Study Documents Extinction Threats to World's Freshwater Species Washington, 13 Jan (ONA) --- Freshwater environments cover about 1% of Earth's surface while accounting for more than 10% of known species. Like many marine and terrestrial ecosystems, however, they are in distress. A new study looking at some of the denizens of freshwater habitats offers a stark illustration of this biodiversity predicament. Researchers assessed the status of 23,496 species of freshwater animals in groups including fishes, crustaceans such as crabs, crayfish and shrimp, and insects such as ...