Climate change is likely the greatest long-term threat to polar bears. Over-harvesting, environmental contaminants and increasing industrial development in Ontario’s far north are factors that may also affect the long-term survival of polar bears in the province.
Climate Change
In Hudson Bay and James Bay, climate change is causing sea ice to break-up (thaw) earlier and freeze-up later. It’s believed this reduces the amount of time polar bears can spend on the ice feeding on seals to put on fat to support their seasonal fast. Over the last 30 years, the break-up of sea ice has occurred about 9.5 days earlier per decade in northern James Bay and between five and eight days earlier per decade along the southern Hudson Bay coast of Ontario.
The Southern Hudson Bay subpopulation of polar bears is showing declines in body condition and trends towards lower survival rates, although the number of bears has remained stable. If these trends continue in southern Hudson Bay, they may lead to a decline in the size of the subpopulation. Such declines have been observed elsewhere. For example, the Western Hudson Bay subpopulation of polar bears has shown declines in body condition, reproductive success, survival (in young and old bears near Churchill, Manitoba and in years with early sea ice melt) and the number of bears (a 22 per cent reduction) over the past 20 years.
Harvest
Because of their low reproductive potential, polar bear populations are especially vulnerable to the over-harvesting of adult females. Aboriginal communities in Ontario, Nunavut, and Quebec all hunt polar bears from the Southern Hudson Bay subpopulation. Sustainably harvesting this subpopulation depends on continued cooperative monitoring and managing of harvest activities among all three jurisdictions. For information on current harvest levels and management in Ontario, refer to the Harvest Management section of this report.
Environmental contaminants
Polar bears are a top carnivore and environmental contaminants accumulate in their bodies. Contaminants such as PCBs (polychlorinated biphenyls) and various pesticides like DDT (dichlorodiphenyltrichloroethane) enter their bodies through the food they eat. These contaminants are produced by people in populated areas and are transported to remote northern and arctic regions by wind and water currents. If contaminant levels rise or new contaminants are introduced polar bear mortality may increase. This might also affect their ability to reproduce.
Industrial development
Development in Ontario’s Far North has increased in recent years. For example, a diamond mine was recently established, a new electricity transmission corridor was built along the James Bay coast, and winter roads were built linking Shammatawa (Manitoba) to Fort Severn and Peawanuck (Ontario). More developments, such as wind power, additional electrical transportation corridors, all-weather roads, and accelerated mining exploration are being proposed. With increased development, more frequent bear-human encounters (and associated bear mortalities), increased harvest, and loss of polar bear habitat are growing concerns.
Previous page... The state of polar bears | Next page... Polar bear management
