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The role of tropical forests in supporting biodiversity and hydrological integrity: a synoptic overview

By Ellen M. Douglas, Kate Sebastian, Charles J. Vorosmarty, Stanley Wood and Kenneth M. Chomitz


Conservation of high-biodiversity tropical forests is sometimes justified on the basis of assumed hydrological benefits - in particular, the reduction of flooding hazards for downstream floodplain populations. However, the"far-field"link between deforestation and distant flooding has been difficult to demonstrate empirically. This simulation study assesses the relationship between forest cover and hydrology for all river basins intersecting the world's tropical forest biomes. The study develops a consistent set of pan-tropical land cover maps gridded at one-half degree latitude and longitude. It integrates these data with existing global biogeophysical data. The study applies the Water Balance Model - a coarse-scale process-based hydrological model - to assess the impact of land cover changes on runoff. It quantifies the impacts of forest conversion on biodiversity and hydrology for two scenarios - historical forest conversion and the potential future conversion of the most threatened remaining tropical forests. A worst-case scenario of complete conversion of the most threatened of the remaining forested areas would mean the loss of another three million km2 of tropical forests. Increased annual yield from the conversion of threatened tropical forests would be less than 5 percent of contemporary yield in aggregate. However, about 100 million people - 80 million of them in floodplains - would experience increases of more than 25 percent in annual water flows. This might be associated with commensurate increases in peak flows, though further analysis would be necessary to gauge the impact on flooding. The study highlights basins in Southeast Asia, southern China, and Latin America that warrant further study.Wetlands,Forestry,Climate Change,Drylands&Desertification,Earth Sciences&GIS

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  1. (1995). Agriculture Organization of the United Nations (FAO).
  2. (1980). Conversion of Tropical Moist Forests. National Research Council,
  3. (2001). Cover Characteristics Database (GLCCD).
  4. (2003). Description available at http://www.unep-wcmc.org/protected_areas/. Data made available through the Millennium Ecosystem Assessment Intranet
  5. Development of a Global Land Cover Characteristics Database and IGBP DISCover from 1 km
  6. (1991). eds.,
  7. (2003). Effects of large-scale changes in land cover on the discharge of the Tocantins River, Southeastern Amazonia.
  8. (1996). Effects of slash-and-burn agriculture and deforestation on climate change,
  9. (1988). Effects of tropical forest on water yield, in Forest, Climate, and Hydrology: Regional Impacts,
  10. (1965). Evaporation and environment. In: The State and Movement of Water in Living Organisms.
  11. (2003). Food and Agriculture Organization of the United Nations, Statistical Databases. Online at: http://apps.fao.org.
  12. (2002). Global Agricultural Extent v2.0. Available online at:
  13. (2000). Global Soil Data Products CD-ROM (IGBP-DIS).
  14. (2002). High-resolution fields of global runoff combining observed river discharge and simulated water balances,
  15. (2004). Hydrological functions of tropical forests: not seeing the soil for the trees? Agriculture, Ecosystems and the Environment,
  16. (2002). Hydrology of altered tropical forest,
  17. (1996). Intercomparison of methods for calculating potential evaporation in regional and global water balance models,
  18. (1989). Keeping Options Alive: the Scientific Basis for Conserving Biodiversity.
  19. (2000). Pilot Analysis of Global Ecosystems: Agroecosystems. World Resources Institute/International Food Policy Research Institute.
  20. (2004). Policy analysis and environmental problems at different scales: asking the right questions.
  21. (1998). Possible impacts of climate variability and change on tropical forest hydrology.
  22. (1998). Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling,
  23. (1996). Predicting the hydrological impacts of land cover transformation in the humid tropics: the need for more research,
  24. (2002). Predictors of deforestation in the Brazilian Amazon,
  25. (1993). Recent scientific developments and research needs in hydrological processes,
  26. (1998). Representing twentieth century space-time climate variability, Part II: Development of 1901-1996 monthly grids,
  27. (2001). Scaling gridded river networks for macroscale hydrology: Development, analysis, and control of error.
  28. (2003). Sensitivity of annual evaporation to soil and root properties in two models of contrasting complexity,
  29. (2005). Synthesis of Rapid Land Cover Change: An assessment for the Millennium Ecosystem Assessment – draft version. Full report forthcoming.
  30. (2004). Technical Report For Activity 2: Landscape and (Sub) Catchment Scale Modeling of Effects of Forest
  31. (1999). Terrestrial Ecoregions of North America: A Conservation Assessment,
  32. (2000). Terrestrial Ecoregions of the Indo-Pacific: A Conservation Assessment.
  33. (1999). The Blue Revolution.
  34. (1998). The domestic benefits of tropical forests: a critical review, The World Bank Research Observer,
  35. (2001). The economics of tropical deforestation.
  36. (2001). Timber trade restrictions and tropical deforestation: a forest mining approach.
  37. (2000). Tropical Ecosystems and Ecological Concepts. Cambridge U.P.,
  38. (1998). Tropical forests in the future climate: changes in biological diversity and impact on the global carbon cycle.,
  39. (2003). World Agriculture towards 2015/2030. Rome: Food and Agriculture Organization.

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