Tuesday, May 17, 2005
Ecosystem Engineering
Jax
Efforts are under way to restore part of Siberia to the way it was more than 10,000 years ago, before the end of the last ice age.
The "Pleistocene Park" experiment will try to turn the wet, boggy tundra back to the dry grasslands that once were home to large herds of stampeding mammals.
These creatures included bison, horses, reindeer, musk-oxen, elk, saiga, and yaks and even woolly rhinos and mammoths. There were top predators, too, such as cave lions and wolves.
It is hoped that by re-introducing some of the still-surviving species, grazing will begin again and restore the landscape.
"The idea is to do some scientific experiments which would explain why there was such a dramatic change in the ecosystem 10,000 years ago," said Sergey Zimov, director of the Northeast Science Station in Cherskii, Russia.
"We want to construct the ecosystem that existed here - an ecosystem that had a very big density of bison, horses, rhinos and many other herbivores and predators," he told the BBC World Service's Science In Action programme.
Theory tests
Dr Zimov believes that the vegetation of an area is determined by the animals that live there - rather than the other way around.
He hopes that by putting a lot of large grazing animals on to the modern tundra, they will chew up the mosses that currently keep the soil moist. The drier earth will then be suitable for grassland, which is what the animals prefer.
Dr Zimov plans to test his theory initially in a small area, and has the support of the government of the Republic of Yakutia to work in 160 sq km of Ko lyma lowland.
The reintroduced herbivores will include reindeer, moose, Yakutian horses and recently reintroduced musk-oxen, along with other smaller plant-eaters such as hares, marmots and ground squirrels.
Eventually, as the numbers of animals climb, the boundaries of the park will be increased and bison will be brought in from Canada. Ultimately, predators also will be re-introduced, such as Siberian tigers.
Human hunters
However, Pleistocene mammal expert Professor Adrian Lister, of University College London, UK, said that he did not know if this idea would actually work.
"[Dr Zimov] quite properly says that he appreciates that this is a theory, and I think the idea of massive landscape reconstruction on the basis of a theory is perhaps a bit dodgy," he added.
"But he says that he is going to take a relatively small area and try it out - take a fenced area, put some bison and horses in, and see if it works."
One of the points of the experiment is to try to prove why some of the great beasts, such as the mammoth and woolly rhino, became extinct.
"One of the prevailing ideas is that the climate changed at the end of the last ice age; it became wetter and warmer, and the normally accepted model is that that change turned the dry grasslands into the modern, wet tundra," explained Professor Lister.
"There is another idea - which I think Zimov is championing - which says it's actually the entry of modern humans into these vast areas which killed off the animals; they were over-hunted, and because those animals were no longer there to graze the grasses, it turned into this boggy tundra."
Dr Lister said he had problems with this "overkill" model. In particular, he explained that when people entered that area, it was in "pretty small numbers".
"You're talking about the extinction of probably millions of individuals, of huge animals like mammoth and woolly rhino. Even if they had the capacity to kill that many animals, why would they have needed to?"
Mammoth home
One further proposed benefit of restoring the grassland at Pleistocene Park is that it may prevent a large amount of carbon currently locked up in the permafrost of the tundra from being released into the atmosphere - with obvious consequences for global warming.
"The amount of carbon now sequestered in soils of the former mammoth ecosystem, and that could end up as greenhouse gases if released into the atmosphere by rising global temperatures, surpasses the total carbon content of all of the planet's rainforests," Dr Zimov wrote in an essay in Science magazine this month.
He believes the returning grasses and their root systems would help dry out and stabilise the soil.
"The albedo - or ability to reflect incoming sunlight skyward - of such ecosystems is high, so warming from solar radiation also is reduced. And with lots of herbivores present, much of the wintertime snow would be trampled, exposing the ground to colder temperatures that prevent ice from melting.
"All of this suggests that reconstructed grassland ecosystems, such as the ones we are working on in Pleistocene Park, could prevent permafrost from thawing and thereby mitigate some negative consequences of climate warming," he told Science readers.
And if the mammoth ecosystem is restored what chance is there we might one day see the mammoths themselves back on the plains? Fanciful perhaps but the recent development of cloning technology has at least got people talking about the subject.
Dr Lister said that even if it were possible to recreate the great beast, he would be against it.
"Of course it would be wonderful to actually see the thing alive, rather than just working with piles of bones all the time," he explained.
"Having said that, I've always been anti the idea of cloning these animals... just to create one or two lonely individuals in Pleistocene Park just for our own enjoyment wouldn't, I think, be quite the right thing to do." (Link)
