Wetland Drainage: Page 1 Endangered Species Handbook

Aquatic Ecosystems

Wetland Drainage: Page 1

South America's Pantanal, the world's largest wetland, is a vast network of tree-lined rivers, lakes, marshes, savannahs, palm groves and hillocks in southwestern Brazil, neighboring Paraguay and Bolivia (Simon 1995). Estimates of its size vary widely. Some are apparently based on the entire floodplain, and others on the wetland's size during the dry season. They range from 39,000 square miles (Dugan 1993) to 77,200 square miles, the size of South Dakota (Eckstrom 1996). By any definition, it is an immense region, having one of the most distinctive mosaics of vegetation and richest wildlife diversity in Latin America (Dugan 1993).^* It is highly endangered by water diversion and drainage programs.

The Pantanal forms the upper waters of the Paraguay River system and is fed by the Cuiaba, Taquari and Miranda Rivers (Eckstrom 1996). During the rainy season, from December to June, the Pantanal drains the entire center of southern South America, fed by runoff from Bolivian highlands and the sources of the Paraguay River, forming a vast, shallow lake 7 feet deep with islands of vegetation (Eckstrom 1996). Amazonian fauna and flora meet with those of southern Chaco grasslands and pampas, creating a center of diversity: 3,500 plant species, 102 mammal species, 652 bird species, 177 reptile species, 40 amphibian species, at least 264 fish species and 1,132 butterfly species are native (EI 2001, Schemo 1996b). This huge wilderness is of vital importance to a host of animals that have disappeared from other parts of their ranges. They are threatened by the presence of 8 million cattle and the cattle management, which includes introduction of non-native grasses and clearing forest land monkeys and other terrestrial animals require (EI 2001). A new ecotourism industry is gaining ground in the Pantanal, and is bringing in funds to the region at a time when its natural treasures are most at risk (Schemo 1997).

Marsh deer (Blastocerus dichotomus) are South America's largest deer. They are superbly adapted to living in marshes and wet savannah. Their long, coarse coats repel water, and broad, webbed hooves prevent them from sinking into soft ground (Nowak 1999). Leaping over high grass, these deer move swiftly in this watery environment, using the hillocks and islands of vegetation to rest and have their young. Marsh deer formerly lived in the marshes along the Rio Parana and Rio Paraguay and perhaps as far north as the Amazon River (Nowak 1999). They are gone from Uruguay and have become very rare in Argentina, Bolivia, Peru and Paraguay (Nowak 1999). The Pantanal provides a last retreat for an estimated 7,000 deer, but even here they are declining (Nowak 1999). The species is listed as endangered in the Endangered Species Act, and as vulnerable on the 2000 IUCN Red List. The estimated five million cattle who graze in the Pantanal (Eckstrom 1996) compete with these deer for habitat and forage. Moreover, cattle have spread brucellosis, which causes reproductive failure, to the deer (Nowak 1999, Thornback and Jenkins 1982). Cattle ranchers have persecuted these deer, and hunting, especially when these deer become stranded on islands during flooding, is another cause of decline (Nowak 1999, Thornback and Jenkins 1982). Dams and drainage for agriculture in the Parana River Delta on Brazil's coast have destroyed much of the once vast marshes there (Thornback and Jenkins 1982).

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^*A film that gives an excellent environmental and wildlife portrait of this wetland, “Pantanal: Prairie of the Great Waters,” was made in 1986 (see Video, Regional, Latin America). It features many of the endangered species described here, along with views of the Pantanal in rainy and dry seasons. A book by Vic Banks (1991), The Pantanal: Brazil's Forgotten Wilderness, from the Sierra Club, also gives an overview.

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The vast Pantanal is also the most important habitat for the engaging and highly endangered giant otter (Pteroneura brasiliensis), which is extinct in most of Brazil and absent from all the larger tributaries of the Amazon (Simon 1995). Killing for otter pelts has been a major factor their decline, and loss of prime habitat is another cause. Degradation of river banks needed for dens by illegal gold miners and cattle, deforestation that affects the water quality and fish with sedimentation and other changes to this wetland have resulted in declines in Giant Otter populations. These otters live in large family groups of up to 20 individuals and require large, high-quality ranges. They are among the noisiest of otter species, uttering a variety of squeals and screams to communicate with one another in the often murky water. This has attracted hunters, who have killed off families and eliminated the species in entire river systems. These otters depend on help from one another, such as loud warning calls about the presence of their major predator, caiman. Their fur is still valuable, although illegal in virtually every market in South America and elsewhere in the world (Nowak 1999).

South America's largest tropical mammal, the South American Tapir (Tapirus terrestris), is also native to the Pantanal. Young tapirs have striking white horizontal stripes and spots, which fade into a solid gray as they grow older. Tapirs find the wetlands and abundant vegetation of the Pantanal to be an ideal habitat, and they can be seen swimming in the ponds and bywaters with only their snouts above the water. Like the other three tapir species, the South American tapir has declined throughout its range from hunting and habitat destruction. The IUCN classifies it as near-threatened, and it is listed on the Endangered Species Act.

The Pantanal shelters the largest jaguar population (Panthera onca), a threatened species heavily hunted for its pelt and as a trophy. Even in the Pantanal, it was poached until recently, when anti-poaching programs and the Convention on International Trade in Endangered Species (CITES) ban on the sale of spotted cats destroyed the market for pelts and trophies. In this wilderness, jaguars prey on capybara, the world's largest rodent, various deer species and occasionally, domestic cattle. Once heavily persecuted by cattle ranchers, a growing number of cattle ranchers have opened their ranches to ecotourists and now protect jaguars as a prime attraction (Schemo 1997). If there were fewer cattle in the Pantanal, marsh deer, South American tapir and other large mammals would increase, creating a more balanced ecosystem with the jaguar as major predator. This may happen in the future, as the cattle industry is no longer as profitable as it once was (Schemo 1997).

The greatest concentration of water birds in Latin America resides in the Pantanal (Dugan 1993). The jabiru (Jabiru mycteria), a large and rare stork, is numerous here, building its great stick nests apart from other water birds. A colony of wood storks (Mycteria americana), a species that is endangered in Florida, may total 20,000 birds in the Pantanal. Egrets, herons and Roseate Spoonbills are abundant. Migrants on their way from southern South America to North America, such as the Arctic Tern (Sterna paradisaea), use the Pantanal as an important stopover place (Simon 1995), and three major flyways pass through it (Eckstrom 1996). Snail kites (Rostrhamus sociabilis), on the verge of extinction in the Everglades, are abundant here, feeding on the huge apple snails common in the Pantanal. This wetland's palm groves are an important food source and refuge for the largest parrot in the world, the magnificent and endangered blue-violet hyacinth macaw (Anodorhynchus hyacinthinus) (Sick 1993).

A zoologically important fish species that has been on Earth for 300 million years is also resident in the Pantanal. The South American lungfish (Lepidosiren paradoxa) is a member of a family with only six species remaining, all on other continents. Lungfish can breathe air with their single lung and are thought to be an evolutionary bridge between fish and land animals. At about 32 inches in length, this scaled, eel-like fish breathes at the surface when waters are high, and during the dry season, buries itself in the mud, breathing through a narrow tunnel leading to the surface, or entering a torpor-like state (Dorst 1967). Although not restricted to the Pantanal, this wetland provides ideal habitat for lungfish, and a large population is found here.

The Pantanal is decreasing in size as a result of drainage for agriculture, which has altered the flooding cycle (Dugan 1993). The major threat to this wetland is a 2,000-mile canal for shipping being dredged and channeled from the Paraguay-Parana Rivers, which link below the Pantanal. Five countries, Brazil, Bolivia, Paraguay, Argentina and Uruguay, border these rivers and support this massive program, known as the Hidrovia Project (Schemo 1996b). The canal is intended to open up new markets for a growing agricultural trade for soybeans and sugar, as well as mining products from western Brazil (Brooke 1995). It will extend from Caceres, Brazil to Punta del Este, Uruguay, creating an inland seaport in Bolivia; construction involves blasting through rock formations, straightening and dredging rivers and controlling tributaries to allow year-round shipping (Schemo 1996). Although originally estimated to cost $1 billion, by the time the gates of the Porto Primavera Hydro Dam on the Parana River were closed in November 1998, costs had expanded far beyond the original estimate. At least $3 billion will be required for future maintenance (Eckstrom 1996).

A critic of the Hidrovia Project pointed out that an old railway crossing the southern Pantanal already exists, and new railways could be built to Sao Paulo (Eckstrom 1996). Biologists and ecologists are extremely worried that the basic hydrology of the Pantanal is not sufficiently understood to make such major changes, and the long-term effects of Hidrovia may be totally unforeseen, ending in destroying this wilderness (Eckstrom 1996).

Ignoring the delays imposed for completion of the $10.5 million environmental studies, Paraguay began work blasting through rock on the Paraguay River north of Asuncion in June 1996. The Inter-American Development Bank contributed $7.5 million in 1991 for feasibility studies, but the studies were carried out by the same company performing the engineering work, and they did not appraise the work as a whole. The United Nations Development Programme's ecological advisor on the project, Dr. Enrique Bucher, protested this approach: "In order to understand the hydrological response of the system, you have to analyze it in its globality" (Schemo 1996b). The Hidrovia Project, may result in draining the Pantanal, according to a study by Victor Ponce of San Diego State University (Schemo 1996b, 1997). The Pantanal acts like a vast sponge, releasing rainwater gradually and year-round into the Paraguay River; the dams and drainage of wetlands will expose down-river areas to flash flooding and start drying out this vast marshland (Brooke 1995)

Pantanal wildlife has already been impacted by the Porto Primavera Dam, the first of several dams in the Hidrovia Project, which drowned 300,000 acres of floodplain, forest and grasslands. The dam builders financed "rescue" of animals as the area filled with water in late 1998, filmed for the National Geographic Explorer program ("Paradise Lost," April 28, 1999). This "rescue" was marked by extreme mistreatment of animals and a low survival rate. Black howler monkeys were knocked from tree tops by ramming the tree trunks with motorboats, causing babies to fall off their mothers' backs. Many of the monkeys had just given birth and were separated from family members. Injuries such as broken tails occurred. The monkeys were treated so roughly that they panicked and thrashed about. To subdue them, they were put in bags for transport. One monkey in a bag was hung over the side of the boat into the water, where it must have drowned during the trip to a holding area. Surviving animals were unceremoniously dumped in enclosures and cages in the holding area. Many of the monkeys, armadillos, opossums, foxes, snakes and other wildlife were crated and transported out of the area for donation to zoos and research institutes. Caiman were also captured, apparently for their hides, since they were not at risk if left in the water. Marsh deer were caught in nets dropped from helicopters, placed in a net and sent by helicopter to their permanent new home in a concrete enclosure. Many died in the process. Only a few of the animals, including some of the monkeys, were released in woodland nearby. The rescuers admitted only about 5 percent of the wildlife was "saved."

Although gold mining has been banned in the Pantanal, illegal mining is fouling the rivers with mercury and other pollutants (EI 2001). Only two small areas in the Pantanal have received official protection (Dugan 1993). The Pantanal National Park protects less than 1 percent of this wetland, covering only 550 square miles, of which 53 square miles are dry land; most of the park has been underwater for the past 20 years (Eckstrom 1996). The Taiama Ecological Station covers 43 square miles (Emory 1990). Thus, well over 90 percent of the Pantanal is privately owned, mainly by cattle ranchers. Whether it will be possible to preserve large portions of the Pantanal remains to be seen. A budding ecotourism industry has begun, but the damage may already be done. By 2010, the Pantanal may have dried out, or its hydrology been so altered that only remnants of this once vast wetland will remain, as occurred in wetlands of the upper Nile River after the building of the Aswan Dam.

A biological diversity survey of the Pantanal is being carried out under the direction of Conservation International, an organization that specializes in such studies, using Brazilian and American scientists and volunteers from Earthwatch Institute, a group that helps fund scientific studies. Many individual projects will be carried out by various Conservation Research Centers, where scientists, educators and conservationists can cooperate to help preserve the Pantanal (EI 2001). One project on a 7,000-hectare ranch will study ecosystem components and create a series of corridors for the future management of the region (EI 2001). Another will study the avian diversity of the Rio Negro region. The fish of the Pantanal, their diversity, ecology and environmental needs, will be the subject of another study (CI 2001). Should the Pantanal begin to die as an ecosystem, a very real possibility in view of its threats, conservationists can use the data that these scientists are compiling of the great wealth of wildlife and plants and how they are affected by the downstream water projects in order to urge protection through alteration or even cancellation of water projects. As the planet's greatest wetland, interest in its conservation reaches around the world, and the better its functioning is understood, the more coherent will be its defense.