Global warming is already affecting North American species and could cause major shifts in ecosystems across the continent, according to new research by U.S. wildlife experts. Caribou, polar bears, migratory songbirds, waterfowl and alpine amphibians are among the North American species that have already responded to global warming by shifting habitats, altering breeding patterns, or rerouting their migrations.

Sustained and broad changes in wildlife behavior due to climate change will cause the restructuring of entire plant and animal communities, the researchers said, and could result in the disappearance of some forest types.

The study, produced by The Wildlife Society, a 9,000 member association of wildlife professionals, is the first comprehensive analysis of global warming's impact on North American wildlife.

It adds to a growing body of scientific work that suggests global warming may be the leading threat to biodiversity.

A study by the Center for Applied Biodiversity Science at Conservation International, published last January in the journal "Nature," predicted climate change could drive more than a quarter of all land animals and plants into extinction.

Warmer spring temperatures have had a negative impact on migrating caribou in Alaska. (Photo by Jon Nickles courtesy U.S. Fish and Wildlife Service (FWS))

And a report released Tuesday by WWF, the global conservation organization, says many researchers may have underestimated the risk climate change poses to species because they failed to analyze the impact of extreme weather events.

The new study on North American wildlife also spells out a dire warning, said Douglas Inkley, an ecologist with the National Wildlife Federation and chair of the eight person committee that wrote the report.

"We face the prospect that the world of wildlife that we now know - and many of the places we have invested decades of work in conserving as refuges and habitats for wildlife - will cease to exist as we know them, unless we change this forecast," Inkley said.

Climate change will affect the habitat conditions of virtually every species - either directly or indirectly, the report says, predicting that as temperatures increase, the ranges of habitats and the wildlife that depend on them will shift northward in search of cooler areas.

If development and habitat destruction have already altered the more northerly areas, the species often have no safe haven.

Some species are unlikely to survive because their ability to make this shift will be inhibited by migratory pathways, pollinator availability and the concurrent movement of forage and prey.

Many wood warblers have shifted their ranges north in the past two decades. (Photo courtesy FWS)

"The case of a pollinator bird being able to make the range shift while the plant it pollinates cannot may be replicated in innumerable interdependent relationships, leaving us a world of wildlife diminished beyond our current capacity of prediction," Inkley explained.

Rising temperatures will further disrupt essential ecological processes, displace or wipe out coastal wetlands species, decrease coastal marshes, and disrupt alpine and Arctic ecosystems, the report details.

In the Prairie Pothole Region from northern Iowa to central Alberta - the duck factory of North America - "most scenarios and models projected significant declines in wetlands, and thus declines in the abundance of breeding ducks in this region by the 2080s."

Some species will benefit at the cost of others.

For example, the dominant pine and hardwood forests found in the southeastern United States are projected to expand northward.

The conifer forests of New England and much of the Northeast are expected to change to temperate deciduous forests similar to those today found in southeastern Pennsylvania and northern Virginia.

"Some forest species such as sugar maple are projected to disappear entirely from the United States over the next century," according to the study.

Projected sea level rise due to global climate change may cause some wildlife species to be displaced inland or disappear entirely if their lowland wetlands are rapidly inundated, the wildlife experts said.

"Critical mudflats used by migratory shorebirds" may be flooded, and "submergence of coastal marshes is expected to be most severe along the U.S. Gulf and Atlantic coasts."

Climate change is expected to diminish wetlands in the Prairie Pothole Region, causing a decline in breeding ducks. (Photo courtesy Fish and Wildlife Service)

In areas where warming is greatest, "changes in forest dynamics due to disease and insects are very likely," said the report, which points out that rapid Arctic warming in the mid-1990s coincided with a massive outbreak of spruce bark beetles.

Understanding how the changing climate will affect species could prove critical to wildlife conservation efforts.

"Wildlife managers can enhance a species' ability to withstand global climate change by ensuring widespread habitat availability and managing for self-sustaining populations," the report recommends.

Based on the study, The Wildlife Society said it would consider adopting formal policy recommendations at its March meeting.

In draft form, those recommendations now include measures such as reduction of carbon dioxide and other greenhouse gas emissions and that state and federal wildlife agencies consider climate change in developing long range wildlife management plans and strategies.

"Decades of conservation progress and our responsibility to assure a wildlife legacy for future generations rest upon our determination to overcome this threat," Inkley said.