In recent decades, we've become increasingly aware of the dire global environmental consequences of destruction of the earth's tropical forests - shrunken habitat for animal species, lost biodiversity, more soil erosion, and fewer "carbon sinks" to absorb greenhouse gases.
There are a variety of ways one can assist in arresting tropical forest destruction, such as supporting forestry conservation or enhancing markets for "rain forest friendly" products such as shade-grown coffee. Recycling is also helpful.
But if you want to do one thing for Earth Day - Tuesday, April 22 - to conserve forests and even reverse deforestation: stay away from cocaine and heroin.
The strong link between illegal drug use and tropical forest destruction became obvious to me when I visited Colombia last year for the inauguration of Colombia's President Alvaro Uribe and discussed the drug trade with several members of his cabinet.
To cultivate coca and avoid being detected by law enforcement, farmers need to clear fields in fragile tropical forest areas, most often by slashing and burning. Colombia reports that, during the 1990s, more than 3 million acres of rain forest - an area larger than Yellowstone National Park - were cut for the cultivation of opium poppy and coca.
Similarly, Peru estimates that coca cultivation has caused the loss of 5.7 million acres of rainforest - a quarter of its total deforestation.
Deforestation is only one consequence of coca and poppy cultivation. Highly toxic insecticides and herbicides are used indiscriminately by coca and poppy growers in Colombia and Peru and can persist in the environment and harm a variety of wildlife. These products are used at rates that exceed the manufacturers' recommendations by individuals with no training or personal protection. They're often stored in or near the farmers' homes or food supplies, exposing them and their families to hazardous levels of these substances.
Once the coca and opium-poppy crops are harvested, coca leaves and poppy latex are mixed with more industrial chemicals, including sulfuric acid, acetone, potassium permanganate, and gasoline, to make cocaine base and heroin. The Colombian government estimates that in 2000, gasoline, in amounts equivalent to three days of gas consumption in California, were used for coca-leaf processing.
And in the middle of the forest where the processing pits and drug labs exist, you will not find toxic waste-management systems; those deadly chemicals are haphazardly dumped on the land and into the streams and rivers that supply drinking water for local populations.
In the case of Colombia, the drug trade has yet another devastating environmental consequence: It provides funding for the violent activities of three illegally armed groups, all of which are on the US list of known terrorist organizations: the National Liberation Army, the United Self-Defense Forces, and the Armed Revolutionary Front of Colombia.
Illegally armed groups also regularly bomb Colombia's oil pipelines. One pipeline built in 1986, for example, has suffered 700 attacks in which a total of 2.5 million barrels of crude oil were spilled along the Columbia-Venezuela border. That's roughly 10 times the amount of crude oil dumped into Prince William Sound in the 1989 Exxon Valdez disaster.
Unfortunately, the US remains the world's No. 1 consumer of the cocaine that originates in the Andes. And Americans consume virtually all of the heroin originating in that region.
A reduction in consumption of these illegal drugs in the US alone would cause a drastic decline in their production in the Andes, slowing deforestation and lessening pollution of the rainforest.
As concerned citizens have Earth Day discussions about how to stop global warming and save the earth's rainforests, they need to think about this linkage that may not be so obvious on the streets of the US. Truly concerned citizens also need to think about it the next time they are tempted to snort cocaine or use heroin, even if it's "just for fun." It's not just their own bodies they'll be polluting.
• Paula Dobriansky is the US undersecretary of State for global affairs.