Amazon Freshwater Ecosystems: Under Threat

colossoma

Colossoma

The Amazon Basin is a fecund region containing more than 50% of the world’s remaining rainforests, the largest and most diverse section of tropical forest, and the world’s largest river by discharge, expelling as much as the seven next largest rivers combined. The Amazon region encompasses more than 2.2 million square miles, and the territories belong to 9 nations, with a population of approximately 20 million, including 400 different indigenous groups. It is also home to 2.5 million insect species and 2,000 bird and mammal species; one in five of all fish species in the world lives in the Amazon.

Despite terrestrial protections that are high by global standards, in a recent study, WHRC Research Associate Leandro Castello has identified key gaps in protection of the region’s freshwater systems and species.

Damage to Amazon freshwater ecosystems greatly impacts Amazonians, who have historically been so dependent on freshwater ecosystem goods and services that they have been called “water peoples”. Current per capita fish consumption in the Brazilian Amazon averages 94 kg/yr in riverine populations, which is almost six times the world average. Increasing fishing pressure has shrunk the size of harvested species, partly due to the progressive depletion of high-value, large-bodied species. A century ago, the mean maximum body length of the main species harvested in the basin was ~206 cm; today it is ~79 cm.

Three decades of effort have generated an understanding of some key biophysical transitions in the basin and have established a network of protected areas, largely designed to preserve forests and their biodiversity. Little attention has been paid to freshwater ecosystems, which through the hydrological cycle are interconnected to other ecosystems at local and distant locations, being highly sensitive to a broad array of human impacts. Oil exploration, deforestation and dams in its headwaters, for example, threaten the Madeira River basin, even though protected areas cover 26% of the catchment area.

Adequate protection of Amazon freshwater ecosystems requires broadening the forest-centric focus of prevailing environmental management and conservation strategies to encompass aquatic ecosystems. By building upon existing protected areas, it is possible to develop a river catchment-based conservation framework that protects both aquatic and terrestrial ecosystems, effectively protecting the Amazon river-forest system.

Castello, L., D.G. McGrath, L.L. Hess, M.T. Coe, P.A. Lefebvre, P. Petry, M.N. Macedo, V.F. Renó, and C.C. Arantes. 2013. The vulnerability of Amazon freshwater ecosystems. Conservation Letters. doi:10.1111/conl.12008