The Role of Tropical Forests in Supporting Biodiversity and Hydrological Integrity : A Synoptic Overview

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 k