Anthropogenic activities which may affect marine mammals generally and ringed seal specifically can be divided into two main categories: habitat degradation and oceanographic change due to climate change. Climate change denotes changes in major weather patterns over a long time-scale, and results from both natural variability and the influence of human activities. Climate change is by far the most serious threat to Arctic biodiversity and exacerbates all other threats (CAFF 2013).
A potential long-term and alarming threat to ringed seals is human-induced global warming.
Both the observed and the projected effects of a warming global climate are most extreme in northern high‐latitude regions (e.g., ACIA 2005, CAFF 2013). It has become clear that climate change is occurring and that the Arctic has already undergone significant physical environmental change due to global warming (e.g. ACIA 2005, CAFF 2013, Kovacs 2014 for review). There has been a decrease in the extent, duration and area of Arctic sea ice since the 1970s (Johanessen et al. 1995, Jeffries et al. 2013). This has led to a decrease in the condition and survival of polar bears in Western Hudson Bay in Canada (Stirling et al. 1999), probably because of reduced access to their major prey, the ringed seal. The observed and projected changes with significant potential to affect the ringed seal’s range and habitat, both its physical and biological components, are changes in sea ice, snow cover, ocean temperature, ocean pH (acidity), and associated changes in ringed seal predator and prey species.
Ringed seals are the most ice-associated/adapted pinnipeds in the Arctic and are perhaps the most vulnerable of the high-arctic pinnipeds because they are reliant on sea ice as a platform for resting, whelping, nursing, and moulting, and they depend on snow cover to provide protection from cold and predators and successfully rear young. Ice and snow cover are changing and will continue to do so as the climate warms. Numerous authors have studied and/or warned against the possible impact that global warming will have on the ringed seal (e.g. Stirling et al. 1999, Stirling and Smith 2004, Meier et al. 2004, Ferguson et al. 2005, Stirling 2005, Rosing-Asvid 2006, 2010, Learmonth at al. 2006, Lydersen et al. 2007, 2010, 2014, Sipilä et al. 2007, Freitas et al. 2008b, Härkönen 2008, Kovacs and Lydersen 2008, Laidre et al. 2008, Moore and Huntington 2008, Kovacs et al. 2012).
The impacts of climate change on ringed seals and other Arctic species will be both direct and indirect (e.g. ACIA 2005, CAFF 2013) and are reviewed in Kelly et al. (2010b) and Kovacs (2014). The impacts of climate change and the potential resilience of species are complex, but it is necessary to assess them so that suitable conservation actions can be taken (Moore and Huntington 2008).
A reduction in the extent and duration of ice cover would directly reduce the habitat available to ringed seals. It might also lead to poor condition of pups and higher pup mortality due to the early destruction of birth lairs. In the southern Baltic Sea, a series of nearly ice-free winters from 1989-1995 led to very high pup mortalities (Härkönen et al. 1998). Insufficient snow cover to protect pups in lairs in the spring will also likely lead to higher mortality due to increased predation. In warm years, the ringed seal pups are more exposed to predation from polar bears due to a higher density of lairs on the smaller area of available sea ice and the fact that the lairs are weaker because there is less snow. The seals may also experience periods of thaw that can destroy their lairs and expose the pups (Hezel et al. 2012, Rosing-Asvid 2010). Ice is also needed by ringed seals for moulting, resting, and in some populations foraging, but the type of ice and its stability is not as important for the seals outside of the breeding season. Northern ringed seals still exhibit a clear preference for areas with considerable ice coverage (e.g. Freitas et al. 2008).
Beyond the direct changes to their habitat, climate change will pose risks to ringed seals by inducing indirect changes. These will include changes to their forage base (species and density shifts, and distributional shifts of prey species, etc.), increased competition from temperate species, increased predation rates from polar bears and arctic foxes (at least initially) as well as killer whales, increased disease and parasite risks, greater potential for exposure to increased pollution loads and impacts via increased human traffic and development in previously inaccessible, ice-covered areas (Kelly et al. 2010b, Kovacs 2014).
It is predicted that, within the foreseeable future, the number of Arctic ringed seals will decline substantially, and they will no longer persist in substantial portion of their range (Kelly et al. 2010). Kovacs (2014) stresses the importance of developing and implementing an Arctic ringed seal monitoring program, given the ecological and subsistence importance of this species in the Arctic. See under 'Status and Outlook' for more details.
Things are indeed happening in the Arctic: see for example the figures below taken from the The Arctic Report Card: update for 2013 - Sea Ice (Perovitch et al.2013) and Greenland Ice sheet (Tedesco et al. 2013) in Jeffries et al. (2013).
Time series of Arctic sea ice extent anomalies in March (the month of maximum ice extent, black symbols) and September (the month of minimum ice extent, red symbols)(Perovich et al. 2015, read more).
Monthly changes in the total mass of the Greenland ice sheet (Tedesco et al. 2015, read more)
A range of human activities has the potential to degrade habitat important to ringed seal survival:
In addition to their direct toxicity, anthropogenic contaminants may affect resilience and increase susceptibility to disease in marine mammals (Reijnders and de Ruiter-Dijkman 1995).
Contaminant loads in ringed seals have been investigated in most parts of the species’ range (although not in the Sea of Okhotsk), reflecting the ringed seal’s importance in the diets of coastal people and polar bears (e.g., Dietz et al. 1998, Hyvarinen et al. 1998, Muir et al. 1999, Bang et al. 2001, Fisk et al. 2002, 2005, Sonne et al. 2002, 2009, Rigét et al. 2005, 2006, Dietz 2008, Wolkers et al. 2008, Sonne et al. 2009, Routti et al. 2009, and Kelly et al. 2010b and Kovacs 2014 for review). The levels of persistent organic pollutants (POPs), mercury, and radionuclides are particularly high in communities that have traditional dietary habits and consume a lot of marine mammal meat and blubber (e.g. Polder et al. 2003). The Arctic Monitoring and Assessment Programme (AMAP) was established in the 1990s to address the risks and trends in contaminants in the Arctic, and ringed seals were selected as a key monitoring species because of their broad circumpolar distribution, high abundance, high trophic status and their frequency in the diet of coastal peoples (Wilson et al. 1998).
Pollutants such as organochlorine (OC) compounds and heavy metals have been found in all ringed seal populations, with males tending to have higher toxic loads than females for many substances. Relatively high levels of chlorinated hydrocarbons have been found in the blubber of ringed seals in some areas, probably as a result of atmospheric transport to the Arctic (Reeves 1998) and OC contamination is greater in the European Arctic than in the Canadian or U.S. Arctic (Borgå et al. 2005). In addition, metals including cadmium, mercury, zinc and selenium accumulate in other tissues (Dietz et al. 1998).
Mercury contamination is a particular problem for some freshwater populations, and is thought to have contributed to elevated mortality of ringed seal pups in Lake Saimaa (Sipilä and Hyvärinen 1998, Kostamo et al. 2002). Environmental contaminants have also been implicated as a factor in the reduced fertility of Baltic Sea seals, which has inhibited the recovery of the population (Härkonen et al. 1998, Harding and Härkönen 1999). For most other areas, however, there is little evidence that contaminants are an immediate threat to ringed seals (Kovacs 2014) and following restrictions on the use and release of POPs into the environment, levels of these substances are dropping rapidly in the Baltic and in the Arctic (e.g. Kostamo et al. 2002, Wolkers et al. 2008).
A suite of new-use chemicals previously unreported in the Arctic has recently been documented in arctic biota including ringed seals, however little information exists for these compounds in terms of spatial patterns, food web dynamics, or species differences in levels (Kovacs 2014). Kovacs underlines that although levels of these compounds are currently low, there is concern because some are increasing rapidly in concentration in some areas (e.g., polybrominated diphenyl ethers, Riget et al. 2006) and some have unique toxicological properties. Some of these compounds were presumed to have low potential for long-range transport, and so were not expected to make their way into arctic biota. Kovacs also stresses that a better understanding of the effects of contaminants exposure is needed, especially given the risks of climate change stresses.
Reduction in sea ice cover due to global warming (see above) will likely lead to increased human activity in the Arctic in the form of shipping and resource extraction industries, with associated increased threats of marine accidents, pollution discharge and human created noise.
Increased oil exploration, exploitation and possible oil spills, drilling and shipping are potential threats to ringed seals in some areas. Ice breakers may directly disrupt the ice habitat of ringed seals, although this affects only a small area in relation to the total habitat available. Noise from shipping and industrial activities may disturb ringed seals and disrupt their activities, possibly leading to the abandonment of prime habitat (Reeves 1998). To date, the rather isolated and inaccessible habitat of ringed seals had provided them some protection from these threats.
Habitat disturbance, through manipulation of water levels, recreational snow machine operation, boating, tourism, shoreline construction, wind farms, etc., have been highlighted as specific threats for the Lakes Ladoga and Saimaa ringed seals (e.g., Sipilä and Hyvärinen 1998, Agafonova et al. 2007). Routine day-tourism seems to have caused the desertion of at least two previously used haulout sites at Lake Ladoga (Agafonova et al. 2007, Verevkin et al. 2006). As many as 2,000 wind generators are planned to be erected in Bothnian Bay, the main breeding area for Baltic ringed seals, but the impacts on ringed seals of the disturbance associated with the construction and operation of wind farms are unknown.
Artic ringed seals have little interaction with commercial fisheries, both because they do not consume commercial fish species to any great extent, and because their distribution does not coincide with intensive fisheries in most areas. They are therefore seldom caught in fishing gear. However, capture in fishing gear and other negative impacts associated with fisheries is a major problem for the ringed seals in Lakes Saimaa and Ladoga (e.g., Sipilä and Hyvärinen 1998, Agafonova et al. 2007, Kovacs et al. 2012) and in the Baltic Sea (Härkonen et al. 1998). Young seals seem particularly susceptible to capture in nets. Bycatch alone accounts for 10-16% of the annual mortality of the Lake Ladoga population (Verevkin et al. 2006).