Key Threats to Wildlife

While Wisconsin is blessed with many natural areas, our wildlife still face several threats over the long term. We need to support programs that will protect wildlife and endangered species, or risk losing some of them.

1. Habitat Loss

Canvass Back Duck

Because our population is growing and our cities are sprawling into the countryside, fewer natural wildlife habitat areas are left each year. The habitat that remains has often been degraded to bear little resemblance to the natural wild areas which existed in the past. In many areas, only islands of habitat remain, isolated in the middle of large agricultural or urban development. This prevents normal interactions, healthy breeding and safe travel for many species.

Some wildlife species, such as deer, rabbits and chipmunks, are adaptable to many conditions, but other creatures have very specific plant, moisture and temperature requirements. These are the species that we risk losing if we don't preserve adequate amounts of habitat for their survival.

2. Climate Change

Because many types of plants and animals have specific habitat requirements, climate change could cause disastrous losses of wildlife species in Wisconsin. A one or two degree change in average annual temperature will translate into large changes in Wisconsin, affecting snow cover in the winter and excess heat in the summer. Many northern Wisconsin plants and animals depend on a blanket of snow to insulate them from the extreme low temperatures of winter. It may be 25 degrees below zero in the open air, but barely freezing (32 degrees) beneath the snow.

Without this insulation, many plant species, including trees, will decline or disappear entirely. Hibernating mammals, reptiles, amphibians and insects will also be harmed. Similarly, higher temperatures would increase evaporation year round, and may reduce rainfall, leading to drier than normal conditions across the state. Plants and wildlife are sensitive to moisture changes, so they will be harmed by this dryness. Coldwater trout streams may become too warm to support trout, or may even dry up.

Unfortunately, trees and plants can't simply pick up and move to a more hospitable location. Instead, they will die where they stand, exposing and starving the wildlife that depend on them. Drought tolerant plants and trees will gradually spread to replace them by seed, but this process takes time. In many parts of Wisconsin, natural habitat is chopped up and isolated in small islands. This means plants and animals have no bridge to allow them to move with the changing climate.

3. Pesticides and Toxic Chemicals


Pesticides are deliberately spread to make the environment toxic to certain plants, insects or rodents, so it shouldn't be surprising that other plants and wildlife are often harmed at the same time. While many of the worst pesticides have been outlawed in the past 30 years, scientists are finding new concerns with some pesticides that are still legal and commonly used. In addition, many chemical pollutants are toxic to wildlife, such as PCBs, mercury, petroleum byproducts, solvents, and anti-freeze.

The presence of toxic substances in the Great Lakes continues to be a significant concern. Of the 362 contaminants known to exist in in the lakes, only about one-third has been evaluated for their potential toxic effects on wildlife or human health.

4. Non-native Species

Over the past 150 years, many non-native plants, mollusks, insects, fish, birds, mammals, and diseases have found their way to Wisconsin. These include well-known invasives such as buckthorn, carp, zebra mussels, spiny water fleas, purple loosestrife, gypsy moths, Eurasian milfoil, feral cats, white perch, West Nile Virus, Japanese beetles, and starlings. These "aliens" are often aggressive competitors with native wildlife, or predatory, especially after they've left their own natural environments and controls.

5. Mismanagement

Some native wildlife can become a problem when released from their natural population controls. When wolves are scarce and hunters too few, white-tailed deer will often strip the woods of native wildflowers, such as Trilliums, and even certain tree species, such as Hemlock, when their populations are allowed to become too high.

Canada geese are beautiful birds, but when city folk feed native geese as if they were pets, their populations can rise to uncomfortable levels in urban areas, resulting in polluted waterways and manure-laden lawns. Gulls can become similar problems when they scavenge for scraps from our garbage heaps and landfills.

For more information:

© Clean Water Action Council

P.O. Box 9144

Green Bay, WI 54308

(920) 421-8885

Office location:
A307 MAC Hall, UW-Green Bay
2420 Nicolet Drive
Green Bay, WI 54311