Both provide water filtration and flood control over a large expanse. Rich in nutrients, both are nurseries for wildlife. The land is ruled by a seasonal pulse. Periodically the highland rivers swell with rains, and the Pantanal fills up like a shallow bowl. By March a sheet of water seven feet deep usually covers thousands of square miles.
Marshy grasslands become lagoons of water lilies.
Drowned pastures swirl with shoals of fish, and every patch of dry ground becomes an ark of wildlife-jaguar and marsh deer, anteater and armadillo, howler monkey, tapir, and anaconda. Plants and animals from the Amazon and Atlantic forests to the north and south and from the cerrado and the Chaco grasslands to the east and west converge and overlap creating a refuge for uncounted flocks of ibis, spoonbills, herons, and limpkins. Three major flyways pass through, bringing wood storks from the Argentine pampas to the south, flycatchers from the western slopes of the Andes, and ospreys and yellowlegs from the wetlands of North America. There are maned wolves and marsh deer, giant otters, giant anteaters, and giant armadillos -each the largest of its kind in South America. All are endangered, and all live amid a population of 10 million caimans - the highest concentration of crocodilians in the world.