Raymond F. Dasmann, 83, a field biologist whose research and writings about threats to the natural world helped mold the modern environmental movement, died of pneumonia Nov. 4 in Santa Cruz, Calif.

He began talking about the need for environmental conservation in the late 1950s, almost two decades before the concept took hold in the American mainstream. Although not a household name like Rachel Carson or Jacques Cousteau, his contributions included the concept of "ecodevelopment," or sustainable development, the idea that a community's progress should not rely on exploitation of its natural resources.

Dr. Dasmann was the author of more than a dozen books. His 1965 book, "The Destruction of California," became a staple of university ecology courses in the 1970s. He produced two memoirs in his last few years: a 232-page oral history published by the University of California Press last year; and "Called by the Wild: The Autobiography of a Conservationist," published in April. Other works included the 1959 textbook "Environmental Conservation," now in its fifth edition.

He coined what he called the first law of the environment: "No matter how bad you think things are, the total reality is much worse."

Dr. Dasmann was born in San Francisco, the son of a police sergeant. His brother worked for the state Department of Forestry and helped spark Dr. Dasmann's interest in the natural world.

During World War II, he served with the Army in the southwestern Pacific theater. After the war, he received bachelor's, master's and doctoral degrees from the University of California at Berkeley.

As a graduate student, he studied deer populations in Northern California, a topic that acquainted him with the complexities of environmental politics. Finding that the number of deer was growing far faster than their range could support, he and his colleagues argued that a doe hunt was necessary to restore balance. But they failed to convince deer hunters, who feared it would lead to extinction and ruin their sport.

Beginning in the mid-1950s, he taught at Humboldt State University and later UC-Berkeley. In between, he studied African wild game as a Fulbright field biologist in what is now Zimbabwe.

In 1966, he became an ecologist for the Conservation Foundation in Washington and then, in 1970, for the International Union for Conservation of Nature in Switzerland. From 1977 until retiring in 1989, he taught ecology at the University of California at Santa Cruz.