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Big Game: The Issue in Brief
Maybe it’s a virulent disease ripping through a Texas herd of whitetail. Or maybe it’s a deep and prolonged drought in the Midwest. The threats to big game are real, persistent . . . and about to become much worse. “You’d think that a warmer climate would take some stress off the big game populations,” says Mark Van Deusen, an avid deer hunter from Prescott Valley, Arizona. “But it appears to me just the opposite is going to happen.”
Scientists agree. Their projections show that global warming
will expand the range of disease-carrying insects,
accelerate the impact of crippling parasites and reduce the
big game forage base.
“Cold temperatures are a barrier that limits the spread of potentially devastating outbreaks of disease in our northern big game herds,” says Jim deVos, retired chief of research for the Arizona Game and Fish Department. “If that barrier comes down, big game will die from those diseases at a steadily increasing rate.”
Of equal concern is the effect of global warming on the big
game food web as elevated levels of carbon dioxide reduce
the nutritional value of forage. “The leafy portions of
plants will become more fibrous and tough and will contain
concentrations of substances that diminish the ability
to digest food,” says Ted McKinney, a research biologist
for the Arizona Game and Fish Department. “As a
consequence, big game will weaken and eventually die
from malnutrition.”
In addition, high carbon dioxide levels will allow trees to out-compete other kinds of vegetation and reduce critical forage such as shrubs and forbs. This domination by woody species could diminish big game numbers by reducing critical habitat.
Scientists have concluded that global warming will stress big game populations in several ways:
- Big game health will decline and mortality will rise as
infestations of parasites, pests and disease-carrying insects, no longer held in check by cold, increase in severity
and geographic range. - Across the continent, deer, elk and other big game populations will shrink as high levels of greenhouse gases
make the plants they eat less nourishing and tougher to
digest. - Desert shrub zones, pinyon-juniper woodlands and numerous other big game ecosystems will be increasingly at risk from wildfires, which will burn with greater intensity and frequency as invasive species replace less fire-prone native plants.
- Pronghorn, elk and mule deer will lose vital habitat in many regions of the American West as rising temperatures allow trees and shrubs to overwhelm sagebrush ecosystems.
- Rising temperatures will allow forests to climb to higher elevations, severely limiting the alpine habitats that support bighorn and other mountain sheep.
- As temperatures rise, moose, uniquely suited to cold weather, will continue to experience declining pregnancy rates and suffer poor individual health, due largely to increased winter tick infestations. Populations will shrink and drift northward, eventually disappearing from the upper Midwest.
- As fragmentation and loss of winter ranges continue, mule deer and elk will dwindle in number in the Rocky Mountain states, the Intermountain West and the Northern Boreal Forest. In some locations, over time both species will disappear entirely.