Freshwater species are sometimes considered an afterthought in conservation planning, which typically prioritizes terrestrial ecosystems and their inhabitants. But protection of tropical freshwater ecosystems can be vastly improved without undermining terrestrial conservation goals, according to a new study, by integrating the needs of aquatic species into traditionally terrestrial-focused conservation planning. Although freshwater ecosystems comprise less than one percent of Earth's surface, they host nearly 10% of all known species, including a third of all vertebrates. They are also among the most threatened ecosystems - suffering declines at nearly twice the rate of terrestrial or marine ecosystems. But despite their essential nature in preserving global biodiversity, freshwater species are often considered an afterthought in conservation planning. The designs of protected areas and conservation strategies overwhelmingly prioritize terrestrial ecosystems and species and generally assume that any freshwater systems they contain will also benefit by extension. Using data for more than 1,500 terrestrial and freshwater species in the Amazon, Cecília Leal and colleagues simulated conservation across the two realms and found that such assumptions are, in fact, far from accurate. According to the study's findings, terrestrially focused conservation planning provided an average of just 22% of the freshwater benefits that would be achieved through freshwater-focused conservation planning. However, Leal et al. found that by using an integrated terrestrial-freshwater approach, the protection of freshwater species could be increased by up to 600% with only a 1% reduction in protection for terrestrial species. Even in tropical areas lacking detailed freshwater biodiversity data - as is often the case - protections could still be doubled using a combined terrestrial-freshwater approach. "There are always trade-offs associated with any prioritization, but the study by Leal et al., combined with complementary analyses of the multiple benefits of healthy freshwaters and their watersheds, suggests that those trade-offs may be more acceptable than we think," write Robin Abell and Ian Harrison in a related Perspective.