As the global climate continues to warm, will polar bears become extinct soon?

In recent years, the threat of climate warming to polar bears has overwhelmed the Internet. I would like to remind everyone that the hotly debated area of ??32°C is located in Northern Europe. Affected by the North Atlantic warm current, Europe has always been hotter than other areas at the same latitude. The southern limit of polar bear distribution here has always been much further north than Siberia and Canada. Climate warming is a long-term cumulative process. Sea ice will not melt due to one day's high temperatures, nor will polar bears die due to one day's heat. We do not need to worry too much about local weather events in a certain area.

Many editors associate climate warming with polar bears, but they do not know the reason. They regard normal phenomena such as the seasonal melting of sea ice and the landing of polar bears as the consequences of climate warming. Now, Zoology will give you some popular science about the living habits of polar bears and how climate warming affects the lives of polar bears.

The living environment of polar bears: sea ice is crucial

To understand the harm of climate warming to polar bears, we must first understand what kind of environment polar bears need. Nowadays, under the propaganda of some media, many people have a misunderstanding that polar bears need very low temperatures to live. If the temperature rises, polar bears will be heated to death, or they will become extinct due to melting sea ice and no place to go. In fact, unlike cold-blooded animals such as sharks and crocodiles, the mammals to which polar bears belong are endothermic animals that can regulate their body temperature very well and usually will not be directly heated to death. Polar bears are also kept in some temperate zoos. Very good proof. Polar bears are good swimmers and can cross large areas of ocean without drowning.

For warm-blooded animals, temperature usually affects animal distribution indirectly by affecting food acquisition. The staple food of polar bears is seals, the most important of which are ringed seals. Although polar bears are good at swimming, they cannot swim underwater like pinnipeds such as seals. To hunt seals, you need sea ice. Sea ice limits seals' access to oxygen, and when seals surface to breathe, polar bears' opportunity comes. In addition, seals give birth to pups on the ice. In short, polar bears always sit on the ice and wait for seals to appear, catching and eating them immediately. As a result, polar bears are found in areas covered by sea ice most of the year, primarily the Arctic Ocean, but also the northernmost reaches of the Pacific and Atlantic Oceans.

Then the more and thicker the sea ice, the better? Neither. If the ice is too thick and there is little unfrozen water, the number of seals will be very small due to lack of food and difficulty in contacting the air, and polar bears will also lack places to hunt seals. How could they like such an environment?

The environmental needs of polar bears are such a paradox. If the temperature is too high, there will be more fish, and there will be more seals that feed on fish, but there is less sea ice, and polar bears cannot capture seals; if the temperature is too low, seals will There is not much, and there is too much and too thick sea ice, so it is still difficult for polar bears to catch seals. Polar bears have an optimal temperature range, as do virtually all animals.

The most suitable environment for polar bears to survive requires both closed ice and open water. Now the areas in the world that best meet these conditions are some sea areas near the Arctic Circle and close to mainland and island coastlines. . In the higher latitudes of the Arctic, some sea areas are affected by wind, ocean currents, topography and other factors, forming some open water surfaces, which we call polynya; the surrounding areas of polynya are also very suitable for polar bears to survive. The picture below shows a polynya in the northern waters of Baffin Bay.

Do polar bears need land to survive?

The polar bear was named by Phipps in 1774. Its scientific name, Ursus maritimus, means "Beach Bear". This reflects the understanding of early naturalists: polar bears live along the coast of the Arctic Ocean. There is a misunderstanding here. Although polar bears are more numerous in waters near the coast, they are distributed throughout the Arctic Ocean. People have also found polar bears very close to the North Pole. Polar bears are not only bears of the seaside, but also bears of the ocean.

There are two situations when polar bears land. First, in lower latitudes such as the Hudson Bay, polar bears have to land for refuge when the sea ice completely melts. Apart from human garbage, whale carcasses and fungal fruiting bodies, they can hardly obtain any useful food on land. They can survive these months of food shortage on land by hunting on sea ice in winter and spring. Second, pregnant female bears usually dig nests on land to give birth. They give birth in the cave and continue to live there with their babies for three to four months. Once the cubs grow large enough to adapt to the cold sea ice and sea water, they immediately take the cubs back to the ice to look for food.

Can’t polar bears survive off land? In the past, naturalists and hunters believed that female polar bears must build nests on land to give birth to cubs. Where there is no centralized nesting site, there is no fixed population of polar bears, but only a temporary population composed of some wanderers. Modern scientific research proves that this statement is unfounded. Female polar bears in the Beaufort Sea area never go to land to give birth, because the adjacent land here - northern Alaska's terrain is very flat and cannot form thick snow, and female polar bears need to have deep enough snow in early winter. There was snow for them to dig holes, and after they dug the holes, heavy snow continued to fall to cover them. The female polar bear in the Beaufort Sea has been building nests and giving birth on the ice floes, and she is still surviving well.

In addition, zoologists have only discovered in recent years that there is still a population of polar bears in the ocean basin area in the center of the Arctic Ocean. The center of the Arctic Ocean is far away from the mainland and has no islands. The polar bears here will almost certainly never land. The picture below shows a pregnant female polar bear in the Arctic Ocean basin.

Whether polar bears are marine animals or land animals has always been controversial. The most accurate term may be "marine land-based animals". Marine means that polar bears obtain food from the ocean and belong to the marine ecosystem. Land-based means that polar bears need to stand on land, where land is represented by ice floes on the sea. In this sense, polar bears are both marine and land animals. For more information about the landing of polar bears, you can read Zoology or click on the link at the end of the article.

Differences in the survival of polar bears between the north and the south

The distribution range of polar bears is generally in the north, and it is the northernmost point of the earth. But there are also more than 40 latitudes spanning from north to south, and the lives of polar bears at different latitudes are very different.

Southern polar bears represented by Hudson Bay. Hudson Bay is the southernmost point of polar bear distribution in the world. The sea ice here begins to melt in June every year, and from July to September most of the sea is not covered by ice. At this time, polar bears will land on land. Polar bears usually find a hole in the ground to hide in to avoid the heat and save energy. Starting from October, the sea surface begins to freeze again, and most polar bears return to the ice to hunt in late October and early November. What's special are the pregnant female bears. They move directly from the earth cave to the snow cave to prepare for giving birth. They give birth in December, and then emerge from the nest in March of the following year and return to the ice with their cubs. The female polar bear in Hudson Bay does not eat, drink or excrete for 8 consecutive months, which is the longest fasting period for mammals. During this period, she has to complete the tasks of giving birth and suckling her cubs, and the cubs weigh from 1.5 kg to 1.5 kg. Raise to around 15kg. Therefore, female polar bears are the most amazing mothers in the animal world. A similar area is Davis Strait.

Central polar bears represented by the Beaufort Sea. Zoologists have discovered that polar bears here have two major migrations throughout the year, migrating north in June and July and migrating south in November and December. In June, the ice in the southern sea near the coast of Alaska melts, and polar bears begin to move north to find ice, hunting in the north from August to October. October is the first month when ice floes appear in the shallow coastal areas of the South Beaufort Sea. Polar bears that previously migrated north begin to return south, occupying the entire South Beaufort Sea coast from November to December, and hunt here in winter and spring. This pattern of heading north to find ice in the summer and returning south in the winter is also seen in many areas, such as the Chukchi Sea and the Bering Sea. The polar bears in these two seas are actually the same population. In the summer, the polar bears completely withdraw from the Bering Sea and retreat to the Chukchi Sea. Come back again.

Northern polar bears represented by Viscount Melville Strait in the Canadian High Arctic (northern Arctic Archipelago). The temperature here is very low and sea ice is abundant all year round. Polar bears neither need to land for refuge nor go north to find ice. On the contrary, in winter, the temperature here is too low, and the sea ice is too much and too thick. It is difficult for polar bears to hunt seals. To avoid blizzards and poor hunting conditions, they have to use some shelters to rest temporarily. They usually enter in mid-December. Shelter, coming out of it in early February. Zoologists found that their hunting activities began to increase in January, remained at a high level from March to September, and began to decline in October.

Baffin Bay is a relatively special area. There is both the problem of ice melting in summer and autumn and the problem of too much sea ice in winter. The polar bears here use the shelter for two periods of time each year. The time to use the shelter in autumn is from mid-September to early November, while the time to use the shelter in winter is mainly from late December to March. The duration of shelter use in autumn was 50-70 days (average 56 days), while the duration of shelter use in winter was 35-86 days (average 65 days). Similar areas include some areas in the eastern Canadian Arctic Archipelago.

In summary, the higher the latitude, the more polar bears use shelters in winter and the less they use shelters in summer. At the highest latitudes in the center of the Arctic Ocean, polar bears should spend longer entering shelters during the winter.

The above table shows the differences in seasonal rhythms of polar bears in different regions. The text describes the activities of male bears and non-pregnant female bears. The gray areas are the additional hibernation and birth seasons of pregnant female bears. The number of pregnant female bears every year It has three or four months less normal hunting time than other bears.

The different impacts of climate warming on polar bears in the north and south

Many readers can’t help but worry about the polar bears in the Hudson Bay after reading the table above. The pregnant female bear has just finished her four months of ice The evacuation during the thaw period will directly enter the hibernation production season, and there will be no food for 8 months. In fact, the polar bears there lived quite well before. Polar bear cubs are born around December and follow their mothers out of their dens from March to April of the following year to hunt on the sea ice. In most areas, polar bear cubs follow their mothers until the spring of the third year of their lives, when they are about 2.3 years old. . They are weaned at this time and live independently. Even if the female bears immediately go into heat, court, mate, and become pregnant with adult male bears, they will not be able to give birth to their next litter of cubs until winter, so they will have one litter every three years. . Research in the Beaufort Sea shows that female bears give birth to a litter of cubs on average every four years.

In the Hudson Bay, most cubs are weaned and live independently in the second spring, when they are 1.3 years old. Many female bears immediately go into estrus and become pregnant, and give birth that winter, achieving an average of two cubs. Breed one litter per year. Research has confirmed that the polar bears in Hudson Bay were once the most prosperous population in the world. Not only were the cubs here the earliest to become independent, but the male bears also matured the fastest. Many male bears can reach physical maturity at the age of 5, while male bears in many other areas require After growing up to ten years old. The polar bears here have always been under heavy hunting pressure from humans, but they are still able to maintain population balance, relying on the unique seal resources and hunting environment.

However, climate warming has changed all this. In the late 1990s, the average date of sea ice loss in Hudson Bay was two weeks earlier than in the 1970s and early 1980s. Polar bears here, especially pregnant females, mainly rely on foraging for seals in spring and early summer to survive the melting period in late summer and autumn. Pregnant females differ from other polar bears in that they remain on shore after the ice refreezes in the fall, going eight months without eating. They must have accumulated enough fat in the spring and early summer to be able to go without food for such a long time. Early ice melt results in a shorter time for the female bear to forage, which means that the female bear accumulates significantly less fat before entering the den. It was found in Hudson Bay that adult female bears have lost weight and their age at first birth has increased. More and more bears leave their mothers as young as 2.3 years old, instead of being weaned a year earlier and living independently. Hudson Bay is located at the southernmost limit of polar bear distribution and is most affected by climate warming. If sea ice continues to degrade, the living conditions of polar bears in this area will further deteriorate.

Conversely, climate warming may be beneficial to polar bears in areas where thick sea ice limits their access to food, at least in the short term. Thinning ice caps and shorter ice seasons can increase seal numbers in northern areas and improve hunting conditions for polar bears, thereby greatly increasing the amount of energy transferred up the food chain. If the polar bears in the center of the Arctic Ocean heard that the sea ice was thinning and some polynyas were about to appear, they would jump for joy!

Fauna has consulted the latest data and found that there are currently about 22,000-31,000 polar bears in the world, slightly more than ten years ago. The two to thirty thousand polar bears are divided into 19 identified populations and one controversial population (center of the Arctic Ocean). These populations have no downward trend, no habitat fragmentation, and no risk of extinction, including due to climate change. Hudson Bay populations most affected by warming. Generally speaking, the living conditions of polar bears have been relatively stable in recent decades.

At present, experts studying polar bears around the world recognize that climate warming is the biggest concern for the survival of polar bears. Although polar bears at high latitudes may benefit in the short term, if sea ice extent continues to decrease, polar bears around the world will eventually be affected. Polar bears are closely related to ice floes, and they carry out a series of life activities such as hunting and mating on it. Therefore, the continued large-scale reduction of ice caps will eventually affect their survival. What we have to do now is, on the one hand, to be more vigilant to prevent polar bears from being annihilated by the increasing climate warming. On the other hand, we must correctly understand the impact of climate warming on polar bears. If we continue to spread alarmist stories and spread rumors, there will undoubtedly be many more cases. Unnecessary panic and useless work are also detrimental to polar bear conservation.