Deer climate change

Climate change and chronic wasting disease will affect deer populations and deer hunting, neither of which are good for the environment.

Two scourges in our midst, chronic wasting disease and climate change, have implications for deer hunters in Pennsylvania far beyond the obvious.

CWD, which is always fatal to deer, will kill many deer. Infected deer on captive deer farms have been found in two locations in Lancaster County. The northern part of the county is now in a quarantine zone to stop the spread of the dreaded disease and next year it’s likely almost all of the county will be under quarantine.

Across Pennsylvania, hunters are wondering if it is safe to eat the deer they kill. So far, there has been a species barrier, but scientists are worried that at some point CWD could affect humans.

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The effects of climate change are expected to create conditions favorable to boost deer populations, but that could have devastating effects on other wildlife and native plants and trees.

Deer’s role in the environment and society is complex, and Pennsylvania’s managers of wildlife and forests are worried about the far-reaching negative effects of both climate change and CWD.

Let’s start with climate change. One study suggests that higher, uncomfortable temperatures in autumn may drive down the number of deer hunters entering the woods. That would be bad because climate change is expected to increase deer numbers and hunters may be asked to kill more whitetails in the future to thwart overbrowsing of young trees trying to regenerate.

As a deer hunter, you might think projections of more deer are good as that might help populations ravaged by CWD rebound faster. But too many deer can quickly overbrowse not only new trees but also habitat crucial to other native plants and wildlife. Studies are showing that over-eaten forests tend to be filled with invasive, nonnative plants of little value to wildlife.

Then there are the other threats of too many deer: more Lyme disease from ticks, more crop damage, more deer-vehicle collisions. More blows to Pennsylvania’s rich hunting tradition and fewer deer camps.

An interesting study by the U.S. Forest Service found that while too many deer is always harmful to ecosystems, too few deer can be, as well. Researchers studying a Pennsylvania site found that with too few deer around to keep them in check, some undesirable species of trees outcompete desirable ones.

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And, the right balance of deer tends to actually increase the carrying capacity (the maximum number the environment can support without detrimental effects) of the landscape. The study found that in West Virginia, where deer levels were found to be lower than the carrying capacity of the landscape, a mix of deer, ground fire and canopy gaps increased diversity compared to enclosures where deer were excluded entirely from reaching the forest.

Now CWD. The decline of deer numbers in Pennsylvania from the spread of the disease is inevitable. It’s a question of time and how well we contain the damage. Bucks have an infection rate three times that of does.

But the fallout from decreasing deer numbers goes far beyond hunters facing unfilled tags.

“Chronic wasting disease is a threat to Pennsylvania’s forests because it is really cutting down on the deer take, and now we’re starting to see big herds of deer again — 40 to 50 deer moving around has effects on the plants of Pennsylvania,” said Cindy Adams Dunn, secretary of the state Department of Conservation and Natural Resources, in a talk last month at a forum on Pennsylvania’s forests.

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“One of the biggest problems with Pennsylvania’s native plants is deer overabundance,” continued Dunn, whose agency manages 2.2 million acres of state forests, as well as state parks. “People don’t see it directly with a disease like CWD. The restraint that hunters feel about harvesting in those areas and the hassle they have to go through (with new regulations on removing carcass parts) is slowing down hunting.”

Conversely, Dunn said, if CWD kills too many deer and hunters drop out, they no longer will buy licenses that largely fund the Pennsylvania Game Commission. The agency is responsible for the management of all Pennsylvania’s birds and mammals, not just game species.

Not to mention the millions of dollars Pennsylvania hunters spend each season, often boosting the economies of rural towns.

Ad Crable is an LNP outdoors writer. Email him at

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