Why Are Bears Endangered? The Major Threats Explained

Bears aren’t one story. American black bears and brown bears are doing well overall, but the other six of the eight species are listed as Vulnerable. The main reasons are that people are destroying and cutting up their habitat, warming the climate, and killing bears for parts, in retaliation, or through hunting that disrupts their social lives.

Which Bears Are Actually at Risk

The global Red List ranks species from Least Concern up to Critically Endangered. Vulnerable means a high risk of extinction in the wild, one step below Endangered.

Least Concern is a worldwide judgment on the whole species, and it can hide local trouble. Brown bears vanished from Britain and much of Western Europe, and they survive there only in scattered pockets.

Losing and Splitting Up Habitat

As tropical forests are cleared, the best habitat for many animals shrinks and breaks into pieces.9Biodiversity and Conservation. Survival strategies of a frugivore, the sun bear, in a forest-oil palm landscape Borneo, a key stronghold for sun bears, is losing forest rapidly, mainly to oil palm plantations.10Biodiversity and Conservation. Survival strategies of a frugivore, the sun bear, in a forest-oil palm landscape

A plantation is rows of a single crop. It lacks the variety of fruiting trees a forest bear relies on. In a natural forest, fruit ripens at different times across many species, giving a bear something to eat in most months. A bear that wanders into plantation land for food is exposed to people and may be treated as a pest.

Isolation shows up in bears’ genes. Andean bears in Ecuador show only moderate genetic variety in markers that reflect recent history, possibly because fragmentation caused by people and climate change is cutting populations off from one another.11PubMed Central. Effects of the Andes on genetic structure of the spectacled bear with new genetic datasets Small isolated groups are fragile. One bad year, a disease, or local killing can wipe a group out, and young bears looking for new territory can’t reach other groups.

Roads add their own damage. More roads in an area mean lower grizzly survival and weaker reproduction.12PubMed Central. The Impact of Roads on the Demography of Grizzly Bears in Alberta In Yellowstone, human development was the main factor affecting grizzly survival.13PubMed Central. The Impact of Roads on the Demography of Grizzly Bears in Alberta Roads bring vehicle collisions and easier access for poachers and hunters, and bears that avoid them lose the land beside them. Grizzlies strongly avoid land within about 500 metres of a busy highway.14The Journal of Wildlife Management. EFFECTS OF TRANSPORTATION INFRASTRUCTURE ON GRIZZLY BEARS IN NORTHWESTERN MONTANA

Still, about half of the grizzlies tracked near one Montana highway crossed it at least once, mostly at night when traffic was around 10 vehicles an hour.15The Journal of Wildlife Management. EFFECTS OF TRANSPORTATION INFRASTRUCTURE ON GRIZZLY BEARS IN NORTHWESTERN MONTANA Crossings cluster in flat spots near cover, which shows where crossing structures would help.16The Journal of Wildlife Management. EFFECTS OF TRANSPORTATION INFRASTRUCTURE ON GRIZZLY BEARS IN NORTHWESTERN MONTANA

Climate Change and the Polar Bear

Arctic warming driven by people has melted sea ice, and several polar bear populations have declined alongside it.17Science. Energetic constraints drive the decline of a sentinel polar bear population Climate change is the biggest threat to polar bears, with trade in their parts adding to the pressure.18Defenders of Wildlife. New safeguards for polar bears voted down at CITES meeting

Ice matters because polar bears hunt seals mainly from the sea ice surface. Less ice means a shorter hunting season and longer fasts on land. Bears feed heavily on seals when ice is present and live partly off their fat reserves when it is gone. In some regions, bears are stranded on land for longer, where they cannot reach their main prey. They burn stored fat and grow thinner, especially mothers and young. It is this energy shortfall, not heat itself, that drives the declines.

Warmer Winters and Disrupted Hibernation

Hibernation is the months-long winter sleep in which bears live on stored fat with little or no eating. Mothers give birth and nurse tiny cubs inside the den, and the timing is set so bears wake when food returns.

Warmer temperatures shorten black bears’ hibernation and bring them out earlier in spring.19Journal of Applied Ecology. Human development and climate affect hibernation in a large carnivore with implications for human–carnivore conflicts Easy access to human food shortens it further on top of warming.20Journal of Applied Ecology. Human development and climate affect hibernation in a large carnivore with implications for human–carnivore conflicts

Early waking has costs. Too-warm dens can raise a bear’s metabolism and drain its fat reserves faster.21PubMed Central. The seasonal sensitivity of brown bear denning phenology in response to climatic variability Bears emerging early may find spring foods not yet available.22PubMed Central. The seasonal sensitivity of brown bear denning phenology in response to climatic variability In polar bears, a mother leaving the den about three weeks early cut her cubs’ early survival from about 9 in 10 to about 4 in 10.23PubMed Central. Denning Phenology Mediates Sea‐Ice Loss Impacts on Early Reproductive Success in Polar Bears

Hungry bears with little wild food turn to garbage, bird feeders and crops. Those encounters often end with bears being killed, so climate change can feed directly into conflict deaths.

Pandas, Bamboo, and Specialized Diets

Giant pandas rely almost entirely on bamboo.24Biological Conservation. Climate-induced spatial mismatch may intensify giant panda habitat loss and fragmentation Their range has warmed over the past half-century.25Biological Conservation. Climate-induced spatial mismatch may intensify giant panda habitat loss and fragmentation If bamboo and panda habitat shift apart, usable habitat could shrink and fragment further.26Biological Conservation. Climate-induced spatial mismatch may intensify giant panda habitat loss and fragmentation

Bamboo is a risky food to depend on. It is low in nutrition, so a panda has to eat large quantities for much of the day. It also grows only in particular places, so a panda cannot easily move to a new food source if its bamboo disappears. If warming pushes bamboo to different elevations, pandas would have to follow it through landscapes that may be broken up by roads and farms.

Black and brown bears eat almost anything, which helps explain their Least Concern status. Yet even adaptable bears can pay a price. As whitebark pine, a key fall food, declined in Yellowstone, grizzlies switched to other local foods.27PubMed Central. Influence of whitebark pine decline on fall habitat use and movements of grizzly bears in the Greater Yellowstone Ecosystem But the remote high-elevation pine forests had kept bears away from people, so losing them may raise their risk of death.28PubMed Central. Influence of whitebark pine decline on fall habitat use and movements of grizzly bears in the Greater Yellowstone Ecosystem

Poaching and the Trade in Bear Parts

Strong black-market demand for bear parts puts Asiatic black bears under intense poaching pressure.29Diversity. The Status and Spatial Patterns of Poaching, Illegal Trade, and Human–Bear Conflict of Asiatic Black Bears in China, 2010–2020 International trade also adds to the pressure on polar bears, though proposed new trade limits were voted down.30Defenders of Wildlife. New safeguards for polar bears voted down at CITES meeting

Gall bladders and bile are used in traditional medicine. Paws are sold as a luxury food, and skins and claws as trophies. Asian bears whose ranges overlap with the trade are hit hardest.

Poaching is hard to stop. Bears live in remote forests that are difficult to patrol, and high prices make the risk worth it for poachers. Legal and illegal products can also be hard to tell apart.

Conflict With Farmers and Herders

Retaliatory killing of bears that damage property is a major conservation problem in the Himalayas and elsewhere.31PubMed Central. Living with a large predator: Assessing the root causes of Human–brown bear conflict and their spatial patterns in Lahaul valley, Himachal Pradesh In one Himalayan valley, residents reported a couple of bears killed after damage.32PubMed Central. Living with a large predator: Assessing the root causes of Human–brown bear conflict and their spatial patterns in Lahaul valley, Himachal Pradesh

Conflict can be as simple as a bear killing a yak or raiding a store of food in a remote home. For a herder, one loss can be a serious hit to income, and with no help, killing the bear can seem like the only option.

Many families in the Himalayas keep livestock and stored food close to their homes, within reach of bears. Rural families often have few ways to recover a loss, such as insurance or a quick replacement animal. And a bear that has found food at a home may return, so people fear repeat losses.

How Hunting Can Shrink Bear Numbers Indirectly

In Scandinavia, hunting is the main force shaping brown bear numbers.33Bear Project. The effects of hunting It shifts the age and sex balance, social structure and behavior.34Bear Project. The effects of hunting

When adult males are shot, incoming males are more likely to kill cubs they didn’t father.35PubMed Central. Hunting promotes spatial reorganization and sexually selected infanticide Killing cubs brings the mother back into breeding condition sooner, so the new male can father his own. A stable resident male otherwise keeps rivals away. This cub killing lowered cub survival and explained about 14% of the swings in population growth.36PubMed Central. The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears

Trophy hunting works similarly. Selectively removing a few large males can destabilize social order and push mothers into poorer habitat.37PubMed. Demographic side effects of selective hunting in ungulates and carnivores

Pollution and Disease

Industrial chemicals reach the Arctic and build up in polar bears.38PubMed. State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic They can disturb thyroid hormones, fat metabolism, brain chemistry and immune defenses.39PubMed. State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic East Greenland polar bears carried pollutant levels above risk thresholds every year from 1983 to 2013, mostly from PCBs.40PubMed. Immunologic, reproductive, and carcinogenic risk assessment from POP exposure in East Greenland polar bears (Ursus maritimus) during 1983-2013 Chemicals like PCBs build up in fat and move up food chains: seals carry them, and polar bears eat seal fat.

Disease is a problem too. Mange, a skin disease caused by mites, has become more common in Pennsylvania black bears since the 1990s and spread to other states.41PubMed. Resolution of Clinical Signs of Sarcoptic Mange in American Black Bears (Ursus americanus), in Ivermectin-Treated and Nontreated Individuals The mites cause severe itching and hair loss, leaving bears thin and patchy. Badly affected bears may struggle in winter.

Why Losing Bears Affects Whole Ecosystems

Bears work as gardeners. They eat huge amounts of berries and pass seeds far away. Brown bears feeding on salmon spread seeds of fruiting shrubs widely and feed small mammals with seed piles,42Ecosphere. Salmon-supported bears, seed dispersal, and extensive resource subsidies to granivores and those small mammals in turn support owls, foxes and more.

This bear-salmon link once spanned northern lands worldwide but has declined across most of its range.43Ecosphere. Salmon-supported bears, seed dispersal, and extensive resource subsidies to granivores Without bears, wind-spread plants may replace fruit shrubs after disturbance.44Ecosphere. Salmon-supported bears, seed dispersal, and extensive resource subsidies to granivores

What Helps Bears Recover

A wildlife corridor in Florida successfully linked two black bear populations, with bears crossing and breeding between them.45PubMed. Effectiveness of a regional corridor in connecting two Florida black bear populations Corridors let young bears reach new areas and mix genes, and overpasses and underpasses cut road deaths.

Preventing conflict can be cheap. Tibetan herders found traditional grazing methods about 88% effective at protecting livestock.46MDPI (Animals). Mitigation Strategies for Human–Tibetan Brown Bear (Ursus arctos pruinosus) Conflicts in the Hinterland of the Qinghai-Tibetan Plateau Removing food from winter homes and having someone watch the homes were each about 87% effective.47MDPI (Animals). Mitigation Strategies for Human–Tibetan Brown Bear (Ursus arctos pruinosus) Conflicts in the Hinterland of the Qinghai-Tibetan Plateau Nearly all used more than two measures at once.48MDPI (Animals). Mitigation Strategies for Human–Tibetan Brown Bear (Ursus arctos pruinosus) Conflicts in the Hinterland of the Qinghai-Tibetan Plateau

Policy can help as well. Pressure over polar bear trade led Canada to lower a hunting quota for a key population.49Defenders of Wildlife. New safeguards for polar bears voted down at CITES meeting

Readers can help too. In bear country, secure garbage, take down bird feeders and store food so bears don’t learn to raid homes. Avoid products containing bear parts and products tied to forest clearing, such as uncertified palm oil.