Brett Smith for redOrbit.com – Your Universe Online
While some studies have come to the conclusion that global warming is threatening to cause extinctions and lower the biodiversity of ecosystems, a new report published in the journal Science has found that a changing climate isn’t lowering biodiversity – but it is creating new mixes of species within various ecosystems.
The new report reviewed 100 long-term monitoring research studies executed around the world – in both marine environments and on land. They found that the amount of species in many of these locations has not transformed significantly, or has actually risen.
Instead of finding a decrease in biodiversity as some might have expected, the study team found an increase in species richness in 59 out of 100 studies and a decrease on 41. The rate of change in all of these studies was modest, the researchers said.
The study team did find one major change: shifts in the species living in the locations being studied. Nearly 80 percent of the communities they analyzed exhibited substantial shifts in species composition, averaging around 10 percent change per decade, much greater than the rate of change predicted by models.
Study author Nick Gotelli, a biology professor at the University of Vermont, said an enormous turnover of species in environments around the globe is taking place, creating novel biological communities.
“Right under our noses, in the same place that a team might have looked a decade earlier, or even just a year earlier, a new assemblage of plants and animals may be taking hold,” he said.
Gotelli added that prevention strategies are currently focused on preserving biodiversity – working under the theory that biodiversity will decrease as average temperatures rise as they are expected to do.
“A main policy application of this work is that we’re going to need to focus as much on the identity of species as on the number of species,” he said. “The number of species in a place may not be our best scorecard for environmental change.”
In their report, the scientists cited the example of disturbed coral reefs in some areas are being replaced with a group of species dominated by algae. While biodiversity in this situation might remain the same – the overall impact on the ecosystem is significant – particularly to fisheries and tourism that relies on healthy coral reefs.
“In the oceans we no longer have many anchovies, but we seem to have an awful lot of jellyfish,” Gotelli said. “Those kinds of changes are not going to be seen by just counting the number of species that are present.”
The study team noted that their find is similar to what science writer David Quammen described as our “planet of weeds” – in which invasive species or successful colonists may be spreading into new places. This phenomenon would keep the local species count up, but even the overall biodiversity on a macro level is degraded.
“We move species around,” Gotelli says. “There is a huge ant diversity in Florida, and about 30 percent of the ant species are non-natives. They have been accidentally introduced, mostly from the Old World tropics, and they are now a part of the local assemblage. So you can have increased diversity in local communities because of global homogenization.”
In their report, the researchers concluded there “is need to expand the focus of research and planning from biodiversity loss to biodiversity change.”
Image 2 (below): With survey data from every continent and climate type, a new study found species compositions changing — but not systematic losses of biodiversity — around the globe. Each dot represents a site included in the analysis. Credit: Courtesy of Science Magazine