Friday, January 10, 2014
New research co-written by University of Montana scientists finds steep declines in the worldwide populations and habitat range of 31 large carnivore species. The analysis, published Jan. 9 in Science, shows that 77 percent of the studied species – including tiger, lion, dingo and puma – are decreasing in number.
Associate Professor of ungulate habitat Mark Hebblewhite and John J. Craighead Chair and Professor of Wildlife Conservation Joel Berger, both of the UM College of Forestry and Conservation, co-wrote the study with scientists from Oregon State University, the University of California, Yellowstone National Park, University of Washington, Yale University and researchers in Australia, Italy and Sweden.
The study shows that 17 of the species occupy less than half their normal habitat range. These changes have serious environmental consequences, the authors argue.
Large carnivores are vulnerable to extinction because of their low population densities and their need to roam widely to search for food. These animals are essential to the health of an ecosystem and also provide social and economic benefits for humans.
“Ecosystems depend on large carnivores to control herbivores like deer and populations of smaller carnivores,” Hebblewhite said. “We suggest that losing a population of large carnivore doesn’t just impact that species, but an entire landscape.”
Further declines in the populations of these large carnivores will lead to changes in plant species diversity, biomass and productivity. These vegetation changes will have a wide-ranging influence on other species. Carnivore losses also will impact wildlife disease dynamics, wildfire and carbon sequestration.
Hebblewhite points to several success stories, like the reintroduction of gray wolves to Yellowstone National Park, potential delisting of grizzly bears in the Northern Rockies and the Global Tiger Initiative, to demonstrate that reintroducing and recovering carnivores has many benefits.
In Yellowstone National Park, the return of wolves has contributed to aspen and willow restoration, stabilized carrion availability for scavengers like grizzly bears and magpies, and has increased carbon storage by allowing plants to flourish.
But beyond the large carnivore conservation successes of the Northern Rockies, carnivore populations are declining worldwide, especially in Asia and Africa. These declines are mostly due to habitat loss, overhunting and trade of endangered wildlife parts.
“We haven’t yet untangled all the ways in which these large carnivore population declines will play out in the future – but we know they will have profound ecosystem impacts,” Berger said.
Hebblewhite and Berger agree that lessons learned from carnivore reintroduction in the Northern Rockies can serve as a model to the rest of the world. At UM, training international students in large carnivore conservation is a key focus.
Wildlife biology doctoral student Tshering Tempa currently applies some of these advances in carnivore science and conservation to Bengal tigers in his home country of Bhutan.
“Conservation has to be underpinned by sound science,” Tempa said. “In Bhutan, there is a real chance of ensuring that large carnivores and their prey persist perpetually. I am applying the skills I have learned at UM to contribute toward this.”
With looming threats to global distributions of large carnivores, Hebblewhite concludes that more science is needed to better understand all the benefits of every large carnivore species, which human activities are most in conflict with large carnivores, and what management activities will have the most impact on sustaining large carnivore populations.
Thursday, January 9, 2014
A fascinating paper released today from a team of leading scientists, including Dr. Joel Berger of the Wildlife Conservation Society and University of Montana, reports on the current status of large carnivores and the ecological roles they play in regulating ecosystems worldwide, and finds that a world without these species is certainly scarier than a world with them.
From sea otters that keep sea urchins in check and enable the rise of kelp beds thus increasing the productivity in inland coastal areas to pumas that mediate the browsing of mule deer and thus enhance the growth and reproduction of woody plants, the scientists profile seven of the 31 largest species of the order Carnivora and their well-studied ecological effects.
The paper, "Status and Ecological Effects of the World's Largest Carnivores," appears in the January 10, 2014 issue of the journal, Science. More than 100 published studies were reviewed to offer a comprehensive look at the state of carnivores and their impacts on the world today.
WCS Executive Vice President of Conservation and Science John Robinson said, "This important paper explores how carnivores regulate the structure and functioning of ecosystems and what happens when they are lost. For many people, it will be an eye-opener and hopefully bring about a change in attitudes and a deeper appreciation of these key species. Around the world, WCS continues to work to preserve the ecosystems that are vital to carnivores and to understand the critical benefits they provide to both wildlife and people."
Among their many impacts, carnivores are a benefit to ecotourism. Yellowstone National Park's restored wolf population, for example, brings in tens of millions of dollars in tourist revenue each year. And when wolves are absent, the effect on natural selection is dramatic. "In Badlands National Park, we have observed bison born with deformed hooves or portions of their legs missing," said WCS Conservation Scientist and author of The Better to Eat You With, Joel Berger. "Historically, these bison would have been selected out for predation by wolves, contributing to the overall health of the herd. Today, without wolves, these bison survive and reproduce. This is not the way healthy ecosystems are maintained."
The ecological services provided by carnivores are multifarious. Carnivores control herbivores to the relief of plants, mitigate global warming, enhance biodiversity, restore rivers and streams, and regulate wildlife disease and livestock disease spillover.
However, many of the largest carnivores are listed as threatened on the International Union for the Conservation of Nature (IUCN) Red List, and most are still declining in number. These 'top or apex predators' have one great competitor: humans.
The authors note that "large-carnivore population declines are typically precipitated by multiple, and sometimes concurrent, human threats including habitat loss and degradation, persecution, utilization (such as for traditional medicine, trophy hunting or furs), and depletion of prey."
Oregon State University professor and lead author of the paper, William J. Ripple said, "Globally, the ranges of carnivores are collapsing and many of these species are at risk of either local or complete extinction. It is ironic that large carnivores are disappearing just as we are learning about their important ecological and economic effects."
Looking to the future, the scientists expect that the loss of apex predators will bring degradation to ecosystems that include reductions in plant diversity, biomass and productivity as well as wide-ranging impacts to other species. Greater rates of herbivory and concurrent decline of plant species may hasten global warming and desertification.
Critical to living with carnivores, the scientists conclude, is an understanding of the benefits they provide and where human/predator conflicts arise. Linking policy issues facing people such as population growth, meat consumption and exploitation of wild prey, livestock production, greenhouse gas emissions, food security, deforestation and desertification, and water quality/quantity with carnivore conservation is a necessary step toward coexistence.