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Extreme rainfall years in Benin (West Africa)
Quaternary International 262 (2012) 39e43
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Extreme rainfall years in Benin (West Africa) Ibouraïma Yabi*, Fulgence Afouda Laboratory Pierre Pagney “Climate, Water, and Ecosystem Development”, Department of Geography and Regional Planning, University of Abomey-Calavi, BP: 922 Abomey-Calavi, Benin
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 22 December 2010
This research examines recent years’ rainfall extremes and their socioeconomic and environmental impacts in Benin. The annual rainfall amounts of the 1922e2005 series for 16 stations spread throughout the country were used, as recorded in the files of the Agency for Air Navigation Safety (ASECNA-Cotonou). In addition, investigations in the environment have been conducted to understand the impacts experienced by communities. The data and information collected were processed using statistical tools and maps. Analysis shows a strong incidence of extreme rainfall during the 1950s and 1960s, particularly in the south, while the 1970s and 1980s recorded very dry years. In all cases, wet and dry years pose problems for rural and urban communities. The projected climate change will increase the frequency and intensity of extreme rainfall and drought and their consequences, and development policies must take that into account. Ó 2011 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction Recent decades have been marked by rapid change of climate on a global scale (IPCC, 1991; Olaniran, 1991) and a high occurrence of extreme rainfall events (IPCC, 2007). West Africa in the last three decades has been marked by unprecedented rainfall variability, differing from the past century. Most studies have shown that annual rainfall totals of the 1970s and 1980s are characterized by significant decreases (Nicholson, 1980; Paturel et al., 1995; Brou et al., 1999), together with the occurrence of especially wet years, some with considerable socio-ecological consequences. In Benin, the weather trend is identical to that of the remainder of West Africa. Since the late 1960s, the country has experienced high rainfall variability. This occurs, in particular, from changing rainfall patterns and a decrease in annual totals (Bokonon-Ganta, 1987; Boko, 1988; Afouda, 1990; Houndénou, 1999; Yabi, 2002; Ogouwalé et al., 2005; Yabi and Afouda, 2007). However, within this context of a general downward trend, heavy rainfall that generates floods occurs at times. Sometimes, dramatic and disastrous socioeconomic impacts occur, particularly connected to agriculture (IPCC, 2007). In a context where most economic activities are influenced by rainfall, disturbances to previous patterns could lead to socioeconomic problems or political consequences (Boko, 1988).
* Corresponding author. E-mail address: yafi[email protected] (I. Yabi). 1040-6182/$ e see front matter Ó 2011 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2010.12.010
The West-African monsoon is the principal generating factor of the rains, which are differently distributed from south to north in Benin. The south has a subequatorial climate with an annual average rain ranging between 900 mm (Bopa) and 1300 mm (Cotonou). The rainy rhythm is bimodal with a long dry season (mid-November to mid-March), a long season of rains (from midMarch to mid-July), a small dry season (mid-July to midSeptember) and a small season of rains (mid-September to midNovember). In the north, the climate is of tropical moist type and annual average rain is rather variable (1300 mm at Natitingou, 1100 mm at Nikki and Bembéréké, 900 mm at Kandi). The rainfall mode is unimodal everywhere with one rainfall season which lasts 7 months (AprileOctober) and a dry season (NovembereMarch). Everywhere, the particular agricultural activities are controlled by the rainy distribution. 2. Methodological approach The data used in this research are related to annual rainfall amounts between 1922 (year of establishment of the oldest stations) and 2005 for 16 stations spread throughout the country (Table 1). These data were extracted from the file of the Agency for Air Navigation Safety (ASECNA-Cotonou). Missing data (4.6% of total observations) were reconstructed by the method of least squares (Houndénou, 1999). The identification of extreme years was made by calculating the percentage of rainfall deficit or surplus over the average (Boko, 1988; Klassou, 1996). Pa denotes the total annual rainfall of a year
40
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
Table 1 Stations. No
Stations
Latitude
Longitude
Time series covered by data
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16
Kandi Natitingou Bembéréké Nikki Djougou Parakou Savè Abomey Zagnanado Applahoué Pobè Sakété Adjohoun Allada Bopa Cotonou
11 080 N 10 190 N 10 120 N 09 360 N 09 420 N 09 210 N 07 560 N 07 110 N 07 150 N 06 550 N 06 560 N 06 430 N 06 420 N 06 390 N 06 310 N 06 210 N
02 560 E 01 230 E 02 400 E 03 120 E 01 400 E 02 370 E 02 260 E 01 590 E 02 200 E 01 400 E 02 400 E 02 100 E 02 290 E 02 080 E 01 580 E 02 260 E
1921e2005 1921e2005 1922e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1922e2005
and Pm the mean total annual rainfall in the series. A year is extremely deficient for a station when Pa < 70% Pm (30% deficit); the year was extremely wet for a station when Pa > 120% Pm (20% excess). The frequency of extreme rainfall years (FAPE) surplus or deficit is calculated according to:
FAPE ¼ ðNAPE=NTAÞ where NAPE is the number of years with rainfall extremes; and NTA is the total number of years studied. Intensity (I) abnormalities were determined by the following formula:
I ¼ ðPa PmÞ=Pm Field investigations have provided further insight into the socioenvironmental results of extreme rainfall years, particularly in rural areas. Mapping has been used for spatialized analysis.
Fig. 1. Frequency of years of extreme rainfall deficiency.
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43 Table 2 Spatiotemporal distribution of rainfall deficit years. Deficient rainfall years in the south (between the coast and 7 450 N) Deficient rainfall years in the North (north of 7 450 N) General deficient rainfall years (all Benin)
Table 3 Spatiotemporal distribution of surplus rainfall years.
1937, 1946, 1964, 1973, 1977, 1982, 1983, 1984, 1988, 1995 1932, 1961, 1981, 1946,
1934, 1971, 1982, 1973,
1946, 1973, 1983, 1977,
41
1950, 1956, 1958, 1976, 1977, 1979, 1980, 1984 1982, 1983, 1984
Wet years in the South (between the coast and 7 450 N) Wet years in the North (north of 7 450 N) General wet years (all Benin)
1929, 1962, 1947, 1962, 1947,
1933, 1963, 1953, 1998 1957,
1947, 1957, 1968, 1998 1957, 1962, 1998
3. Results 3.1. Review of extremely deficient rainfall years The frequency of extreme rainfall deficit years is shown in Fig. 1. The frequency of extremely dry years varies between 0.05 and 0.17. Overall, the northern sites are more affected by drought.
Fig. 2. Frequency of very wet years.
42
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
Fig. 3. Maize farm flooded (left) and flooded road (right) after heavy rains in 1998.
Stations Nikki, Kandi, and Bembéréké record respectively 0.17, 0.14 and 0.13. As for the southern stations, they are slightly affected with the exception of Adjohoun. Table 2 provides a better understanding of the spatiotemporal distribution of these abnormalities in deficit. The analysis of the table confirms that the northern part has seen more years of deficits relative to the south (17 years in the north against 10 in the south). A total of six years were marked by deficits throughout Benin. Most years of general deficits belong to the 1970s and 1980s in line with the trend toward sub-regional rainfall. The intensity of deficits varies between 0.30 and 0.50. High deficits were also recorded during the 1970s and 1980s. 3.2. Extremely wet years The spatial distribution of extremely wet years is illustrated in Fig. 2. The frequency of very wet years varies between 0.08 and 0.17. Stations in the south recorded the highest values compared to the north. Thus, at Zagnanado, Pobe, Applahoué, and Adjohoun the frequencies are respectively 0.17, 0.14, 0.14, and 0.13, compared to 0.08, 0.08, 0.08, and 0.09 in order at Kandi, Bembéréké, Nikki, and Natitingou. The spatiotemporal distribution of these years is summarized in Table 3. Southern stations record more wet years than those in the north (8 years compared to 5). In all cases, the 1950s and 1960s are marked by positive rainfall anomalies. The intensity of the surplus is between 0.8 and 0.55, and the highest values are registered in the south (Cotonou and Bopa). In one way or another, the occurrence of extreme rainfall years is associated with socioeconomic and environmental consequences of greater or lesser importance.
3.3. Impacts of extreme rainfall The investigations showed that during extreme rainfall years, agricultural activities are disrupted. Excess or deficient rainfall causes drops in agricultural production and makes vulnerable populations at risk of food insecurity, in addition to a reduction in income of producers who find it more difficult to properly deal with their socioeconomic needs. Extremely wet years result in offal input to continental rivers. These offal-laden floods are major rainfall disasters, feared by both communities and by decision makers. Indeed, they lead to more flood-caused socio-environmental damage, including devastation of fields, flooding or destruction of homes, bridges, and roads, and the proliferation of waterborne diseases (Fig. 3). The cultivation of cotton, which accounts for 80% of export earnings and over 24% of state revenue is particularly vulnerable to major floods caused by excess rainfall (http://www.ambassadebenin.org/article30.html). The heavy rains coincide with critical phases of flowering and fruiting of cotton. According to the technical staff, this has rendered plant treatments and the use of chemical fertilizers ineffective (MDR, 1996). Even a flood of short duration is detrimental to cotton. If heavy rains occur immediately after pesticide treatments, some of the products used is washed into rivers, a portion is redistributed to the lower leaves of cotton, and some is directly eliminated by draining. This reduces the efficiency of treatment and in turn affects the yield of cotton. Also, heavy rains reduce the action of chemical fertilizers (they have promoted their leaching and drainage to rivers). In addition, during very wet years, rural roads and even a few tarred roads become impassable, interfering with the collection, transport and trade of
Fig. 4. Parched rice fields in Dangbo in February 2006 (left) and planted maize damaged in Diho in May 1995 (right) due to low rainfall.
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
food products and causing the shortfalls to both producers and traders (Djossou, 1993). As for the years that are extremely deficient, they are characterized by a late start and early end of the rainy season, and rainfall breaks during the heart of the growing season. The disturbance and seasonal rainfall deficits disrupt crop cycles, upset the peasant agricultural calendar and interfere with cultural activities among peasant populations. Under these conditions, planting dates are pushed back. If sowing has occurred, a large water deficit can cause early drying of crops (Fig. 4). In different regions of Benin, the vulnerability is manifested by deteriorations in yield and crop losses. Food crises have marked the history of communities, and have destabilized traditional economies (Boko, 1988). For example, between 1976 and 1977, approximately 46% of Benin suffered food shortages (Odjo, 1997) and the hunger of those hard years remains in the memory of the population of Benin. In addition, in years of deficits, water levels in rivers and lakes drop considerably, and the tanks and wells dry up. However, rivers and lakes are the main sources of water supply for rural populations in particular. Communities face enormous difficulties in accessing water for their various needs. Under these conditions, they may travel long distances in search of water, and waterborne epidemics could cause loss of human lives. 4. Conclusion This research revealed that extreme deficit years were more frequent in the 1970s and 1980s, and have affected the northern part of Benin to a greater degree. The south is more affected by extreme rainfall years, occurring mostly before 1970. In both cases, the occurrence of extreme years disrupts the socioeconomic balance of rural and urban communities (Cotonou, Sèmè-kpodji, Godomey, etc.). According to the forecasts of the IPCC (2007), extreme years will increase in future as part of climate change, and the examples of the years 2009 and 2010 are evocative. Future development policies should therefore take this into account.
43
References Afouda F., 1990. The water and crops in central and northern Benin: study of the variability of water balance in their relations with the rural environment of the African savannah. PhD Thesis New Regime, Paris IV-Sorbonne, 428 pp. Boko, M., 1988. Climate and rural communities of Benin: rhythms climate and pace of development. PhD Thesis, University of Dijon, 607 pp. Bokonon-Ganta E., 1987. The climates of the Gulf of Benin. PhD Thesis of 3rd cycle, Institute of Geography, University of Paris-Sorbonne, Paris, 248 pp. þ appendix. Brou, Y.T., Servat, E., Paturel, J.E., 1999. Contribution to the Analysis of Interrelations between Human Activities and Climate Variability: The Case of South Ivorian Forest. In: Comptes Rendues Academie des Sciences (Paris), vol. 327 (ser II). Djossou V., 1993. Frequency analysis of rainfall anomalies positive early dry season in the Low-Benin. Master’s Thesis in Geography. DGAT/FLASH/UNB, 77 pp. þ appendix. Houndénou, C., 1999. Climate variability and corn production in the humid tropics, diagnosis and modeling. PhD Thesis, Single, UMR CNRS 50 80, tropical climate of space, 341 pp. IPCC [Intergovernmental Panel on Climate Change], 1991. Climate Change: The IPCC Response Strategies. Island Press, Washington, DC, 44 pp. IPCC [Intergovernmental Panel on Climate Change], 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp. Klassou K.M., 1996. Evolution and climate-hydrological effects on the environment: The example of River Basin Mono (Togo-Benin). PhD Thesis, Geography, Université Bordeaux III, Institute of Geography Louis Papy, 472 pp. MDR [Ministry of Rural Development], 1996. Study of Strategy of Development of under Cotton Sector, Cotonou, Benin, 154 pp. Nicholson, S.E., 1980. The nature of rainfall fluctuations in subtropical West Africa. Monthly Weather Review 108, 473e487. Ogouwalé, E., Yabi, I., Boko M., 2005. Singularity of rainfall variability between the 9th and 10th parallel in Benin (West Africa). Proceedings of 2nd International Scientific Days of National Universities of Benin, vol. 2, pp. 62e71. Odjo, S., 1997. Climate rhythms and food constraints in district of Atacora. M.Sc. Geography, UNB/FLASH, 97 pp. þ tables þ plates. Olaniran, O.J., 1991. Evidence of climatic change in Nigeria based on annual rainfall of different series of daily amounts, 1919e1985. Climatic Change 19, 319e341. Paturel, J.E., Servat, E., Kouame, B., Masson Lubes, J., 1995. The drought in nonSahelian West Africa (Côte d’Ivoire, Togo, Benin). Drought Review 6, 95e102. Yabi, I., 2002. Characteristics of rainfall variability between 7 and 8 N in Benin. M.Sc. Geography FLASH - UAC, Abomey-Calavi. 96 pp. Yabi, I., Afouda, F., 2007. Variability of rainfall early in the growing season and adaptation measures in the department of Collines in Benin (West Africa). Proceedings of first conference of the UAC of Science, Culture and Technology, Geography: pp. 315e327.
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Extreme rainfall years in Benin (West Africa) Ibouraïma Yabi*, Fulgence Afouda Laboratory Pierre Pagney “Climate, Water, and Ecosystem Development”, Department of Geography and Regional Planning, University of Abomey-Calavi, BP: 922 Abomey-Calavi, Benin
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 22 December 2010
This research examines recent years’ rainfall extremes and their socioeconomic and environmental impacts in Benin. The annual rainfall amounts of the 1922e2005 series for 16 stations spread throughout the country were used, as recorded in the files of the Agency for Air Navigation Safety (ASECNA-Cotonou). In addition, investigations in the environment have been conducted to understand the impacts experienced by communities. The data and information collected were processed using statistical tools and maps. Analysis shows a strong incidence of extreme rainfall during the 1950s and 1960s, particularly in the south, while the 1970s and 1980s recorded very dry years. In all cases, wet and dry years pose problems for rural and urban communities. The projected climate change will increase the frequency and intensity of extreme rainfall and drought and their consequences, and development policies must take that into account. Ó 2011 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction Recent decades have been marked by rapid change of climate on a global scale (IPCC, 1991; Olaniran, 1991) and a high occurrence of extreme rainfall events (IPCC, 2007). West Africa in the last three decades has been marked by unprecedented rainfall variability, differing from the past century. Most studies have shown that annual rainfall totals of the 1970s and 1980s are characterized by significant decreases (Nicholson, 1980; Paturel et al., 1995; Brou et al., 1999), together with the occurrence of especially wet years, some with considerable socio-ecological consequences. In Benin, the weather trend is identical to that of the remainder of West Africa. Since the late 1960s, the country has experienced high rainfall variability. This occurs, in particular, from changing rainfall patterns and a decrease in annual totals (Bokonon-Ganta, 1987; Boko, 1988; Afouda, 1990; Houndénou, 1999; Yabi, 2002; Ogouwalé et al., 2005; Yabi and Afouda, 2007). However, within this context of a general downward trend, heavy rainfall that generates floods occurs at times. Sometimes, dramatic and disastrous socioeconomic impacts occur, particularly connected to agriculture (IPCC, 2007). In a context where most economic activities are influenced by rainfall, disturbances to previous patterns could lead to socioeconomic problems or political consequences (Boko, 1988).
* Corresponding author. E-mail address: yafi[email protected] (I. Yabi). 1040-6182/$ e see front matter Ó 2011 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2010.12.010
The West-African monsoon is the principal generating factor of the rains, which are differently distributed from south to north in Benin. The south has a subequatorial climate with an annual average rain ranging between 900 mm (Bopa) and 1300 mm (Cotonou). The rainy rhythm is bimodal with a long dry season (mid-November to mid-March), a long season of rains (from midMarch to mid-July), a small dry season (mid-July to midSeptember) and a small season of rains (mid-September to midNovember). In the north, the climate is of tropical moist type and annual average rain is rather variable (1300 mm at Natitingou, 1100 mm at Nikki and Bembéréké, 900 mm at Kandi). The rainfall mode is unimodal everywhere with one rainfall season which lasts 7 months (AprileOctober) and a dry season (NovembereMarch). Everywhere, the particular agricultural activities are controlled by the rainy distribution. 2. Methodological approach The data used in this research are related to annual rainfall amounts between 1922 (year of establishment of the oldest stations) and 2005 for 16 stations spread throughout the country (Table 1). These data were extracted from the file of the Agency for Air Navigation Safety (ASECNA-Cotonou). Missing data (4.6% of total observations) were reconstructed by the method of least squares (Houndénou, 1999). The identification of extreme years was made by calculating the percentage of rainfall deficit or surplus over the average (Boko, 1988; Klassou, 1996). Pa denotes the total annual rainfall of a year
40
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
Table 1 Stations. No
Stations
Latitude
Longitude
Time series covered by data
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16
Kandi Natitingou Bembéréké Nikki Djougou Parakou Savè Abomey Zagnanado Applahoué Pobè Sakété Adjohoun Allada Bopa Cotonou
11 080 N 10 190 N 10 120 N 09 360 N 09 420 N 09 210 N 07 560 N 07 110 N 07 150 N 06 550 N 06 560 N 06 430 N 06 420 N 06 390 N 06 310 N 06 210 N
02 560 E 01 230 E 02 400 E 03 120 E 01 400 E 02 370 E 02 260 E 01 590 E 02 200 E 01 400 E 02 400 E 02 100 E 02 290 E 02 080 E 01 580 E 02 260 E
1921e2005 1921e2005 1922e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1921e2005 1922e2005
and Pm the mean total annual rainfall in the series. A year is extremely deficient for a station when Pa < 70% Pm (30% deficit); the year was extremely wet for a station when Pa > 120% Pm (20% excess). The frequency of extreme rainfall years (FAPE) surplus or deficit is calculated according to:
FAPE ¼ ðNAPE=NTAÞ where NAPE is the number of years with rainfall extremes; and NTA is the total number of years studied. Intensity (I) abnormalities were determined by the following formula:
I ¼ ðPa PmÞ=Pm Field investigations have provided further insight into the socioenvironmental results of extreme rainfall years, particularly in rural areas. Mapping has been used for spatialized analysis.
Fig. 1. Frequency of years of extreme rainfall deficiency.
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43 Table 2 Spatiotemporal distribution of rainfall deficit years. Deficient rainfall years in the south (between the coast and 7 450 N) Deficient rainfall years in the North (north of 7 450 N) General deficient rainfall years (all Benin)
Table 3 Spatiotemporal distribution of surplus rainfall years.
1937, 1946, 1964, 1973, 1977, 1982, 1983, 1984, 1988, 1995 1932, 1961, 1981, 1946,
1934, 1971, 1982, 1973,
1946, 1973, 1983, 1977,
41
1950, 1956, 1958, 1976, 1977, 1979, 1980, 1984 1982, 1983, 1984
Wet years in the South (between the coast and 7 450 N) Wet years in the North (north of 7 450 N) General wet years (all Benin)
1929, 1962, 1947, 1962, 1947,
1933, 1963, 1953, 1998 1957,
1947, 1957, 1968, 1998 1957, 1962, 1998
3. Results 3.1. Review of extremely deficient rainfall years The frequency of extreme rainfall deficit years is shown in Fig. 1. The frequency of extremely dry years varies between 0.05 and 0.17. Overall, the northern sites are more affected by drought.
Fig. 2. Frequency of very wet years.
42
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
Fig. 3. Maize farm flooded (left) and flooded road (right) after heavy rains in 1998.
Stations Nikki, Kandi, and Bembéréké record respectively 0.17, 0.14 and 0.13. As for the southern stations, they are slightly affected with the exception of Adjohoun. Table 2 provides a better understanding of the spatiotemporal distribution of these abnormalities in deficit. The analysis of the table confirms that the northern part has seen more years of deficits relative to the south (17 years in the north against 10 in the south). A total of six years were marked by deficits throughout Benin. Most years of general deficits belong to the 1970s and 1980s in line with the trend toward sub-regional rainfall. The intensity of deficits varies between 0.30 and 0.50. High deficits were also recorded during the 1970s and 1980s. 3.2. Extremely wet years The spatial distribution of extremely wet years is illustrated in Fig. 2. The frequency of very wet years varies between 0.08 and 0.17. Stations in the south recorded the highest values compared to the north. Thus, at Zagnanado, Pobe, Applahoué, and Adjohoun the frequencies are respectively 0.17, 0.14, 0.14, and 0.13, compared to 0.08, 0.08, 0.08, and 0.09 in order at Kandi, Bembéréké, Nikki, and Natitingou. The spatiotemporal distribution of these years is summarized in Table 3. Southern stations record more wet years than those in the north (8 years compared to 5). In all cases, the 1950s and 1960s are marked by positive rainfall anomalies. The intensity of the surplus is between 0.8 and 0.55, and the highest values are registered in the south (Cotonou and Bopa). In one way or another, the occurrence of extreme rainfall years is associated with socioeconomic and environmental consequences of greater or lesser importance.
3.3. Impacts of extreme rainfall The investigations showed that during extreme rainfall years, agricultural activities are disrupted. Excess or deficient rainfall causes drops in agricultural production and makes vulnerable populations at risk of food insecurity, in addition to a reduction in income of producers who find it more difficult to properly deal with their socioeconomic needs. Extremely wet years result in offal input to continental rivers. These offal-laden floods are major rainfall disasters, feared by both communities and by decision makers. Indeed, they lead to more flood-caused socio-environmental damage, including devastation of fields, flooding or destruction of homes, bridges, and roads, and the proliferation of waterborne diseases (Fig. 3). The cultivation of cotton, which accounts for 80% of export earnings and over 24% of state revenue is particularly vulnerable to major floods caused by excess rainfall (http://www.ambassadebenin.org/article30.html). The heavy rains coincide with critical phases of flowering and fruiting of cotton. According to the technical staff, this has rendered plant treatments and the use of chemical fertilizers ineffective (MDR, 1996). Even a flood of short duration is detrimental to cotton. If heavy rains occur immediately after pesticide treatments, some of the products used is washed into rivers, a portion is redistributed to the lower leaves of cotton, and some is directly eliminated by draining. This reduces the efficiency of treatment and in turn affects the yield of cotton. Also, heavy rains reduce the action of chemical fertilizers (they have promoted their leaching and drainage to rivers). In addition, during very wet years, rural roads and even a few tarred roads become impassable, interfering with the collection, transport and trade of
Fig. 4. Parched rice fields in Dangbo in February 2006 (left) and planted maize damaged in Diho in May 1995 (right) due to low rainfall.
I. Yabi, F. Afouda / Quaternary International 262 (2012) 39e43
food products and causing the shortfalls to both producers and traders (Djossou, 1993). As for the years that are extremely deficient, they are characterized by a late start and early end of the rainy season, and rainfall breaks during the heart of the growing season. The disturbance and seasonal rainfall deficits disrupt crop cycles, upset the peasant agricultural calendar and interfere with cultural activities among peasant populations. Under these conditions, planting dates are pushed back. If sowing has occurred, a large water deficit can cause early drying of crops (Fig. 4). In different regions of Benin, the vulnerability is manifested by deteriorations in yield and crop losses. Food crises have marked the history of communities, and have destabilized traditional economies (Boko, 1988). For example, between 1976 and 1977, approximately 46% of Benin suffered food shortages (Odjo, 1997) and the hunger of those hard years remains in the memory of the population of Benin. In addition, in years of deficits, water levels in rivers and lakes drop considerably, and the tanks and wells dry up. However, rivers and lakes are the main sources of water supply for rural populations in particular. Communities face enormous difficulties in accessing water for their various needs. Under these conditions, they may travel long distances in search of water, and waterborne epidemics could cause loss of human lives. 4. Conclusion This research revealed that extreme deficit years were more frequent in the 1970s and 1980s, and have affected the northern part of Benin to a greater degree. The south is more affected by extreme rainfall years, occurring mostly before 1970. In both cases, the occurrence of extreme years disrupts the socioeconomic balance of rural and urban communities (Cotonou, Sèmè-kpodji, Godomey, etc.). According to the forecasts of the IPCC (2007), extreme years will increase in future as part of climate change, and the examples of the years 2009 and 2010 are evocative. Future development policies should therefore take this into account.
43
References Afouda F., 1990. The water and crops in central and northern Benin: study of the variability of water balance in their relations with the rural environment of the African savannah. PhD Thesis New Regime, Paris IV-Sorbonne, 428 pp. Boko, M., 1988. Climate and rural communities of Benin: rhythms climate and pace of development. PhD Thesis, University of Dijon, 607 pp. Bokonon-Ganta E., 1987. The climates of the Gulf of Benin. PhD Thesis of 3rd cycle, Institute of Geography, University of Paris-Sorbonne, Paris, 248 pp. þ appendix. Brou, Y.T., Servat, E., Paturel, J.E., 1999. Contribution to the Analysis of Interrelations between Human Activities and Climate Variability: The Case of South Ivorian Forest. In: Comptes Rendues Academie des Sciences (Paris), vol. 327 (ser II). Djossou V., 1993. Frequency analysis of rainfall anomalies positive early dry season in the Low-Benin. Master’s Thesis in Geography. DGAT/FLASH/UNB, 77 pp. þ appendix. Houndénou, C., 1999. Climate variability and corn production in the humid tropics, diagnosis and modeling. PhD Thesis, Single, UMR CNRS 50 80, tropical climate of space, 341 pp. IPCC [Intergovernmental Panel on Climate Change], 1991. Climate Change: The IPCC Response Strategies. Island Press, Washington, DC, 44 pp. IPCC [Intergovernmental Panel on Climate Change], 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp. Klassou K.M., 1996. Evolution and climate-hydrological effects on the environment: The example of River Basin Mono (Togo-Benin). PhD Thesis, Geography, Université Bordeaux III, Institute of Geography Louis Papy, 472 pp. MDR [Ministry of Rural Development], 1996. Study of Strategy of Development of under Cotton Sector, Cotonou, Benin, 154 pp. Nicholson, S.E., 1980. The nature of rainfall fluctuations in subtropical West Africa. Monthly Weather Review 108, 473e487. Ogouwalé, E., Yabi, I., Boko M., 2005. Singularity of rainfall variability between the 9th and 10th parallel in Benin (West Africa). Proceedings of 2nd International Scientific Days of National Universities of Benin, vol. 2, pp. 62e71. Odjo, S., 1997. Climate rhythms and food constraints in district of Atacora. M.Sc. Geography, UNB/FLASH, 97 pp. þ tables þ plates. Olaniran, O.J., 1991. Evidence of climatic change in Nigeria based on annual rainfall of different series of daily amounts, 1919e1985. Climatic Change 19, 319e341. Paturel, J.E., Servat, E., Kouame, B., Masson Lubes, J., 1995. The drought in nonSahelian West Africa (Côte d’Ivoire, Togo, Benin). Drought Review 6, 95e102. Yabi, I., 2002. Characteristics of rainfall variability between 7 and 8 N in Benin. M.Sc. Geography FLASH - UAC, Abomey-Calavi. 96 pp. Yabi, I., Afouda, F., 2007. Variability of rainfall early in the growing season and adaptation measures in the department of Collines in Benin (West Africa). Proceedings of first conference of the UAC of Science, Culture and Technology, Geography: pp. 315e327.