Introduction/Background/Justification: Expanding human populations, increasing energy demands, and a shift towards low-emissions energy sources have together triggered a rapid rise in hydropower. Much of the expansion of this industry has occurred in developing nations, where hydropower now represents a key driver of habitat loss in tropical forests. Threatened species and entire ecological communities may be imperiled by the growth of hydropower. At the same time, research in hydropower reservoirs has advanced our understanding of fragmentation science, providing insights which can help predict consequences of fragmentation in terrestrial landscapes.

Objective(s)/hypothesis(es): There are two objectives: (1) to quantify the extent to which hydropower has and will continue to drive threatened species towards extinction, and (2) to assess the contributions of studies based in hydropower reservoirs and the extent to which they have advanced our understanding of fragmentation. For the former, we selected tigers and jaguars as focal species.

Methods: We compiled information on existing and planned hydropower dams intersecting the current distribution of tigers and jaguars. We then matched the reservoir footprint with published estimates of species densities for tigers/jaguars. We also reviewed studies from hydropower reservoirs and their insights into fragmentation science.

Results: We identified 164 existing dams overlapping the current range of jaguars and 421 dams intersecting the distributions of tigers. In total, these reservoirs covered 25,397 km2 in the Neotropics and 13,750 km2 in the Paleotropics. This habitat loss potentially accounts for the loss of 915 individual jaguars (0.53% of the total population) and 729 individual tigers (20.8-22.8% of the total population). Looking forward, we identified 429 dams planned within the distribution of jaguars and 41 within the distribution of tigers.

Implications/Conclusions: Our findings suggest that hydropower has already become an important driver of population decline for tigers, and will likely become the same for jaguars in the decades ahead given rampant hydropower development in the Neotropics. However, this energy source has also become vital towards electricity generation in many tropical countries (e.g., >70% for Brazil, which sustains more than half of the global jaguar population). At the same time, hydropower reservoirs have offered insights into fragmentation science, spanning topics including (1) ecosystem disassembly, (2) extinction debt, and (3) evolution. Existing hydropower study sites should remain a key focus for research to provide further insights into the consequences of fragmentation, but the expansion of this industry should be curtailed to avoid further threats to apex predators and tropical forest ecosystems.