Soil erosion in Denmark: processes and politics

Environmental Science & Policy 6 (2003) 37–50

Soil erosion in Denmark: processes and politics A. Veihe a,∗ , B. Hasholt b , I.G. Schiøtz a a

Department of Geography and International Development Studies, Roskilde University, P.O. Box 260, 4000 Roskilde, Denmark b Institute of Geography, University of Copenhagen, Øster Voldgade 10, 1350 K, Denmark

Abstract Denmark has been dealing seriously with wind erosion problems for the past 125 years whereas water erosion did not come into focus until serious euthrophication appeared in the coastal waters in 1986. This paper describes the problems and processes of soil erosion in Denmark and how these are inter-linked with the political system through subsidies, production systems, etc. The dominant soil erosion processes in Denmark are wind, sheet, rill, tillage and bank erosion. Whereas wind erosion is predominant on sandy soils with low soil fertility, sheet, rill and tillage erosion are mainly on till from the last glaciation and is largely caused by snowmelt events and prolonged rain on saturated and/or partly frozen soil. Danish laws and subsidies have played a major role in managing soil erosion. This has for instance been manifested by the extensive planting of windbreaks and the establishment of buffer zones along water courses. On the other hand, the focus on reducing nitrate leaching has led to increased sheet and rill erosion resulting from a larger number of fields with winter crops. When it comes to reducing phosphorous transport to the aquatic environment, soil erosion has been recognized as an important process but a thorough understanding of the mechanisms are lacking. Finally, the case study of the Water Environmental Protection Plan I shows that both the media and NGOs can play an important role in pushing environmental problems associated with soil erosion onto the political agenda and with the NGOs having a great say in the actual shaping of the laws. © 2003 Elsevier Science Ltd. All rights reserved. Keywords: Soil erosion; Denmark; Agricultural policies

1. Introduction On 8 October 1986, dead lobsters were presented on Danish television as a result of eutrophication problems in Danish coastal waters. This became a big issue and the beginning of a long political process to address the problem. The Danish public had been aware of the eutrophication problem since 1981 and environmental organizations had continuously pinpointed the problem since 1984 when eutrophication started occurring on a regular basis. It was part of the NPo-report (nitrogen, phosphorous and organic matter) (Danish Environmental Protection Agency, 1984) which had put the focus on soil erosion as an important process for transporting phosphorous from the fields to the aquatic environment in an attempt to quantify sources of pollution. The NPo-report was meant to provide the basis for further political action. The serious off-site effects of soil erosion on the environment may seem surprising in view of European soil erosion risk assessments that place Denmark as an absolute low risk country as compared to southern Europe (European ∗

Corresponding author. Fax: +45-4674-3032. E-mail addresses: [email protected] (A. Veihe), [email protected] (B. Hasholt), [email protected] (I.G. Schiøtz).

Environment Agency, 2000; Van der Knijff et al., 2000). Also, Denmark definitely is not a country where spectacular soil erosion phenomena is an everyday phenomenon, mainly due to the relatively low relief characterizing the landscape. Although erosivity seems to have increased from 1967 to 1994 especially during autumn, erosivity calculated from daily rainfall observations is generally low, i.e. <10 and with maximum values around 35 (Leek and Olsen, 2000). Soil erosion rates are generally low (see Table 1), i.e. below 3 t/ha as determined through plot studies (Hasholt, 1990; Schjønning et al., 1990; Kronvang et al., 2000a) although annual soil loss values around 25 t/ha have been recorded (Sibbesen et al., 1994a; Hasholt, 1995). Generalised risk assessments poorly reflect the enormous variability in space and time and do not take into account the tremendous effect of the extreme events as discussed in detail by Boardman (1998). Observed soil erosion rates in Denmark are in the range observed for lowland areas in the UK (Arden-Clarke and Evans, 1993) but in the high end as compared to parts of Poland (Ryszkowski, 1993). Rates are in the range of values found for Belgium (Govers, 1991). However, this may partly be explained by the methods used for determining soil erosion rates (Evans, 1995). In spite of the generally low erosion rates, Denmark is placed as a probable high risk area in terms of diffuse

1462-9011/03/$ – see front matter © 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S1462-9011(02)00123-5

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Table 1 Types of water erosion processes in Denmark and typical soil erosion rates Erosion types

Soil erosion rates (t/ha)

References

Sheet erosion

Bare soil (0.42) Winter wheat across contours (0.95) Winter wheat, contours (0.26) Catchments (0–0.14) Permanent ryegrass (0.03) Spring barley followed by rye grass during winter, ploughed in spring (0.13–0.42) Spring barley, ploughed in autumn (0.45–2.69) Winter wheat drilled up and down slope, ploughed in autumn (1.17–12.79) Winter wheat drilled across the slope, ploughed in autumn (0.49–11.08) Fallow, ploughed in spring and harrowed from time to time to remove weeds (5.93–10.87)

Schjønning et al., 1990

Rill erosion

Plots (0.58–26.2) Slopes (0.35–18.6) 2.4

Hasholt, 1995

Tillage erosion

Net erosion rate approximately 6.00

Heckrath, 2000

Bank erosion

0.020 m3 /m stream reach 0.023 m3 /m stream reach

Laubel et al., 1999 Laubel et al., 2000

contamination due to the country’s high use of chemicals (European Environment Agency, 2000). It should be mentioned here that the sale of pesticides has gone down from an average 6972 t in the period 1981–1985 to 2841 t in 2000 though this may be attributed to more powerful pesticides where less volume is needed. The amount of phosphorous fertilizer has gone down from an average 49,000–17,000 t over the same period. For phosphorous supplied as manure, a slight increase has been observed from an average 49,000–54,000 t in the period 1981–1985 to 2000 (Landbrugsrådet, 2001). Meanwhile, there has been an average increase in phosphorous within the top 50 cm by 25 kg P/ha in the period 1986–1997/1998 (Rubæk et al., 2001). Detailed monitoring of riverine phosphorus loading in 1993 showed that 52% came from diffuse sources including transport associated with soil erosion (Kronvang et al., 1996a). Another erosion process of major importance in Denmark is wind erosion. Wind erosion has been known as a serious problem since way back in the Viking Ages and during the Iron Age wind drift caused several fields to be covered by sand. Later in the 17th century, several areas along the coast were covered by marine sand blown 10 or more kilometres inland. The process continues to be a serious problem up till this century. The government has hence been forced to pay out compensation to farmers whose crops have been seriously affected by wind erosion in years of extreme and accelerated wind erosion (Kuhlman, 1986; Knudsen and Vestergaard, 2001). Erosion problems and processes in Denmark are hence rather diverse and have historically been handled in very different ways. The aim of this paper is to describe the problems and processes of soil erosion in Denmark and how these are inter-linked with the political system through subsidies, production systems, etc. The future perspectives for

Hasholt, 1990 Sibbesen et al., 1994b

Kronvang et al., 2000b

dealing with the problem of soil erosion in Denmark are further discussed.

2. A theoretical framework The significance of politics and socio-economic issues for soil erosion has long been recognized as essential elements of soil erosion studies and programs in developing countries (e.g. Darkoh, 1987; Stocking, 1988; Driver, 1999; Veihe, 2000). This can be attributed to the fact that several soil conservation projects failed through the late 1980s, not because of inadequate conservation measures seen from a technical point of view, but because these measures did not fit into the local setting from either a political or socio-economic point of view. It is hence surprising that so little work has been done on the interaction between soil erosion on the one side and socio-economic and political parameters on the other side at a European scale. One of the few studies that has been carried out is by Boardman (1990), who studied costs, attitudes and policies relating to soil erosion in Britain. A more recent study by Pretty et al. (2000) assessed the total external costs of UK agriculture and found soil erosion and the associated loss of phosphate to be of importance. The fact that so little research has been put into the appraisal and evaluation of soil and water conservation is in many ways surprising, but on the other hand, it has proven difficult to value natural capital and non-market goods. Bojö (1987) and Pagiola (1994) have tried to apply cost-benefit analysis, but pinpoint the general lack of site-specific information regarding the effect of farming activities and degradation on soil in general and yield in particular, as well as basic economic data on costs and prices related to soil erosion.

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Fig. 1. A theoretical framework for the interaction between socio-economic and political parameters and soil erosion problems.

In terms of policies affecting soil erosion rates, studies within the EU are limited. This is interesting when compared to the US, where the Food Security Act of 1985 requires that farmers who participate in the USDA price support and other programs, use soil conserving methods where needed (Zinn, 1993; Helms et al., 1996). Within the EU, De Graff and Eppink (1999) made an interesting study which showed how subsidy systems consisting of price support for olive products and structural policies to improve infrastructure and production systems have promoted the change from traditional systems to semi-intensive and intensive systems in Spain. The last mentioned are characterized by regular harrowing and herbicide use and with terracing being occasional or rare. As a consequence of this, soil erosion rates are increasing. In the UK, Boardman (1990) has pointed to the growing of winter cereals combined with intensification of agriculture in the 1980s as a cause of increased soil erosion. This problem is also recognized in Denmark (Hasholt, 1990) though the extent of the problem and its importance through time has not been investigated. Looking at the problem from a general point of view, the interrelationship between soil erosion on the one hand and political and socio-economic parameters on the other hand is rather complex (Fig. 1). The importance of the various parameters in the model will vary depending on the specific case, as we will return to later in this paper by analyzing the situation in Denmark. It is questionable what

role research plays. While providing a lot of information about the status of the environment and possible measures which may be taken to address problems, research is often more or less disconnected from the political agenda. This is not only because research results are published mainly in scientific journals, but also because economic interests play a more important role in the political process as compared to environmental issues. This will be illustrated with a case study on the Water Environmental Protection Plan I in Denmark.

3. Processes of soil erosion in Denmark This section will present the specific erosion processes in Denmark and their importance for agricultural production and the environment. 3.1. Wind erosion Wind erosion is a problem on sandy soils (0.1–0.5 mm) in western Denmark though only when sowing takes place. The finer particles (<1 mm) including considerable amounts of organic matter are removed preferentially from the surface. Fig. 2 shows areas (altogether about 0.5 million ha) which in the 1960s experienced wind erosion which was also observed in the 1970s and 1980s. The areas subject to wind erosion are to a large extent identical to areas previously

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also yields little shelter against the soil-slaking effect of raindrops, little resistance to surface runoff and has little soil binding capacity (Sibbesen et al., 1994b). The relative potential risk of soil erosion in Denmark calculated with the USLE is illustrated in Fig. 3 and shows that the high risk areas are located in eastern Denmark on soils developed on material from the last Weichsel glaciation. It is important to note that the applicability of Fig. 3 for policy measures is limited since it only shows the potential risk of erosion whereas the actual risk as obtained through a national monitoring scheme does not exist. The erosion risk map has hence not been validated. There are many places where soil erosion does take place on a regular basis. But either farmers do not take any notice as soil erosion does not seem to affect yields, or farmers want to ‘hide’ the problem as they are afraid of repercussions from the government and/or council in the long term. 3.3. Rill and gully erosion

Fig. 2. Major agricultural areas affected by wind erosion during the period 1960–1970 (modified after Kuhlman, 1986).

described as heathland with sandy soils characterized by low soil fertility (Kuhlman, 1986). In order to reduce the risk of wind erosion, soils are ploughed in winter and are compacted while wet. Seedbeds are prepared by harrowing to 3–5 cm depth at low speed and are left as rough as possible. In many cases, drilling and harrowing are done using combined equipment (Hansen, 1989). 3.2. Sheet erosion Sheet erosion observed by means of alluvial fan deposits is seen from time to time on most soil types in Denmark, most often in autumn and winter. This process seems not to be the most important process in terms of movement of coarser sediment, but its importance can be significant for finer grain sizes and nutrients. The most severe cases seem to be related to snowmelt and/or rainfall on partly frozen ground, but also during high intensity storms with saturated soil conditions, sheet erosion can be quite severe, especially when ground cover is low. Fields with winter cereals are more prone to water erosion than ploughed ones as seedbed preparation promotes surface runoff and erosion by leveling the surface, compacting the soil and breaking down soil structure. The sparse vegetation in winter-cereal fields during winter time

Rills occur on all kinds of soils in Denmark. They are mainly formed on rather steep concave slopes, or below places, where water can concentrate such as roads or other areas with partly sealed surfaces. Clayey subsoil seems to stimulate the formation of rills in the overlying soil. Rills mainly occur in connection with thunderstorms during summer and early autumn. The most prone areas during this time of year are areas with row crops, newly tilled areas or areas with sparse vegetation cover. Recently ploughed and harrowed fields are particularly prone to erosion, because of their low roughness and lack of protective vegetation. In autumn and winter, rill erosion typically occurs during four types of events. Firstly by prolonged rainfall on moist soil, secondly in situations with rain on partly frozen soil, thirdly during snow-melt events and last but not least during high intensity storms combined with low plant cover (Hasholt and Breuning-Madsen, 1989; Thers, 2001). To prevent leaching of nutrients, a policy of “green fields” has been adopted, including winter wheat or barley which is often sown perpendicular to the contours. The most severe cases of rill erosion are found on such fields, in particular in combination with clayey subsoils. Some of the rills are large enough to be classified as ephemeral gullies, whereas larger gullies typically found in loess areas, are not found in Denmark. From a mass transport point of view, rill erosion is important and may act as a kind of point source for the nutrient and sediment transport in the watercourses. Buffer zones have been found to be very efficient in terms of retaining sediment and phosphorous associated with rill erosion. Experiments have shown that all sediment and phosphorous is retained within the first 12 m of a 27 m buffer zone where the slope gradient is 14%, but that changes in slope gradient have a large effect on the trapping efficiency (Kronvang et al., 2000b).

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Fig. 3. Areas of potential erosion risk in Denmark calculated with the USLE (after Olsen and Kristensen, 1998).

3.4. Tillage erosion Tillage erosion has not been recognized until recently (Djurhuus and Heckrath, 2000). The presence of this type of erosion has probably been increasing because of heavier machinery and more efficient plough types. In steeper areas, this type of erosion is indicated by terrace-like steps, of up to two meter between single fields. Tillage erosion rates can be relatively high (Table 1), but this type of erosion is less important for long distance transport of sediments and nutrients as also shown by Heckrath (2000) in Denmark. Harrowing of fallow plots also favours tillage erosion by lowering the capacity of the surface soil for water assimilation and storage of ponded water (Sibbesen et al., 1994b). A special type of tillage erosion is the removal of soil while harvesting sugar beet and potatoes. A denudation rate of 100 mm/year from a single field has been

observed based on the amount of sediment that is washed off the beet and potatoes at the factory (Hasholt, 1983). 3.5. Bank erosion Studies in Danish lowland catchments have shown that stream bank and bed erosion are very important processes, accounting for 40–80% of suspended sediment export with the largest contribution coming from the lower parts of the bank (Hasholt, 1988; Laubel et al., 1999, 2000). There is considerable spatial variation in bank erosion rates depending on site-specific factors such as soil type, bank vegetation, bank angle, bank height, stream power, stream form, buffer zone width, and land use on the adjacent fields (Laubel et al., 1999, 2000). Average bank erosion rates in the Gjern stream system in central Jutland was about 11 mm/year per stream bank over a 1 year period

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corresponding to 0.020 m3 /m stream reach and was generally found to be lower in forest streams than in streams on grassland used for grazing cattle (Laubel et al., 1999). Similar studies along 15 small Danish lowland streams representative of the Danish landscape types revealed mean geometric bank erosion rates over the 11-month measuring period of 2.7 mm equivalent to 0.023 m3 /m stream reach (one streamside only). Erosion rates were significantly lower for sites adjacent to uncultivated areas than for those adjacent to agricultural fields as well as for sandy soils as compared to loamy sites (Laubel et al., 2000). It should be noted that all studies have been carried out over short-term periods and hence did not systematically record major bank collapses that may occur with longer time intervals. 4. Projects and policy measures to address soil erosion This section presents the various projects addressing soil erosion and the policy measures used, i.e. different laws affecting soil erosion in Denmark. An overview of projects and policy measures is outlined in Tables 2 and 3. 4.1. Wind erosion The serious problems with wind erosion in the middle of the 19th century made Enrico Mylius Dalgas, the founder of Hedeselskabet in 1866 (Danish Land Development Service), to develop a pamphlet in 1874 on the establishment of windbreaks. This turned out to be the beginning of a long involvement in the establishment of windbreaks. During the first years, Hedeselskabet gave out free plants for the establishment of windbreaks but from 1888 the govern-

ment started subsidizing the expenses (Grosen, 1976). To speed up the process of planting windbreaks, Hedeselskabet started organizing ‘planting societies’ from 1882 of which some are still active. A serious storm in 1938, with devastating effects for farmers in Jutland, made Hedeselskabet and the Ministry of Social Services set up a task force of unemployed to establish windbreaks. During the 25-year period (1938–1963) in which the task force was active, around 43,000 km of windbreaks were established (Grosen, 1976). Today, Hedeselskabet continues to provide technical support with respect to the establishment of windbreaks. Windbreaks may be established either through individual initiatives or through ‘planting societies’, i.e. collective planting societies. The majority of the money allocated by the government is ear-marked for activities carried out within planting societies (Knudsen and Vestergaard, 2001). For farmers deciding to establish windbreaks on an individual basis, government subsidies are provided for the purchase of certified plants. However, for farmers deciding to establish windbreaks through established ‘planting societies’, of which around 150 exist today, government subsidies are given to cover part of the expenses associated with the design, the removal of old windbreaks as well as planting and maintenance of the windbreak over a 3-year period (Hedeselskabet, 2001; Knudsen and Vestergaard, 2001). The development of collective and individual plantings since 1977 is illustrated in Fig. 4. The slight increase in number of plants being used from 1993 is because from this period onwards, about half the windbreaks were established as 6-row windbreaks as opposed to predominantly 3-row windbreaks before 1993. The length of newly established windbreaks is on average about 1000 km/year throughout the whole monitoring period and from 1993 statistics show

Table 2 Water erosion projects and sites in Denmark Site

Purpose/duration of project

Size of plots

References

Foulum

Tillage erosion and cropping systems, 1989–1992 Tillage erosion and cropping systems, 1989–1992 Tillage erosion since the 1950s, 137 Cs-studies, yields and soil quality, 1997–2000 (FAIR3) Sheet and rill erosion and sediment transport in streams, 1987–1990 Sheet and rill erosion and sediment transport in streams, 1987–1990 Rill erosion, 2000–2001 Sheet and rill erosion associated with frost processes and loss of phosphorous, rainfall simulator experiments and gerlach troughs, 2001–2003 Rill erosion and the effect of buffer zones, 1993–1999 Bank erosion, 1994–1995 Bank erosion, 1998–1999

22.1 × 3.0 m plots, 10% slope

Sibbesen et al., 1994b

22.1 × 3.0 m plots, 10% slope

Sibbesen et al., 1994b

Field size (approximately 1.5–8.0 ha)

Djurhuus and Heckrath, 2000

Catchment scale and plots (approximately 0.5 ha) Catchment scale and plots (approximately 0.5 ha) Field size 1 m2 plots and catchment scale

Hansen, 1990; Hasholt, 1991

Ødum Sæby + Årslev

Rabis Brook Syv Brook Lejre Haraldsted

20 localities all over Denmark Gjern stream Various sites in Denmark

88 slope units (1993–1997) 140 slope units (1997–1999) 33 stream reaches (1.3–4.7 m width) 33 stream reaches with associated slope units

Hansen, 1990; Hasholt, 1991 Thers, 2001 Schiøtz (not yet published)

Kronvang et al., 1996b, 2000b Laubel et al., 1999 Laubel et al., 2000

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Table 3 Major laws affecting soil erosion in Denmark Law Wind erosion Law no. 812 of 21 December 1988 Notification no. 17 of 18 January 1996 Notification no. 812 of 21 September 2001

Water erosion Law no. 302 of 9 June 1982 Law no. 392 of 10 June 1987 Notification no. 655 of 9 October 1987

Law no. 9 of 3 January 1992

Title

Aim

Law on windbreaks Notification on windbreaks and subsidies for planting windbreaks Notification on subsidies for planting schemes to improve biotopes and to reduce wind speed

Establishment of windbreaks To reduce wind speed over areas which are being or are going to be used for agricultural purposes To reduce wind speed on agricultural areas and/or to act as connecting lines in the landscape and to increase the percentage of small biotopes on farms as well as to facilitate public access

Law on water courses Water Environment Protection Plan I Notification on crop rotation and fertilizer/manure plans as well as green fields within agriculture Law on environmental protection

To protect the environment in water courses Protection of the water environment To reduce nitrate leaching associated with agricultural activities and to ensure optimum use of fertilizers/manure Protection of the environment including a section on water courses (Law no. 302) To regulate the agricultural sector’s use of fertilizers/manure and to establish a demand for establishment of plant cover with the aim to reduce nitrate leaching To maintain and secure the buffer zone and in that way to protect the water course from bank erosion associated with the use of heavy machinery in the agricultural production

Law no. 472 of 1 July 1998

Law on agriculture’s use of fertilizers/manure and on plant cover

Notification no. 632 of 23 June 2001

Notification on water courses (section on buffer zones)

that more windbreaks are being established as compared to the numbers being removed (Knudsen, personal communication). However, studies in Eastern Denmark in the period 1981–1996 have shown that the number of windbreaks has been decreasing, following the general decline in small biotopes (Brandt et al., 2001). The planting of windbreaks in Denmark can be described as a success story. This has been attributed to key ele-

ments such as farmer participation, good products and the involvement of the government. The government has provided subsidies since the 1880s, but it was only in 1976 that the government passed a law specifically on windbreaks. Since then, the law has been revised several times, the latest in 1996 (Law no. 17 of 18 January 1996) followed by a notification in September 2001 (Knudsen and Vestergaard, 2001; De danske plantningsforeninger, 2001). The interesting thing about the new notification is that it differentiates the amount of subsidies given to planting societies with larger subsidies for ecological farmers (45% as opposed to 40%) as well as farmers who provide access to the public by establishing footpaths (50% subsidy) (De danske plantningsforeninger, 2001). Apart from the law specifically dealing with windbreaks, there are a number of other laws and notifications that influence the establishment and maintenance of windbreaks. These relate to the division of land in general, the improvement of flora and fauna in the biotopes, the protection of areas next to lakes, rivers and coasts, archaeological sites and any local decisions relating to for instance road crossings (Knudsen and Vestergaard, 2001). 4.2. Sheet and rill erosion

Fig. 4. Number of plants used for collective and individual plantings in the period 1977–2001. The year 2000/2001 is estimated figures (based on data from Knudsen, Landsforeningen De danske plantningsforeninger, 2001).

Prior to the mid-eighties concern about water erosion in Denmark was low. Awareness was concentrated on protection against wind erosion, while erosion by water was mainly a problem in watercourses where larger amounts

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of sand settled, causing a rising water level and poorer drainage of the surrounding areas. Measurements of sediment delivery from Danish catchments (Hasholt, 1983), confirmed that transport was rather low (5–30 t/km2 per year) when compared to world scale. However, to solve the growing problem of eutrophication of lakes and coastal waters, sources must be known. A Nordic symposium on particle bound transport was held in Copenhagen (Hasholt, 1986). Here it was demonstrated that soil erosion could be an important source, because nitrate and in particular phosphorus adheres to sediment particles, and is transported from the fields into the streams. At the same time it was demonstrated that the knowledge of all aspects of erosion was rather poor. A Water Environmental Protection Plan I (WEPP I) was initiated simultaneously with the initiation of a research program named the NPo (nitrogen, phosphorus and organic matter) program. Two typical Danish agricultural areas were monitored with respect to erosion processes and nutrient transport over a 3-year period (1987–1990). The two catchments, Syv Brook on clayey soil, typical of eastern Denmark, and Rabis Brook on sandy soil (see Fig. 5), typical of western Jutland, were monitored frequently at their respective outlets. Inside the catchments, two erosion plots of Norwegian design were established (Hasholt, 1990). Erosion processes were recorded weekly and if possible quantified. Soil erosion was monitored using Gerlach troughs and rill measurements. Bank erosion was monitored using erosion pins and mapping of cross sections. The investigation confirmed that the amount of sediment delivered was small, varying from 1.5 to 9.9 t/km2 per year.

Fig. 5. Location of major soil erosion research sites in Denmark. Excluded are National Environmental Research Institute monitoring sites (see Grant et al., 2000).

The percentage resulting from erosion varied from 17 to 82%, with the highest percentage on the clayey soil. The amount of phosphorus lost was 19–73 kg/km2 per year while organic matter amounted to 0.4–2.5 t/km2 per year. Surface erosion measured at the plots was extremely low. A possible explanation is that the monitoring cellar was very deep and it caused the groundwater to be lowered so that saturated overland flow could not take place. Bedand bank erosion was only slight. Also for the rill erosion, the overall contribution was low, and confined to a few steeper slopes in the clayey soil catchment. Winter wheat and barley fields proved to be sensitive to rill development. An erosion-risk map based on K factor and slope showed that no less than 3% of the land surface was at risk (Hasholt, 1990). Parallel to the work described above, a group participated in the development of the EUROSEM model (Morgan et al., 1998), and some of the data were used for evaluation of processes and validation of this model within the STEP program (Hasholt and Styczen, 1993). More information was needed for agricultural purposes, therefore the agricultural research station at Foulum established two sites for plot studies, one on a clay loam at Ødum and the other on a sandy loam at Foulum (see Fig. 5). Plots consisted of the Wischmeier type using typical Danish crops and tillage practices. Two of the plots were used for determination of USLE K factors with replicates of winter wheat sown up and down. The result clearly showed that the maximum erosion was from the winter wheat plot up/down on both soil types. However, replicates could differ as much as 50% (Schjønning et al., 1990). Winter wheat sown along contours gave slightly lower values, but in some cases a single rill could break through and cause severe erosion. Ploughed soil, without harrowing showed less erosion and up to 20% less runoff, because of higher infiltration resulting from the rough surface (Schjønning et al., 1995). The lowest erosion rates were found on the permanently grass covered plots. The relative erosion was the same for both soil types, but the sandy loam had higher overall values. The experiment confirmed that the “green field” strategy introduced by the government in 1987 had some unwanted side effects as also shown by Sibbesen et al. (1994b) and Hasholt et al. (1997). The law had been introduced with the aim to reduce nitrate leaching. Through existing Law no. 472 of 1 July 1998, there is a requirement that a plant cover should be established on a minimum 65% of the farmland. However, if crop residues are being incorporated, the percentage of farmland with winter crops may proportionally be reduced to a minimum of 45%. From 7 June 2001, a law (Law no. 458) has been passed which allows different rates of nitrate leaching depending upon the region. The law from 1987 has meant that the area with winter wheat has gone up from an average 241,000 ha in 1982–1984 to 643,000 ha in 2001 (Landbrugsrådet, 2001). Parallel with the experiments on sheet and rill erosion carried out by the agricultural research station Foulum, the

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Danish Land Development Society carried out an experiment to determine the appropriate width of protection zones along water courses (Hansen, 1992). The experiments showed that a 2 m wide buffer zone collected about 90% of the sediment carried down from upslope and a 6 m wide zone collected about 96%. As a result of this work, a 2 m wide buffer zone was by law prescribed by the government around all water courses in the rural areas from 1992 (included in Law no. 9 of 3 January 1992). A Nordic program aimed at better understanding of phosphorus transport processes, NORPHOS, was initiated. Within this program the studies of rill development on the plots were carried out. These studies confirmed that formation of rills accounted for a major part of the erosion, when the erosion was high. They also confirmed that fields sown up and down were particularly prone to rill erosion. Normally the plots could only be operated manually on an event basis, and the sediment could settle on its way to the collecting trough, so that a sedigraph could not be obtained. To overcome this, and to get a better insight into the erosion processes during a storm, an automatic monitoring system was constructed allowing in-stream samples to be taken, with no accumulation of coarser particles in the system (Hasholt and Hansen, 1995). While the plot studies gave quite consistent information about the effect of tillage practice and choice of crops, information was still missing about sediment transport routes and of the amount of sediment and nutrients that actually reached a watercourse from the adjacent slopes. The previous established knowledge was used to point out erosion prone slopes along watercourses in different landscape types all over Denmark. The slope morphology was mapped and tillage and crops were registered. Twice a year, just after tillage in autumn and before tillage at the end of winter, the slope units were inspected. All signs of erosion were described using a code system, photos were taken and if possible the amount of erosion was quantified, mainly by measuring rill volume and volume of alluvial fan deposits on the lower parts of the slope. Bank erosion was also studied, together with sedimentation in protection zones (Kronvang et al., 1996b). The results confirmed the significance of rill formation in the contribution of eroded material to the watercourses. It also showed that often a significant part of the sediment eroded on the upper part of the slopes settled on the lower parts of the slope before it could reach the watercourse. The investigation also showed that in several cases the protection zone was unlawfully narrow. The influence of crop was in good accordance with the relative importance found during the plot studies. Information gathered from slopes of old marine environments with fine sandy soil, showed that they were very prone to rill formation. It was also found that steep sandy soil can be severely eroded when left bare. The slope unit study has later been expanded to cover all major types of landscape, in order to create a data set, that could be used to develop an expert system for guiding farm-

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ers in terms of soil conservation issues (Kronvang et al., 1996b). From the beginning of the 1990s, the time evolution in the nutrient transport to streams within 66 small catchments covering about 60% of the Danish land mass has been sampled frequently. This includes evaluation of information about output from drainpipes (Kronvang et al., 1996a). A special concern has been pesticides associated with the eroded material. Some investigations have been carried out, but it is still open for discussion which types of analysis are appropriate, partly because the processes in the unsaturated zone and the interaction with groundwater is not yet fully understood. During the winter 2001/2002 studies on winter erosion processes both at catchment scale and plot scale are being studied in the Haraldsted catchment (12.5 km2 ) on Zealand (Fig. 5). The predominant soil types are loamy soils, typical of eastern Denmark, and the most prevalent land use type is intensive agriculture. At the outlet of the catchment, discharge is measured flow proportional, together with phosphate and suspended matter concentration. At 14 different locations within the catchment, a set of two 1 m2 plots have been established, representing different crop covers, slope degrees and management practices. One set of plots is being used for rainfall simulator experiments to determine infiltration capacity by runoff, sediment and loss of phosphorous. The other set of plots is equipped with Gerlach troughs, where total runoff, sediment load and phosphorous are determined at regular intervals throughout the monitoring period. Additionally, several small transects have been distributed within the catchment, where soil physical measurements are undertaken and freezing depth monitored. The results are expected to enable the identification of “standard” scenarios for soil erosion on frozen soil, which can be used in a modelling context. 4.3. Tillage erosion Research in soil tillage has been carried out over the last 30 years in Denmark (Hansen, 1989) though it is only recently that tillage erosion per se has been recognized as a problem. In 1997, the Research Centre Foulum started a 3-year EU-funded project (FAIR3) with the primary aims to determine how much soil has been moved as a result of tillage erosion since the 1950s and its effect on soil fertility, to investigate the effect of current tillage practices on soil erosion and finally to build a soil tillage model for the evaluation of the effect on soil quality (Djurhuus and Heckrath, 2000). The FAIR3-project has shown that tillage erosion is most severe on convex slope units amounting to a yearly soil loss of as much as 3–4 mm whereas deposition associated with tillage erosion is highest on concave slope units (Djurhuus and Heckrath, 2000; Munkholm et al., 2000). Conservation tillage has been looked into as a means of minimizing soil erosion and securing soil fertility although compaction of

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the topsoil may be a problem unless traffic in the fields is controlled (Munkholm et al., 2000). Studies at Sæby in Jutland (Fig. 5) showed substantial soil redistribution over the past 40 years as indicated by the distribution pattern of 137 Cs percentage residuals with tillage translocation being the dominant process (Heckrath, 2000). However, one has to be cautious drawing quick conclusions as there is a range of problems associated with this method such as its dependence on soil type and the model used for converting Cs in the soil into the volumes of soil moved. Studies on tillage erosion have so far only been carried out in a few locations in Denmark. There is hence limited knowledge about its importance in regions of the country where no investigations have taken place. There is currently no law dealing specifically with tillage erosion. 4.4. Bank erosion One of the aims of Law no. 9 of 3 January 1992 was to prescribe a 2 m wide buffer zone around all water courses in order to prevent bank erosion caused by heavy machinery (see Section 4.2 for further details). However, it should be mentioned that the law does not explicitly prevent the use of fertilizers and/or pesticides in the buffer zone. Policy measures to address water erosion in Denmark is mainly done through the appointment of ‘Specifically Vulnerable Agricultural Areas’ (SVAA) at the county level. Measures taken consist of set-aside, buffer strips or the use of a rye-grass catch crop, all measures being subsidized by the government (Sibbesen and Iversen, 1997).

5. Interactions between soil erosion and politics: a case study from Denmark The previous section on soil erosion projects in Denmark has shown how crucial an instrument laws and subsidies are as regulating mechanisms against soil erosion. However, for a law to be put in place, the issue in question has to be brought on to the political agenda, a process that is far from easy. A case study based on the Water Environmental Protection Plan I will hence be presented which reveals the different political processes which took place prior to the launch of the plan. 5.1. The water environmental protection plan I The making of the Water Environmental Protection Plan I started with the presentation of dead lobsters on TV in 1986 (Fig. 6) as a result of eutrophication problems. Initially, the government was very reluctant to deal with a problem that was not considered to be important. It was only the Danish Nature Council’s resolution followed by a concrete action plan (Danish Nature Council, 1986) to reduce nutrients, combined with the media’s continued coverage of the problem, which pushed the problem onto the political agenda. In the beginning, the NGOs representing industry and agriculture stayed quiet as any actions to reduce nutrients would affect their members economically. But gradually, a number of political parties took interest in the issue backed by the population which at that time saw environmental issues as the biggest threat to society. This forced the

Fig. 6. The political process associated with the Water Environmental Protection Plan I.

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government to launch an action plan which became the issue of negotiation with a range of key organizations as listed in Fig. 6. The Agricultural Council in particular was successful in terms of influencing this process by focusing on the reduction of nitrate leaching, as opposed to a reduction in the use of fertilizers, and by pushing the problems with phosphorus associated with waste water disposal from industries and waste water plants. The end result was the passing of Law no. 392 of 10 June 1987. When looking at the overall process, it was the Danish Nature Council and the media which put the problem on the political agenda, but after the initial stage, the Danish Nature Council had limited influence in spite of the fact that they pinpointed several weaknesses associated with the Water Environmental Protection Plan I (WEPP I) based on scientific evidence. It was a range of powerful, industrial organizations, and in particular the Agricultural Council that had the biggest influence in the negotiation process leading to the law. Soon after the initiation of WEPP I, it became clear that the reduction targets could not be achieved and the plan was followed by a number of plans and strategies. In 1998, WEPP I was followed by WEPP II. The focus is now primarily on the reduction of nitrate, among other things through the establishment of wetlands, but also by increasing the number of fields with winter crops. Although it is recognized that a reduction in phosphorous is needed and that soil erosion processes play a significant role in this, the scientific evidence about transport mechanisms and how to reduce soil erosion is lacking with regards to Danish conditions (Danish Environmental Protection Agency, 2000).

6. Future perspectives With respect to the use of windbreaks in Denmark as a means of reducing wind erosion, there has been an increasing recognition that windbreaks are important features of the landscape, not just as means of reducing wind erosion, but also because they are crucial features in terms of biodiversity. The fact that the program of establishing and maintaining windbreaks in Denmark is so successful, combined with integrated planning which addresses both biodiversity and recreational issues, does seem to give some rather interesting and promising prospects for the future. In terms of issues relating to water erosion, recent assessments of the environmental conditions in coastal areas have shown that the quality is not acceptable and that a reduction in the nutrients supplied through agriculture is necessary if the set targets for water quality are to be achieved (Danish Environmental Protection Agency, 2000). The total loss of phosphorous from agricultural areas to watercourses has been estimated to be 0.4–0.5 kg/ha and although net input has been reduced from 15 kg/ha in 1985 to 11 kg/ha in 1999 for the country as a whole, there has been a surplus input of phosphorous to agricultural areas within the same period

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(Danish Environmental Protection Agency, 2000). This is primarily associated with animal husbandry farms (Danish Environmental Protection Agency, 2000; Grant et al., 2000). Studies by Rubæk et al. (2001) have shown that from 1986 to 1997/1998, the yearly increase in phosphorous within the top 50 cm has increased by 25 kg P/ha on average, though the increase is mainly on sandy soils where the number of animals per ha is highest. There is consequently a high potential for future eutrophication problems in Danish watercourses and coastal areas if phosphorous is lost, a loss which has previously been underestimated (Grant et al., 2000; Kronvang et al., 2000a). However, there is presently very limited knowledge about the transport processes of phosphorous including particulate phosphorous though sheet and bank erosion have been pointed out as some of the most important processes (Danish Environmental Protection Agency, 2000; Kronvang et al., 2000a). More research is needed which looks into soil erosion associated with frost since this is one of the main parameters determining soil erosion processes in Denmark. There is an urgent need for modelling tools which can be used for identifying hot spot areas within Denmark and provide useful planning tools. This includes a proper validation of these modelling tools. The long-term effect of soil erosion on soil fertility is also of major concern, especially in relation to tillage erosion and finally the development of better management tools for reducing bank erosion is needed. The case study on the WEPP I has demonstrated how the media can be used as a powerful tool to bring the issue of soil erosion on to the political agenda. A dimension which far too often is overlooked by researchers. It also showed that the problem of soil erosion needs to be presented to the politicians and the public in a way that relates to their everyday life in order for funds to be made available for research. The question is how to obtain funding for long-term research projects that can provide reliable data for policy maker’s decision-making. Another challenge for the future will be to ensure that action plans and laws to a much larger extent take into account the complexity of environmental issues by enabling more than one problem to be solved at the same time while ensuring that plans/laws to address one specific issue do not have unwanted side-effects regarding other environmental issues. One example in Denmark is the use of winter cereals to reduce nitrate leaching. Although it has been documented that winter cereals is a main factor increasing soil erosion, the WEPP II stresses the demand for an increase in areas covered by winter crops (Danish Environmental Protection Agency, 2000). With the change of government in November 2001, major cut-backs across the environmental sector are being carried out in 2002. In addition, the new government is trying to simplify laws to improve working conditions and increase profit within the agricultural sector based on the concept that farmers themselves are the best placed to make decisions regarding farming practices and their effects on the

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environment. It will be interesting to see what effect this will have. One dimension in the political process which will become of increasing importance is the European Union. One example is the European Parliament and Council’s directive 2000/60/EF which is a joint European plan to protect all water sources and which will be of importance in relation to water erosion. The directive provides a minimum level of achievement but enables national governments to enforce more strict laws and regulations (Danish Environmental Protection Agency, 2000). One of the big challenges at the European level will be to grasp the diverse problems of soil erosion encountered from north to south representing rather diverse processes. For this to be successful, the processes and politics of soil erosion need to be mapped out in detail for each individual country. Finally, there is a need for pricing both the on-site and off-site effects of soil erosion in Denmark. The councils in Denmark use considerable amounts of money each year to address issues of water quality, but this is normally not related to soil erosion processes. The other aspect here is the on-site effects in terms of loss of soil fertility in the long-term if the problem is not dealt with.

Acknowledgements The authors would like to thank Ingrid Jensen, Roskilde University, for drawing several of the figures. References Arden-Clarke, C., Evans, R., 1993. Soil erosion and conservation in the United Kingdom. In: Pimentel, D. (Ed.), World Soil Erosion and Conservation. Cambridge University Press, Cambridge, UK, pp. 192–215. Boardman, J., 1990. Soil erosion in Britain: costs, attitudes and policies. Social Audit Paper 1, Countryside Research Unit, Brighton Polytechnic. The Education Network for Environment and Development, Institute of Education, Brighton, UK, 25 pp. Boardman, J., 1998. An average soil erosion rate for Europe: myth or reality? J. Soil Water Conserv. 53 (1), 46–50. Bojö, J., 1987. An introduction to cost-benefit analysis of soil and water conservation projects. Southern African Development Coordination Conference, Report no. 6, Soil and water conservation and land utilization, Ministry of Agriculture and Marketing, Maseru, Lesotho, 60 pp. Brandt, J., Holmes, E., Agger, P., 2001. Integrated monitoring on a landscape scale—lessons from Denmark. In: Groom, G., Reed, T. (Eds.), Strategic landscape monitoring for the Nordic countries, TemaNord, vol. 523. Nordic Council of Ministers, Copenhagen, Denmark, pp. 31–41. Danish Environmental Protection Agency, 1984. NPo report: the supply of nitrogen, phosphorus and organic matter to groundwater, fresh and marine surface water, the influence of this supply, suggestions on how to address the problem (in Danish). Danish Environmental Protection Agency, Copenhagen, Denmark, 218 pp. Danish Environmental Protection Agency, 2000. Water Environment 2000—status and perspectives for a cleaner water environment (in Danish). Report no. 7. The Danish Environmental Protection Agency

and Danish Forest and Nature Agency, The Ministry for Environment and Energy, Denmark, 47 pp. Danish Nature Council, 1986. Save the sea now, the North Sea (in Danish). Danish Nature Council, Copenhagen, Denmark. Darkoh, M.B.K., 1987. Socio-economic and institutional factors behind desertification in Southern Africa. Area 19 (1), 25–33. De danske plantningsforeninger, 2001. http://www.laeplant.dk/doc/index. html. De Graff, J., Eppink, L.A.A.J., 1999. Olive oil production and soil conservation in southern Spain, in relation to EU subsidy policies. Land Use Policy 16, 259–267. Djurhuus, J., Heckrath, G., 2000. Jordbearbejdningserosion (in Danish). JordbrugsForskning 2, 15–17. Driver, T., 1999. Anti-erosion policies in the mountain areas of Lesotho: the South African connection. Environ. History 5, 1–25. European Environment Agency, 2000. Down to earth: soil degradation and sustainable development in Europe. A challenge for the 21st century. Environmental issues series no. 16, Copenhagen, Denmark. Evans, R., 1995. Some methods of directly assessing water erosion of cultivated land—a comparison of measurements made on plots and in the fields. Prog. Phys. Geogr. 19 (1), 115–129. Govers, G., 1991. Rill erosion on arable land in central Belgium: rates, controls, and predictability. Catena 18, 133–155. Grant, R., Blicher-Mathiesen, G., Jørgensen, J.O., KloppenborgSkrumsager, B., Kronvang, B., Jensen, P.G., Pedersen, M., Rasmussen, P., 2000. Landovervågningsoplande 1999 (in Danish), NOVA 2003. Research Report no. 334. National Environmental Research Institute, Silkeborg, Denmark, 147 pp. Grosen, S., 1976. Praktiske aspekter i forbindelse med plantning af læhegn (in Danish). In: Miljøværnscentret (Ed.), Læhegn. Special issue of weekly journal for agronomists, horticulturalists, foresters and Ph.D. candidates. The Royal Veterinary and Agricultural University, Copenhagen, Denmark, pp. 440–442. Hansen, A.C., 1992. Effect of length of buffer strips. Danish Land Development Society, Internal Report, Denmark. Hansen, L., 1989. Soil tillage, soil structure and soil erosion in Denmark. In: Schwertmann, U., Rickson, R.J., Auerswald, K. (Eds.), Soil Erosion Protection Measures in Europe. CATENA Verlag, Cremlingen-Destedt, Germany, pp. 127–131. Hansen, B., 1990. Discharge and transport to Rabis and Syv Brook (in Danish). NPo research from the Danish Environmental Protection Agency. Report no. 9. The Danish Environmental Protection Agency, Copenhagen, Denmark, 32 pp. Hasholt, B., 1983. Dissolved and particulate load in Danish water courses. IAHS Publication no. 141, pp. 255–264. Hasholt, B., 1986 Particulate bound transport in water and soil erosion (in Danish). Nordic Hydrologic Program, NHP report no. 14, Copenhagen, Denmark, 369 pp. Hasholt, B., 1988. On identification of sources of suspended sediment transport in small basins with special references to particulate phosphorus. In: Bordas, M.P., Walling, D.E. (Eds.), Proceedings of the Symposium on Sediment Budgets. Porto Alegre, Brazil, 11–15 December 1988. IAHS 174. Hasholt, B., (Ed.), 1990. Erosion and transport of phosphorus to watercourses and lakes (in Danish). NPo research from the Danish Environmental Protection Agency. Report no. C 12, The Danish Environmental Protection Agency, Copenhagen, Denmark, 120 pp. Hasholt, B., 1991. Influence of erosion on the transport of suspended sediment and phosphorus. In: Proceedings of the Vienna Symposium on Sediment and Stream Water Quality in a Changing Environment: Trends and Explanation. August 1991, pp. 329–338. IAHS Publication no. 203. Vienna 11–24. Hasholt, B., 1995. Formation of rills and their contribution to sediment yield. In: Schjønning et al. (Eds.), Surface runoff, erosion and loss of phosphorous at two agricultural soils in Denmark. SP report no. 14, 1995. Danish Institute of Plant and Soil Science, Ministry of Agriculture and Fisheries, Denmark.

A. Veihe et al. / Environmental Science & Policy 6 (2003) 37–50 Hasholt, B., Breuning-Madsen, H., 1989. On evaluation of soil erosion risk and sources of suspended load in Denmark. In: International Symposium on Erosion and Volcanic Debris Flow Technology. Yogyakarta, Indonesia, 1989, pp. S12-1–S12-16. Hasholt, B., Styczen, M., 1993. Measurements of sediment transport components in a drainage basin and comparison with sediment delivery computed by a soil erosion model. In: Hadley, R.F., Mizuyama, T. (Eds.), Proceedings from International Symposium on Sediment Problems, Yokohama, 1993, pp. 147–161. IAHS Publication no. 217. Hasholt, B., Hansen, B.S., 1995. Monitoring of rill erosion. In: Effects of Scale on Interpretation and Management of Sediment and Water Quality. IUGG/IAHS General Assembly, Boulder, USA, pp. 285– 291. Hasholt, B., Hansen, B.S., Olsen, C., Olsen, P., Sibbesen, E., 1997. Sediment delivery to streams from adjacent slopes on agricultural land in Denmark. In: Proceedings of the International Symposium on Human Impact on Erosion and Sedimentation. Rabat, Morroco, 1997, pp. 285–291. IAHS Publication no. 245. Heckrath, G., 2000. Tillage erosion: current state, future trends and prevention. FAIR3-CT96-1478 project coordinated by Govers, G., Catholic University of Leuven, Belgium. Annex III, Individual Progress Report for the Period 1 March 1999 to 29 February 2000, pp. 1/24–24/24. Hedeselskabet, 2001. http://www.Hedeselskabet.dk/. Helms, J.D., Pavelis, G.A., Argabright, S., Cronshey, R.G., Raymond Sinclair Jr., H., 1996. National soil conservation policies: a historical case study of the driftless area. Agric. History 70 (2), 377–394. Knudsen, H., Vestergaard, G., 2001. Hedgerows—and small biotopes (in Danish). Landbrugets Rådgivningscenter, Landskontoret for Uddannelse, Landbrugsforlaget, 88 pp. Kronvang, B., Græsbøll, P., Larsen, S.E., Svendsen, L.M., Andersen, H.E., 1996a. Diffuse nutrient losses in Denmark. Water Sci. Technol. 33 (4–5), 81–88. Kronvang, B., Svendsen, L., Sibbesen, E. (Eds.), 1996b. Proceedings from an International Workshop on Sediment and phosphorous. Silkeborg, 9–12 October 1995. NERI Technical Report no. 178, Denmark. Kronvang, B., Grant, R., Laubel, A., Iversen, H.L., Svendsen, L.M., Hansen B., 2000a. Comparison of phosphorus losses at the field and catchment scale (in Danish). DJF report, Markbrug 34, pp. 63–72. Kronvang, B., Laubel, A.R., Larsen, S.E., Iversen, H.L., Hansen, B., 2000b. Soil erosion and sediment delivery through buffer zones in Danish slope units. In: Proceedings of the Symposium on The Role of Erosion and Sediment Transport in Nutrient and Contaminant Transfer. Waterloo, Canada, July 2000, pp. 67–73. IAHS Publication no. 263. Kuhlman, H., 1986. The wind and agriculture (in Danish). In: Jensen, K.M., Reenberg, A. (Eds.), Landbrugsatlas Denmark, The Royal Danish Geographical Society, C.A. Reitzels Publisher, Copenhagen, Denmark, pp. 17–23. Landbrugsrådet, 2001. Danish Agriculture—Past and Present. Landbrugsrådet, Copenhagen, Denmark, 32 pp. Laubel, A., Svendsen, L.M., Kronvang, B., Larsen, S.E., 1999. Bank erosion in a Danish lowland stream system. Hydrobiologia 410, 279– 285. Laubel, A.R., Kronvang, B., Larsen, S.E., Pedersen, M.L., Svendsen, L.M., 2000. Bank erosion as a source of sediment and phosphorus delivery to small Danish streams. In: Proceedings of the Symposium on The role of erosion and sediment transport in nutrient and contaminant transfer. Waterloo, Canada, July 2000, pp. 75–82. IAHS Publication no. 263. Leek, R., Olsen, P., 2000. Modelling climatic erosivity as a factor for soil erosion in Denmark: changes and temporal trends. Soil Use Manag. 16, 61–65. Morgan, R.P.C., Quinton, J.N., Smith, R.E., Govers, G., Poesen, J.W.A., Auerswald, K., Chisci, G., Torri, D., Styczen, M.E., 1998. The European soil erosion model (EUROSEM): a dynamic approach for predicting sediment transport from fields and small catchments. Earth Surf. Processes Landforms 23, 527–544.

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Munkholm, L.J., Schjønning, P., Heckrath, G., Jørgensen, M.H., 2000. Autumn seminar: farming without ploughing: effects on soil fertility (in Danish). Tidsskrift Landøkonomi 4, 306–310. Olsen, P., Kristensen, P.R., 1998. Using a GIS system in mapping risks of nitrate leaching and erosion on the basis of SOIL/SOIL-N and USLE simulations. Nutr. Cycling Agroecosyst. 50, 307–311. Pagiola, S., 1994. Cost-benefit analysis of soil conservation. In: Lutz, E., et al. (Eds.), Economic and Institutional Analyses of Soil Conservation Projects in Central America and the Caribbean. World Bank Environment Paper no. 8, pp. 21–39. Pretty, J.N., Brett, C., Gee, D., Hine, R.E., Mason, C.F., Morison, J.I.L., Raven, H., Rayment, M.D., van der Bijl, G., 2000. An assessment of the total external costs of UK agriculture. Agric. Syst. 65, 113–136. Rubæk, G.H., Heckrath, G., Olesen, S.E., Østergaard, H.S., 2001. Phosphorous saturation and leaching of phosphorous in Danish agricultural soil (in Danish). JordbrugsForskning 5 (2), 3–4. Ryszkowski, L., 1993. Soil erosion and conservation in Poland. In: Pimentel, D. (Ed.), World Soil Erosion and Conservation. Cambridge University Press, Cambridge, UK, pp. 217–232. Schjønning, P., Hansen, A.C., Sibbesen, E., Dissing Nielsen, J., Heidmann, T., Bisgård Madsen, M., Waagepetersen, J., 1990. Water erosion, phosphorus loss and tillage methods (in Danish). Ugeskrift Jordbrug 25/26, 395–400. Schjønning, P., Sibbesen, E., Hansen, A.C., Hasholt, B., Heidmann, T., Madsen, H.B., Nielsen, J.D., 1995. Surface runoff, erosion and loss of phosphorous at two agricultural soils in Denmark. SP report no. 14. Danish Institute of Plant and Soil Science, Ministry of Agriculture and Fisheries, Denmark. Sibbesen, E., Iversen, B.V., 1997. Set-aside and land-use regulations with relation to surface runoff in Denmark. In: Sibbesen, E. (Ed.), Set-Aside and Land Use Regulations with Relation to Surface Runoff in Finland, Denmark, Scotland, Netherlands, Belgium, France and Spain, SP report no. 14. Danish Institute of Agricultural Sciences, pp. 14–16. Sibbesen, E., Hansen, A.C., Nielsen, J.D., Heidman, T., 1994a. Runoff, erosion and phosphorus loss from various cropping systems in Denmark. In: Rickson, R.J. (Ed.), Conserving soil resources, European perspectives. Selected papers from the First International Congress of the European Society for Soil Conservation, Silsoe, UK, 6–10 April 1992, pp. 87–93. CAB International. Sibbesen, E., Schjønning, P., Hansen, A.C., Nielsen, J.D., Heidmann, T., 1994b. Surface runoff, erosion and loss of phosphorus relative to soil physical factors as influenced by tillage and cropping systems. In: Jensen, H.E., Schjønning, P., Mikkelsen, S.A., Madsen, K.B. (Eds.), Soil Tillage for Crop Production and Protection of the Environment, vol. I. Proceedings of the 13th International ISTRO Conference, Aalborg, Denmark, 24–29 July, pp. 245–250. The Royal Veterinary and Agricultural University and The Danish Institute of Plant and Soil Science. Stocking, M., 1988. Socioeconomics of soil conservation in developing countries. J. Soil Water Conserv. 43 (5), 381–385. Thers, M., 2001. Rill erosion, in: Gl. Lejre (Ed.) (in Danish). Student report, Roskilde University, Denmark, 52 pp. Van der Knijff, J.M., Jones, R.J.A., Montanarella, L., 2000. Soil erosion risk assessment in Europe. EUR 19044 EN. European Soil Bureau, Joint Research Centre and Space Applications Institute, Ispra, Italy, 34 pp. Veihe, A., 2000. Ghanaian Farmers’ perception of soil erosion and their use of conservation measures. Environ. Manag. 25 (4), 393–402. Zinn, J., 1993. How are soil erosion control programs working? J. Soil Water Conserv. 48 (4), 254–259. Anita Veihe is an associate professor in environmental geography at the Institute of Geography and International Development Studies, Roskilde University. She has a PhD in physical geography and a BA in political science from the University of Copenhagen. Research interests are within hydrology, modelling and associated policy issues particularly in the Faroe Islands, Denmark and West Africa.

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Bent Hasholt is an associate professor in the Institute of Geography, University of Copenhagen where he carries out research on hydrology, sediment transport and soil erosion. He has been in charge of the Danish NPo (nitrogen, phosphorous, organic matter) erosion research and is a former President of the International Commission of Continental Erosion within IAHS.

Iris Gunia Schiøtz is a PhD student in the Department of Geography and International Development Studies at Roskilde University working on modelling of soil erosion under winter conditions. She has a BSc in geoinformatics and a MSc in geoecology from Potsdam University, Germany. She has worked as a programmer of GPS real-time solutions for GIS.