Death by a thousand cuts: Small local dams can produce large regional impacts in the Brazilian Legal Amazon

Abstract

In the Amazon Basin, large-scale problems, such as deforestation, over-fishing, climate change and large hydroelectric dams, are now recognized. However, many small-scale activities could exert significant cumulative, negative environmental impacts. We conducted a spatial analysis of small-scale dams used for hydropower and aquaculture in the central and southwestern portions of the Brazilian Amazon Basin. We found a very high density of small dams in these areas, and suggest that these dams, in the aggregate, are in fact pernicious because they are likely to have large impacts on the aquatic environment of these sub-basins in the Amazon. We recommend increasing the size and number of protected areas where dams are not allowed, and restricting the number of licenses for dams in order to reduce future intensification of their impacts.