Two pioneers in the field of conservation biology will share the 2001 Tyler Prize for Environmental Achievement.

They are Jared M. Diamond, a professor of physiology at the UCLA School of Medicine, and Thomas E. Lovejoy, a Smithsonian biologist who is chief biodiversity adviser to the president of the World Bank.

Diamond and Lovejoy will share a $200,000 cash prize and receive gold medallions April 20 at a banquet in the Four Seasons Hotel in Beverly Hills.

They will also be honored by the international environmental community at a luncheon at the USC Davidson Conference Center April 19, followed by public lectures beginning at 2:30 p.m., and a public reception.

"The contributions of these two scientists have not only significantly advanced science on several fronts, but they have also increased the chance of survival of countless species, including humans," said Robert P. Sullivan, chair of the 11-member Tyler Prize Executive Committee.

Diamond, 63, has applied Darwinian theory to diverse fields such as physiology and ecology. His work has led to the recognition of a sub-field of community ecology based on "assembly rules," competition and community dynamics.

As a researcher, Diamond led 19 grueling expeditions to remote mountain ranges and tropical rain forests on New Guinea and other Southwest Pacific islands to understand the community ecology of the hundreds of coexisting species of birds. His novel theories relating species extinction rates to habitat size helped give birth to the discipline of conservation biology and served as a justification for large nature reserves.

Much honored for his scientific work, he received a National Medal of Science in 1999 and also won the 1998 Pulitzer Prize for nonfiction for "Guns, Germs, and Steel: The Fates of Human Societies." "The Third Chimpanzee," an account of human evolution, won Britain's Science Book Prize.

Lovejoy a 59-year-old tropical biologist, elucidated the Minimum Critical Size of Ecosystems concept and was thus central to calling to world attention the critical problem of dwindling tropical forests.

He has worked in the Amazon basin of Brazil since 1965 and is credited with coining the term biological diversity, now shortened to biodiversity. His research led to the adoption of conservation measures in the Amazon.

For 14 years, Lovejoy led the World Wildlife Fund - U. S. and helped to build its programs. Perhaps his best-known idea is the "debt-for-nature swap," through which developing nations could convert foreign debt to nature reserves and conservation programs.

Lovejoy was the founder of the public television series "Nature" and served as its principal adviser for many years.

The Tyler Prize for Environmental Achievement is administered by USC. The late John and Alice Tyler established the prize in 1973. For more information, visit http://www.usc.edu/tylerprize.