Large carnivores are sensitive indicators of ecosystem health. A polar bear at risk is often a sign of something wrong somewhere in the Arctic marine ecosystem.
Climate change, and the loss of sea ice habitat, is the greatest threat to polar bears. The impacts of this change are felt first and worst in the Arctic.
How does climate change affect polar bears?
Polar bears rely on sea ice to hunt and store energy for the summer and autumn, when food can be scarce. Sea ice now melts earlier in the spring and forms later in the autumn in the bears’ southern range, like Hudson Bay and James Bay in Canada. As the bears spend longer periods without food, their health declines. For every week earlier the ice breaks up in Hudson Bay, bears come ashore roughly 10 kg (22 lbs) lighter and in poorer condition.
Unhealthy bears can mean lower reproduction rates, higher cub mortality – and eventually, local extinction. The main causes of death for cubs are lack of food or lack of fat on nursing mothers.
As top predators, polar bears are exposed to high levels of pollutants through their food. The popular image is of polar bears living in a pure, frozen wilderness is misleading. The Arctic food chain contains high levels of some toxic chemicals.
How do toxic chemicals affect polar bears?
Bears with high levels of some POPs (persistent organic pollutants) have low levels of vitamin A, thyroid hormones, and some antibodies. These are important for a wide range of biological functions, such as growth, reproduction, and the ability to fight off diseases. Females with partially-developed male sexual organs -- Pseudohermaphrodites -- have been observed in 1.5 % of the polar bears sampled on Svalbard in recent years. Scientists believe this could be the result of long-range pollutants.
In some areas, the mother bears’ milk contains particularly high concentrations of these chemicals. The milk can actually poison the cubs, leading to lower survival rates.
The oil and gas business is increasingly moving into the Arctic as more accessible reserves in the south dry up. Polar bear populations are expected to come under increased pressure if oil developments in the Arctic go ahead according to industry plans. Offshore operations pose the greatest risk, since routine emissions, spills or leaks will be discharged directly into the sea or on the sea ice.
How does oil exploration affect polar bears?
Contact with oil spills can reduce the insulating effect of the bears' fur. The bear must then use more energy to keep warm, and compensate by increasing its caloric intake—which may be difficult.
Polar bears can ingest oil through grooming and through eating contaminated prey. The ingested oil can cause liver and kidney damage, and has long-term toxicity. Bears can be poisoned by even a limited amount of oil on their fur.
Seismic blasting, construction, transportation and operation of oil facilities can negatively affect polar bears.
If a major oil spill occurs at or near areas with high concentrations of polar bear denning sites, for example Hopen Island in the Barents Sea, it could have population-wide consequences.There is currently no proven effective method for cleaning or controlling an oil spill in icy, arctic waters, where difficult weather conditions are common.
The legality of polar bear hunting varies among the Arctic countries. The international Agreement on the Conservation of Polar Bears allows for the taking of polar bears for use by local people using traditional methods and exercising traditional rights. WWF supports the right of Indigenous Peoples to continue to sustainably hunt local animals.
In countries with monitoring programs, hunting quotas are designed to keep the bears' populations stable. But in some countries, the extent of polar bear hunting--and its effect on populations--is unknown.
There are estimated to be 22,000 to 31,000 polar bears worldwide living in 19 populations. The general status of polar bears is currently stable, though there are differences between the populations.
The Polar Bear Specialist Group (PBSG) regularly reviews the countries' monitoring of polar bear size, age and gender distributions. For populations with functioning monitoring programs, the PBSG can estimate the status of the population. The PBSG urges governments to start monitoring populations whose stability is unknown so that population estimates can be made and trends documented. Only then can the sustainability of hunting be secured.