Targeting these hotspots helps insure that conservation efforts have the greatest payoff.
A symposium at the annual meeting of the American Association for the Advancement of Science focused on "the hottest of the biodiversity hotspots," the world's lakes, streams and wetlands. Speaking in that symposium Feb. 18, Gerald R. Smith, a professor in the departments of Geological Sciences and Ecology & Evolutionary Biology at the University of Michigan, described the methods he used to pinpoint three regions where North American freshwater fishes are at greatest risk. The regions he identified are:
- The southern Appalachian region, where fish species diversity is highest, the species have highly restricted ranges, and their habitats are threatened by dams, strip mining and mining wastes.
- The Klamath River Basin of southern Oregon and northern California, where controversy has raged over the effects of diverting water for irrigation. "What has been lost in the controversy is that the whole fish community there is really quite remarkable compared to the rest of the continent," Smith said.
- The Caribbean coastal drainages of eastern and southern Mexico, where high numbers of endemic species are confined to very small ranges and threatened by habitat destruction.
Smith used a two-step method to locate the hotspots. Using a grid system developed by paleontologist George Gaylord Simpson, he divided Canada, the United States and Mexico into 350 equal-sized squares (quadrats), each 150 miles on a side, and assembled a database on the presence or absence of about 1,080 fish species in the quadrats.
"The highest-diversity quadrat for the whole continent is a spot in eastern Tennessee/Western Virginia that has 226 fish species," Smith said. "In the whole Great Lakes region we have only 175 or so species, so this one little spot has more fish species than the entire Great Lakes region."
In the second part of the analysis, he again used the grid system to look only at endemic species---those with highly restricted ranges. "These species are especially at risk, because there's no way for them to replenish themselves after a local extinction," Smith said. "Local is all they've got." The regions with the highest numbers of endemic species turned out to be the same areas that showed the highest diversity in the first part of his analysis.
"What this means is that a huge proportion of the diversity represented here is made up by species that are found nowhere else," Smith said. "In all three of the areas I identified, habitat destruction by water diversion, agriculture, deforestation, coal mining, mine wastes and barrier dams is causing extinction and endangerment of aquatic organisms. I hope this analysis will help show where conservation activities and public education about rich fish biodiversity at risk should be concentrated."
The University of Michigan
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