Seals are diverse marine mammals (pinnipeds) found from the icy poles to tropical coastlines. They function as top predators in marine food webs, helping regulate fish and invertebrate populations. Their health often indicates the overall condition of the ecosystems they inhabit. However, the rapidly changing climate is fundamentally altering the oceans and coastal areas seals rely on, creating immense pressures on their populations worldwide.
Disruption of Essential Ice Habitat
For many species, including Harp, Ringed, and Hooded seals, stable sea ice is necessary for their life cycle. Ice platforms function as safe environments for giving birth, nursing young, and resting during molting periods. This frozen habitat also offers protection from marine predators.
Climate change causes sea ice to form later, be thinner, and break up earlier in the spring. This premature loss of the pupping platform leads to severe results for young seals. Pups lack the necessary blubber layer or swimming skills, forcing them into the water too soon, resulting in drowning or separation from their mothers.
The consequences of this habitat loss can be severe for entire year classes of seals. In low-ice years, studies have documented pup mortality rates approaching 100% in certain key whelping areas. Satellite records tracking the ice conditions in Harp seal breeding grounds show a decline in sea-ice cover by as much as six percent per decade. When adult seals are unable to find thick, stable ice, they may be forced to give birth on fragile ice that is easily crushed by storms or breaks apart.
The reduction in stable ice forces adults to expend greater energy searching for suitable resting and molting sites. This increased energy expenditure reduces the seals’ overall body condition. It may also compromise their reproductive capacity in subsequent seasons, representing a direct threat to ice-dependent species.
Shifts in Food Sources and Feeding Behavior
Warming ocean temperatures trigger large-scale shifts in the marine food web seals depend on. The distribution and abundance of prey, such as krill, copepods, and fish, are changing as they seek cooler waters or are affected by altered currents. This disruption forces seals to adapt their foraging strategies or face nutritional stress.
In the Arctic, the fat-rich Arctic cod is becoming less prevalent in some regions. Smaller fish like capelin and sand lance may become more common, requiring seals to consume a higher volume of prey for the same energy. This dietary change demands more time and effort spent foraging. Furthermore, the body mass of key prey species is predicted to shrink, with some fish becoming 18 to 35 percent smaller.
The need to find food also affects the behavior of deep-diving species, such as Southern Elephant seals. As ocean layers warm, prey can migrate to greater depths, forcing seals to dive farther down to capture them. These longer, deeper dives require a greater physiological cost and may result in less successful foraging overall. Poor foraging conditions for mothers during pregnancy and nursing have been linked to declines in pup body condition, reducing the offspring’s survival chances.
Increased Exposure to Stressors and Disease
Climate change introduces health stressors that compromise seal populations beyond habitat and food loss. The stress from struggling to find food and stable ice suppresses a seal’s immune system, making it more susceptible to illness. This physiological vulnerability coincides with an increased presence of pathogens in the marine environment.
Warming waters enable bacteria, viruses, and parasites, once constrained by colder temperatures, to thrive and spread into new areas. This shift in pathogen distribution exposes seals to novel diseases against which they have little natural resistance. For example, the parasite Toxoplasma gondii is spreading more easily due to contamination carried into marine environments.
The increased frequency and intensity of extreme weather events, such as severe storms, is another physical consequence of climate change. These powerful storms can lead to mass stranding events, especially for vulnerable seal pups born on exposed coastal rookeries. Grey seal pups can be swept into the water prematurely before they swim proficiently, leading to injuries and malnutrition.
Conservation and Monitoring Efforts
Scientists and conservation groups are implementing strategies to understand and mitigate the threats seals face from a changing climate. Population tracking is a fundamental component, often utilizing satellite telemetry to monitor seal movements and habitat use. Researchers also conduct aerial surveys to estimate population sizes and track breeding success in traditional areas.
Innovative monitoring involves seals carrying sensors to collect valuable oceanographic data, such as water temperature, salinity, and currents. This information provides a clearer picture of environmental changes occurring in their habitats. The resulting data is used to perform climate vulnerability assessments, identifying the species and populations most at risk.
Conservation projects focus on protecting key habitats and enhancing species resilience. For instance, the LIFE ADAPTS project targets the Mediterranean monk seal by identifying breeding sites and implementing conservation measures in Marine Protected Areas. Ultimately, the long-term protection of seals requires international cooperation to address the root cause of the problem by reducing global greenhouse gas emissions.