Polar bear conservation
population sizes and trends are difficult to estimate accurately because they occupy remote home ranges and exist at low population densities. Polar bear fieldwork can also be hazardous to researchers. As of 2015, the International Union for Conservation of Nature reports that the global population of polar bears is 22,000 to 31,000, and the current population trend is unknown. Nevertheless, polar bears are listed as "Vulnerable" under criterion A3c, which indicates an expected population decrease of ≥30% over the next three generations due to "decline in area of occupancy, extent of occurrence and/or quality of habitat". Risks to the polar bear include climate change, pollution in the form of toxic contaminants, conflicts with shipping, oil and gas exploration and development, and human-bear interactions including harvesting for food and possible recreational polar-bear watching. Climate change is occurring at high rates, which is affecting the population of Polar Bears. Specifically in ecology, morphology, reproduction, and extinction risk.
According to the World Wildlife Fund, the polar bear is important as an indicator of Arctic ecosystem health. Polar bears are studied to gain understanding of what is happening throughout the Arctic, because at-risk polar bears are often a sign of something wrong with the Arctic marine ecosystem.
Climate change
Nutrition
The key danger for polar bears posed by the effects of climate change is malnutrition or starvation due to habitat loss. Polar bears hunt seals from a platform of sea ice. Rising temperatures cause the sea ice to melt earlier in the year, driving the bears to shore before they have built sufficient fat reserves to survive the period of scarce food in the late summer and early fall. Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning. Thinner sea ice tends to deform more easily, which appears to make it more difficult for polar bears to access seals. Insufficient nourishment leads to lower reproductive rates in adult females and lower survival rates in cubs and juvenile bears, in addition to poorer body condition in bears of all ages.Reproduction
The International Union for Conservation of Nature, Arctic Climate Impact Assessment, United States Geological Survey and many leading polar bear biologists have expressed grave concerns about the impact of climate change, with some predicting extinction by 2102.In addition to creating nutritional stress, a warming climate is expected to affect various other aspects of polar bear life: changes in sea ice affect the ability of pregnant females to build suitable maternity dens. As the distance increases between the pack ice and the coast, females must swim longer distances to reach favoured denning areas on land. Thawing of permafrost would affect the bears who traditionally den underground, and warm winters could result in den roofs collapsing or having reduced insulative value. For the polar bears that currently den on multi-year ice, increased ice mobility may result in longer distances for mothers and young cubs to walk when they return to seal-hunting areas in the spring. Disease-causing bacteria and parasites would flourish more readily in a warmer climate.
With the ongoing changes in the climate, this has had overall effects on the female Polar Bears. Specifically population demography which is influenced by life history and the environment. Environmental factors, age, and body condition all play a role in successful reproduction in Polar Bears. For polar bears to remain pregnant, it requires a lot of energy investment. If female polar bears try to reproduce during times with low nutrient availability it can detrimental to their litter's health and their own health. Losing a litter can then decrease the chances of them being successfully reproductive. The reproduction process of polar bears can be delayed because polar bears mate between the months of March and June, but the egg doesn't implant until September or October. The most common litter's polar bears have are twins, and they the moms average age is between 5 and 7. Polar bears over the age 20 aren't commonly seen pregnant due to aging. A study was done to evaluate trends in female polar bears to see specifically factors that contribute the most to pregnancy. This study was completed over 20 years, from 1991-2021. One important thing found, was that body mass played an important role on reproduction. The minimum mass required for pregnancy is 195-196 kg. Additional kg increase in mass increases the reproductive chance by 3.88%..
Problematic interactions between polar bears and humans, such as foraging by bears in garbage dumps, have historically been more prevalent in years when ice-floe breakup occurred early and local polar bears were relatively thin. Increased human-bear interactions, including fatal attacks on humans, are likely to increase as the sea ice shrinks and hungry bears try to find food on land.
Western Hudson Bay(WHB)
Researchers analyzed long-term commonalities in Polar Bears that were pregnant. The study was done from 1991 to 2021, and then they compared data from 1982 to 1990. They hypothesized that pregnancy rates would be lower over time, which would be caused by the seal ice conditions and the availability of prey. Also, that older Polar Bears would have a harder time getting pregnant, and heavier bears would be able to get pregnant easier than bears that weighed less. Polar Bears were caught in Northeastern Canada, and used immobilization techniques. Researchers were able to capture 541 Polar Bears and collect data. The study was done during late summer to early autumn. Then again, in the spring to observe the pregnancies and litter loss. When the bears were captured, they collected blood samples from the femoral or jugular veins. Once the study was finished they found that there was a significant difference in weight for females older than five. The researches had four decades of data to analyze. They found that age and weight is an important factor for Polar Bears to get pregnant. Specifically, pregnant females were heavier than polar bears that were not pregnant. Although, polar bears that were not pregnant were much heavier than polar bears with yearlings, and polar bears with cubs. The meaning of this, is that heavier females are more likely to get pregnant, with a minimum weight of 196 kg. When analyzing pregnancy rates of the decades, it has declined. The researchers found that Sea Ice metrics did not have an effect on pregnancy rates. Lastly, food availability and body condition were the prominent factors in Polar Bears being able to reproduce.The effects of climate change are most profound in the southern part of the polar bear's range, and this is indeed where significant degradation of local populations has been observed. The Western Hudson Bay subpopulation, in a southern part of the range, also happens to be one of the best-studied polar bear subpopulations. This subpopulation feeds heavily on ringed seals in late spring, when newly weaned and easily hunted seal pups are abundant. The late spring hunting season ends for polar bears when the ice begins to melt and break up, and they fast or eat little during the summer until the sea freezes again.
Due to warming air temperatures, ice-floe breakup in western Hudson Bay is currently occurring three weeks earlier than it did 30 years ago, reducing the duration of the polar bear feeding season. The body condition of polar bears has declined during this period; the average weight of lone female polar bears was approximately in 1980 and in 2004. Between 1987 and 2004, the Western Hudson Bay population declined by 22%, although the population was listed as "stable" as of 2017. As the climate change melts sea ice, the U.S. Geological Survey projects that two-thirds of polar bears will disappear by 2052.
In Alaska, the effects of sea ice shrinkage have contributed to higher mortality rates in polar bear cubs, and have led to changes in the denning locations of pregnant females. The proportion of maternity dens on sea ice has changed from 62% between the years 1985 through 1994, to 37% over the years 1998 through 2004. Thus, now the Alaskan population more resembles the world population in that it is more likely to den on land. In recent years, polar bears in the Arctic have undertaken longer than usual swims to find prey, possibly resulting in four recorded drownings in the unusually large ice pack regression of 2005.
A new development is that polar bears have begun ranging to new territory. While not unheard of but still uncommon, polar bears have been sighted increasingly in larger numbers ashore, staying on the mainland for longer periods of time during the summer months, particularly in North Canada, traveling farther inland. This may cause an increased reliance on terrestrial diets, such as goose eggs, waterfowl and caribou, as well as increased human–bear conflict.
Evolution
Polar Bears are a symbol of the threat climate change has to the world's biodiversity and evolution. Researchers recovered a genome of a 130,000-150,000 year old polar bear. This bear was uncovered from Svalbard Archipelago. Polar Bears depend on the Sea Ice to survive and they need it to continue their future stability. Using this ancient genome, researchers hoped it would help provide insights on polar bear's has adaptive resilience to past environmental extremes. They compared the ancient genomes with the new genomes of polar bears and brown bears. Researchers used a 10x coverage genome sequence of the ancient and 10 of the new. What they found is due to climate change black bears and brown bears are migrating more towards the North into polar bear territory. This can have a cause an increase in the overlap between those species. This also may cause competition and hybridization. From those genomes they found that ancient polar bears hybridized a lot. Hybridizations allows for genetic variation and evolutionary change. Researchers believe it will be small compared to the sea ice shrinking and habitat loss.Researchers also predict that the decreasing of sea ice in the Arctic will isolate the polar bear populations. Even though, other bear populations will be migrating, they will be cut off from other populations. This will have great effects on the polar bear population, including a decrease in genetic diversity and inbreeding can occur. Since climate change is happening faster today then in the past, it might not give polar bears enough time to have evolutionary responses.