Species multiply as Earth heats up
Biodiversity increases with gentle warming.
The tropics are hotbeds of biodiversity — as, it seems, were warm periods in Earth's history.
T. Laman/naturepl.com
Rather than kicking off the expected cycles of extinction, periods of warming in Earth's history were accompanied by increased biodiversity, according to a report published this week. But this does not mean that the mass extinctions that are taking place today, with Earth warming at an unprecedented rate, will be reversed in future.
Researchers examined the number of known families of marine invertebrates, as well as sea-surface temperatures, over the course of 540 million years of Earth's history1. They found that when temperatures were high, so was biodiversity. When temperatures fell, biodiversity also declined.
The results contradict previous work, including findings from lead author Peter Mayhew's group2, that reported an inverse correlation between high temperatures and biodiversity.
The reason for the about-face, says Mayhew, an evolutionary ecologist at the University of York, UK, is that the earlier work measured fossil diversity by tallying the first and last appearances of each group of species, then assuming that the creatures existed only during the intervening years. This might sound logical, but overlooks the fact that some geological periods are better studied than others.
To correct this, the new study looked only at the well-sampled periods. And, instead of interpolating organisms' presence from origination and extinction dates, it merely tallied species groups present during each period.
Even so, given that climate change is generally viewed as disruptive, Mayhew admits it was a "big surprise" to find that eras of warming were accompanied by increases in biodiversity. The work also provided a solution to another puzzle, Mayhew says. Tropical ecosystems are known to be Earth's most diverse, and the tropics would be expected to expand during warm eras. Yet in the past these eras were thought to be species-poor compared with cooler ones. The new results resolve that contradiction.
Speed kills
Warming produces both extinctions and originations, and in the past the originations of new species have outstripped the loss of old ones, says Mayhew. But this does not mean that today's climate change will be beneficial.
"The rate of change is very important," Mayhew says. For diversity to rise, he explains, new species need to evolve. And that takes between thousands and millions of years — much slower than the rate at which extinctions are likely to occur with today's rapid change.
Scott Wing, a palaeobiologist at the Smithsonian Institution in Washington DC, agrees. "This article has nothing to say about the effects of global warming at any timescale of interest to most humans," he says. But he adds, "this is definitely of interest to evolutionary biologists, palaeontologists and ecologists seeking to understand very broad patterns of diversity".
However, Shanan Peters, a palaeobiologist at the University of Wisconsin-Madison, isn't so sure the paper is noteworthy. Its primary result, he points out, is to overturn Mayhew's own prior finding and bring the long-term diversity results into line with ecological common sense. "Palaeobiologists and climatologists have long referred to warm intervals as 'climate optima'," he notes, "precisely because it is during such times that palm trees and alligators inhabit the Arctic and life appears to be diverse and flourishing."
More interesting, he says, will be the next generation of results, when palaeobiologists turn their attention to major climate transitions, such as that which may be occurring now.
Mayhew agrees that focusing in on such transitions is the next step. "The time periods we're really interested in now," he says, "are decades and hundreds of years — at maximum 1,000 years."
"You can't get that kind of detail by looking into the deep past," he says. "If you want to know how temperature change is affecting things on that timescale, you're going to have to look at the more recent fossil record."
- Nature
- doi:10.1038/nature.2012.11350
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
WARNING FROM RAEL: For those who don't use their intelligence at its full capacity, the label "selected by RAEL" on some articles does not mean that I agree with their content or support it. "Selected by RAEL" means that I believe it is important for the people of this planet to know about what people think or do, even when what they think or do is completely stupid and against our philosophy. When I selected articles in the past about stupid Christian fundamentalists in America praying for rain, I am sure no Rael-Science reader was stupid enough to believe that I was supporting praying to change the weather. So, when I select articles which are in favor of drugs, anti-semitic, anti-Jewish, racist, revisionist, or inciting hatred against any group or religion, or any other stupid article, it does not mean that I support them. It just means that it is important for all human beings to know about them. Common sense, which is usually very good among our readers, is good enough to understand that. When, like in the recent articles on drug decriminalization, it is necessary to make it clearer, I add a comment, which in this case was very clear: I support decriminalizing all drugs, as it is stupid to throw depressed and sad people (as only depressed and sad people use drugs) in prison and ruin their life with a criminal record. That does not mean that there is any change to the Message which says clearly that we must not use any drug except for medical purposes. The same applies to the freedom of expression which must be absolute. That does not mean again of course that I agree with anti-Jews, antisemites, racists of any kind or anti-Raelians. But by knowing your enemies or the enemies of your values, you are better equipped to fight them. With love and respect of course, and with the wonderful sentence of the French philosopher Voltaire in mind: "I disapprove of what you say, but I will defend to the death your right to say it".
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tell your friends that they can subscribe to this list by sending an email to:
subscribe@rael-science.org
- - -
To unsubscribe, send an email to:
unsubscribe@rael-science.org
- - -
0 ความคิดเห็น:
แสดงความคิดเห็น