Polar bear

Last updated 31 May 2022

The polar bear in the Barents Sea lives on disappearing sea ice. Climate warming is the main threat to polar bears. The polar bear habitat is changing rapidly, and the Polar Basin could be ice-free in summer within a few years. To gain access to preferred denning areas and their favorite prey, ringed seals, polar bears depend on good sea ice conditions at the right time and place. The population probably increased considerably during the years after hunting was banned in 1973, and new knowledge indicates that the population has not been reduced the last 10-15 years, in spite of a large reduction in available sea ice in the same period.

Status and trend

A period of intensive hunting in and around Svalbard began about 1870, and on average some 300 bears were harvested annually in the following 100 years. The population was consequently at a low level when it was protected in 1973.

In 2004, it was estimated to number between 1900 and 3600, which means that it is not threatened by the effects smaller populations may be impacted by, such as loss of genetic diversity or random demographic processes. Furthermore, genetic studies show that exchange between neighboring subpopulations to the west and east is large. Another aerial survey over Norwegian territories in the Barents Sea and in Svalbard was conducted in 2015, and the results indicate that the number of local bears had not changed much when compared to the results from the previous survey in 2004. The number of bears that live north in the pack ice in the fall most likely has been stable or even increased in the period between the surveys.

Lack of earlier estimates of good quality makes it impossible to say anything certain about historical trends, but various types of data indicate that the subpopulation grew rapidly following its protection and into the 1980s. Using demographic data, it has been suggested that the subpopulation also grew up to the turn of the century. Even though the loss of sea ice has been marked around Svalbard in recent years, and is expected to continue in the coming decades, the size of the subpopulation may still be below the carrying capacity. It is therefore possible that the subpopulation currently is still growing, or at least is stable, even though the availability of habitats has become poorer for much of the year.

The occurrence of dens on the islands of Hopen and Kongsøya clearly show that few females reach there in the autumn if the ice comes late, sometime after the first part of November. Whether this means that the proportion of females in the subpopulation that have cubs is declining, or that they den elsewhere, is not clear.

The number of days with sea ice around all the five most important denning areas has experienced a dramatic negative trend since 1979. In some years, the ice has come late in all the areas the same year, and such years can prove challenging for females who have spent the summer in the pack ice to reach one of the relevant areas.

Causal factors

The availability of sea ice has always varied a great deal from year to year and through the seasons. The changes in large parts of the Arctic towards the period with ice-free water becoming longer and longer are explained by a milder climate with especially large changes in the Arctic. With current levels of greenhouse gas emissions, and the forecasts for the coming decade, it is expected that the areas around Svalbard will experience particularly large changes.

Observations so far are unable to document that changes in the climate have had clear effects on the subpopulation. Habitat availability may still be good enough to be able to maintain a population at the current level. Declining trends in reproduction or fitness may not be explainable just by variations in climate impact or corresponding trends in sea ice distribution. Density-dependent responses on reproduction are not an unlikely future scenario and may become prominent with time due to the growth in the subpopulation following its protection in 1973. Such density dependence will also be expected to increase if habitat availability decreases, but not before the population size approaches the carrying capacity.

Very high levels of several fat-soluble substances are found in polar bears in the Barents Sea area, and it is likely that this has effect at the population level, but it is very difficult to quantify how important they are.

The large annual variability in available sea ice makes it possible to study the effects of habitat changes more directly and may eventually enable the effects of density-dependence, habitat changes and other pressure factors to be quantified and separated from one another.

Consequences

The polar bear is an important species in the arctic ecosystem. Changes in their population size and the way bears use their habitat, which can be expected to be particularly large if changes in the availability of sea ice continues, will therefore be likely to have consequences beyond the changes for the species itself.

The polar bear is entirely dependent upon seals that live in the ice, and will have an impact on these species, at least locally. When the sea ice does not freeze in the fjords in Svalbard before late winter, ringed seals may, for lack of snow to make lairs, give birth to their pups directly on the ice. If, in addition, the areas of sea ice are limited, the pups will quickly be taken by bears, foxes and gulls. Over time, it is conceivable that poor seal recruitment leads to less food being available for polar bears.

Perhaps more importantly, less ice makes it difficult for the polar bear to hunt. More bears on land in years with little ice also increases predation on eggs and birds in several areas and may thus also influence ecosystems on land.

It is impossible to say anything now about exactly how changes in the number of bears and available habitats will affect the ecosystems, but a total loss of sea ice will necessarily also lead to a loss of the ecosystems that depend upon it.

Changes in the distribution and availability of sea ice are already leading to great changes in the distribution of polar bear dens. Historically important denning areas, especially on the more peripheral islands, may become unsuitable in the future. Increased use of alternative areas will also lead to greater changes in habitat. This might impose a larger predation pressure on potential prey species in new areas.

About the monitoring

The polar bear is monitored because it is Red Listed and is vulnerable to pressures deriving from climate change and environmental pollutants. It is also a species that has great appeal so that knowledge about how it is being affected will more easily lead to enhanced focus on the effects of climate change, pollutants and other pressures linked with human activity which may harm the ecosystem in the Arctic.

The most important human-induced pressure factor for polar bears is the loss of sea ice due to changes in climate. To be able to detect the effects of this as quickly as possible, the population monitoring of the polar bear is focusing on reproduction and body condition.

An aerial survey to estimate the size of the shared Norwegian-Russian Barents Sea subpopulation was carried out in 2004, and the resulting estimate was 2650 bears +/- ca 30 %. A new survey of the Norwegian part of the population was conducted in August 2015, and the results do not show any sign of a reduction in population size.

Due to the covid-19 pandemic situation in 2020 no fieldwork was conducted this year, and thus no data is available for any of the parameters.