IMPACTS AT THE ECOSYSTEM LEVEL: DAMAGING THE ARCTIC WEB OF LIFE

Climate change is having profound impacts not only on individual species but also on the ecosystems to which they belong—the interconnected assemblages of species and their physical environment. Observed ecosystem-level changes in the Arctic include the disappearance of essential habitats, shifts in species’ timing and ranges, disruption of species’ relationships, declines in abundance, and looming extinctions. Unless we reduce greenhouse gas emissions rapidly, we will lose the Arctic as we know it.

VANISHING HABITATS. Climate change is triggering the rapid loss of entire Arctic habitats, most notably sea ice and glaciers, and is leading to the degradation of others. For example, ocean acidification is making Arctic waters unlivable for many calcifying creatures, melting permafrost threatens to drain tundra wetlands, and erosion is degrading coastal habitats.

MOVING EARLIER. As the onset of spring arrives earlier, some Arctic species are advancing the timing of important activities to try to keep pace. The flowering of plants, egg-laying of birds, and emergence of insects have shifted by up to 30 days earlier per decade in some Arctic regions. [1] However, species may not shift their timing in synch with each other, which can disrupt important relationships. For example, the plant-growing season in Greenland is beginning earlier, but caribou have not advanced the timing of migration and calving to keep up, creating a mismatch between caribou and their food.

MOVING NORTHWARD.  Many Arctic species, from shrubs to insects to mammals, are moving northward to keep pace with rising temperatures. [2] However, as species enter new areas, communities are altered and disrupted. For example, the red fox has been moving northward into the tundra, following the expansion of shrubs, which has been linked to declines of the smaller, less dominant tundra-dwelling Arctic fox.  

CHANGING SPECIES INTERACTIONS. Climate change is altering relationships among species in the Arctic by changing the availability of food resources and exposing them to new predators, competitors and pathogens as species shift their ranges. For example, as temperatures warm and sea ice vanishes, ringed seals are facing pressure from reduced availability of ice-associated prey, a heightened risk of predation from killer whales moving into once inaccessible ice-covered areas, increased competition for food from harbor seals moving northward, and exposure to novel pathogens. [3, 4]

DECLINES AND EXTINCTIONS. Climate change has already been linked to lower survival or population declines of Arctic species from the sea-ice dependent polar bear, to the glacier-affiliated Kittlitz’s murrelet, to the tundra-dwelling caribou, to the marine sea butterfly. Researchers have forecast that at least one species, the polar bear, will be faced with extinction within this century if sea-ice loss is not halted. The loss of species can have far-reaching effects on the functioning of entire ecosystems.

MULTIPLE LAYERS OF IMPACT. Climate change is having multilayered, synergistic impacts on Arctic ecosystems, including threats from increasing human use. As previously ice-covered areas become more accessible, human activities like shipping, oil and gas exploration, commercial fisheries and tourism are on the rise, putting more pressure on already stressed systems. Ecosystem impacts will only worsen the longer greenhouse gas pollution goes unchecked.