Excerpted From:  Swarts, Frederick, "The Pantanal in the 21st Century: For the Planet's Largest Wetland, an Uncertain Future" in The Pantanal of Brazil, Bolivia and Paraguay (Hudson MacArthur 2000). Copyright 2000 by Waterland Research Institute.

A rich diversity

The Pantanal is one of the world's great reservoirs of plant and animal life. This floodplain wetland system is highly productive, supporting both a large number of species and an abundantly high concentration of these species. It has been said that the Pantanal has the highest concentration of fauna in the New World, comparable to the densest animal populations in Africa (Magnanini et al. 1985; Pádua 1991). Not infrequently, producers of films or videos on Amazonian fauna send their camera crews to the Pantanal to film animals too rare or hard to spot in the rainforest. 

Bird species are particularly diverse. The region is an important migratory bird stopover point and wintering ground, used by birds from three major migratory flyways — bringing ospreys from the Nearctic latitudes to the north, woodstorks from the Argentine pampas to the south and flycatchers from the Andes to the west (Eckstrom 1996). The result is one of the planet's most diverse avian communities. According to the 1997 PCBAP report, 656 species of birds, belonging to 66 families, have been identified in the Upper Paraguay River Basin (Brasil Ministério do Meio Ambiente 1997). This includes such North American migratory birds as the Upland Sandpiper (Bartramia longicauda), the American Golden Plover (Pluvialis dominica) and the Black-necked Stilt (Himantopus himantopus). 

The Pantanal's ichthyofauna is likewise quite diverse, although far below the Amazon region. A recent publication by Britski et al. (1999) identifies 263 species of fish in the Pantanal itself, including 109 species of Characiformes, 105 Siluriformes, 12 Gymnotiformes, 16 Cichlidae, 11 Cyprinodontiformes and 11 species pertaining to other groups. The study covers all of the Pantanal proper, including the Paraguayan and Bolivian portions; it does not include headwater areas of the rivers draining into the Pantanal that are poorly known and likely harbor a high number of species. The principal author of this study, Heraldo A. Britski, estimates that the number of 263 species represents about 95 percent of the existing species in the Pantanal (Britski 1999). Others consider the 263 species number to be quite conservative. Bonetto and Weis (1995) consider one of the factors for the Pantanal ichthyofauna being so diverse — the most diverse of the Parana-Paraguay system — is due to contact with some Amazonian headwaters during heavy rains. They also conclude that interchanges between these two systems enrich many other groups of the biotic communities in these hydrographic basins (Bonetto & Weis 1995; Bonetto et al. 1990). 

Common figures cited for other fauna identified in the Upper Paraguay River Basin are 95 species of mammals and 162 species of reptiles (Brasil Ministério do Meio Ambiente 1997), although many of those species occur in the highlands outside of the Pantanal. Forty-six mammal species are considered rare or in danger of extinction. Amphibians have been only partially identified, with 40 species recognized as of 1997 (Brasil Ministério do Meio Ambiente 1997). 

Not a lot of faith should be placed in any of these numbers. Along with the Amazon, the Pantanal is a mother lode of unrecorded life. The discovery of new vertebrate species, and the sighting of known species previously unrecorded in the Pantanal, is not an infrequent occurrence. In particular, vast sections of the Bolivian and Paraguay Pantanal are poorly researched. The invertebrate and plant diversity is likewise remarkable but overall inadequately assessed. Pott and Pott (1997) collected over 1,700 flowering plants during a ten-year period — not counting aquatic plants, sedges or grasses — and presented 500 in their book, Plants of the Pantanal. Overall, this immense and not easily accessible region is poorly known. 

More than diversity, the Pantanal is particularly renowned for its concentration of animals, which makes it a visual paradise for naturalists, photographers and ecotourists. The wildlife density is considered to be the greatest in the neotropics. 

Caimans are particularly abundant. Eckstrom (1996) reports a figure of 10 million caimans in the Pantanal — the "highest concentration of crocodilians in the world." The 1997 PCBAP report estimated a 1993 average "visible" density of 7.4 individuals/km2 of the common species, Caiman crocodilus yacare, an estimate that likely undercounts by millions the adult caimans, given the problems of visibility (Brasil Ministério do Meio Ambiente 1997). In the 1970s and 1980s, an estimated one million skins a year were illegally poached. 

The population of capybaras (Hydrochoerus hydrochaeris) is estimated to approach a half-million in the Brazilian Pantanal. The Pantanal continues to be one of the best places to see jaguars (Panthera onca), giant river otters (Pteronura brasiliensis), giant anteaters (Myrmecophaga tridactyla), giant armadillos (Priodontes giganteus), the endangered maned wolves (Chrysocyon brachyurus) and marsh deer (Blastocerus dichotomus) — each of which is considered to be the largest of its kind in South America (Eckstrom 1996). Hunting is proscribed throughout the Brazilian portion of the Upper Paraguay River Basin, as it is throughout most of Brazil. 

There have been 15 species of parrots identified in the Pantanal, including the blue and yellow macaw (Ara ararauna), blue-fronted amazon (Amazona aestiva), green winged macaw (Ara chloroptera), and red-shouldered macaw (Ara nobilis). The Pantanal remains one of the best environments to see the endangered hyacinthine macaw (Anodorhynchus hyacinthinus), the largest member of the parrot family. Various reports put the scarlet macaw (Ara macao) in the state of Mato Grosso (Magalhães 1992) but not within the Pantanal (Pittman 1999). 

Other species commonly encountered in the Pantanal include the anaconda (Eunectes murinus), howler monkey (Allouatta caraya), Capuchin monkey (Cebus apella), coati (Nasua nasua), ocelot (Felis pardalis), cougar (Felis concolor), tapir (Tapirus terrestris), anhinga (Anhinga anhinga), great egret (Casmerodius albus), snowy egret (Egretta thula), roseate spoonbill (Ajaia ajaja) and what is often referred to as the symbol of the Pantanal, the jaburu stork (Jabiru mycteria). 

With its variety of ecological landscapes, from terrestrial forests to seasonally inundated grasslands to perennial lakes, the Pantanal is a "complex of ecosystems." From area to area, it exhibits a wide diversity in terms of its community of organisms and the controlling environment. The Pantanal is thus commonly delineated into several distinct sub-regions, based on various ecological, geopolitical and physiomorphological aspects. Sanchez (1977) delineated 17 such sub-regions, Magalhães (1992) reported ten, and Silva et al. (1998) settled on 11 subregions. The Pantanal is also a dynamic system which can show substantial changes from year to year. This wide variety of ecological sub-regions, seasonal cycles and successional changes, combined with abundant water and high primary productivity, contribute to the Pantanal being one of the most remarkable and biologically diverse systems on the planet.