Connections among individuals within a species aren't the only things that can be disrupted: global warming can also threaten the ties that bind members of different species to one another. Many biologists, including Darwin, once believed that species responded to temperature changes as a group, thus preserving their relationships to one another.
But scientists are finding that this is often not the case. Instead, different species respond to environmental stressors in different ways, and this can lead to what Root calls the "tearing apart of communities.
The second prediction was that the timing of natural events like flowering, migration, and egg-laying could shift. Ecosystems are intricately connected webs, and even if a species doesn't rely on temperature and daylight cues to trigger certain behaviors, it may interact with other species that do.
Third, the body size and behaviors of species may change in response to rising temperatures. For example, scientists believe that as a general rule, bodies become smaller in response to general warming and larger with cooling. A study led by Philip Gingerich, a geological sciences professor at the University of Michigan, looked at horse fossils from a warming period that occurred 55 million years ago.
They found that as temperatures rose, the fossils shrank, from the size a small dog to a house cat. The researchers believed the dwarfing might have resulted from the horses eating plants whose tissues were low in protein but high in toxic compounds -- plants that flourished in the carbon dioxide-rich environment of the time.
Finally, species can undergo genetic changes. This last prediction has been documented in at least two species, the red squirrel and the fruitfly Drosophila.
Not all scientists are convinced humans have anything to do with climate change or the shifts seen in the animal world. Patrick Michaels, an environmental science professor at the University of Virginia, believes the current warming is part of a natural cycle.
Half of it is at best, probably less than half. The study notes that ancient extinctions have often been concentrated at specific latitudes and in specific ecosystems when the climate changed rapidly. Future warming is likely to trigger the loss of more marine species from local habitats and more species turnover in the ocean. Materials provided by Rutgers University. Note: Content may be edited for style and length.
Science News. Story Source: Materials provided by Rutgers University. Journal Reference : Malin L. McCauley, Jonathan L. Payne, Jennifer M. Greater vulnerability to warming of marine versus terrestrial ectotherms. The polar bear standing on a chunk of shrinking ice, apparently stranded, has become a familiar image, a symbol of the devastating effects of climate change. This image is somewhat misleading since polar bears are powerful swimmers and climate change will primarily affect them by restricting access to prey.
Nevertheless, researchers agree that even small changes in temperature are enough to threaten hundreds of already struggling animals. Up to half of the animal and plant species in the world's most naturally rich areas, such as the Amazon and Galapagos, could face extinction by the turn of the century due to climate change, according to a study published in the journal Climate Change. The key impact of global warming on wildlife is habitat disruption, in which ecosystems—places where animals have spent millions of years adapting—rapidly transform in response to climate change, reducing their ability to fulfill the species' needs.
Habitat disruptions are often due to changes in temperature and water availability, which affect the native vegetation and the animals that feed on it. Affected wildlife populations can sometimes move into new spaces and continue to thrive. Cities and roads can act as obstacles, preventing plants and animals from moving into alternative habitats. Beyond habitat displacement, many scientists agree that global warming is causing a shift in the timing of various natural cyclical events in the lives of animals.
The study of these seasonal events is called phenology. Many birds have altered the timing of long-held migratory and reproductive routines to better sync up with the warming climate.
And some hibernating animals are ending their slumbers earlier each year, perhaps due to warmer spring temperatures. To make matters worse, research contradicts the long-held hypothesis that different species coexisting in a particular ecosystem respond to global warming as a single entity. Instead, different species within the same habitat are responding in dissimilar ways, tearing apart ecological communities millennia in the making.
As wildlife species struggle and go their separate ways, humans can also feel the impact. A World Wildlife Fund study found that a northern exodus from the United States to Canada by some types of warblers led to a spread of mountain pine beetles that destroy valuable balsam fir trees. Similarly, a northward migration of caterpillars in the Netherlands has eroded some forests there.
According to Defenders of Wildlife , some of the wildlife species hardest hit by global warming include caribou reindeer , arctic foxes, toads, polar bears, penguins, gray wolves, tree swallows, painted turtles, and salmon.
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