Dolphins are one of the world’s most charismatic creatures, beloved by many for their playful nature. And among the many dolphins that cavort in the world’s oceans, a small handful of them have adapted to thrive in some of the world’s greatest rivers, becoming integral parts of people's lives. For instance:

• The Irrawaddy dolphin, found in the Mekong River, has helped local villagers corral fish into nets, even communicating vocally as they did so.
• And in the mighty Amazon River, locals adore the distinct pink color of their dolphin, the boto.

It was with heavy hearts, therefore, a group of scientists recently declared one such species — the baiji of eastern China's Yangtze River — extinct.

“We have lost the race. The Baiji has gone,” announced August Pfluger, the CEO of the Baiji.org Foundation, in late December 2006. The announcement ended a six-week-long expedition that scoured a 1,000-mile-long section of the Yangtze to search for the rare dolphin.

Pollution is a factor in the decline of large freshwater species such as the baiji. But even more important are the changes humans are making to riparian ecosystems through dams and diversions.

Big Rivers, Big Fish…Big Threats

Other big creatures share the water of many of the world’s great rivers. Sharing the Yangtze waters with the baiji is a prehistoric giant: the Chinese paddlefish, the nation’s largest freshwater fish.  Its cousin — the American paddlefish — thrives in the waters of the Mississippi.

It is the immensity, the sheer scale, of these great rivers that allow not only these big fish to thrive, but also the myriad birds, plants and mammals who call rivers home. The American paddlefish roams up to 230 miles through the river and its tributaries. One fish, tagged on the Arkansas River in Oklahoma, later was recaptured in the Tennessee River.

But both species of paddlefish are in a fight for survival. In America, paddlefish have disappeared from four states and Canada. They are also considered endangered, threatened or a species of special concern in 11 of the 22 states where they remain.

Indeed, scientists caution that we are the in midst of a downward spiral for freshwater wildlife, with about 20 percent of the world’s 10,000 known freshwater fish species now endangered, threatened or already extinct.

The risks to biodiversity are enormous: About 12 percent of the animals known to science live in Earth’s freshwater habitats, and many more depend on them for survival.

The Human Factor

Although pollution is partly to blame, it is not the biggest reason for this worldwide decline. Instead, the changes humans have made to rivers and their connected freshwater habitats — such as backwater wetlands — are the culprits.

The American paddlefish, for example, depends on a variety of habitats through every stage of its life, from its birth in gravel beds of small river tributaries to its adulthood in the main channels of rivers, where it continues to feed off zooplankton coming from the same backwaters in which it was born.

We’ve severed the delicate connection that sustains these freshwater habitats, partly through river modifications that cut off the Mississippi River from its floodplain, where backwater wetlands, lakes and sloughs interact with the river.

Threats to Freshwater Species Threaten Us, Too

The media have chronicled the problems with freshwater species — from the great salmon runs in the American northwest to the plight of the shortnose sturgeon in the east. Less reported, however, is how these changes affect humans.

The world’s great rivers and their interconnect habitats provide an array of ecological services that support us. They purify water, control floods and provide abundant food sources. But our changes to river systems are causing more people to experience poor water quality, scarcity of water, increased flooding and low levels of native fishes and birds for food. 

A growing group of experts — from biologists to economists — are coming to understand the critical link between the health of the world’s precious freshwater resources and the people who depend on them.

It is precisely because the nexus between people and fresh water is inescapable that The Nature Conservancy has made working with communities an important part of its freshwater conservation.

From the Sustainable Waters Program to the Great Rivers Partnership — two Conservancy initiatives focused on river conservation at a global scale — new land and water management strategies are being designed and tools are developed, which together are giving birth to new policies and practices for the world’s great rivers.

These programs are helping to ensure that great river diversity and human communities continue to thrive side-by-side. Their work is bolstered by the countless freshwater conservation projects taking place throughout the world, from the American Midwest’s Mackinaw River in Illinois to Africa’s Zambezi River.

Nature picture credits (top to bottom, left to right): Photo © Dou Weiyang (Yangtze River); © Mark Godfrey/TNC (Capybara); ©  Mark Godfrey/TNC (Mississippi River)