On December 9, nationally syndicated radio host Rush Limbaugh falsely claimed that "[t]here is no evidence that we could destroy ecosystems." Limbaugh made his comments after a caller asked him for help in “combat[ing] the myth of global warming” that, the caller claimed, had been “spoon-fed” to his son. Limbaugh purported to debunk the “myth” that “humanity is causing” global warming -- a process that, according to Limbaugh, “relies on the theory that we are destroying ecosystems.”

The Pew Center on Global Climate Change defines "ecosystem" as "[a] community of organisms and its physical environment." While it may not be possible to demonstrate that all of a given community's organisms, as well as the entirety of their physical environment, have been destroyed by human activities, there is ample evidence that humans can -- and do -- devastate ecosystems.

In a 2002 report titled, "Global Environment Outlook 3" (GEO-3), the United Nations Economic Programme (UNEP) -- in collaboration with 40 organizations from around the world -- noted that: “Over the past three decades, decline and extinction of species have emerged as major environmental issues. The current rate of extinction is many times higher than the 'background' rate -- that which has prevailed over long periods of geological time.” According to the report, the “unprecedented rate” of biodiversity loss is caused by “human population growth together with unsustainable patterns of consumption, increasing production of waste and pollutants, urban development, international conflict, and continuing inequities in the distribution of wealth and resources.” GEO-3 further noted that “conversion of forests or grasslands into croplands results in the local extinction of plant and animal species.” The report explained:

Worldwide about 1.2 million km² [square kilometers] of land have been converted to cropland in the past 30 years. In a recent global survey, habitat loss was found to be the principal factor affecting 83 per cent of threatened mammals and 85 per cent of threatened birds. ... Habitat modification arises from many different types of land use change including agricultural development, logging, dam construction, mining and urban development.

There are a number of specific examples of massive ecosystem devastation caused by humans. For example, GEO-3 described the desiccation of the Aral Sea as “a human-induced environmental and humanitarian disaster.” The sea, which lies on the border of Uzbekistan and Kazakhstan, was once the world's fourth-largest lake and supplied the fishing industry with roughly 40,000 tons of fish each year before Soviet planners began draining it to irrigate the region. As described in GEO-3:

The result was the collapse of the prevailing water balance in the basin. Waterlogging and salinization eventually affected about 40 per cent of irrigated land. Overuse of pesticides and fertilizer polluted surface water and groundwater, and the delta ecosystems simply perished: by 1990, more than 95 per cent of the marshes and wetlands had given way to sand deserts and more than 50 delta lakes, covering 60 000 ha [hectares], had dried up.

The surface of the Aral Sea shrank by one-half and its volume by three-quarters. The mineral content of the water has increased fourfold, preventing the survival of most of the sea's fish and wildlife. Commercial fishing ended in 1982. Former seashore villages and towns are now 70 km [kilometers] from the present shoreline.

Communities face appalling health problems. In Karakalpakstan, Uzbekistan, drinking water is saline and polluted, with a high content of metals that causes a range of diseases. Over the past 15 years, there has been a 3 000 per cent increase in chronic bronchitis and in kidney and liver diseases, especially cancer, while arthritic diseases have increased 6 000 per cent. The infant mortality rate is one of the world's highest.

On a broader scale, worldwide deforestation, particularly in the tropics, continues to threaten ecosystems around the globe. The UN's Food and Agriculture Organization (FAO) has found that from 2000 to 2005, “the net forest loss was 7.3 million hectares per year - an area the size of Sierra Leone or Panama and equivalent to 200 km² per day.” Citing the FAO, GEO-3 noted: “The depletion of forest-based wildlife as a result of the commercial harvesting and trade of bushmeat is of growing concern. This has reached crisis dimensions in parts of tropical Africa, where many species of primates and antelopes, among others, are threatened.”

In addition, Media Matters for America has noted that the overwhelming weight of scientific opinion contradicts Limbaugh's oft-made assertion that global warming is not caused by human activities. In its 2001 “Third Assessment Report,” the Intergovernmental Panel on Climate Change (IPCC) concluded that it is “very likely” (defined in the report as a 90-percent to 99-percent chance) that “the 1990s was the warmest decade, and 1998 the warmest year, in the instrumental record (1861-2000).” Moreover, it is “likely” (defined as a 60-percent to 90-percent chance) that "[t]he increases in surface temperature over the 20th century for the Northern Hemisphere" were “greater than that for any other century in the last thousand years.”

Citing multiple studies that provided “evidence for an anthropogenic signal [indication of human influence] in the climate record of the last 35 to 50 years,” the IPCC stated: “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.” Similarly, a 2001 National Academy of Sciences report commissioned by the Bush administration found that greenhouse gases are “causing surface air temperatures and subsurface ocean temperatures to rise” and that "[t]he changes observed over the last several decades are likely mostly due to human activities."

While humans' obvious ability to devastate ecosystems is not, as Limbaugh suggested, the basis for the scientific consensus that humans are causing global warming, there is significant evidence that human-caused global warming has already affected ecosystems in the United States and around the world.

A 2004 Pew study titled "Observed Impacts of Global Climate Change in the U.S." assessed “the scientific evidence compiled to date on the observed ecological effects of climate change in the United States and their consequences.” Pew concluded: “There is an emerging link between observed changes in wild plants and animals across the United States and human-driven global increases in greenhouse gases.” The study found that "[t]he implications of this link are that current biological trends will continue over future decades as greenhouse gas emissions continue to rise." Specifically, Pew found:

• “The timing of important ecological events, including the flowering of plants and the breeding times of animals, has shifted, and these changes have occurred in conjunction with changes in U.S. climate.”
• “Geographic ranges of some plants and animals have shifted northward and upward in elevation, and in some cases, contracted.”
• “Species composition within communities has changed in concert with local temperature rise.”
• “Ecosystem processes such as carbon cycling and storage have been altered by climate change.”
• “The findings that climate change is affecting U.S. biological systems are consistent across different geographic scales and a variety of species, and these U.S. impacts reflect global trends.”

Looking toward the future, Pew concluded that "[t]he addition of climate change to the mix of stressors already affecting valued habitats and endangered species will present a major challenge to future conservation of U.S. ecological resources." Pew cited a study that appeared in the January 8, 2004, issue of Nature. That study's authors “use[d] projections of the future distributions of 1,103 animal and plant species to provide 'first-pass' estimates of extinction probabilities associated with climate change scenarios for 2050.” Using “mid-range climate-warming scenarios for 2050,” the authors predicted that “15-37% of species in our sample of regions and taxa will be 'committed to extinction.' " The Pew study noted: “Such extinction rates are unprecedented in historical times.”

From the December 9 broadcast of The Rush Limbaugh Show:

CALLER: Need your help. I have a 16-year-old son, he's been spoon-fed the global warning myth through school and the media. And besides the six inches of snow we just received and some South Park episodes, where can I steer him to combat the myth of global warming?

[...]

LIMBAUGH: When we hang up here, stay on the phone and we'll get somebody to give you the information necessary to make this happen, because I have something on the website called the “essential stack of stuff,” and it's categorized by topic. And we have -- it's an encyclopedia. It is a -- it is a database of countless stories that have been in the media, speeches made by experts, debunking every myth about global warming. Now, this is not to say the earth isn't warming; it's not to say this. But the idea that humanity is causing it is something that has swept liberalism. Liberalism believes in doom and gloom. They believe we are destroyers, especially prosperous people. They think that we have no regard for what is here. They try to make it sound like that -- well, this is really too complicated for your son to understand, but between you and me, these people think they're secularists. In truth, they are as -- they are as devoted to religion as anybody else is. They just have a different god. And [author] Michael Crichton made a speech once that is eerie in its -- in its perceptiveness about the militant environmentalist wackos. Their belief system parallels the story of Genesis in striking ways, except there's one big difference: There never has been a Garden of Eden. If you go back a hundred years, you find horse manure all over the streets. If you go back 200 years, you find pestilence and disease. If you go back farther than that -- we are living in the best times possible. Life expectancy is at an all-time high. Global warming relies on the theory that we are destroying ecosystems. There is no evidence that we could destroy ecosystems.