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.