Climate Change Impacts On Wisconsin

Squirrel Wisconsin is rich in natural resources. Our cultural identity and economy are tied to the wealth of species, both plants and animals that inhabit our state. With 16 million acres of forested land, more than 1,800 native plant species, more than 500 terrestrial animal species, more than 80,000 miles of streams and rivers, and more than 800 miles of Great Lakes coastline, biological diversity abounds in our state. These varied an diverse natural resources serve vital roles both in their ecosystems, by providing benefits such as soil formation and water purification, and in our society, by providing aesthetic, economic and recreational value and by contributing to our food supply.

Climate change is impacting these ecosystems and their inhabitants by affecting individuals and communities of species and changing habitats and the processes that act within them. Rising temperatures, shifting precipitation patterns and an increasing number of heavy rainfalls set of ripple effects that bring physical changes to natural habitats, triggering biological responses among the plant and animal species in them. Climate change is manifested differently across habitats, ecosystems and the state, with direct and indirect impacts resulting in 'winner' and 'loser' species. While some species will indeed fare better in a warmer Wisconsin, scientists expect the majority of species influenced by climate change to fare worse.

Climate projections indicate that snow will drop by about 40% in northern Wisconsin over the next half century.

Early Onset of Spring

The earlier arrival of spring is one of many effects of climate change on the physical and biotic characteristics of Wisconsin's natural habitats and ecosystems. Across the state, temperatures are warming earlier in the year than in decades past. In the last 57 years, we have seen a state-wide compression of the length of winter as spring weather arrives 6 - 20 days earlier than it used to, extending the growing season by 2 weeks. Trees and flowers are blooming sooner and the last of the ice is disappearing from the lakes earlier.

Canada Goose in flight These changes in growing season and the early onset of spring will affect the timing of life-cycle events. Some plants and animals respond to temperature as a cue to initiate growth and reproductive activities and others depend on photoperiod or respond to each other's life-cycle cues. These relationships may be thrown out of sync as climate change continues.

Migration behavior among wildlife is shifting in response to advances in signals of spring such as earlier snowmelt, warmer temperatures, more precipitation and other moisture signals. The Canada goose now arrives a month earlier than in the 1930s and is now a year-round resident in the southern portion of the state.

The shift in migration patterns can have cultural and economic implications. For example, year-round residence of the Canada goose may degrade water quality and increase damage to corn crops.

Rising Water Temperatures

Temperature increases mean more than just warmer weather. As air temperatures rise, so will the temperature of water in streams, rivers, lakes and, to a lesser extent, groundwater.

Brook Trout Wisconsin is renowned for its abundance of cold-water streams that contribute to our state's cultural identity and legacy. These streams, which dissect the landscapes of northern Wisconsin and the western Driftless Area, provide fisheries for brook trout and brown trout. But these trout are very sensitive to changes in water temperature and can survive and reproduce only if temperatures remain below a certain threshold. For example, with an increase in the average summer air temperature of just 5 degrees, models predict that rising stream temperatures could eliminate up to 95% of brook trout habitats.

Many warm-water species, including several game fish species such as channel catfish, smallmouth bass, largemouth bass and black crappie, will benefit from rising stream temperatures. Non-game fish, including various minnows and darters, will also gain habitat as well.

Fish are not the only wildlife that will be affected as stream temperatures fish. Wisconsin is one of the few remaining states where the Hine's emerald dragonfly, an endangered species, is found. The dragonfly's larvae require ephemeral cool spring for development. As water warm or increased rainfall prolongs wet condition, this species may go extinct.

Reduced Snow and Ice Cover

Hine's Emerald Dragonfly With warmer temperatures during winter months, Wisconsin will see more of its winter precipitation falling as rain rather than snow, resulting in fewer days with snow on the landscape and ice cover on the lakes. These changes in winter precipitation will affect both plant and animal communities and will impact land and aquatic ecosystems.

Reduced snow cover threatens plant and animal species that are adapted to and rely on snow cover for their winter survival. Climate projections indicate that snow will drop by about 40% in northern Wisconsin over the next half century.

Snow is a moisture source and thermal insulator. It provides an insulating cover for the fragile root systems of lowland conifers. Some wildlife, such as the American marten, relies on hollow trees and other areas in and under layers of snow for insulation and protection from predators. Statewide loss of snow cover during winter increases opportunities for white-tailed deer to forage that my hurt native vegetation, forests and croplands.

Freezing Rain

Prediction for warmer winters and more precipitation falling as rain rather than as snow suggest we will see an increase in freezing rain. While all trees and other plants face the threat of ice damage, conifer trees are particularly vulnerable. Because of their structure, with a single trunk and branches that extend from it, one break in the trunk can severely injure or kill a conifer tree.

Reduced Soil Moisture

Eastern Tiger Salamander A warmer climate will likely result in a reduction in soil moisture. Hotter days, and more of them, will mean more evaporation and transpiration, and this includes water in the soil. Changes in soil moisture will affect plants, animals and stream hydrology ad habitats.

Drier soils can reduce the vigor of plants and their overall vitality. Trees and other plants require moisture to regenerate, and less moisture will make it more difficult for many plants to replace damaged cells.

Forests such as conifer lowlands, which are wet, boggy areas dominated by trees like tamaracks, black spruce and white cedar, depend on very moist soils. A reduction in soil moisture threatens the integrity of these forests and would lead to dead trees or even a gradual shift in the type of plants that grow in these regions.

Even a minor reduction in precipitation combined with high temperature
can cause rapid water loss in amphibians.

Wildlife also will be affected by a reduction in soil moisture. Amphibians such as the American toad and eastern tiger salamander rely on humidity and moisture in the soil to maintain the water balance in their bodies. In warm, dry weather, they burrow underground to prevent dehydration. If soils dry out, these amphibians will die, impacting the rest of the forest ecosystem because they are an important food source for birds, reptiles and small mammals. Even a minor reduction in precipitation combined with high temperatures can cause rapid water loss in amphibians, and heat and water stress result in low survival rates.

Less moisture in the soil also means less groundwater recharge to streams. When soils have adequate moisture, some of the water that falls as rain and soaks into the ground makes its way through the soil to recharge the base flow of rivers and streams. As air temperatures rise, so will stream temperatures, threatening populations of fish and insects that require cold water for their survival.


Even more extreme than the impacts that accrue from reductions in soil moisture is the threat of drought. While climate predictions project an overall increase in precipitation across the state, especially in the winter and spring, climate models are less certain about what will happen in the summers. More frequent or extreme period of localized drought could impact a variety of habitats and natural communities, including water levels in lakes and wetlands, stream temperatures, forests and grasslands.

Tamarack tree, Larix laricina The north central part of Wisconsin contains a high concentration of the state's inland lakes. If temperatures rise and precipitation decreases in the areas, the resulting droughts will dry out wetlands and reduce habitat and nesting success for the diverse group of birds that inhabit these areas and amphibians that require wet conditions for suitable breeding sites.

Lakes in norther Wisconsin are currently receding and the trend is project to continue in future years.

Suitable nesting sites are becoming increasingly inaccessible to many birds. Loons, which typically nest within 3 to 6 feet of the water's edge, will have trouble coping with these reconfigured shorelines.

Drought conditions can also make trees and other plants more susceptible to pests. For example, tamaracks require moist soils and are vulnerable to summer droughts. They already experience attacks from the tamarack bark beetle, but an increase in stress from droughts could reduce the trees' resilience.

While many trees and other plants will struggle to survive if drought conditions occur or persist, other species will fare better. For example, in northern Wisconsin where drought conditions have persisted for about 7 years, the rare Assett's locoweed is thriving.


American Toad, Anaxyrus americanus While climate projections show a modest increase in precipitation across most of the state, they also include an increase in the magnitude and frequency of intense rainfall. More heavy downpours would increase the likelihood of flooding, which can damage or destroy habitats both in and outside of floodplains, essentially reestablishing floodplain boundaries. Soil conditions, the presence or absence of frost on the ground and land use affect the degree to which rainfall runs off or is absorbed into the soil, determining the extent of flooding.

After an intense rainfall event, streams and rivers often flood, saturating soils in the floodplain. Trees that grow in these areas, such as river-bottom hardwood trees including river birch and ash, cannot tolerate the saturated soils that come with prolonged flooding, and invasive plants such as reed canary grass grow their place. Flooding also adds sediment, which covers struggling tree seedlings that cannot compete with the hardy canary grass.

Flooding could benefit other plant and animal species. Stinging nettles do well in floodplain forests, and if flooding results in new gaps in the forest canopy, vines like poison ivy, Virginia creeper and grapes will benefit. Annual native plants such as giant ragweed and jewelweed also respond well to flooding.

As for animals, trout can benefit indirectly from flooding. The heaving rainfall increased the base flow of man trout streams, creating a more suitable habitat for the fish. Amphibians, turtles and birds may also indirectly benefit from flooding if shallow depressions near streams capture water during floods.

Species that inhabit both wetlands and grasslands are also vulnerable to flooding. In wetlands, increased flooding puts the fragile nests and habitats of many water birds at risk, and in grasslands, young birds such as the greater prairie chicken are very sensitive to rainfall and temperatures early in life because increase in heavy storms during the nesting season may chill or drown your birds.

Pollination Disruption

Eastern Prairie Fringed Orchid, Platanthera leucophaea While some plants are pollinated by either wind or water, insects pollinate many other plants. These plants depend on their pollinators for survival. Changes in the timing of flowering caused by early spring temperatures may disrupt that relationship or eliminate those mutually beneficial interactions. For example, some spring flowers are opening earlier than in the past, when the flies and bees that pollinate them may not yet be present. In the southern upland forests, the suite of ephemeral herbs growing on the forest floor is likely to be moderately to highly affected by climate change because of interference in pollination. These herbs bloom and drop their seeds before the forest canopy has formed its leaves. They have a very short window for reproduction and changes in the timing of pollination caused by changes in climate may adversely affect these species.

For specialist pollinators that are associated with certain plants, these relationships can be highly vulnerable to disruptions and can even present the threat of extinction. For example, the eastern prairie fringed orchid has only one known group of pollinations, the sphinx moths. If this endangered orchid blooms early and the moth is not on a similar lifecycle schedule, the pair will come uncoupled, making pollination unlikely.

Changing Fire Regimes

Common Loon, Gavia immer Climate influences fire regimes in two ways: directly by affecting weather patterns such as droughts, which are conducive to the fire ignition and spread, and indirectly, by causing shifts in plant communities through temperature and precipitation changes that favor or discourage fire-adapted plant species. Changes in fire regime may be most apparent for the most fire-prone natural communities, particularly in landscapes that are not fragmented, such as the jack pine dominated barrens in central and northwestern Wisconsin. Some disturbance-dependent communities such as grasslands, sedge meadows, savannas and barrens may benefit from more numerous fires, while other natural communities will far worse.

Further Reading on Climate Change:

 Climate Change Impacts On The Great Lakes
 Climate Change Impacts On Bees and Food Production
 Lake Michigan Warming: Climate Threats
 Growing Corn Is Changing The Climate
 How Climate Change Affects Wisconsin Winters
 How Climate Change Affects Butterflies

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