Global assessment of alien freshwater megafauna reveals complex socio-economic impacts

Freshwater megafauna are frequently introduced to new ecosystems for their perceived economic benefits. Meanwhile, these large alien animals can have unintended negative impacts on these ecosystems and the people who depend on them. However, socio-economic impacts of alien freshwater megafauna have not been systematically assessed at a global scale. Here, we integrate a novel scoring system with the nature's contributions to people framework to quantify by magnitude and categorize by type the detrimental and beneficial impacts of alien freshwater megafauna on people. Benefits include commercial opportunities such as sport fishing or aquaculture; detriments include ecosystem changes undermining people's livelihoods and health. Some detrimental effects were indirect and hence difficult to identify, suggesting that they may be underreported. Since introductions of freshwater megafauna are likely to continue due to their economic benefits, we call for risk assessments and communication of potential consequences for people reliant on freshwater ecosystems.