Title: South Africa: The climate-change aliens are thriving
[allAfrica.com 19 August 2010 by Jocelyn Newmarch] Johannesburg - MOST people think Antarctica is a block of ice, but it's not," says Steven Chown. He should know better than most. Chown was recently named winner of the inaugural Martha T Muse prize, administered by the international Scientific Council on Antarctic Research, for his work in the field of Antarctic science and policy. Antarctica, he says, is a diverse and fascinating place and, although parts of it are too cold and hostile for plant life, the mountainous Antarctic Peninsula does have a summer melting season and can support a tundra ecosystem.
That ecosystem, however, is a fragile one, and Chown has spent much of his career documenting its biodiversity and the changes experienced in Antarctica and on the sub-Antarctic Prince Edward Island and Marion Island.
"I have always been interested in how biodiversity works," he says.
Chown is the head of Stellenbosch University's Centre for Invasion Biology, which looks at species that are "in the wrong place, at the wrong time," as he puts it.
"I examine the interactions between climate change and biological invasions in the South Antarctic and also some areas of Antarctica," he explains in an interview.
His work includes grass species, some flowering plants, and springtails - tiny, wingless animals closely related to insects that are essential for soil ecosystem functioning. That's important because, as he points out, soil ecosystems are the basis for terrestrial functioning, as plants derive most of their nutrients from the soil.
You might think that Cape Agulhas is the southernmost point of SA, but in fact our territory includes Prince Edward Island and Marion Island, about 1800km south of Port Elizabeth, which were annexed in 1947.
Marion Island has been run as a research station ever since, by the South African National Antarctic Programme (Sanap). It is especially important for weather monitoring, but also for biological research.
The island is also important for climatological research - which is concerned with long-term trends in climate rather than short-term fluctuations - because the research station has been in existence for so long in an almost unchanged condition and without unnatural influences, according to Sanap.
What Chown has found so far is sobering.
While the world has experienced a 0,4° C average increase in temperature, Marion Island has warmed by 1,5° C over the past 60 years, when weather records began to be kept on the island. At the same time, the annual rainfall has dropped by 600mm or 700mm. "That's the same rainfall, on a yearly basis, received by Johannesburg or Somerset West, which has been lost," Chown says.
A stationary glacier has also disappeared from the island.
Marion Island has experienced such an extreme change partly because of its high latitude, at 47°C south, but also because it is on the cusp of ocean fronts, he says.
The changes in the island's climate mean that introduced species do far better than the native species, says Chown.
"It's fascinating, because it gives some indication of what may happen in SA," he says, but adds that climate change tends to have specific effects in different regions.
SA, unlike its uninhabited islands, must also deal with the effects of human development and solve social issues made worse by the stresses of climate change.
The lesson, so far, seems to be that invasive plant species often do better in a changing climate, in part because they're tougher to begin with.
"It's not a great prognosis for climate change," he says.
Unfortunately, Marion Island suffers from several invasive species, many of them introduced unknowingly by researchers themselves.
And in several instances, Chown says, they're taking over from indigenous species.
In the 1940s, five domestic cats were introduced to deal with a mouse problem at the research station.
Those five cats, with no natural predators, swiftly multiplied and preyed on the island's abundant bird life, which were easier targets than the mice they were supposed to hunt. By 1975, there were more than 2000 cats on the 25km- long island, eating more than half a million birds that year.
The feline panleucopenia disease, which is highly specific to cats, was introduced in 1977, and over the next five years it reduced the number of cats from 3400 to 615. The remaining cats were shot and trapped. In 1991, only eight cats were trapped and no cat sightings were recorded for a year. Sanap says it believes the cats have been completely eradicated after a 19-year effort.
Nevertheless, petrel species such as the common diving petrel, the soft plumage petrel, and the grey petrel are now extinct as a result of the cats.
We'd like to think we know better than to introduce new species, having learned from the mistakes of the past, but Chown's work shows this is not the case.
"It's difficult to predict what species will be invasive. Often they're weedy, they like disturbed ground, and they grow rapidly," he says.
Other characteristics include self-fertilisation and profuse seed production.
"But it's more complex than that ," he says, citing invasive tree species as a counterexample. "What counts a lot is that people put effort into moving species."
Australian acacias, for example, were deliberately introduced to the Western Cape in order to stabilise the dunes, but are now considered pests.
Many of the invasive species Chown studies are ultimately of European origin, but are also found in the Western Cape. It is likely they were transferred from there to Marion Island and Prince Edward Island, he says, possibly by long-ago sealers, but most showed up after 1947.
Even Mediterranean mussel species have reached the Antarctic, transported on the hulls of ships.
Scientists and tourists carry invasive seeds in camera bags and clothing, and the risks are high, he says.
The Antarctic Peninsula, which has exposed land as well as ice and where ice shelves have been retreating, is particularly vulnerable to annual winter grass, a plant species that was introduced from neighbouring King George Island. Scientists now fear that this grass species has been able to colonise the Antarctic mainland itself.
"The threat is real. The peninsula itself is warming quickly," Chown says.
Simple, straightforward interventions - such as storing equipment under cover, vacuuming camera bags, and issuing clothing just prior to departure - can help minimise these risks, and visitors should also take care when moving between regions in Antarctica.
The risk presented by climate change, however, requires greater action. A 4°C rise in global temperatures would be impossible to deal with, says Chown, and would cause enormous social problems.
"We are very close to dangerous levels of climate change. Public scepticism needs to be informed, because life is going to become more complicated," he says.