Geography and the Restoration of Rivers for Wildlife

July 10, 2003

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Since its establishment in 1973, the Endangered Species Act (ESA) has assumed a gradually increasing importance in environmental management in the United States. The effect of the Act is especially significant in matters related to water management in rivers. This brief article addresses the following questions: why has ESA become so important in water and river matters? And what is the role of geographic technology and knowledge in addressing these issues? The article concludes with two case examples where restoration is underway in attempts to reverse the loss of wildlife.

The ESA has become so important in river management that it virtually trumps all other legal constructs for water and river management. This situation has developed because the ESA mandates that any project with federal interests must take into account the potential for negatively impacting specific species that are listed as endangered under the precepts of the Act. Because most management activities on rivers include manipulating the flow of the streams, and because almost all streams of consequence are "Waters of the United States" which are of concern to the federal government, consideration of the Act is a widespread fact of life for river managers. Changes to flows through water diversions, storage systems, dams, use of engineering works on channel margins and flood plains inevitably have effects on wildlife populations that have evolved in concert with natural conditions that are now altered. The riparian forests that once lined many rivers have shrunk, or disappeared altogether, jeopardizing plant species, mammals, reptiles, and birds that depended on the forests. The flow changes also affect aquatic habitats that hosted everything from aquatic plants to mussels and fish. The ESA comes into play in all those cases where such species have been declared endangered (in danger of becoming extinct) or threatened (a less severe concern than endangered), regardless of the consequences for holders of water rights or concerns of those who have invested in the river control works.The ESA considerations are superior to other considerations such as interstate compacts and water delivery contracts. For a review of the ESA, visit

The importance of water management to endangered species in general is obvious when we consider all the listed species and the primary causes of the impairment of their populations. In most cases, individual plants or animals are not at issue, but rather water management alters the habitats of wildlife populations so that they can no longer survive. The short-nosed sturgeon and American eel, for example, migrated upstream through East coast rivers for part of their reproductive cycle, but the construction of dams has blocked these migrations, and the populations of sturgeons and eels have plummeted. This is a story familiar to West coast river managers who have seen similar declines in several salmon species for similar reasons. Of the almost 800 ESA listed species examined in a recent study (Losos et al., BioScience 45[1995]:446-455), about one third were negatively affected by water development efforts (more than any other major activity such as livestock grazing, mining, logging, or recreation).

Thus, the answer to the question why has ESA become so important in water and river matters is three-fold: first the Act concerns all rivers in the United States, second it sometimes overrides other laws and rights, and finally rivers are integral components of the habitats used by many wild species yet these habitats are also greatly affected by economic and technological development.

The role of geographic technology is pivotal in assessing and managing populations of endangered species. By their nature and circumstance, endangered wildlife species have populations with small numbers, so that in many cases it is possible to map the location and movements of all individuals or nesting pairs of a particular species. For example, it is likely that there are about 1,000 nesting pairs of the southwestern willow flycatcher, an endangered riparian bird. With global positioning systems, field investigators have specified the locations of each of the nesting sites for the species, so that it is now possible to produce a map showing the population distribution. Such an all-encompassing picutre supplies a uniquely valuable view of the connection between nesting sites and the rivers, lakes, and reservoirs upon which the birds depend for food sources. Spatial analysis of these data show that some water courses are important for the bird, while other water bodies nearby are not. For more on the southwestern willow flycatcher, visit and link to several useful sites.

Geographic knowledge and methods are essential in interpreting the stressors on endangered species and in designing strategies for restoration of the endangered populations. The individual endangered species have particular geographies that in turn are responses to the geographies of natural and societal limitations. Human demands on land and water for economic development determine which habitats will be affected most through habitat change. Geographical analysis of these connections depends on regional approaches, definition of flows (for example, of water, species, or nutrients), and the explanation of spatial arrangements (patterns, arrangements, or networks).

Two examples illustrate the geographic aspects of river restoration for wildlife: the Colorado River in Grand Canyon and the Everglades of South Florida. Glen Canyon Dam, completed in 1963, has altered and controlled the flow of the Colorado River through Grand Canyon. The dam impounds sediment that previously sluiced through the canyon and replenished beaches after erosion losses. Dam operations suppressed flood peaks, resulted in lowered water temperatures, and introduced artificial rhythms in daily, monthly, and annual flow fluctuations. Native fishes such as the hump-back chub, razorback sucker, and the Colorado pikeminnow evolved in tune with warm, sediment-rich waters and large annual floods. Accurate mapping of aquatic habitats and spatial analysis of sediment flows are key geographic components of restoration efforts by the operators of the dam, the U.S.Bureau of Reclamation. For more on the Colorado River, Glen Canyon Dam, and the Grand Canyon, visit and link several sources.

A second example of river restoration for wildlife is the Everglades of south Florida where hundreds of relatively small water control structures have dramatically altered the flow and distribution of water. The "river" is a flow zone about 100 km wide but only about a meter deep during periods of high flow, but the hydrologic issues are the same as with rivers elsewhere: reduced flow volumes along with changes in flow timing and variability. These alterations have led to reduced populations of several species, including the Cape Sable sea-side sparrow and the Florida panther.The world's most ambitious restoration project envisions an investment of more than $15 B over a 40-year period to restore more natural conditions to the Everglades. This restoration is founded on the concept of "getting the water right" in restoring the timing, quantity, and most importantly the geographic distribution of water. The regionalization of flows places spatial analysis at center stage in a landscape where local relief is measured in centimeters, and where engineering works exert overall control. From the standpoint of the endangered species, the over-riding issue is geographic space and its management through controlled flows of water. Visit for information about the Everglades and their restoration.

In summary, geographers and geographic information scientists have critical roles in critical issues related to rivers, restoration, and endangered species. Public debates about endangered species are in fact debates about geographic space that may have value as habitat or as the bases of land uses that contribute to economic well-being. The exacting description of those spaces, and extensive analyses of their operations through environmental and engineered processes are unique, significant geographic contributions to an improved relationship between nature and society.


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