The black bear has carved out a unique niche for itself within almost every ecosystem in the world. They are omnivores they will eat meat if it presents itself but they are just as easily satisfied with berries, pine nuts, and leaves. This helps the berries and nuts that they eat to much more widely disperse the seeds of future generations of berries and trees, in a rich fertilizer mix. Black bears provide a very necessary service as the cleaning crew for the annual die off of salmon, who after struggling back to their birth waters to mate and lay their eggs, die of exhaustion. The wealth of dead salmon in streams and rivers could easily foul the water with bloated rotting shoals of fish being pushed back downstream. Bears also keep the number of predators within their range down by stealing kills and killing the young when they can be found. Black bears have also long been hunted for their fat and fur, as well as their meat by both Native Americans and those who settled throughout North America.
Up to 85% of a black bears complete diet is made up of vegetation. Black bears do not tend to dig as much as their brown bear cousins, thus their diet consists of far fewer, corms, bulbs, and tubers and more fresh green buds, berries, and young leaves. They strip young saplings allowing more space between young trees thus giving the young trees a better chance at getting enough sunlight to survive. They also eat winter dead carrion as well as the numerous dead salmon after spawning season. They eat a lot of berries, fruits, and vegetables that grow within their territories, carrying away the seeds, which are passed right through their digestive tract unharmed. These seeds are then carried far away from the parent plant or bush, and are deposited with a rich dose of fertilizer by the bear. This helps to propagate not only fruit and berry plants and trees but also the evergreen trees like pines and spruce with their nearly indestructible pine nuts and hard seed pods which are hardly effected by passing through the bears digestive tract.
Bears steal kills from wolves, big cats, and other predators as well as their early spring meals of opportunity, when cleaning up winter dead carrion which has remained conveniently frozen solid awaiting the beats waking and need for food in the spring. They also kill young left behind in dens while their predator parents are out on the hunt. Black bears keep the number of more aggressive predators in their territories within more acceptable numbers. With their bulkier body they are able to run other smaller predators, especially solitary predators, off from their kills.. Not getting enough to eat reduces numbers in any population.
Bears are extremely territorial, during both mating season and after cubs are born, they are territorial at any given time, but at these two times they are sovereign within their territory and other predators clear out any time that they are in the area, lest they risk injury or death at the paws of an aggressive bear. Bears of all kinds are opportunists, rarely killing the meat that they do eat. They kill in territorial aggression, and when instinct demands the destruction of infant predators. A bear is much less likely to aggressively attack humans, than is a hungry big cat or a pack of wolves, much preferring to forage for vegetables than to hunt down prey like the carnivorous competitors that share their range. This eases the strain on the non predator animal populations, allowing them to flourish. Deer and other herbivorous prey animals that comprise the diets of big cats, wolverines, and other forest dwelling meat eaters, tend to have their mating and birthing cycles around the periods when bears are more territorial and aggressive, their young normally being quite safe from becoming a meal to a hungry carnivore when they live in or near the territory of a black bear.
Black bears also eat a fair amount of insect larvae and insects which helps to reduce the insect populations in their areas and keep them in balance with the needs and stresses of the forest ecosystem that they inhabit. The meat that they consume when it is available often contains trace elements and minerals that need to be converted to more soluble elements like nitrogen. The nitrogen contained within a decomposing animal carcass is of little or no use to the trees in the forest because those nitrates are not easily dissolved into the water which is drawn up into the trees of the forest. Once eaten, digested, and eliminated, these nitrates are then soluble enough to be dissolved into ground water, to be drawn upon by the trees of the forest. The black bear is uniquely evolved for the place that it inhabits within the food chain and the ecosystem of the forested regions throughout the world.