By Chelsea Harvey
As climate change continues to cause massive melting and ice loss in Antarctica, new habitats may begin to open up for wildlife across the thawing continent, scientists reported Wednesday. But while that may sound like a boon for plants, microbes, birds and other organisms, they caution that this is not necessarily a good thing for the fragile Antarctic ecosystem.
As more ice-free space opens up across the continent, previously isolated species may begin to spread out and come in contact with each other. And as they're increasingly forced to compete for resources, some organisms may emerge dominant - and others may start to disappear, write a team of researchers in a new study, just published in the journal Nature.
While Antarctica is a largely frozen continent, isolated ice-free areas - including exposed mountaintops, cliffs, valleys and islands - are already scattered across the region, and may range in size from less than a square mile to hundreds of square miles. They may be separated by anywhere from a few feet to dozens or hundreds of miles.
"It's not a simple picture, and ice-free areas occur in many forms," said study co-author Thomas Bracegirdle, a climatologist with the British Antarctic Survey, in an email to The Washington Post, adding that these zones may be distributed both along the coastline and further inland across the continent.
Secluded as they may be in some cases, these areas can be home to various species of vegetation, microbes, worms or insects and other small organisms, and may also serve as breeding grounds for animals like seals and seabirds. These species tend to be highly specialized for the extreme conditions in which they live, said Peter Convey, a terrestrial ecologist with the British Antarctic Survey, who was not involved with the new study. Some of them may be dormant throughout much of the year. Others may have developed specific adaptations that allow them to survive in conditions with high winds, little water or extreme low temperatures.
Additionally, some species are found only in very specific areas - in fact, a few have only been recorded in a single ice-free zone. Others may be more widespread across the continent, but may have developed different adaptations in different areas. In general, Antarctica is home to many diverse and fragile communities that may be highly susceptible to environmental change.
"From the outside, we look at Antarctica as one big continent - it's all covered in ice, it's all the same thing," Convey told The Washington Post. " And actually, we wouldn't do that with any other continents. Any other continent has got different zones in it, different habitats that host different things. And what's actually become clear in recent research is that Antarctica divides up into a lot of other biogeographic zones."
But according to the new paper, there's been very little research so far on how climate change and ice melt in Antarctica may affect the life-forms it hosts. The study suggests that, in fact, these influences have the potential to cause profound changes in Antarctic biodiversity.
Led by Jasmine Lee of the University of Queensland, the team of researchers used a model to make projections of future Antarctic ice melt under two hypothetical climate trajectories: a business-as-usual scenario, which assumes unabated greenhouse gas emissions and high levels of future climate change, and a slightly more moderate scenario.
The researchers found that the Antarctic Peninsula - one of the most rapidly warming areas on the continent, where large levels of glacial ice loss are already occurring - will likely suffer the most extreme changes through the rest of this century. Between the two climate scenarios considered, the model suggests that Antarctic continent may see anywhere from 800 square miles to more than 6,600 square miles in new ice-free area opening up by the year 2100, with more than 85 percent of this area emerging on the North Antarctic Peninsula.
And not only will there be more ice-free area, but previously isolated ice-free zones may begin to merge with one another - meaning populations of organisms that were previously isolated could begin to come into contact.
These changes could come with good and bad consequences for native Antarctic species, the researchers suggest. On the one hand, more ice-free area means more habitat space for plants and animals. When considering only native species, the increase in liveable space - along with the milder conditions likely to be brought by climate change - could actually be a positive for many organisms.
On the other hand, the expanding habitat area could also lead to the spread of invasive species, which are often less specialized than native Antarctic organisms and better equipped to compete for resources, especially as conditions grow milder and more favorable in Antarctica.
"If they can get to a place and survive, then [invasives] are strong competitors," Convey said. "The ultimate problem with most real invading species is that they can out-compete the native species."
Humans have already inadvertently carried multiple nonnative species down to Antarctica from other parts of the world on ships or planes, either through industrial or research voyages. Invasive insects, such as midges and beetles, have already established themselves on certain islands in the Southern Ocean. And there's evidence that invasive species on the Antarctic Peninsula could eventually become cause for concern as well. Studies suggest that an invasive meadow grass, called Poa annua, is already showing signs that it could begin to out-compete native species in the region, the new paper says.
And the researchers add that even native species could begin to compete with each other as they come into contact for the first time. While they aren't strong competitors in the same sense as invasive species, Convey said, "they could certainly survive in a new region if we moved them - a and that very clearly has an impact on the biology in the new region."
That said, Convey added, even without humans carrying new species to the South Pole, the Antarctic ecosystem would be unlikely to remain the same forever - and that's not necessarily preventable or even always a bad thing. Particularly as the climate continues to change, organisms may move around the world and end up in new places all on their own, a process known as natural colonisation. And in a warming world, scientists have suggested that these types of migrations may even be necessary to the survival of certain species.
"There is a danger of seeing conservation as saying we must keep everything as it is now," Convey said. And while limiting the harmful influences of human activities is important, he added that "we shouldn't think of Antarctica as being hermetically sealed and it must always look like it does now."