Genghis Khan was famous for building pyramids made from his enemies' heads. He also liked to tie their children to wagon wheels and then roll the wagon.

Still, if there's a Great Ledger in the Sky on Genghis Khan, you'll find entries on the good side as well as the bad. In the early 1200s, when Genghis Khan was busy marauding in Mongolia, he insisted that the headwaters of all the rivers be protected. No one was to cut down trees in these areas.

The conservation implications of this have been immense, and the legacy for the people of Mongolia a benefit beyond price. The reason, according to Dr. Clyde Goulden from the Institute for Mongolian Biodiversity and Ecological Studies, is that in dry areas like Mongolia, if the headwaters of rivers are not protected, the rivers will go dry.

Mongolia receives only about 12 inches of rain a year. When trees at the headwaters of rivers are cut down, this rainwater races off the hillsides, eroding the soil as it does. A vicious cycle ensues with less and less soil available to hold the water.

Whatever water does remain has no shade to protect it and so evaporates. The result, Goulden explains, is that in countries like India, Pakistan, and some parts of China, all too often, floods are followed by droughts.

On the other hand, when forests are left undisturbed, the trees, and particularly their root systems, act like giant sponges. During rainstorms, the forests slow the run-off , and then the shade from the trees reduces the amount of water lost to evaporation.

Genghis Kahn's attitude on protecting the environment has lasted down through the

centuries. Today Mongolia boasts one of the world's most pristine environments, and it's becoming a major attraction for eco-tourists.

Accommodations can be primitive, and some areas don't have electricity. Still, this unspoiled environment has proved to be, in the words of Dr. Adyasuren, Minister for Nature and the Environment , "an irreplaceable capital of immeasurable value." Tourism and particularly, eco-tourism, is the fastest growing business in the world, and Mongolia is perfectly positioned to benefit from it.

Mongolia has many riches to attract ecotourists. Besides Buddhist temples and a rich history, Mongolia also has the Gobi desert with its extraordinary fossil beds, and an abundance of species that have become rare or extinct elsewhere. These include the Bactrian Camel, the Gobi Desert bear, the snow leopard, the saiga antelope, and Przewalski's horse.

According to Goulden, the current government of Mongolia is working vigorously to preserve this legacy. When Mongolia got its first democratically elected government in 1992, one of the first acts was to designate more than 100,000 square miles for nature reserves. That's an area nearly the size of Texas.

As the country transitions from a centrally planned economy to a market economy, the government wants to make sure that any development is ecologically sustainable. Eco-tourism can help with this goal.

Currently 14% of the land is protected, and the long term goal is to keep 30% of the land in national parks and protected forests. "It will be one of the largest conservation project in the world," says Goulden.

Genghis Kahn may have done some monstrous things 700 years ago, but the people of Mongolia have reason to be grateful to him today. If he had acted differently, Mongolia might not have one of its greatest national treasures, it's protected watersheds.