单选题
University of York biologist Peter Mayhew recently found that global warming might actually increase the number of species on the planet, contrary to a previous report that higher temperatures meant fewer life forms—a report that was his own.
In Mayhew"s initial 2008 study, low biodiversity among marine invertebrates (无脊椎动物) appeared to coincide with warmer temperatures on Earth over the last 520 million years. But Mayhew and his colleagues decided to reexamine their hypothesis, this time using data that were "a fairer sample of the history of life". With this new collection of material, they found a complete reversal of the relationship between species richness and temperature from what their previous paper argued: The number of different groups present in the fossil record was higher, rather than lower, during "greenhouse phases".
Their previous findings rested on an assumption that fossil records can be taken to represent biodiversity changes throughout history. This isn"t necessarily the case, because there are certain periods with higher-quality fossil samples, and some that are much more difficult to sample well. Aware of this bias, Mayhew"s team used data that standardized the number of fossils examined throughout history and accounted for other variables like sea level changes that might influence biodiversity in their new study to see if their old results would hold up.
Two years later, the results did not. But then why doesn"t life increasingly emerge on Earth as our temperatures get warmer? While the switch may prompt some to assert that climate change is not hazardous to living creatures, Mayhew explained that the timescales in his team"s study are huge—over 500 million years—and therefore inappropriate for the shorter periods that we might look at as humans concerned about global warming. Many global warming concerns are focused on the next century, he said—and the lifetime of a species is typically one to 10 million years.
"I do worry that these findings will be used by the climate skeptic community to say "Look, climate warming is fine"," he said. Not to mention the numerous other things we seem to do to create a storm of threats to biodiversity—think of what habitat (栖息地) destruction, overfishing, and pollution can do for a species" viability (生存能力). Those things, Mayhew explained, give the organisms a far greater challenge in coping with climate change than they would have had in the absence of humans.
"If we were to relax all these pressures on biodiversity and allow the world to recover over millions of years in a warmer climate, then my prediction is it would be an improvement in biodiversity," he said. So it looks like we need to curb our reckless treatment of the planet first, if we want to eventually see a surge in the number of species on the planet as temperatures get warmer. We don"t have 500 million years to wait.
单选题
What is the finding of Peter Mayhew"s recent study?