In the Hudson Valley, a great wildlife migration is taking place out of sight. River herring, striped bass, American shad, Atlantic sturgeon, American eel, and many other species enter the Hudson every year to spawn. Baby eels the size of sewing needles travel 1,800 miles from their birthplace, the Sargasso Sea, to mature in the fresh waters of the Hudson’s tributaries.

These critical species are under threat. Overharvest, habitat alteration, and contamination have all led to a decline in the populations of many animals that call the Hudson River estuary home. But we have an opportunity to both prevent this decline and help restore the health of our ecosystems.

More than 2,000 dams, most of them obsolete and long-forgotten, fragment the rivers and streams of the Hudson Valley. Dams disconnect aquatic ecosystems — blocking natural flows and drainage patterns, the mobility of fishes and other aquatic organisms, the gene flow of isolated populations of aquatic organisms, as well as keeping vital nutrients and sediments from reaching the estuary. Dams also alter the thermal and chemical properties of waterways while causing physical scouring of in-stream habitat and streambanks.

Removing these dams is crucial to restoring the biotic potential of the Hudson River by reconnecting critical spawning and nursery habitat for aquatic migratory species.

The vast majority of dams in the Hudson Valley are old mill dams that do little to alleviate flooding. In fact, many dams actually heighten the intensity of flooding. As climate change alters rainfall patterns and increases the risk of major flooding events in New York state, it is even more important that we keep our rivers and tributaries healthy, resilient, and free flowing.

Recent research has shown that, in addition to damaging ecosystems, dams increase emission of harmful greenhouse gasses into the atmosphere. Sediments trapped behind dams typically include high levels of organic matter which break down over time, releasing both carbon dioxide and methane into the atmosphere. Impoundments and reservoirs artificially created by dams are also hotspots for Harmful Algal Blooms (HABs), which release toxins and emit methane — a powerful greenhouse gas that is 80 times more potent than carbon dioxide.