Surprising global species shake-up discovered

The diversity of the world's life forms -- from corals to carnivores -- is under assault. Decades of scientific studies document the fraying of ecosystems and a grim tally of species extinctions due to destroyed habitat, pollution, climate change, invasives and overharvesting. Which makes a recent report in the journal Science rather surprising. Nick Gotelli, a professor at the University of Vermont, with colleagues from Saint Andrews University, Scotland, and the University of Maine, re-examined data from one hundred long-term monitoring studies done around the world -- polar regions to the tropics, in the oceans and on land. They discovered that the number of species in many of these places has not changed much -- or has actually increased. Now wait a minute. A global extinction crisis should show up in declining levels of local biodiversity, right? That's not what the scientists found. Instead they discovered that, on average, the number of species recorded remained the same over time. Fifty-nine of the one hundred biological communities showed an increase in species richness and 41 a decrease. In all the studies, the rate of change was modest. But the researchers did discover something changing rapidly: which species were living in the places being studied. Almost 80 percent of the communities the team examined showed substantial changes in species composition, averaging about 10 percent change per decade -- significantly higher than the rate of change predicted by models...more