Free-flowing rivers are the lifeblood of wild landscapes, providing habitat and food to myriad aquatic and terrestrial plant and animal species. Rivers are also the source of more than two-thirds of the drinking water in the United States, yet fewer than 1 percent of those waterways fall under federal or state protection. In addition, the ecological health of many rivers has been disrupted by dams and diversions to support irrigated agriculture, power generation, flood control, and transportation. Protecting rivers that are still ecologically intact, and reestablishing the natural flow of others, may prove to be two of the most important things we can do to help protect our planet. Here are five reasons why.

Washington state’s Hamma Hamma River is one of the Olympic Peninsula’s 19 free-flowing rivers that would be safeguarded by the Wild Olympics Wilderness and Wild and Scenic Rivers Act. Local communities depend on these rivers and tributaries for their drinking water. Douglas Scott

1. Sources of clean drinking water

Nothing is more vital for human health than clean water, and the condition of rivers directly affects the quality of the drinking water they provide. Healthy rivers help ensure safe drinking water. In addition, water sourced from clean rivers requires less filtration—and lower costs to communities—than does water from polluted rivers.

A northern red-legged frog moves through frogspawn in the North Umpqua River in Oregon. Paul Colangelo/iLCP

2. Reservoirs of wildlife and biodiversity

Riparian areas—those lands and waters within rivers corridors—are some of the most diverse, dynamic, and complex habitats on Earth, according to research published by the Ecological Society of America. These zones are critical for the survival of many wildlife species, especially in the American West, and facilitate increased biodiversity. According to a report published by the U.S. Department of Agriculture, although riparian habitat makes up less than 1 percent of the land in the Western states, it plays a vital role. That research found that 80 percent of terrestrial wildlife in New Mexico and Arizona uses riparian areas during their lives, and that more than 75 percent of terrestrial wildlife in southeastern Oregon and southeastern Wyoming is “dependent upon riparian area for at least a portion of their life cycle.”

Rafters on the Rogue River in Oregon. Outdoor recreation is an economic engine for local communities. Rolf Skar

3. Fuel for the recreational economy

Free-flowing rivers are a recreational haven for boaters, fishermen, swimmers, campers, and other outdoor enthusiasts. An Outdoor Industry Association economic report found that outdoor recreation accounts for nearly $887 billion in direct consumer spending in the U.S. annually, about $140 billion of which is spent on watersports, including kayaking, stand-up paddling, rafting, canoeing, and motorized boating. That’s the third-highest revenue stream identified in the report. The bottom line: Free-flowing rivers boost the economic vitality of rural and urban communities.

Alaska’s Anvik River flows into the Yukon River, the spawning grounds for much of the world’s chum salmon and a vital source of food for local communities. David W. Shaw

4. Sites of cultural significance

Rivers have always played central roles in American culture and history, from George Washington crossing the Delaware and the fictional Tom Sawyer coming of age on the Mississippi to Lewis and Clark’s exploration of the Missouri and Columbia. For many Native Americans, rivers held spiritual significance and served as critical transportation corridors, gathering spots, trading posts, and sources of food. In fact, in the 19th century, some tribes signed treaties with the U.S. government ceding their rights to much of the land in present-day Oregon, Washington, and Idaho in exchange for continued access to salmon fishing on rivers. The U.S. government has an obligation to work for a healthy future for those salmon, and the rivers they call home, both to meet the treaty obligations and for future generations.

The 51-year-old Oroville Dam in California sustained serious damage to its main and emergency spillways in 2017, forcing the evacuation of more than 180,000 residents downstream. Paul Hames

5. Barriers to flood damage

Preventing rivers from functioning as intended through development, including the construction of dams and culverts, can have severe consequences during floods. Dams often disconnect rivers from critical floodplains, lessening how much floodwater an area can safely absorb. And where dams lack the capacity to deal with major floods, river water can accumulate behind the dam and flood nearby lands and communities. In addition, many dams in the U.S. are outdated, posing a significant risk to those who live nearby. Failures in 2017 at Northern California’s Oroville Dam and Puerto Rico’s 90-year-old Guajataca Dam exacerbated storm flooding and forced the evacuation of tens of thousands of people. Of the more than 87,500 dams in this nation, greater than one-third are older than 50 years—the average expected lifespan of a dam—and in need of repair. The federal government has labeled more than 15,500 dams as “high hazard,” meaning that their failure would cause fatalities. More than 2,000 of those were also rated structurally “deficient,” meaning that they were at serious risk of failure.

Nicole Cordan oversees Pew’s U.S. river corridor protection work and leads the team’s efforts to restore free-flowing rivers in the West to allow safe passage for salmon and other aquatic species.