Rapid Warming of Antarctic Seas Shrinks Range of Key Species

Antarctic krill, the thumb-sized crustaceans that form the foundation of the Southern Ocean food web, are facing increasing pressure from climate change, underscoring the need to protect this keystone species and its habitat.

A study analyzing 90 years of data, published Jan. 21 in the journal Nature Climate Change, found that the center of the krill population near the Antarctic Peninsula has shifted about 440 kilometers (nearly 275 miles) southward, and that the number of juveniles has dropped since 1970. This news has huge implications: As warming waters and sea ice loss force krill to retreat toward the continent—where the landmass blocks further southward movement—their available habitat decreases, which might lead to further drops in their numbers, and cascading impacts on the entire Southern Ocean food web.

Source: British Antarctic Survey

The Antarctic Peninsula is one of the fastest-warming regions in the world, and changes in the krill population—and the broader food web—are a direct result of rising ocean temperatures and reduced sea ice. Krill are the primary food source for many species in the Southern Ocean, including penguins, seals, and whales. The reduction in the numbers and overall health of krill could lead to similar negative effects among species that rely on the lynchpin crustacean.

Simeon Hill, one of the lead authors of the Nature Climate Change study, explains: “Our analysis reveals a species facing increasing difficulty in replenishing itself and maintaining high numbers at the northern edge of the Southern Ocean. These northern waters have warmed, and conditions throughout the Scotia Sea have become more hostile, with stronger winds, warmer weather, and less ice. This is bad news for young krill.”

Industrial fishing is also threatening krill, with China, Norway, and other countries increasing the number of vessels targeting the species around the Antarctic Peninsula, where the fishery is concentrated.  The combination of that fishing and climate change could prove to be too much for the krill population to withstand.

To counter these threats, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the governing body for Southern Ocean conservation, must fulfill its commitment to create a network of marine protected areas (MPAs) in the waters surrounding the continent. In October, Chile and Argentina formally submitted a proposal to create an MPA to protect a large section  of the Antarctic Peninsula region. This proposal, crafted with input from a global network of Antarctic scientists, would protect key areas of the region, such as penguin and seal foraging grounds, important bird areas, vulnerable marine ecosystems, and critical whale habitat. CCAMLR delegates will vote on the proposal at the commission’s annual meeting in October.

Designating an MPA in the peninsula would create a climate refuge for krill and other species and would permanently protect the region’s unique marine ecosystem.  The Pew Charitable Trusts calls on CCAMLR to designate the Antarctic Peninsula MPA and offer some hope of maintaining the delicate balance of this vibrant marine wilderness, even in the face of change.

Andrea Kavanagh directs The Pew Charitable Trusts’ campaign to protect Antarctica’s Southern Ocean.