A Case for Big Wildlife
Decimation of Large Predators and Herbivores Has Caused Widespread Ecosystem Disruption
A planet without the big predators that usually inspire fear — lions, sharks, and wolves — would be scarier than a planet with them. According to a study published in the journal Science, the disappearance of major predator and big herbivore populations, which scientists call “apex consumers,” is already having detrimental effects on land, marine and freshwater ecosystems, as we muddle our way through the sixth mass extinction on Earth,
Photo by David Berkowitz
Across the world, from the African savanna to the open ocean to the American plains, ecosystems are spiraling into a state of unprecedented disorder as a combination of climate change and human intrusion severely deplete top hunters in the animal kingdom.
In sub-Saharan Africa, the dwindling numbers of lions and leopards have allowed the olive baboon population to expand unchecked. As the baboons venture nearer and nearer to human settlements in search of food, they have increasingly transmitted intestinal parasites to humans. Dramatic changes in coastal ecosystems have followed the collapse and recovery of sea otter populations; Sea otters have long been the guardians of kelp forests. They prey upon sea urchins, which would otherwise eat away the kelp.
These cases are only a few cause and effect examples of what happens when an ecosystem loses its apex consumers.. But researchers say the total impact of predator loss is often broader than the cause-effect approach of a food chain would imply.
“Recent research suggests that the disappearance of these animals reverberates further than previously anticipated, with far-reaching effects on processes as diverse as the dynamics of disease; fire; carbon sequestration; invasive species; and biogeochemical exchanges among Earth’s soil, water, and atmosphere,” the study, authored by 24 scientists from six different countries, states.
The study says that the loss of apex consumers (big cats, wolves, bison, elephants, whales, sharks, etc.) from an ecosystem triggers an ecological phenomenon known as a "trophic cascade," a chain of effects moving down through lower levels of the food chain, especially when exacerbated by factors such as land use practices, climate changes, habitat loss, and pollution.
“This is the first paper to brings together studies that present strong empirical evidence of what naturalists and ecologists have long suspected,” Justin Brashares, an associate professor at the UC Berkeley Department of Environmental Science, Policy and Management and a co-author of the study, said in a press release about the study.
Brashares researched the impacts from rinderpest, an infectious viral disease introduced by human activity in the late 1800s. The disease severely reduced populations of wildebeest, buffalo and other grazers in the Serengeti until it was eliminated in the 1960s by a vaccination program. During the time that these populations of grazing animals were low, plant biomass accumulated, fueling large wildfires in the region. After the elimination of rinderpest, the native ungulate populations bounced back, shrublands were reduced to grasslands, and the frequency and intensity of wildfires decreased.
Apex consumers have often been studied by ecologists as ecological passengers riding atop the trophic pyramid but having little impact on the structure below.
But these researchers have argued that anything from pandemics to population collapses of species we value to major changes in ecosystem states have occurred because of a shift in the animals at the top of the food chain. Only where predator populations are returned to their natural states have ecosystems been able to recover.
Time to reconsider the upcoming wolf hunt in the Northern Rockies?