Threats to polar bears
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 is scarce.
- Sea ice now melts earlier in the spring and forms later in the autumn in the bears’ southern range, like the Hudson and James Bays of Canada.
- As the bears spend longer periods without food, their health declines.
- Unhealthy bears can lead to lower reproduction rates – and local extinction.
- Scientists have found the main cause of death for cubs to be either lack of food or lack of fat on nursing mothers.
- For every week earlier the ice breaks up in Hudson Bay, bears come ashore roughly 10 kg (22 lbs) lighter and in poorer condition.
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.
- 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.
- 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.
What's a POP?Persistent organic pollutants (POPs) include a wide range of poisonous substances. Most POPs are officially banned, but they are still sometimes used, and they stay in the environment for many years. Because of inadequate screening systems, new chemicals are showing up in the Arctic. The effects of some of these chemicals are still being studied.
POPs found in the Arctic
- heat resistant chemicals, like PCBs
- industrial by-products such as dioxins and furans
- pesticides like DDT, dieldrin and lindane
How does oil exploration affect polar bears?
- Reduced insulation
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.
- Destruction of habitat
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.
Offshore operations pose the greatest risk, since routine emissions, spills or leaks will be discharged directly into the sea or on the sea ice.
Polar bear populations are expected to come under increased pressure if oil developments in the Arctic go ahead according to industry plans.
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 harvest local animals.
Is polar bear hunting sustainable?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 at least 22,000 polar bears worldwide living in 20 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.