Conservation initiatives overwhelmingly focus on terrestrial biodiversity, and little is known about the freshwater co-benefits of terrestrial conservation actions. The authors of this article sampled more than 1500 terrestrial and freshwater species in the Amazon and simulated conservation for species from both realms.

Prioritizations based on terrestrial species yielded on average just 22% of the freshwater benefits achieved through freshwater-focused conservation. However, by using integrated cross-realm planning, freshwater benefits could be increased by up to 600% for a 1% reduction in terrestrial benefits.

Where freshwater biodiversity data are unavailable but aquatic connectivity is accounted for, freshwater benefits could still be doubled for negligible losses of terrestrial coverage. Conservation actions are urgently needed to improve the status of freshwater species globally. The authors’ results suggest that such gains can be achieved without compromising terrestrial conservation goals.