The Balance Between Large Carnivores, The Environment, And Humans
Despite their fierce claws and fangs, large carnivores are some of the most vulnerable to human activity, due to their large energy and land requirements and low reproduction rates. They are also regarded as enemies to humans, especially in areas dependent on pastoral farming. A reduction in the population of large carnivores has an effect on the rest of the ecosystem, which will in turn have an effect on humans.
Of the 31 large mammalian carnivore species listed as vulnerable, seven have been linked with significant effects on the ecosystem upon population decline. These are the African lion, the leopard, the dingo, the Eurasian lynx, the sea otter, the gray wolf, and the puma, or mountain lion. This study’s goal was to determine the effect of large predators on the ecosystem and their relationship to humans.
The African lion and leopard have long been hunted by humans, often due to their perceived danger to humans and livestock. In addition, much of their habitat has been destroyed by human development. The drop in population has allowed their prey and competition to thrive, including mid-level predators like the olive baboon. In addition to over-hunting their usual wild prey like small ungulates and other monkeys, baboons have learned to exploit human resources. Baboon raids are a constant threat to crops and farmed animals, and in some areas, farmers have withdrawn their children from school and make them full-time guards in response.
Other species have different stories, and resultant effects. The dingo is not technically native to Australia, being descended from domestic dogs in New Guinea and arriving to the continent around 5000 years ago. However, it has become an important part of the Australian ecosystem, being the sole remaining large mammalian predator on the continent. European settlers and modern Australians have sought to control the population of dingoes, both through hunting and erecting barriers.
Pastoral agriculture of sheep is a big industry in Australia, and dingoes are the only predator that truly poses a threat to these animals. However, dingoes also keep other invasive species, like the red fox and rabbit. The decline in dingo population is correlated to a decline in the population of native marsupials and rodents, likely due to competition and predation from other invasive species.
Elsewhere, the Eurasian lynx is still widespread in Eastern Europe, but has been eliminated from much of Western Europe. In areas where it no longer lives, the population of its prey has increased, as has the population of competing predators. A recent conservation and re-introduction program of the lynx in Finland resulted in a decline in red fox population to normal levels, as well as an increase in the declining populations of forest grouse and mountain hare – the foxes’ main prey.
Meanwhile, sea otters were hunted to near-extinction during the 18th and 19th centuries, at the height of the fur trade. Since then, their numbers are stable or recovering in Russia and east of the Kodiak Islands, although the population west of the Kodiaks and on the Aleutian archipelago has not been so lucky. In areas where the otter population has recovered, researchers have found an increase in the density of kelp forests. This is due to the otters’ predation of herbivorous sea urchins, which would otherwise severely limit the growth of kelp and other aquatic plants. In areas where the otter population is low, these urchins are much more abundant.
On a larger scale, gray wolves are one of the most widely distributed predators on the planet, stretching across much of Northern Europe, Eurasia, and North America. However, the once-strong populations in Western Europe, Eastern North America, and Mexico have been all but eliminated. Wolves are the most important predators of cervids (deer, elk, moose, etc.) in their habitats – areas without wolves were found to have six times as many cervids as areas with wolves.
This dynamic has had an effect on plant growth, as cervids will over-graze without predation to keep their numbers in check. Pumas have had a similar effect in North America. They have been mostly eliminated from the Eastern United States, and this has led to a growth in the population of their prey – mainly deer. In areas with pumas, deer populations are much more stable, and this limits their damage to plant growth.
This is by no means an exhaustive list of the predators with an effect on the ecosystem. However, these seven species are the most-studied, and their effects are the best-known. In addition, few predator species can be looked at in a vacuum. Many of them will co-occur in a habitat, and they may have synergistic effects.
The environmental effects of these predators are also somewhat dependent on the type of habitat that is in question. In extreme areas like deserts and mountains, predators are not as necessary to control the population of their prey. The conditions harshly limit the amount of animals that can be supported at once, and therefore the number and effect of predators is lower than in more productive areas. Likewise, individual predators may have less of an effect in extremely productive areas. The competition between prey species may be enough to prevent one from gaining the upper hand and causing too much damage.
Large predators have numerous other effects – from driving tourism to aiding carbon sequestration. Even in industries where they are perceived to be a threat – namely pastoral agriculture – they may be helpful. By controlling the population of native herbivores, predators make their habitats more productive. Grazing on more productive land is more sustainable, meaning that farmers can have larger herds with less environmental impact, if that is their goal.
Of course, it’s important to note that the primary threat to large predators is human activity, both directly through hunting and defensive culling and indirectly through habitat destruction. Human efforts to mimic the ecological effects of these animals have largely failed. Despite their importance to the natural world, the decline in predator populations has not had as much attention as other environmental causes.
The authors recommend that more public outreach be centered around this issue, and that we shift our attitudes towards these animals. Rather than seeing them as enemies of humans, we need to start seeing carnivores as a necessary part of the environment that we must coexist with. This will also require changing our relationship to the land – land-intensive practices like animal agriculture will have to be reduced in order for predator populations to recover. Without changes in our actions and thoughts, we may be looking at a future without lions, tigers, wolves, and many more.