Life on the Rocks: Climate Change and Antarctic Biodiversity

By now, it’s a familiar story: climate change is melting glaciers in Antarctica, revealing an increasing proportion of ice-free terrain. The consequences of this melt are manifold, and one may be surprising: as more ground is bared, Antarctic biodiversity is expected to increase.

Currently, most of the terrestrial biodiversity— microbes, invertebrates, and plants like grasses and mosses— occurs in the less than one percent of continental Antarctica that is free of ice. A recent Nature article predicted that by the end of the 21st century, ice-free areas could grow by over 17,000 square kilometers, a 25 percent increase.

Members of the shrinking Torgersen Island Adélie colony (Source: Rachel Kaplan).

This change will produce both winners and losers in Antarctica’s ecosystems, according to Jasmine Lee, lead author on the above paper, and the game will be problematic. “Some of the winners are likely to be invasive species, and increasing invasive species could negatively impact the native species,” Lee told GlacierHub. “More isn’t necessarily better if new species are alien species.”

The Antarctic Peninsula, an 800-mile projection of Antarctica that extends towards South America,  is one of the fastest-warming places on Earth, and 80 percent of its area is covered by ice. The many outlet glaciers of the Antarctic Peninsula Ice Sheet primarily shrink through surface melting, which reduces volume, while tidal action spurs calving. Lee and her coauthors constructed two models based on two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios. Under the strongest IPCC scenario, ice-free areas in the peninsula are expected to increase threefold, and Lee expects biodiversity changes in this region to be obvious by the year 2100. She predicts that some native species will expand their ranges south in response to the creation of new habitat and milder conditions, and invasive species will thrive for the same reasons.

This pattern is already apparent in the distribution of a number of penguin species. As climate warms, sea ice-obligate species like Adélie and Emperor penguin are shifting and contracting their ranges southward, seeking sea ice. Likewise, ice-intolerant gentoo and chinstrap penguins, typical of the Subantarctic latitudes, are moving south as the ocean becomes increasingly free of ice. As temperatures continue to rise, this biogeographic chess will play out increasingly across Antarctica.

Glaciers in the Antarctic Peninsula converge into one calving front (Source: NASA ICE/ Flickr).

“The greater the degree of climate change, the greater the biodiversity impacts,” predicted Lee. She added that counting an Adélie colony in a “real-life ice-free area” was a highlight of her fieldwork.

Interestingly, Lee and her coauthors found that higher biodiversity in the short-term may yield greater homogeneity in the long-term, as invasive species become established and potentially out-compete native species. It’s hard to know how to feel about these ecosystem-wide transitions, said Lee. “The fact that we are driving these changes through anthropogenic climate change should remind us that our actions impact the entire earth, even in what we consider the remotest and most pristine regions. I think we should feel accountable and know that because humans have the power to change the earth, we should do our best to look after it,” she said.

Curious Adélie penguins assess Lee on Siple Island (Source: Jasmine Lee/Twitter).

On June 1, President Donald Trump made a speech announcing the United States’ exit from the Paris climate agreement, obfuscating international cooperation on climate change mitigation. Lee feels this decision sends the wrong message to the rest of the world, but she hopes that the United States will find a way to continue meeting the environmental standards set forth. “America should be a leader in renewable energy technology and policy. However, I am also hopeful that the American businesses and states can reach the Paris accord milestones for America in spite of Trump. And this will show that every city, state or business can have a positive impact regardless of governance,” she said.

No matter the ebb and flow of the political tide, the Antarctic Peninsula is changing. As Antarctic glaciers melt and biodiversity changes, mitigation will require the cooperative efforts of the world.

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