect of the invasion of alien species.
4. Results The changes between various landscape units in the time periods studied. 4.1. 1965–1974 The relationship of bare shifting dunes to vegetation in 1965 was 69% bare shifting dunes to 31% sand covered by vegetation (Fig. 3). In 1974, the relationship decreased to 64.6% bare shifting dunes to 35.4% sand covered by vegetation. The total change intensity (Ii index) between all of the landscape units during this period was 1.59, the lowest of all the periods during the 34-year period studied (Fig. 4). 75% of all of the landscape units retained their landscape stabilization, 9.5% of the landscape units were given to regressive processes of decrease of vegetation coverage due to sand cover, and 15.4% of the landscape units were in progressive processes of establishment and coverage by vegetation. An area of <1% of all of the landscape transformations included combinations of the Acacia saligna and natural vegetation species.
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Fig. 3. Temporal changes in bare sand and vegetation cover between the years 1965 and 1999.
4.2. 1974–1982
4.3. 1982–1990
During this period, the relationship between bare shifting dunes (64.3%) and dunes covered by vegetation (35.7%) continued to decrease (Fig. 3). In addition, the intensity of landscape changes increased compared to the previous period (Ii 1.72, Fig. 4). During this period, 71.1% of all of the landscape units retained their landscape stability, 14.2% of the landscape units were given to regression processes (re-coverage by sand), and 13.5% of the landscape units were undergoing progressive processes (coverage by vegetation).
The bare shifting dunes/vegetation-covered sand relationship continued to decrease in this period to 53.2% bare shifting dunes versus 35.7% vegetation-covered dunes (Fig. 3). The change intensity in this period increased compared to the previous period (Ii 1.81, Fig. 4). 68.9% of all of the landscape units in this period retained their landscape stability, 5.7% of all of the landscape transformations were in a regressive trend, 23.6% of the transformations were in a progressive trend, the remainder of the area (<2%) included a combination of an acacia copse and
Fig. 4. Trend of change transition diversity (information index): empirical data (upper line) and uni-directional model (lower line).
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indigenous species. In this period, the vegetation establishment and intensity processes are conspicuous. 4.4. 1990–1999 In this period, the reversion point begins in the bare shifting dunes/vegetation-covered dunes relationship: the area of bare shifting dunes is smaller (43.6%) than the vegetation-covered dunes (56.4%, Fig. 3). The change intensity between the various landscape units in this period is highest (Ii = 2.00, Fig. 4). In this period, 67.1% of all of the landscape units retained landscape stability. And 8.4% of all of the landscape transformations were in a regressive trend and 20.3% of the transformations were in a progressive trend. The total number of transformations between natural vegetation units and acacia copses increased significantly in this period compared to the previous period (over 4%). During the entire study period (34 years), the vegetation-covered area grew by 82% at an annual average growth rate of 1.75%. Concurrently, the bare shifting dune area decreased by 37% at an annual average growth rate of 1.34%. The relationship between bare shifting dunes areas and vegetation-covered areas changed over this period from 7:3 in favor of bare shifting dunes areas in 1965 to a ratio of 5.6:4.4 in favor of vegetation-covered areas in 1999. The intensity of change between landscape units increased over the years, reaching its zenith during the 1990–1999 period. The majority of the area in this period is
vegetation-covered (Fig. 5). The conspicuous trend over the period studied, despite regressive processes, is a transition from bare shifting dunes to stabilized, vegetation-covered dunes. The transition of one landscape unit to the other does not happen at the same area proportions nor does it take place mono-directionally. The area covered for 34 years by natural vegetation at a medium density doubled in size (to 2.273 km2 ) from an area that went from thin coverage to dense coverage (1.141 km2 ), and areas that were covered by vegetation became covered by sand (0.62 km2 of dense vegetation and 1.206 km2 of thin vegetation (Table 1)). The transition from vegetation-covered dunes to bare shifting dunes is smaller as compared to bare shifting dunes area that becomes covered with vegetation, and it decreases over the years. If in the period 1965–1974 an area of 0.765 km2 was covered by sand, then in the period 1990–1999, only half of this area was covered by sand. The contribution of the Acacia saligna to the depletion of bare shifting dunes is relatively negligible. A relatively small area of 0.21 km2 of bare shifting dunes was covered over the 34 years by acacias, in contrast to 3.41 km2 of bare shifting dunes that got covered by indigenous vegetation. Of the natural vegetation that covered the bare shifting dunes, the proportion of dense coverage was one-third, as opposed to two-thirds medium coverage. That is, the invasion of sandy areas by medium vegetation coverage is double the increase in landscape units covered by dense
Fig. 5. Decrease in the landscape area of bare shifting dunes over the years.
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Table 1 The changes in the area size (%) of the landscape units within four periods between the years 1965 and 1999
Dense vegetation to dense vegetation Dense vegetation to sparse vegetation Dense vegetation to bare sand Dense vegetation to Acacia Sparse vegetation to dense vegetation Sparse vegetation to sparse vegetation Sparse vegetation to bare sand Sparse vegetation to Acacia Bare sand to dense vegetation Bare sand to sparse vegetation Bare sand to bare sand Bare sand to Acacia Acacia to dense vegetation Acacia to sparse vegetation Acacia to bare sand Acacia to Acacia
1965–1974 (%)
1974–1982 (%)
1982–1990 (%)
1990–1999 (%)
8.52 2.92 2.08 0.16 3.87 3.36 4.47 0.14 3.52 7.32 58.05 0.33 0.11 0.02 0.02 5.10
7.46 4.07 3.82 0.65 3.12 4.03 6.19 0.27 2.41 7.41 54.25 0.57 0.15 0.10 0.15 5.34
10.75 1.10 0.83 0.54 7.90 3.70 3.60 0.45 6.18 8.58 48.59 0.93 0.64 0.20 0.18 5.83
18.38 2.89 2.22 2.00 5.38 3.86 3.11 1.23 4.34 9.39 38.15 1.31 0.65 0.20 0.15 6.75
vegetation. This increase is at the expense of those same areas of bare shifting dunes.
5. Discussion An increase in vegetation cover in the southern coastal dunes of Israel drives a process of their stabilization. It is most important to understand how complex is this process, and for that purpose a reference simple process should be established representing possible simple landscape change scenario. In our case a simplified Uni-Direction Change Model was established (Fig. 6). The main two components of landscape changes are the extension of dense vegetation and the contraction of bare dunes. Trends of change in these two landscape components within the time frames of the data collection seems to be significantly described by linear trends (except for a relatively low figure of dense vegetation cover in 1982 that might be attributed to confusion with sparse vegetation). According to the linear regression (Fig. 7) bare sand will decrease by 0.74% a year and dense vegetation will increase by 0.46% a year. Applying the Uni-Directional Model has resulted in cover type distributions that are very similar to those determined empirically (Table 2), and thus allows us its assessment relative to the real changes. This assessment is facilitated by calculating the landscape transitions us-
ing the Uni-Direction Model, and then calculating the transition information index (Ii ). Temporal changes in the transition information between the model and the empirical results indicate parallel evolution with a significant phase shift of higher diversity in the empirical data (Fig. 4). This higher diversity is attributed mainly to the inverse processes of expansion of the shifting sand into units of sparse and dense vegetation cover. The magnitude of these inverse processes is between 5.5 and 14% of the area, while their effect on the transitions index is generally twice these figures as the existence of inverse processes also reduces the area characterized by other transformation processes. It is the action of the inverse processes that probably forces the only linear rather exponential growth of the dense vegetation cover unit. This result is highly significant Table 2 Total percent cover according to the airphotographs’ retrieval (E) and according to the uni-directional model (M)
Dense vegetation (E) Sparse vegetation (E) Bare sand (E) Acacia saligna (E) Dense vegetation (M) Sparse vegetation (M) Bare sand (M) Acacia saligna (M)
1965
1974
1982
1990
1999
13.85 11.83 69.08 5.24
16.02 13.62 64.61 5.74 15.24 12.21 64.90 7.01
13.22 15.65 64.28 6.85 18.97 13.21 58.93 8.11
25.49 13.58 53.18 7.75 22.70 14.32 53.20 9.22
28.74 16.34 43.63 11.28 27.35 27.35 45.32 10.60
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Fig. 6. The flowchart of the uni-directional model and the calculation of the corresponding elements of the landscape transition matrix. ) Flow of landscape transition calculations. ( ) Feedback loop: updating the cover proportion for each cover type. ( ) ( Updating the landscape transition matrix.
in terms of management planning as there could be an equilibrium reached by local intervention in limiting the vegetation expansion in areas of high potential of continuing dunes migration. The optimal relative cover that may maintain such equilibrium depends on the assessment of sand availability changes due to the reported changes in the sediment transport along the coast of Israel (Golik, 1997; Shoshany et al., 1996). However, such planning needs assessment of the spatial processes, which is beyond the scope of this paper. If the annual average rate of increase of total vegetation (naturally occurring as well as alien acacia) that characterized the 34 years between 1965 and 1999 also characterizes the upcoming years, this means that by 2035, the entire sand dune area will be vegetation-covered (Fig. 8a). A similar scenario arises from the natural landscape units that we chose. According to this scenario, by 2000, the dense
vegetation-bare shifting dunes ratio will be equal, henceforth, the densely covered unit will be the larger of the two. With the shrinkage of the bare shifting dunes, the ratio of bare shifting dunes and medium-coverage vegetation will equalize by 2007; beginning with this year (2001), the medium-coverage vegetation unit is the second largest. According to this forecast, in 2012, no bare shifting dune landscape will remain, and the study area will be covered with medium- and dense-level vegetation. Beginning in 2035, the entire study area will be covered in vegetation whose density is predicted to reach 60–100% (Fig. 8b). According to this forecast, the trend is an increasing density of vegetation. Medium-density vegetation increased as long as the bare shifting dune landscape existed, and concurrently, the landscape unit covered by dense vegetation also increased in size with the
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Fig. 7. Trend of temporal change in vegetation and bare sand cover.
total disappearance of the bare shifting dune landscape, indicating the shrinkage of the medium-density covered area up until its total eventual disappearance in 2035. The expansion of the vegetation cover on the sand dunes and their stabilization during the last four decades was also observed and documented for the northern coastal dunes of Israel (Kutiel, 2001; Kutiel and Sharon, 1996). There is disagreement among the researchers regarding the dominant causes of landscape changes in the dunes of the Israeli coastal plain in the last half of the 20th century. There are those who link global or local climatic change processes that go beyond the direct human impact factor (Alpert and Mandel, 1986; Issar, 1990; Lancaster, 1994; Gvirtzman and Vider, 2000). Others point to causes
related to intensive human interference in these areas (Kumar and Bhandary, 1993; Barth, 1999), and in contrast, there are those who actually link the process to the cessation of human activity in the area as a result of the defining of the statutory status of the areas that came about along with the establishment of Israel, as well as changes in management policies (Tsoar, 2000). Studies around the world based on the luminescence and dedrochronology methods prove that the movement of dunes is dependent upon climatic changes, even the most minor ones. Lancaster (1994) and Gvirtzman and Vider (2000) described a consecutive series of climate-linked events that took place on the eastern coast of the Mediterranean during the past 50 years. Studies show that a high correlation exists
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Fig. 8. A scenario of the continuation of coverage of the dunes by vegetation: (a) scenario based on an average annual growth rate of the general vegetation, both natural and alien invasive acacia in the 34-year study period. The data was collected from the entire study area. (b) Scenario based on a change in landscape units over time in a relatively undisturbed area. The data was collected from landscape units containing natural vegetation.
between the invasion of sand inland during dry periods, as well as the opposite: the stabilization of dunes by vegetation during humid periods and development of red loam soil or sandstone ridges. The development of moist conditions induces the establishment of vegetation that is also seen in other habitats in the world (Gundy et al., 1999). According to Stohlgren et al. (2000), climate is the main factor that determines vegetation structure and species richness and diversity. There are those who indicated that a climatic change can take place even during a short period of a few decades. Issar (1990), for example, pointed out that during the mere 40 years from 600–640 AD, a significant climatic upheaval took place in our area in
which the transition from a moist period to a dry period took place. Such an upheaval left its mark in the drying processes of the area that manifest themselves, among others, in the abandonment of settlements and cultivated land on the coastal plain. An account of sand penetrating the coastal plain from the Hadera Configuration (a top layer of sand in the geological cross-section today covered by vegetation) beginning from the end of the Byzantine era (Netzer, 1994) fits chronologically with Issar’s findings, thus reinforcing his assumptions. Local climatic changes in our area have been reported by several researchers, and have been summarized by Goldreich (1998) and Paz et al. (2000). Alpert
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and Mandel (1986) reported on a decrease in the wind speed and an increase in the rainfall in the southern coastal plain since 1964. In their opinions, this change stems from changes in land use, such as building, agricultural development, and afforestation that began in recent decades all over the coastal plain. These changes in turn caused an increase in soil surface roughness as well as a decrease in its albedo. These phenomena lessened the wind speed and increased the convective rainfall, or “October rains”, in the area. Batz (1996) points out the upward trend of the numbers of synoptic depressions (or “Gaza depressions”) and of events connected to the coastline, that to all appearances stem from exchanges that began in the Nile with the completion of the Aswan Dam. Another explanation for the extensive covering of the dunes by vegetation and their stabilization is connected to essential changes of land use in the area and its management policies. For hundreds of years, a traditional agriculture existed on the coastal dunes, which among others was based on grazing and the cutting down of the woody vegetation in the area. The removal of vegetation by these means prevented the stabilization of the dunes. The shifting of the sands as a result of intensive cutting and grazing activity is known in various places throughout the world (Kumar and Bhandary, 1993; Barth, 1999). With the establishment of Israel in 1948, some of the dunes were declared protected areas that it was forbidden to disturb. This declaration entailed a halt to grazing and cutting. As a result, vegetation returned to cover the dunes. Hester et al. (1994) indicated that protection from grazing was sufficient to bring about the establishment of vegetation in the aeolian system. The rapid establishment of the Nitzanim vegetation is also made possible thanks to the relatively low wind speed that characterizes the area compared to other areas in the world. According to Tsoar (2000), the rate of movement of the sand over the period in question dropped from 3.3 m per year in 1944 to 1.9 m per year during the years 1980–1999. According to Provolotzky (1996), shrubs like the desert broom and the Artemesia monosperma that cover most of the study area are unpalatable to goats and sheep, and therefore it would be difficult to presume that the bulk of the removal of the vegetation came about due to grazing. From a perusal of reports from the British Department of Agriculture
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and Forests for the years 1927–1946, it emerges that only during drought years, when there was a shortage of food for livestock, did Bedouin (nomadic Arab tribes)-owned herds invade the bulk of the dunes despite the sparse vegetation offered there. It might be that the invasion of the dunes by these flocks was enough to break the biogenic and mechanical crusts once every few years in order to stimulate the shifting of the sand and to suppress the successional process that in turn leads to the stabilization of the dunes. The relationship between grazing and the removal of vegetation in the area in question is riddled with disagreement, but the impact of cutting on vegetation is on more solid ground. In the southern coastal plain (Gaza-Rafiah) traditional agriculture dependent upon a high groundwater level in the low depressions between dunes is still practiced. Additionally, those who live on the dunes are still using local woody vegetation for building trenches and for firewood. It is quite possible that even at Nitzanim such a culture existed, in which cutting had a strong impact on the morphology and mobility of the dunes. A comparison of satellite images of the Egypt–Israel border reveals that on the Egyptian side, where intensive human activity takes place, the dunes have remained free of vegetation, whereas on the Israeli side, where law has restricted human activity, the dunes are densely covered with vegetation. Likewise, the convective rain events, and thus the total annual amount of rain, are significantly higher on the Israeli part than that on the Egyptian side (Katz and Kadmon, 2000). In addition to the opinion that links the establishment of vegetation to the halting of human activity (grazing and cutting), the causes of dune stabilization can actually be considered based on intensive human activity of dune afforestration. The movement of sand can be a nuisance to man when the sand covers settled land, agricultural land, airports, and transportation arteries. In order to overcome this nuisance, methods were developed for stabilization of the sand, one of which is the use of suitable plants (Isermann and Cordes, 1992; Barrere, 1992; Sanjaume and Pardo, 1992; Vestergaard and Hansen, 1992; Danin et al., 1998). Nordstrom and Lotstein (1989) point out that part of the degeneration of the aeolian landscape all over the world is related to the extensive human labor invested in limiting the shifting of sand, which they also perceive as ecological and aesthetic spoilage.
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In Mandatory Palestine too, British policy-makers and the first Jewish settlers related to the sand as an environmental defect, a strange and alien landscape in contrast to the European forest, which was perceived as the ideal landscape for the Holy Land (Reuveny, 1993; Lifschitz and Biger, 1994, 1997). The planning-based need for the stabilization of the sand took shape by means of two actions aimed at this objective: Planting and anti-cutting of vegetation legislation, and restrictions on grazing. During this period, a variety of indigenous plants were planted on the dunes, which were collected and acquired from the proximate area, such as maritime grass and Artemisia monosperma, as well as many exotic shrubs and trees, among them eucalyptus (Eucalyptus cornuta, E. lehmany, E. robusta), pine, tamarisk, and various acacias (Acacia arabica, A. cyanophylla, A. cyclopis, A. pycnantha), which were imported from other countries. In order to enable the continuation of the stabilization of the shifting dunes, the British enacted legislation and regulations restricting cutting and grazing activity in the area of the coastal dunes. These laws and restrictions were designed to enable the establishment of the vegetation that was planted. These plantings, the remains of which can still be seen today, and the protection of the area from harm to the plantings, accelerated the establishment processes of vegetation that ultimately caused the stabilization of the dunes and the landscape transformations characteristic of the area prior to the stabilization. In addition, an analysis of the British Department of Agriculture and Forests shows that the total scope of coping with dune stabilization during the Mandatory period did not take on the nature of a sweeping activity throughout the coastal plain. At the beginning of this period, stabilization activity took on a research quality (experiments and observation), and over time, became more hands-on. The main part of the plantings was focused around a few locations along the length of the coastline. The planting strategy was focused on protecting the transportation arteries and preventing sand from moving inland by planting along the coast, which created foredunes, and planting around worn away sites on the sandstone ridge, used as a natural causeway for sand to move inland. Intensive human involvement in coastal areas influenced and still influences even the quantity of sand
washed up onto the shore, as well as the inland balance of sand. The reduction in the supply of sand on Israel’s shores is connected to the building of dams, such as the Aswan Dam on the Nile, the building of ports and power plants all along the coast, which act as sand traps along the length of Israel’s coastal current, and sand quarrying for construction purposes (Nir, 1989; Shoshany et al., 1996; Golik, 1997). A limited supply of sand and low wind speeds can stimulate the establishment of vegetation and the stabilization of the dunes. It is also possible that the simultaneous effects of part or all factors caused the dense cover of woody vegetation. Whatever the reason, it is clear that the aeolian landscape of Israel’s coastal dunes is disappearing, making way for a landscape of dense vegetation. In light of the rate of the process during the 34-year study period, we estimate that by 2030, the dunes will be 100% covered by vegetation of over 60% density. Regarding the uniqueness and the importance of the aeolian sand system in the various relevant scientific spheres, there is no dispute (Fromkin, 1998; Kutiel, 2001; Netzer, 1994; Tsoar, 2000; Malul, 2000). These, now stable areas require effective management for the conservation of this ecosystem. A study that was conducted in a coastal dune nature reserve north of Nitzanim Park aimed to analyze the hypothesis that removal of the above-ground vegetation will encourage repopulation and increase of the existing sand-living herbaceous annual species and rodents (some of which are endemic to Israel). The results of the research demonstrated that removal of perennial vegetation reduces the field mouse (Mus musculus praetextus) population and encourages the endemic gerbil (Gerbillus andersoni allenbyi) dominance. In addition, the annual plant coverage increased significantly in the treated sites, when the species that characterize the sand, such as Rumex pictus, Daucus glaber, Crepis aculeata, Brassica toumefortii, Cutandia philistaea and Corynephorus divaricatus were dominant. This situation persisted for at least 5 years after the removal of the vegetation (Kutiel et al., 2000). The practical conclusion that resulted from this work is that deliberate removal of dense woody vegetation can serve as a management tool for areas that are designated for the conservation of species diversity that characterize the region. Today, after five consecutive years of research, the removal of woody
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vegetation in a patchy form from the crest of the stabilized sand dunes is part of the Nature Reserve and National Authority management in this area.
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Vestergaard, P., Hansen, K., 1992. Changes in the morphology and vegetation of a man-made beach-dune system by natural processes. In: Carter, R.W.G., Curtis, T.G.F., Skeffington, M.J.S. (Eds.), Coastal Dunes. Balkema, Rotterdam, Brookfield, pp. 165–176. Witkowski, E.T.F., 1991. Growth and competition between seedlings of Protea repens (L.) L. and the alien invasive, Acacia saligna (Labill.) Wendle. in relation to nutrient availability. Function. Ecol. 5, 101–110. Pua Kutiel specializes in the dynamics and management of natural and artificial Mediterranean ecosystems. For 10 years, beginning 1985, she was involved with impacts and behavior of prescribed and wildfires in Israel (15 articles in refereed journals. 23 oral presentations at scientific meetings and editing a special issue of Horizons in Geography on forest fires). During this period she acted as the Forest Service Department (Jewish National Fund, JNF) counselor for prescribed fires and management of protected burned ecosystems. Since 1995, after spending a year in the Faculty of Environmental Studies and the Institute of Nature Reserve at the University of Waterloo, Canada (financed by the Canadian Foundation to further the study and research of Canadian subjects), she is involved with the development of sustainable management of open spaces that combine conservation, recreation and ecotourism (20 articles in refereed journals; a book in Hebrew published by “Eretz” publication, more than 20 oral presentations at scientific conferences). She has also acted as an Ecological counselor of the National Parks Board in this field. To this day she is a counselor to the Nature Reserve and National Park Authority (NRNPA) on all subjects involving the development and restoration research and management policies in protected areas for conservation of biodiversity and landscape heterogeneity. In 1997, together with Dr. Gefen of Tel-Aviv University, she was awarded first prize for preserving natural areas in the Henry Ford European Conservation Awards (National Award). Since 1999 she has begun to study, together with graduate and undergraduate students, the urban social and ecological outlook as a basis for developing sustainable eco-urban systems (two articles in preparation and two oral presentations at scientific meetings). Maxim Shoshany, an associate professor, did his BA in physical geography, MA in computerized mapping, GIS and PhD in remote sensing, from the Geodetic Engineering Division, Faculty of Civil Engineering, Techno, Israel Institute of Technology, Haifa, Israel. His fields of interest are remote sensing, GIS, landscape ecology. His research interests include landscape fragmentation and patch dynamics, spatial and contextual knowledge conceptualization, shoreline change monitoring and modelling, environment change detection. Oded Cohen and Merav Shub are students of the Geography Department in Bar-Ilan University. Cohen finished his MA with a thesis on landscape changes in the vegetation coverage in the southern coastal plain of Israel in the years 1965–1999. He is now PhD student in the Department of Geography and Environmental Development, and working on various aspects on the biological invasion of Acacia saligna in the coastal dunes of Israel.