Estimating the environmental costs of Africa's massive "development corridors"

Laurance et al. assess the potential environmental costs of 33 planned or progressing "development corridors" in Africa. If completed, the corridors would total over 53,000 km in length and are likely to imperil many African ecosystems. New corridors in equatorial forests and savanna woodlands are projected to have the greatest environmental costs.\ud \ud In sub-Saharan Africa, dozens of major "development corridors" have been proposed or are being created to increase agricultural production [1, 2, 3 and 4], mineral exports [5, 6 and 7], and economic integration. The corridors involve large-scale expansion of infrastructure such as roads, railroads, pipelines, and port facilities and will open up extensive areas of land to new environmental pressures [1, 4 and 8]. We assessed the potential environmental impacts of 33 planned or existing corridors that, if completed, would total over 53,000 km in length and crisscross much of the African continent. We mapped each corridor and estimated human occupancy (using the distribution of persistent night-lights) and environmental values (endangered and endemic vertebrates, plant diversity, critical habitats, carbon storage, and climate-regulation services) inside a 50-km-wide band overlaid onto each corridor. We also assessed the potential for each corridor to facilitate increases in agricultural production. The corridors varied considerably in their environmental values, and many were only sparsely populated. Because of marginal soils or climates, some corridors appear to have only modest agricultural potential. Collectively, the corridors would bisect over 400 existing protected areas and could degrade a further ∼1,800 by promoting habitat disruption near or inside the reserves. We conclude that many of the development corridors will promote serious and largely irreversible environmental changes and should proceed only if rigorous mitigation and protection measures can be employed. Some planned corridors with high environmental values and limited agricultural benefits should possibly be cancelled altogether