Regional Environmental Change

, Volume 14, Issue 1, pp 145–156

The causes, effects and challenges of Sahelian droughts: a critical review

Original Article

Abstract

This paper is a critical synthesis of the causes, effects and challenges of the Sahelian droughts. The results show that the four main causes of the Sahelian droughts are as follows: sea surface temperature changes, vegetation and land degradation, dust feedbacks and human-induced climate change. However, human-induced climate change is seen as the major drought-determining factor because it controls sea surface temperatures, dust feedbacks and vegetation degradation. Increase rainfall and greening have been observed in the Sahel since the 1990s; yet, food yields remain low while tree mortality rates are high. The implication of this is that the rainfall is not available for agriculture since various human-induced climate change processes such as deforestation and the expansions of arable farms do not make the moisture available for agriculture. The increase in tree mortality has also been found to increase atmospheric CO2 in the study area. However, this study hypothesizes that the increase in CO2 might be responsible for the increase in greening and rainfall observed. This can be explained by an increased aerial fertilization effect of CO2 that triggers plant productivity and water management efficiency through reduced transpiration. Also, the increase greening can be attributed to rural–urban migration which reduces the pressure of the population on the land. The remittances from migrant urban workers may make farming more sustainable in the rural areas, thus enhancing greening. The principal challenges in overcoming the effects of the droughts are HIV/AIDS and Malaria, political instability, data availability, proliferation of extensive non-mechanized farms and lack of adequate observations.

Keywords

Droughts Human-induced climate change Tree mortality CO2 emissions Food yields HIV/AIDS National security 

Supplementary material

10113_2013_473_MOESM1_ESM.docx (214 kb)
Supplementary material 1 (DOCX 213 kb)

References

  1. Adhikari M, Ishizaka Y, Minda H, Kazaoka R, Jensen JB, Gras JL, Nakajima T (2005) Vertical distribution of cloud condensation nuclei concentrations and their effect on microphysical properties of clouds over the sea near the southwest islands of Japan. J Geophys Res 110:D10203. doi:10.1029/2004JD004758 CrossRefGoogle Scholar
  2. Allen CD, Macalady A, Chenchouni H, Bachelet D, McDowell N, Vennetier M, Kitzberger T, Rigling A, Breshears DD, Hogg EH, Gonzalez P, Fensham R, Zhang Z, Castro J, Demidova N, Lim JH, Allard G, Running SW, Semerci A, Cobb N (2009) A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests. Forest Ecol Manag 259:660–684. doi:10.1016/j.foreco.2009.09.001 CrossRefGoogle Scholar
  3. Antwi-Agyei P, Fraser EDG, Dougill AJ, Stringer LC, Smelton E (2012) Mapping the vulnerability of crop production to droughts in Ghana using rainfall yield and socioeconomic data. Appl Geogr 32:324–334. doi:10.1016/j.apgeog.2011.06.010 CrossRefGoogle Scholar
  4. Anyamba A, Eastman J (1996) Interannual variability of NDVI over Africa and its relation to El Niño/Southern Oscillation. Inter J Remote Sens 17:2533–2548CrossRefGoogle Scholar
  5. Anyamba A, Tucker CJ (2005) Analysis of Sahelian Vegetation dynamics using NOAA-AVHRR NDVI data from 1981–2003. J Arid Environ 63:595–614CrossRefGoogle Scholar
  6. Asch F, Dingkuhn M, Sow A, Audebert A (2005) Drought-induced changes in rooting patterns and assimilate partitioning between root and shoot in upland rice. Field Crops Res 93:223–236. doi:10.1016/j.fcr.2004.10.002 CrossRefGoogle Scholar
  7. Bader J, Latif M (2003) The impact of decadal-scale Indian Ocean sea surface temperature anomalies on Sahelian rainfall and the North Atlantic Oscillation. Geophys Res Lett 30:2165–2169CrossRefGoogle Scholar
  8. Baldocchi D (2008) Breathing of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems. Aust J Bot 56(1):1–26CrossRefGoogle Scholar
  9. Biasutti M, Giannini A (2006) Robust Sahel drying in response to late 20th century forcings. Geophys Res Lett 33:L11706CrossRefGoogle Scholar
  10. Camberlin P, Janicot S, Poccard I (2001) Seasonality and Atmospheric dynamics of the teleconnection between African rainfall and tropical sea-Surface temperature: Atlantic vs ENSO. Inter J Clim 21:973–1005. doi:10.1002/joc.673 CrossRefGoogle Scholar
  11. Charney JM, Quirk WJ, Chow SH, Kornfield J (1977) A comparative study of the effects of albedo change on drought in semi-arid regions. J Atmos Sci 34(9):1366–1386CrossRefGoogle Scholar
  12. Chelliah M, Bell GD (2004) Tropical multidecadal and interannual climate variability in the NCEP–NCAR reanalysis. J Clim 17:1777–1803CrossRefGoogle Scholar
  13. Clover J (2010) Food security in sub-Saharan Africa. Afr Food Rev 12(1):5–15. doi:10.1080/10246029.2003.9627566 Google Scholar
  14. De Rouw A (2004) Improving yields and reducing risks in pearl millet farming in the African Sahel. Agric Syst 81:73–93CrossRefGoogle Scholar
  15. Dilley M, Chen RS, Deichmann U, Lerner-Lam AL, Arnold M (2005) Natural disaster hotspots: a global risk analysis. Disaster Risk Management Series No, 5. The World Bank, WashingtonGoogle Scholar
  16. Dinku T, Ceccato P, Grover-Kopec E, Lemma M, Connor SJ, Ropelewski CF (2007) Validation of satellite rainfall products over East Africa’s complex topography. Inter J Remote Sens 28(7):1503–1526CrossRefGoogle Scholar
  17. Eklundh L, Olsson L (2003) Vegetation index trends for the African Sahel 1982–1999. Geophys Res Lett 30(8):1430. doi:10.1029/2002GL016772 CrossRefGoogle Scholar
  18. Epule TE, Peng C, Lepage L, Chen Z (2011) Forest loss triggers in Cameroon. A quantitative assessment using multiple linear regression approach. J Geogr Geol 3(1):30–40. doi:10.5539/jgg.v3n1p30 Google Scholar
  19. Epule TE, Peng C, Lepage L, Chen Z (2012a) Rainfall and deforestation dilemma for cereal Production in the Sudano-Sahel of Cameroon. J Agric Sci 4(2):1–9. doi:10.5539/jas.v4n2p1 Google Scholar
  20. Epule TE, Peng C, Lepage L, Balgah SN, Mafany NM (2012b) Can the African food supply model learn from the Asian food supply model? Predictions with selected variables and quantitative methods. Environ Deve Sus 593–610. doi:10.1007/s10668-012-9341-0
  21. Food and Agricultural Organization of the United Nations (2010) Forest resource assessment. FAO Forestry paper no 163, FAO, Rome. [Online] Available http://www.fao.org [12 January 2013]
  22. Food and Agricultural Organization of the United Nations, FAO (2006) Global forest resources assessment 2005—progress towards sustainable forest management. Rome. FAO Forestry Paper No. 147Google Scholar
  23. Food and Agricultural Organization of the United Nations, United Nations Industrial Development Organization (2008) Agricultural mechanization in Africa…Time for action. Planning investment for enhanced agricultural productivity report of an expert group meeting in January 2008, Vienna Austria. FAO, Rome. Available from http://www.unido.org/fileadmin/user_media/Publications/Pub_free/agricultural_mechanization_in_Africa.pdf. Accessed 1 Feb 2013
  24. Frelich LE, Reich PB (2010) Will environmental changes reinforce the impact of global warming on the prairie–forest border of central North America? Front Ecol Environ 8(7):371–378. doi:10.1890/080191 CrossRefGoogle Scholar
  25. Fuller DO, Ottke C (2002) Land cover, Rainfall and Land-Surface Albedo in West Africa. Clim Chang 54:181–204CrossRefGoogle Scholar
  26. Giannini A, Saravanan R, Chang P (2003) Oceanic forcing of Sahel Rainfall on interannual to interdecadal timescales. Science 302:1027–1030CrossRefGoogle Scholar
  27. Giannini A, Saravanan R, Chang P (2005) Dynamics of the boreal summer African monsoon in the NSIPP1 atmospheric model. Clim Dyn 25:517–535. doi:10.1007/s00382-005-0056-x CrossRefGoogle Scholar
  28. Giannini A, Biasutti M, Held IM, Sobel AH (2008) A global perspective on African climate. Clim Chang 90:359–383. doi:10.1007/s10584-008-9396-y CrossRefGoogle Scholar
  29. Glantz MH (1994) Drought, desertification and food production. In: Glantz MH (ed) Drought follows the plow. Cambridge University Press, Cambridge, pp 9–30Google Scholar
  30. Gleckler PJ, Taylor KE, Doutriauz C (2008) Performance metrics for climate models. J Geophys Res 113:D06104. doi:10.1029/2007JD008972 Google Scholar
  31. Gonzalez P (2001) Desertification and a shift of forest species in the West African Sahel. Clim Res 17:217–228CrossRefGoogle Scholar
  32. Gonzalez P, Tucker CJ, Sy H (2012) Tree density and species decline in the African Sahel attributable to climate. J Arid Environ 78:55–64. doi:10.1016/j.jaridenv.2011.11.001 CrossRefGoogle Scholar
  33. Hagos SM, Cook KH (2008) Ocean warming and the late-twentieth century Sahel drought and recovery. J Clim 21:3797–3814. doi:10.1175/2008JCLI2055.1 CrossRefGoogle Scholar
  34. Haile M (2005) Weather patterns, food security and humanitarian response in sub-Saharan Africa. Philos Trans R Soc 360:2169–2182. doi:10.1098/rstb.2005.1746 CrossRefGoogle Scholar
  35. Held IM, Delworth TL, Lu J, Knutson T, Findell K (2005) Simulations of Sahel drought in the 20th and 21st centuries. PNAS 102(50):17891–17896. doi:10.1073/pnas.0509057102 CrossRefGoogle Scholar
  36. Herrmann SM, Anyamba A, Tucker CJ (2005) Recent trends in vegetation dynamics in the African Sahel and their relationship to climate. Glob Environ Chang 15:394–404CrossRefGoogle Scholar
  37. Hiernaux P, Diarra L, Trichon V, Mougin E, Soumaguel N, Baup F (2009) Woody plant population dynamics in response to climate changes from 1984 to 2006 in Sahel (Gourma, Mali). J Hydrol 375:103–113CrossRefGoogle Scholar
  38. Hoerling MP, Hurrell JW, Eischeid J, Phillips AS (2006) Detection and attribution of 20th century Northern and Southern African monsoon change. J Clim 19:3989–4008. doi:10.1175/JCLI3842.1 CrossRefGoogle Scholar
  39. Hui WJ, Cook B, Ravi S, Fuentes JD, D’Odorico P (2008) Dust-rainfall feedbacks in the West African Sahel. Water Resour Res 44:W05202. doi:10.1029/2008WR006885 Google Scholar
  40. Hulme M (2001) Climatic perspectives on Sahelian desiccation: 1973–1998. Glob Environ Chang 11:19–29CrossRefGoogle Scholar
  41. Hurrell JW (1995) Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science 269:676–679CrossRefGoogle Scholar
  42. Ifejika Speranza CI (2006) Droughts and famines: the underlying factors and the causal link among agro-pastoral households in semi-arid Makueni district, Kenya. Glob Environ Chang 18:220–233CrossRefGoogle Scholar
  43. Janicot S, Mounier F, Gervois S, Sultan B, Kiladis GN (2010) The dynamics of the West African Monsoon. Part V: the Detection and role of the dominant modes of convectively coupled equatorial Rossby waves. J Clim 23:4005–4024. doi:10.1175/2010JCLI3221.1 CrossRefGoogle Scholar
  44. Kang SM, Held IM, Frierson DWM, Zhao M (2008) The response of the ITCZ to extratropical thermal forcing: idealized slab-ocean experiments with a GCM. J Clim 21:3521–3532. doi:10.1175/2007JCLI2146.1 CrossRefGoogle Scholar
  45. Kaufman YJ, Tanré D, Boucher O (2002) A satellite view of aerosols in the climate system. Nature 419:215–223. doi:10.1038/nature01091 CrossRefGoogle Scholar
  46. Knorr W, Gobron N, Scholze M, Kaminski T, Schnur R, Pinty B (2007) Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003. Geophys Res Lett 34:L09703. doi:10.1029/2006/GL029019
  47. Knutson TR, Delworth TL, Dixon KW, Held IM, Lu J, Ramaswamy V, Schwarzkopf MD, Stenchikov G, Stouffer RJ (2006) Assessment of twenty-century regional surface temperature trends using the GFDL CM2 coupled models. J Clim 19:1624–1651. doi:10.1175/JCLI3709.1 CrossRefGoogle Scholar
  48. Koepke D, Kolb T, Adams H (2010) Variation in woody plant mortality and dieback from severe drought among soils, plant groups, and species within a northern Arizona ecotone. Oecologia (Berl.) 163(4):1079–1090. doi:10.1007/s00442-010-1671-8 CrossRefGoogle Scholar
  49. Lamb PJ (1982) Persistence of Sub-Saharan drought. Nature 299:36–47CrossRefGoogle Scholar
  50. Lamprey HF (1975) Report on the desert encroachment reconnaissance in northern Sudan, 21 Oct. to 10 Nov. UNESCO/UNEP, pp 16Google Scholar
  51. Leuzinger S, Quinn TR (2011) How do we improve Earth system models? Integrating Earth system models, ecosystem models, experiments and long-term data. New Phytol 191(1):15–18. doi:10.1111/j.1469-8137.2011.03778.x CrossRefGoogle Scholar
  52. Li X, Maring H, Savoie D, Voss K, Prospero JM (1996) Dominance of mineral dust in aerosol light-scattering in the North Atlantic trade winds. Nature 380:416–422CrossRefGoogle Scholar
  53. Lindell L, Astrom M, Oberg T (2010a) Land-use versus natural controls on soil fertility in the Subandean Amazon. Peru Sci Total Environ 408(4):965–975CrossRefGoogle Scholar
  54. Lindell L, Astrom M, Oberg T (2010b) Land-use change versus natural controls on stream water chemistry in the Subandean Amazon. Peru Appl Geochem 25(3):485–495CrossRefGoogle Scholar
  55. Lintner BR, Chiang JCH (2006) Adjustment of the remote tropical climate system to El Nino conditions. J Clim 20:2544–2557. doi:10.1175/JCLI4138.1 CrossRefGoogle Scholar
  56. Lohmann U, Feichter J (2005) Global indirect aerosol effects: a review. Atmos Chem Phys 5:715–737CrossRefGoogle Scholar
  57. Lu J, Delworth TL (2005) Oceanic forcing of the late 20th century Sahel drought. Geophys Res Lett 32:L22706. doi:10.1029/2005GL023316 CrossRefGoogle Scholar
  58. Lwanga JS (2003) Localized tree mortality following the drought of 1999 at Ngogo, Kibale National Park, Uganda. Afr J Ecol 41:194–196CrossRefGoogle Scholar
  59. Mahowald NM, Kiehl LM (2003) Mineral aerosol and cloud interactions. Geophys Res Lett 30(9):1475. doi:10.1029/2002GL016762 CrossRefGoogle Scholar
  60. Maranz S (2009) Tree mortality in the African Sahel indicates an anthropogenic ecosystem displaced by climate change. J Biogeogr 36:1181–1193CrossRefGoogle Scholar
  61. Maynard K, Royer JF, Chauvin F (2002) Impact of greenhouse warming on the West African summer monsoon. Clim Dyn 19:499–514CrossRefGoogle Scholar
  62. McKee TB, Doesken NJ, Kleist J (1993) The relationship of drought frequency and duration to time scales. In: Proceedings of the 8th conference on applied climatology, Anaheim, California. 17–22 January 1993. American Meterological SocietyGoogle Scholar
  63. Meir P, Metcalfe DB, Costa ACL, Fisher RA (2008) The fate of assimilated carbon during drought: impacts on respiration in Amozon rainforests. Phil Trans Roy Soc B 363:1849–1855CrossRefGoogle Scholar
  64. Molen MK, Dolman AJ, Ciais P, Eglin T, Gobron N, Law BE, Meir P, Peters W, Phillips OL, Reichstein M, Chen T, Dekker SC, Doubkova M, Friedi MA, Jung M, Hurk BJJM, De Jeu RAM, Kruijt B, Ohta T, Rebels KT, Plummer S, Seneviratne SI, Sitch S, Teuling AJ, Weri GR, Wang G (2011) Droughts and ecosystems carbon cycling. Agric For Meteo 151:765–773. doi:10.1016/j.agrformet.2011.01.018 CrossRefGoogle Scholar
  65. Muller TR (2004) HIV/AIDS and agriculture in sub-Saharan Africa. Wageningen Academic Publishers, NetherlandsCrossRefGoogle Scholar
  66. N’Tchayi MG, Bertrand JJ, Nicholson SE (1997) The diurnal and seasonal cycles of wind-borne dust over Africa north of the equator. J Appl Meteo 36:868–882. doi:10.1175/1520-0450(1997)036<0868:TDASCO>2.0.CO;2 CrossRefGoogle Scholar
  67. Neelin JD, Su H (2005) Moist teleconnection mechanisms for the tropical South American and Atlantic sector. J Clim 18:3928–3950. doi:10.1175/JCLI3517.1 CrossRefGoogle Scholar
  68. Niang AJ, Ozer A, Ozer P (2008) Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos. J Arid Environ 72:97–107CrossRefGoogle Scholar
  69. Nicholson SE (1995) Sahel, West Africa. Encycl Environ Biol 3:261–275Google Scholar
  70. Nicholson SE (2001) Climate and environmental change in Africa during the last two centuries. Clim Res 14:123–144CrossRefGoogle Scholar
  71. Nicholson SE, Trucker CJ, Ba MB (1998) Desertification, drought and surface vegetation: an example from the West African Sahel. Bull Am Meteo Soc 79(5):815–829CrossRefGoogle Scholar
  72. Nyariki DM, Wiggins S (1997) Household food insecurity in sub-Saharan Africa: lessons from Kenya. Br Food J 99(7):249–262CrossRefGoogle Scholar
  73. Olsson L (1986) Report on reports-continuing the commitment: agricultural development in the Sahel. Environ 29:25–27CrossRefGoogle Scholar
  74. Olsson L (1993) On the causes of famine: drought, desertification and market failure in the Sudan. Ambio 22:395–403Google Scholar
  75. Olsson L, Mryka H (2008) Greening of the Sahel. The Encyclopedia of Earth. Available from http://www.eoearth.org/article/Greening_of_the_Sahel. Accessed 23 Feb 2012
  76. Olsson L, Eklundh L, Ardo J (2005) The recent Greening of the Sahel-trends, patterns and potential causes. J Arid Environ 63(3):556–566CrossRefGoogle Scholar
  77. Palmer WC (1965) Meteorologic drought. US Department of Commerce. Weather Bureau, Research Paper No. 45. pp 58Google Scholar
  78. Peng C, Ma Z, Lei X, Zhu Q, Chen H, Wang W, Liu S, Li W, Fang X, Zhou X (2011) A drought-induced pervasive increase in tree mortality across Canada’s boreal forests. Nat Clim Chang 1:467–471. doi:10.1038/NCLIMATE1293 CrossRefGoogle Scholar
  79. Prince SD, Brown De Coulston E, Kravitz LL (1998) Evidence from rain-use efficiencies does not indicate extensive Sahelian desertification. Glob Chang Biol 4:359–374CrossRefGoogle Scholar
  80. Prospero JM, Lamb PJ (2003) African drought and dust transport to the Caribbean: climate change implications. Science 302:1024–1027CrossRefGoogle Scholar
  81. Ramanathan V, Crutzen PJ, Kiehl JT, Rosenfeld D (2001) Aerosols, climate, and the hydrological cycle. Science 294:2119–2124. doi:10.1126/science.1064034 CrossRefGoogle Scholar
  82. Reij C, Tappan G, Belemvire A (2005) Changing land management practices and vegetation on the Central Plateau of Burkina Faso (1968–2002). J Arid Environ 63:642–659CrossRefGoogle Scholar
  83. Reynolds JF, Stafford SDM, Lambin EF, Turner BL II, Mortimore M, Batterbury SP, Downing TE, Dowlatabadi H, Fernández RJ, Herrick JE, Huber-Sannwald E, Jiang H, Leemans R, Lynam T, Maestre FT, Ayarza M, Walker B (2007) Global desertification: building a science for dryland development. Science 316:847–851CrossRefGoogle Scholar
  84. Roncoli MC, Ingram KT, Kirshen PH (2002) Reading the rains: local knowledge and rainfall forecasting among farmers of Burkina Faso. Soc Nat Resour 15:411–430CrossRefGoogle Scholar
  85. Rosegrant MW, Cline SA (2003) Global food security: challenges and policies. Science 302:1917–1919CrossRefGoogle Scholar
  86. Rosenfeld D, Rudich Y, Lahav R (2001) Desert dust suppressing precipitation: a possible desertification feedback loop. PNAS 98:5975–5980. doi:10.1073/pnas.101122798 CrossRefGoogle Scholar
  87. Rotstayn LD, Lohmann U (2002) Tropical rainfall trends and the indirect aerosol affect. J Clim 14:2103–2116CrossRefGoogle Scholar
  88. Runnstrom M (2003) Rangeland development of the Mu Us Sandy Land in semiarid China: an analysis using Landsat and NOAA remote sensing data. Land Deg Deve Stud 14:189–202CrossRefGoogle Scholar
  89. Schwalm CR, Williams CA, Schaefer K, Arneth A, Bonal D, Buchmann N, Chen JQ, Law BE, Lindroth A, Luyssaert S, Reichstein M, Richardson AD (2010) Assimilation exceeds respiration sensitivity to drought: a FLUXNET synthesis. Glob Chang Biol 16(2):657–670CrossRefGoogle Scholar
  90. Seaquist JW, Olsson L, Ardo J, Eklundh L (2006) Broad-scale increase in NPP quantified for the African Sahel, 1982e1999. Inter J Remote Sens 27:5115–5122CrossRefGoogle Scholar
  91. Shanahan TM, Overpeck JT, Anchukaitis KJ, Beck JW, Cole JE, Dettman DL, Peck JA, Scholz CA, King JW (2009) Atlantic forcing of persistent drought in West Africa. Science 324:377–380CrossRefGoogle Scholar
  92. Simelton E, Fraser EDG, Termansen M, Forster PM, Dougill AJ (2009) Typologies of crop-drought vulnerability: an empirical analysis of the socioeconomic factors that influence the sensitivity and resilience to drought of three major food crops in China (1961–2001). Environ Sci Policy 12(4):438–452CrossRefGoogle Scholar
  93. Thiaw WM, Bell GD (2005) Mechanisms associated with the June–September 2003 Sahel rainfall and implications for seasonal climate forecasts. CLIVAR Exchang 10(1):29–31Google Scholar
  94. Thiaw WM, Mo K (2005) Impact of sea surface temperature and soil moisture on seasonal rainfall prediction over the Sahel. J Clim 18:5330–5343CrossRefGoogle Scholar
  95. Tippett MK (2006) Filtering of GCM simulated Sahel precipitation. Geophys Res Lett 33:01804. doi:10.1029/2005GL024923 CrossRefGoogle Scholar
  96. UNAIDS (2002) Report on the global HIV/AIDS epidemic 2002. UNAIDS, GenevaGoogle Scholar
  97. Vecchi GA, Soden BJ (2007) Global warming and the weakening of the tropical circulation. J Clim 20:4316–4340. doi:10.1175/JCLI4258.1 CrossRefGoogle Scholar
  98. Vicente-Serrano SM, Begueria S, Lopez-Moreno JI, Angulo M, El Kenawy A (2010) A new global 0.5° gridded dataset (1901-2006) of multiscalar drought index: comparison with current drought datasets based on the Palmer Drought Severity Index. Am Meteo Soc. doi:10.1175/2010jhm1224.1
  99. Vincke C, Diedhiou I, Grouzis M (2010) Long term dynamics and structure of woody vegetation in the Ferlo (Senegal). J Arid Environ 74:268–276CrossRefGoogle Scholar
  100. Wang B, Ding Q, Fu X, Jin K, Shukla J, Doblas-Reyes F (2005) Fundamental challenge in simulation and prediction of summer monsoon rainfall. Geophys Res Lett 32:15711. doi:10.1029/2005GL022734 CrossRefGoogle Scholar
  101. Weldeab S, Lea DW, Ralph R, Schneider RR, Andersen N (2007) 155,000 years of West African monsoon and ocean thermal evolution. Science 316(1):1303–1307CrossRefGoogle Scholar
  102. Wezel A, Lykke AM (2006) Woody vegetation change in Sahelian West Africa: evidence from local knowledge. Environ Deve Sust 8:553–567CrossRefGoogle Scholar
  103. Wolff C, Haug G, Timmermann A, Damste JSS, Brauer A, Sigman DM, Cane MA, Verschuren D (2011) Reduced interannual rainfall variability in East Africa during the last Ice Age. Science 333:742–747CrossRefGoogle Scholar
  104. Woomer PL, Tieszen LL, Tappan G, Toure A, Sall M (2004) Land use and terrestrial carbon stocks in Senegal. J Arid Environ 59:625–642. doi:10.1016/j.jaridenv.2004.03.025 CrossRefGoogle Scholar
  105. Zeng N (2003) Drought in the Sahel. Science 302:999–1000CrossRefGoogle Scholar
  106. Zeng N, Neelin JD, Lau KM, Tucker CJ (1999) Enhancement of interdecadal climate variability in the Sahel by vegetation interaction. Science 286:1537–1540CrossRefGoogle Scholar
  107. Zeppel MJB, Adams HD, Anderegg WRL (2011) Mechanistic causes of tree drought mortality: recent results, unresolved questions and future research needs. New Phytol 192(4):800–803. doi:10.1111/j.1469-8137.2011.03960.x CrossRefGoogle Scholar
  108. Zhang R, Delworth TL (2006) Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes. Geophys Res Lett 33:17712. doi:10.1029/2006GL026267 CrossRefGoogle Scholar
  109. Zhao L, Chen Z, Lee K (2011) Modelling the dispersion of wastewater discharges from offshore outlets review. Environ Rev 19:107–120. doi:10.1139/A10-025 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Institut des Sciences de l’EnvironnementUniversité du Québec à MontréalMontrealCanada
  2. 2.Department of Building, Civil and Environmental EngineeringConcordia UniversityMontrealCanada

Personalised recommendations