For example, the scientists write that disturbed coral reefs can be replaced by a group of species dominated by algae. This replacement might keep the species count the same, but not necessarily provide the fisheries, tourism ("algae diving" doesn't have quite the same appeal as "reef diving") or coastal protections that the original coral reef did.
"In the oceans we no longer have many anchovies, but we seem to have an awful lot of jellyfish," says Gotelli. "Those kinds of changes are not going to be seen by just counting the number of species that are present."
The new research, led by Maria Dornelas at Saint Andrews University in Scotland, carefully looked for previous studies that had tracked and tallied species over many years. The team selected 100 that contained six million observations of more than 35,000 different species including datasets that go back to 1874 and many over the last 40 years. Given widespread observation of habitat change and individual species declines and knowing that extinction rates are many times higher than normal the scientists predicted a drop, over time, in the number of species observed in most of these studies.
Why they didn't find this drop could be driven by many forces. One is related to what science writer David Quammen semi-famously termed our "planet of weeds." In other words, invasive species or successful colonists or weedy generalists think kudzu and rats may be spreading into new places, keeping the local species tally up, even
|Contact: Joshua Brown|
University of Vermont