Ringed seal demography in a changing climate

Abstract

Climate change is affecting species’ distributions and abundances worldwide. Baseline population estimates, against which future observations may be compared, are necessary if we are to detect ecological change. Arctic sea ice ecosystems are changing rapidly and we lack baseline population estimates for many ice‐associated species. Provided we can detect them, changes in Arctic marine ecosystems may be signaled by changes in indicator species such as ringed seals (Pusa hispida). Ringed seal monitoring has provided estimates of survival and fertility rates, but these have not been used for population‐level inference. Using matrix population models, we synthesized existing demographic parameters to obtain estimates of historical ringed seal population growth and structure in Amundsen Gulf and Prince Albert Sound, Canada. We then formalized existing hypotheses about the effects of emerging environmental stressors (i.e., earlier spring ice breakup and reduced snow depth) on ringed seal pup survival. Coupling the demographic model to ice and snow forecasts available from the Coupled Model Intercomparison Project resulted in projections of ringed seal population size and structure up to the year 2100. These projections showed median declines in population size ranging from 50% to 99%. Corresponding to these projected declines were substantial changes in population structure, with increasing proportions of ringed seal pups and adults and declining proportions of juveniles. We explored if currently collected, harvest‐based data could be used to detect the projected changes in population stage structure. Our model suggests that at a present sample size of 100 seals per year, the projected changes in stage structure would only be reliably detected by mid‐century, even for the most extreme climate models. This modeling process revealed inconsistencies in existing estimates of ringed seal demographic rates. Mathematical population models such as these can contribute both to understanding past population trends as well as predicting future ones, both of which are necessary if we are to detect and interpret future observations.

Molting strategies of Arctic seals drive annual patterns in metabolism

“…The 2012 decision to list distinct population segments of bearded seals as threatened under the United States Endangered Species Act was driven by concern that sea ice loss would substantially reduce or eliminate adequate haul-out platforms for pupping and molting, leading to decreases in reproduction and survival ( NMFS, 2012 ). Similar concerns exist for ringed seal populations, which are predicted to be at risk of major declines due to ongoing sea ice loss ( Kelly et al , 2010 ; Kovacs et al , 2011 ; Reimer et al , 2019 ). Spotted seals may be less impacted by reductions in sea ice as they are already known to successfully utilize coastal haul outs for pupping and molting in lower latitudes ( Wang, 1986 ; Nesterenko and Katin, 2009 ); however, the cascading consequences of climate change will inevitably affect all three species.…”

Interrelated ecological impacts of climate change on an apex predator

“…, Reimer et al. ). Over the next century, the conservation of polar bears will depend not only on our ability to understand and quantify the effects of climate change, but also on our capacity to predict how climate change will influence viability and adjust management actions accordingly (Regehr et al.…”

“…, Reimer et al. ). Even if greenhouse gases, the primary drivers of climate change, were limited immediately, sea ice loss would continue for several decades because of inertia in the climate system (Overland and Wang ).…”

Modeling optimal responses and fitness consequences in a changing Arctic

“…Conversely, bears that are encountered may be more desperate and more prone to hunger‐motivated cannibalism. Ringed seal abundance is also expected to decline, with projected concurrent shifts in ringed seal population age structure (Ferguson et al, ; Kelly et al, ; Reimer, Caswell, Derocher, & Lewis, ), changing the availability of energetic rewards in all ice types.…”