Arctic marine mammal conservation

Earth's marine mammals are disproportionately threatened compared to land mammals, and the 11 species of arctic marine mammals (hereafter AMMs) are particularly threatened due to their dependence on sea ice.  Some AMMs require sea ice for certain activities (e.g. reproduction, feeding, resting), while other use ice but are not dependent on it.  AMMs refer to species that occur north of the arctic circle (66° 33' N) for most of the year, as well as some species that seasonally inhabit arctic waters.  AMMs include 3 whales (narwhal, beluga, and bowhead); 7 pinnipeds (ringed, bearded, spotted, ribbon, harp, and hooded seals, and walrus); and the polar bear.  Throughout much of their range, these animals are important nutritional resources for indigenous people.  Recent research indicates that the greatest species richness of AMMs is in the atlantic regions of Baffin Bay, Davis Strait, and the Barents Sea (figure 1); while the lowest species richness was found in the Sea of Okhotsk and the Beaufort Sea.

Figure 1:  Geographic regions of the arctic marine ecosystem.

Warming in the arctic over the past several decades has been about 2 times greater than the global average, and scientists predict an ice-free arctic in summer by 2040.  Of the 12 arctic marine regions, 11 show significant trends (1979-2003) toward earlier spring sea-ice melting, later autumn sea-ice formation, and thus longer summers (figure 2).  Only the Bering Sea showed no trend.  The trend was most extreme in the Barents Sea.  The trend of sea-ice loss is surely guaranteed for at least the next several decades, regardless of global efforts to reduce greenhouse-gas emissions.

Figure 2:  Trends (1979-2013) in length of summer season (time from spring sea-ice melt to autumn sea-ice formation).

In addition to declining sea ice surface area, the thickness of sea ice has greatly decreased.  Continuation of this thinning is expected to further effect summer ice extent, as storms and other weather anomalies substantially impact thin ice.  Loss of sea ice has affected survival in some polar bear populations.  The survival of pinniped pups is impacted by the melting of sea ice because the young need sufficient time for suckling.  Snow depth (which has been decreasing in the arctic) directly affects whether ringed seals can construct lairs on the sea ice.  Additionally, loss of sea ice habitat will affect the ability for indigenous people to harvest AMMs because much of the hunting occurs on the sea ice or near the ice edge.

Climate change has widespread ecological implications for the arctic, yet the effects are under-reported despite changes exceeding those of temperate, tropical, and mountain ecosystems.  This is partly due to logistical challenges in assessing marine mammal populations in the arctic, due to wide distributions, cryptic behavior, and the remoteness of marine areas.  Population data are important for understanding conservation priorities, but estimates for most AMM populations are lacking.  AMMs are highly mobile, seasonally moving long distances, across regional- or international boundaries.  Thus management requires international collaboration.  Given the fast pace of these changes in the arctic, and the uncertainty in how AMM populations will respond, flexible- and adaptive management will be critical.

It is necessary to understand- and mitigate the impacts from industrial activities.  Longer open-water seasons are contributing to increased use of shorter international shipping routes.  Potential threats associated with oil- and gas development include underwater sound and oil spills.  International agreements may be needed to protect AMM habitats of high importance, especially those of industrial interest.

It is critical that all stakeholders recognize AMMs as organisms with innate value, and as resources connected to the well-being of the indigenous people who harvest, interact, and live with them.  Accurate scientific data will be central to making informed- and effective conservation decisions.

LINK to Laidre et al.'s 2015 article in Conservation Biology.