Upper Paraná Rivers & Streams - A Global Ecoregion
Spectacular waterfalls, incredible freshwater biodiversity
Snapshot: Ecoregion 153
Size:
900,000 sq. km ( 350,000 sq. miles)
Habitat type:
Large River Headwaters
Geographic Location:
Central and South-Central South America: Argentina, Brazil, and Paraguay
Conservation Status:
Critical/Endangered
Quiz Time!
Is it true that the Iquazú falls are a Natural Heritage site?
Answer:
Yes and it's easy to see why! The Guarani Indians named Iquazú Falls "Great Water" for nothing - stretching for 2.5 miles and plunging 270 feet, Iquazú Falls is a collection of 275 separate, rocky waterfalls. It is such a spectacular sight that the United Nations declared it a Natural Heritage Site in1986.
About the Area
The upper Paraná River and its tributaries are distinguished both by their spectacular waterfalls, and by their exceptional levels of freshwater biodiversity.
The upper Paraná basin supports over 300 species of fish, with a high degree of local endemism in individual tributaries that is likely the result of isolation by waterfalls.The Rio Iguazu, which is isolated from the Paraná River by the Iguazu falls, supports 65 species of fish, of which about 50 species are endemic. There is also high richness of other aquatic organisms, both vertebrates and invertebrates.
Many fishes in this river system are migratory and may travel hundreds of kilometers upstream to spawn - often timed to coincide with spring flood peaks.
Local Species
Among the migratory species present are a number of characiformes, including Prochilodus lineatus and Salminus maxillosus that migrate hundreds of miles upstream during springtime floods to spawn.
One of the few anadromous species in this ecoregion is Atlantic sabretooth anchovy (Lycengraulis grossidens), which ascends the Paraguay River from the Atlantic and has been reported in the southernmost end of the upper Paraná River.
The only species of lungfish found in the Neotropics - Lepidosiren paradoxa, inhabits these waters. Two well-known piranha species, Serrasalmus spilopleura and S. marginatus, occur here as well.
Threats
Impoundments, water diversions, hidrovias, and agriculture are among the biggest threats in this ecoregion. The Itaipu hydroelectric dam, with a massive generating capacity of over 12,000 megawatt, was built in 1979 on the Iguazu River. Its construction flooded approximately 100,000 hectares of land, and destroyed important aquatic habitats, including Guaíra Falls.
A number of additional dams and waterways are planned within the ecoregion that have the potential to effectively block fish migrations. Burning of land for soybean plantations, desertification of the land, agricultural pesticides, and untreated domestic sewage have affected the quality of water as well.
An oil spill of one million gallons on the Iguazu River in July 2000 highlighted the risks associated with oil development and transportation in the ecoregion. Introduced species, over fishing, and poaching pose further threats to this ecoregion's highly endemic fauna.
Resources
• NationalGeographic.com
