Thursday, January 10, 2013

Antarctica Braces for Influx of Invasive Species

 This post was originally published on the National Geographic Ocean Views blog.

Antarctica and the Southern Ocean may seem very far away from civilization, but they are at great risk of losing their unique qualities due to human activities. Warmer temperatures and human visitation are increasing the likelihood that invasive species can take up residence in the Antarctic, and potentially cause major changes. Two studies have found evidence of invasions both on land (from a midge) and at sea (from crabs). The remoteness of the Antarctic can no longer protect it from potentially destructive invaders. Forget about The Thing – the scariest alien invaders in the Antarctic come from our own planet.

Concern about a possible crab invasion of Antarctica began in 2007, when ecologist Sven Thatje saw a few king crabs on the outer continental slope of the Antarctic Peninsula. Their presence raised immediate alarms. Unlike more famous invaders like lionfish or brown tree snakes, crabs have yet to gain notoriety as ecosystem destroyers. But in the Antarctic, cold water has long kept out crustaceans like crabs and lobsters, which cannot survive at temperatures below 1°C (just under 34°F). The result is that many seafloor creatures in the Southern Ocean today have not evolved the same defenses against crushing claws as species in other regions. So the discovery of Neolithodes yaldwyni, a species of king crab, by a submersible surveying shallower areas closer to the Antarctic Peninsula (one of the fastest warming areas in the world) was unwelcome news. This indicates that the crabs are more firmly established, and have become truly invasive. The researchers who discovered the crabs estimate that there are 1.5 million crabs in the Palmer Deep. As warming of ocean water increases, the range of these crabs will expand further.

On land, researchers have also recently found evidence of unwelcome invaders that could make life very difficult for native species. This time, the invading species is the midge Eretmoptera murphyi, and they appear to be speeding up the rate at which decay occurs in Antarctic soil. The midge hails from the sub-Antarctic South Georgia Island, but the ecosystem on that island is very different from the one on the Antarctic Peninsula, where the midge has now established itself. Decay in peninsular soil is “not very active,” according to Peter Convey, one of the scientists who discovered the presence of the midge, so the insect will introduce a new process to the ecosystem. Unfortunately for the peninsula, though its ecosystem is composed of different species, the midge can still survive in its climate. Although one tiny insect might not seem to be very disruptive on a continent without many terrestrial species, it has been well established that many Antarctic species are highly vulnerable to disturbances, so introducing a new ecosystem process could introduce a major shift.

Unlike the crab invasion, however, the midge invasion and other invasions of land species can be slowed or prevented by following strict rules that reduce the possibility that species can tag along with humans visiting different areas of the Antarctic. Even so, it’s virtually impossible to eliminate the transfer of invasive species entirely. In the sea, it will be very difficult to slow down the global warming that allows new species to colonize the Southern Ocean, so we will have to wait and see if a crustacean-generated apocalypse occurs for Antarctica’s unique seafloor communities. The presence of these invaders, it seems, only further indicates that humans have impacted the environment in virtually every place on earth, with possibly disastrous results for the world’s biodiversity.

The growing problem of invasive species is yet another reason to designate marine protected areas (MPAs) in Antarctica as soon as possible. By restricting some types of human activities, MPAs provide reference areas that can be compared with areas where activities aren’t restricted, thus helping scientists understand what ecosystem changes are caused by invasive species or climate change versus those caused by fishing or pollution. MPAs can also minimize some human-induced stressors on threatened ecosystems. Unfortunately, MPAs can’t keep king crabs out, but they can help scientists obtain a better grasp on the seismic changes taking place in the frozen south.

1 comment:

Irene_J said...

There is no reason to expect organisms of any species to shy away from occupying suitable habitat where they find it. “Truly invasive” is an anthropomorphic, anthropocentric category, born entirely of human sense of place, desires and expectations. It means nothing to a crab, a midge, or [insert taxon of interest]. Invasiveness isn’t a biological or ecological trait. How any of us feel about having precipitated climate changes and subsequent biogeographical dynamics doesn’t cast much useful light on what happens next. Ditto for active transport — intended or otherwise — of organisms via the currents of commerce. Literally and figuratively, there is more heat than light (or effective response) being generated by scapegoating species as ‘invasive’ when we’re socially and politically unwilling to regulate the economic incentives driving global trade and fossil fuel dependency.

regrads,
irene of Dallas IT Consulting