How Global Warming Threatens Antarctic Animals

Adelie penguins stand atop ice near the French station at Dumont d’Urville. Pauline Askin/Reuters

In Antarctica, the movement of icebergs is seasonal. When winter hits, the sea surface freezes, locking icebergs into place and preventing them from colliding on the seabed—where most Antarctic species live. For at least the last half century, however, global warming has led to a dramatic decline in this winter ice, meaning there are more glacial collisions, known as "scouring," on the Antarctic seabed. In a Current Biology paper published Monday, scientists argue that this increase in scouring might negatively alter how species on the shallow portion of Antarctica's seabed interact with one another—and they worry this is a harbinger of climate change–linked ecosystem changes around the globe.

The boulders on Antarctica's shallow seabed play host to a wide variety of filter-feeding, aquatic invertebrates called Bryozoa. These organisms, commonly called "moss animals," often live in colonies, encrusting large rocks. Several years ago, researchers in Western Antarctica, adjacent to the Rothera research station, noticed that a "pioneer species" of moss animal seemed to be dying at an increased rate. (A pioneer colonizes hard-to-inhabit areas and in doing so, makes the area more livable, often by leaving nutrients behind in the rock or soil when it dies and decomposes.) David Barnes, of the British Antarctic Survey, and his colleagues wondered whether the same held for other species and decided to survey the area.

They found that the normal, complex set of interactions once present on the rocks, which involved lots of species competing for space, had been reduced to "a very, very simple one with one competitor (a weak, weedy one!) monopolizing all interactions because other species cannot cope with the rising level of iceberg disturbance," Barnes writes in an e-mail to Newsweek.

This could impact the area's biodiversity—defined as the "variety, of plants and animals and other living things in a particular area or region"—drastically.

"Usually the structure of biodiversity is governed by biological interactions such as competition for resources and predation. The stability and fragility of biodiversity of most networks (such as a food web) depends on these," Barnes writes, adding "This is what has changed."

To see whether this shift is taking place elsewhere in Antarctica, Barnes's team is working with scientists from Argentina operating out of the Carlini Base (formerly known as the Jubany research station), located on King George Island at the top of the Antarctic Peninsula. That team's chief scientist will meet with the British Antarctic Survey in July and discuss their results, Barnes says.

Barnes worries that similar losses of biological complexity might take place in ecosystems beyond the South Pole.

"The Antarctic Peninsula can be considered an early warning system—like a canary in a coal mine," Barnes says in a press statement about the study. "Physical changes [in Antarctica] are amongst the most extreme and the biology considered quite sensitive, so it was always likely to be a good place to observe impacts of climate change—but impacts elsewhere are likely to be not too far behind."

Monday's paper comes a month after two groups of scientists released reports that Antarctic ice melt had passed "the point of no return." According to these reports, melting glaciers will cause sea levels to rise between 10 and 32 inches by the end of the century.