Estimating the number of polar bears and how their populations are changing is challenging because they live in remote areas and are spread out over large regions with few individuals. Studying polar bears in the wild can also be dangerous for researchers. As of 2015, the International Union for Conservation of Nature (IUCN) reported that there are between 22,000 and 31,000 polar bears worldwide, but scientists do not know if the population is increasing, decreasing, or staying the same. However, polar bears are classified as "Vulnerable" because scientists predict their numbers could drop by at least 30% over the next 34.5 years due to the loss of habitat area, the size of their living space, and the quality of their environment. Threats to polar bears include climate change, pollution from harmful chemicals, conflicts with ships, oil and gas activities, and interactions with humans, such as hunting for food or viewing them for recreation. Climate change is happening quickly and is affecting polar bears in ways that impact their biology, body structure, ability to reproduce, and risk of extinction.
According to the World Wildlife Fund, polar bears are important because they show how healthy the Arctic ecosystem is. Scientists study polar bears to learn about changes in the Arctic, as declining polar bear numbers often signal problems in the Arctic marine environment.
Climate change
The main danger for polar bears because of climate change is not having enough food, which can lead to starvation. This happens because their habitat is changing. Polar bears hunt seals from sea ice. Warmer temperatures make sea ice melt earlier in the year, which forces bears to go to shore before they have enough fat to survive the summer and fall when food is scarce. Less sea ice also means polar bears must swim longer distances, using more energy and sometimes leading to drowning. Thinner ice breaks more easily, making it harder for bears to reach seals. Not enough food causes adult females to have fewer babies and makes it harder for young bears to survive. All polar bears also have worse body condition when food is limited.
Groups like the International Union for Conservation of Nature, Arctic Climate Impact Assessment, and United States Geological Survey, along with scientists who study polar bears, are worried about the effects of climate change. Some experts predict that polar bears could become extinct by 2102.
A warming climate also affects other parts of polar bear life. Changes in sea ice make it harder for pregnant females to find good places to build dens. As sea ice moves farther from the coast, females must swim longer to reach land areas where they usually den. Thawing frozen ground can harm bears that den underground, and warm winters might cause dens to collapse or lose their insulating value. For bears that den on older ice, moving ice might force mothers and cubs to walk farther to reach areas where they hunt seals in the spring. Warmer weather also allows more bacteria and parasites to grow, which can harm polar bears.
Climate change has affected how female polar bears reproduce. Factors like the environment, age, and body condition influence their ability to have babies. For a female to stay pregnant, she needs a lot of energy. If she tries to reproduce when food is scarce, it can harm both her and her babies. Losing a litter might make it harder for her to reproduce again. Polar bears mate between March and June, but the egg starts to grow in September or October. Most litters have two cubs, and mothers are usually between 5 and 7 years old when they have babies. Female polar bears older than 20 rarely get pregnant. A study from 1991 to 2021 found that body weight is important for reproduction. The minimum weight needed for pregnancy is 195–196 kg. For every extra kilogram, the chance of pregnancy increases by 3.88%.
When sea ice breaks up early and polar bears are thin, they are more likely to search for food in human areas, such as garbage dumps. As sea ice shrinks, hungry bears may look for food on land more often, which could lead to more dangerous encounters with humans, including attacks.
Researchers studied pregnant polar bears from 1991 to 2021 and compared data from 1982 to 1990. They thought pregnancy rates would decrease over time because of changes in sea ice and food availability. They also believed older bears would have more trouble getting pregnant, while heavier bears would have an easier time. Scientists captured 541 polar bears in northeastern Canada and collected blood samples. They found that female polar bears older than five years weighed more on average than those who were not pregnant. Heavier females were more likely to get pregnant, with a minimum weight of 196 kg. Pregnancy rates have decreased over time, but sea ice conditions did not affect pregnancy rates. Instead, food availability and body condition were the most important factors for reproduction.
Climate change has had the biggest effects on polar bears in the southern parts of their range, where populations have declined. The Western Hudson Bay group, which is in the south and well-studied, relies on ringed seals during late spring when seal pups are easy to catch. This hunting season ends when sea ice melts, and bears fast or eat little during summer until ice returns. Warming temperatures have caused sea ice in Western Hudson Bay to break up three weeks earlier than it did 30 years ago, shortening the time bears can hunt. Between 1980 and 2004, the average weight of female polar bears dropped from 290 kg to 230 kg. The Western Hudson Bay population decreased by 22% between 1987 and 2004, though it was considered stable as of 2017. The U.S. Geological Survey predicts that two-thirds of polar bears could disappear by 2052.
In Alaska, less sea ice has increased the number of polar bear cubs dying and changed where pregnant females build dens. Between 1985 and 1994, 62% of maternity dens were on sea ice, but by 1998–2004, this dropped to 37%. Now, more Alaskan polar bears den on land, like the global population. In 2005, polar bears swam longer distances to find food, and four drownings were recorded during a large ice loss.
Polar bears are now moving to new areas more often. While this is not common, they are being seen more frequently on land, especially in northern Canada, staying on the mainland for longer periods during summer. This may lead to more reliance on land-based food like goose eggs, birds, and caribou, as well as more conflicts with humans.
Evolution
Polar bears are a symbol of the dangers climate change poses to the world's wildlife and how species change over time. Scientists studied the genome of a polar bear that lived 130,000 to 150,000 years ago. This bear was found in the Svalbard Archipelago. Polar bears rely on sea ice to survive and maintain their future stability. By comparing this ancient genome with the genomes of modern polar bears and brown bears, researchers hoped to learn how polar bears adapted to past environmental changes. They used a genome sequence with 10x coverage for both the ancient and modern bears. The study showed that climate change is causing black and brown bears to move north into polar bear areas. This may lead to more overlap between species, causing competition and mixing of genes. The genomes revealed that ancient polar bears often mixed with other species. Mixing genes can increase genetic diversity and help species change over time. Scientists believe this effect will be smaller compared to the loss of sea ice and habitat.
Researchers also predict that shrinking sea ice in the Arctic will separate polar bear populations. Even though other bears may move into the area, polar bears may become isolated. This could reduce genetic diversity and lead to inbreeding. Since climate change is happening faster now than in the past, polar bears may not have enough time to adapt.
Steven Amstrup and scientists from the U.S. Geological Survey predict that two-thirds of the world’s polar bears may disappear by 2051, based on moderate projections of summer sea ice loss due to climate change. Some scientists have questioned the accuracy of this study. Polar bears may vanish from Europe, Asia, and Alaska, and their numbers may drop in the Canadian Arctic Archipelago and near northern Greenland. By 2081, polar bears may disappear entirely from Greenland and the northern Canadian coast, leaving only a few in the interior Arctic. However, in the short term, some polar bear populations in colder Arctic regions may temporarily benefit from milder weather, as thick, long-lasting ice is replaced by thinner ice that allows seals to breathe.
Polar bears split from brown bears 400,000 to 600,000 years ago and have survived past climate changes. Some people say polar bears may adapt to eating land-based food as sea ice disappears. However, most scientists believe polar bears cannot fully replace the energy from seal blubber with land-based food and may struggle to compete with brown bears for land-based resources, leading to population decline.
As Arctic sea ice decreases, polar bears are spending more time on land. Scientists believe this forces them to reduce activity to save energy. Energy is key to successful reproduction and survival. A study from 2019 to 2022 in Manitoba, Canada, tracked 20 polar bears from August to September. Researchers aimed to learn about their daily energy use, diet, behavior, movement, and body condition.
Adult polar bears were defined as those five years or older, and subadults were between two and four years old. Scientists took blood samples and measured oxygen-18 and water levels. They also measured breathing patterns and progesterone levels in female bears. After 19 to 23 days, the bears were recaptured, and the same measurements were compared. The study found that daily energy use varied five times among all bears and four times among adults. Bears were more active on sea ice and less active on land. Some bears reduced their metabolism to levels similar to hibernation, while others increased foraging and activity. The amount of body fat compared to energy use had no clear connection. Researchers say this shows wide differences in how individual bears behave. Berries were the most common food source, even though they provide little energy. Three bears swam more than others and had higher energy use, earlier signs of starvation, and were more active in age and sex. Overall, scientists predict that spending more time on land will increase the risk of starvation, reduce energy reserves, and lower reproduction success.
Pollution
Polar bears have high amounts of long-lasting chemicals, such as polychlorinated biphenyls (PCBs) and chlorinated pesticides. These chemicals often reach the Arctic through long-distance travel. The main ways they move are through primary sources, like waste dumps and old industrial sites, and secondary sources, such as chemicals that build up in the environment over time. Polar bears are at the top of the food chain and eat a lot of blubber, which causes harmful chemicals like halocarbons to collect in their bodies. These chemicals can harm animals by acting like hormones in the body. Studies show that PCBs, which have been studied the most, are linked to birth problems and weak immune systems.
Many chemicals, including PCBs and DDT, have been banned worldwide because of their harm to the environment. Since the ban, levels of PCBs in the Arctic air have decreased over the past few decades. This decline is likely because of the international ban on PCBs. Research from 1989 to 1993 and from 1996 to 2002 supports this. During these same time periods, DDT levels were much lower in the Western Hudson Bay polar bear population.
Oil and gas development
Oil and gas development in Northern Alaska has happened for more than 40 years. Most of this development has taken place between the National Petroleum Reserve-Alaska and the Arctic National Wildlife Refuge (ANWR). In 2017, the United States allowed oil and gas development to happen in the coastal plain of the Arctic National Wildlife Refuge. The ANWR contains important habitats for polar bears. Oil and gas development in these areas can affect polar bears in many ways. An oil spill in the Arctic would likely gather in places where polar bears and their prey are also found, such as sea ice leads. Polar bears rely partly on their fur to stay warm and regulate body temperature. Oil getting on their fur reduces its ability to keep them warm, increasing the risk of hypothermia. Polar bears exposed to oil spills have been seen licking oil from their fur, which can lead to kidney failure. Maternity dens, used by pregnant mothers and mothers with babies, can also be disturbed by nearby oil exploration and development. Disturbing these areas may cause the mother to leave the den too early or abandon her young. Overall, there is no effective way to capture polar bears exposed to oil.
Harvesting
In Russia, polar bear fur was traded for money as early as the 14th century, but it was not as valuable as fur from Arctic foxes or reindeer. As more people lived in the Arctic regions of Eurasia during the 16th and 17th centuries, and as tools like guns became more common, more polar bears were hunted. However, because polar bear fur was not highly valued in trade, records about how many were hunted in the past are incomplete. For example, in the winter of 1784/1785, Russian hunters on Spitsbergen killed 150 polar bears in Magdalenefjorden. By the early 20th century, Norwegian hunters were killing about 300 polar bears each year in the same area. Estimates suggest that about 400 to 500 polar bears were hunted yearly in northern Eurasia from the early 1800s, with numbers rising to 1,300 to 1,500 by the early 1900s before declining as bear numbers dropped.
For people who live in the Arctic, hunting polar bears for food, clothing, and tools is important for their culture, health, and economy. Because there were not many people living in polar bear habitats, traditional hunting did not harm bear populations much. This is because the low number of people meant that hunting was limited and controlled.
In the first half of the 20th century, new hunting methods, such as using snowmobiles, icebreakers, and airplanes, made it easier to hunt polar bears. A 1965 newspaper article compared hunting polar bears from airplanes to "shooting a cow with a machine gun." Norwegian hunters used traps with rifles that fired when a bear pulled a string attached to bait. By the 1960s, the number of polar bears killed each year increased rapidly, reaching 1,250 in 1968.
For some groups of polar bears, the effects of hunting and climate change could be worse. Losing habitat might make bears more vulnerable to overhunting, which could cause their numbers to drop. Female polar bears usually have more babies than males. If more females are hunted, it could harm the long-term survival of polar bear populations.
Because of concerns about polar bear survival, countries began creating rules to control hunting. The Soviet Union banned all hunting in 1956. Canada started limiting how many bears could be hunted in 1968. Norway made hunting rules stricter from 1965 to 1973 and banned hunting completely after that. The United States began regulating hunting in 1971 and passed a law to protect marine mammals in 1972. In 1973, five countries—Canada, Denmark, Norway, the Soviet Union, and the United States—signed an agreement to protect polar bears. The agreement limited hunting, banned hunting from planes and icebreakers, and required more research. It allowed hunting by local people using traditional methods. Norway is the only country among the five that completely bans polar bear hunting. This agreement was unusual because it happened during the Cold War, when countries rarely worked together.
Countries have also made agreements to manage polar bear populations that live in shared areas. In 2000, Russia and the United States agreed to set limits on how many bears could be hunted by Indigenous people in Alaska and Chukotka. This agreement was approved in 2007. In 2015, countries that share polar bear habitats created a plan to protect the species.
Polar bears are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), which means their trade is controlled with permits. The United States has proposed moving polar bears to Appendix I, which would stop all commercial trade in polar bear parts. However, groups like the IUCN and TRAFFIC said this change might not help protect the species. Other organizations, including WWF and Polar Bears International, also opposed moving polar bears to Appendix I.
In Canada, polar bears were first listed as "Not at Risk" in 1986 and later as "Special Concern" in 1991. This status was reviewed and confirmed in 1999, 2002, and 2008. Polar bears remain a species of special concern in Canada because they are sensitive to overhunting and because Arctic sea ice is expected to shrink.
More than 600 polar bears are killed by humans each year in Canada, a number scientists say is too high for some areas, like Baffin Bay. Since 1970, sport hunters have been allowed to hunt polar bears with local guides and dog-sled teams, though this became common later. Hunting provides jobs and income for northern communities where few other economic opportunities exist. Sport hunting can bring up to $35,000 per bear to local communities, mostly from American hunters.
In Nunavut, which is home to 80% of polar bear kills in Canada, the government increased the hunting limit from 400 to 518 bears in 2005, despite warnings from scientists. In some areas, studies show polar bear numbers are declining, and in others, there is not enough data. Most of the bears killed are hunted by the Inuit, but more are being sold to sport hunters each year. In 2010, the government reduced the hunting limit for Baffin Bay from 105 to 65 bears by 2013. The Northwest Territories also set hunting limits for bears in Inuvialuit communities, with some reserved for sport hunters. Canada banned exporting polar bear parts like fur and claws from Baffin Bay in 2010.
In Canada, reducing sport hunting might actually increase the number of polar bears killed in the short term. The government sets a yearly limit on how many bears can be hunted for sport and survival. If fewer bears are hunted for sport, more permits are given to subsistence hunters, which can lead to more bears being killed overall.
Controversy over species protection
The polar bear population is one of the most common land predators in the world. They live in areas near sea ice in regions like the Arctic in Canada. About 60% of all polar bears live in Canada. Over the past 50 years, the number of polar bears worldwide has increased and remains stable today. As of 2021, there are about 26,000 polar bears worldwide.
There is disagreement about whether polar bears should be listed as an endangered species. Conservation groups and the Inuit people of Canada have different views. The government of Nunavut and many northern residents oppose the U.S. plan to add polar bears to the Endangered Species Act. Many Inuit believe the polar bear population is growing, and rules that limit hunting for sport could reduce income for their communities.
Although some polar bear populations are recovering, there is little evidence that polar bears are doing well overall. The difference between past population growth and future predictions has several causes. One reason is that hunting limits were introduced, helping the species recover after being overhunted. Another reason is that climate change has affected sea ice levels differently in various areas.