What is Global Warming?
Geologists tell us that over the past 420,000 years our planet has undergone cycles of cooling — the ice ages — and warming. Indications are that we are currently in a warming cycle. But how much of the change, if any, is man-made (anthropogenic) and how much is simply due to the earth’s natural cycles of heating and cooling? Our speakers will address this issue by discussing scientific studies showing strong evidence of a rise in average temperature in many parts of the globe. This rise is thought to be a major reason for the melting of glaciers in Alaska and the Sierra and Rocky Mountains. It has also resulted in a longer growing season, which, in turn, has altered the annual cycle of carbon dioxide levels in the atmosphere. This is because plants are a major intermediary in what is called the “carbon cycle” — plants can absorb carbon dioxide or, depending on the local temperature, release more than is absorbed.
The rise in temperature is related largely to a significant increase in atmospheric “greenhouse gases”- such as carbon dioxide, a product of burning fossil fuels- that can trap heat near the earth and retard radiation heat loss. The amount of the increase varies from place to place but tends to be greater in northern latitudes. The average temperature increase has been only a couple of degrees Fahrenheit over the past 100 years, but there is abundant evidence that even this small rise in average global temperature has a significant impact on living things.
For several animal species, habitat changes have been documented as populations seek to adapt to rising temperatures by moving northward or to higher elevations. The timing of important ecological events — such as plant flowering and animal breeding — has shifted in conjunction with climate change. For example, some butterfly species have been observed to emerge from their cocoons before or after the blooming of the flowers they depend on for survival. This could lead to declines in population or, in the worst case, to extinction.
During historic ice ages, even though animals shifted their habitats by hundreds or even thousands of miles as glaciers came and went, species extinction is thought to have been rare. But such massive relocations of species are much more problematic now because of today’s human-dominated, artificially fragmented landscapes. The large reduction in area of natural habitats and the growth of urban and agricultural barriers to species migrations make it unlikely that animals can adapt as they did during the ice ages.
Many ecosystems and organisms in the United States are already suffering from other anthropogenic stresses, such as destruction or fragmentation of habitats, introduction of invasive species, and air or water pollution. To date scientists do not have a clear idea of how climate change might affect this already fragile situation. It is likely, however, that climate change will exacerbate current conditions, placing further stress on wild species and their associated ecosystems and accelerate the rate at which biological diversity is lost.
What can be done?
A broad range of strategies can help reduce the negative effects of climate change on ecosystems. To alleviate global warming, humans can try to reduce the amount of greenhouse gases released to the atmosphere. To retain biodiversity, we can promote plans for nature reserves where multiple natural habitats for an animal species will be connected, rather than isolated. This may allow managers to help wild species adjust to changing climate conditions, perhaps through relocation programs. Our speakers will discuss other methods for alleviating stress on biological systems, caused by both human-related climate changes and other human activities.