Water canals may promote large-scale defaunation of the Gran Chaco

Abstract

In the Gran Chaco, one of the most biodiverse, yet imperiled, arid biomes in the world, open-to-air concrete water canals may threaten wildlife via drowning and habitat fragmentation, although these effects are usually overlooked. We performed field surveys and local people interviews along 250 km of canals in the Gran Chaco ecoregion of Argentina during austral spring and summer (six months). We documented 207 drowned individuals of 35 wildlife species, but more realistic estimations could increase this number to the thousands. Six species of conservation concern drowned in the canal, and eight of the drowned species have decreasing population trends. Drownings in some mammal species decreased with time without any mitigation measures implemented at the canal yet, suggesting an ongoing, large-scale population reduction due to this high mortality rate. Since mitigation measures applied in other regions were not effective to stop drowning and population isolation, these infrastructures should be avoided in arid environments worldwide.