We can learn a lot about the health of freshwater habitats overall by studying the animals that live in them. If freshwater animals are on the decline, that’s a sign that the entire ecosystem is in trouble. Freshwater habitats face a host of threats, including increases in the amount of water we take from them; drainage of wetlands; pollution from industry, sewage and farms; invasive plant and animal species; climate change; and infrastructure development in and along waterways. Perhaps the most urgent threat to freshwater animals and their homes is the dams, bridges, roads, and other infrastructure that interfere with the natural flow and connectivity of rivers. Many freshwater fish, for example, rely on free-flowing rivers to eat, reproduce, and access nutrients necessary for their survival.

Connected rivers help people, too. Free-flowing rivers move sediment to floodplains and deltas downstream, providing nutrients and soil for floodplain agriculture, allowing for healthy fisheries, and supporting the resilience of delta habitats under a changing climate.

Keeping rivers connected and flowing

There are currently nearly 60,000 large dams on rivers around the world and over 3,700 more hydro dams—structures that give us energy from the flow of water—are planned globally. While hydropower plays an important role in today’s renewable energy revolution, it must be carefully planned so as to minimize loss of river health. This means considering the health of an entire river basin to find energy opportunities with the least amount of impact on the environment and people. Into the future, the dropping prices of wind and solar power, along with innovations in the ability to store power, provide the possibility for countries to meet energy demands with less hydropower and therefore fewer dams.