Environmental fervor is fading and the reasons are as green as the trees: dollars and cents.

"When faced with real economic trade-offs, whether it's the spotted owl or the Big Green initiative, sometimes good things lose," says Vincent Breglio, a White House pollster who tracks energy and environmental opinion.That doesn't mean recycling is on the way out, reports Changing Times, the Kiplinger magazine. Breglio's surveys still find strong opposition to new nuclear reactors and drilling on public wildlife reserves. Consumers want the government to spend more on such renewable energy sources as wind and solar. But polls also show that people don't want to part with more than $11 a month in higher taxes and prices to advance ecological causes.

Fiscal stress will slow state and local preservation initiatives. Richard Lamm, a public-policy scholar at the University of Denver and former governor of Colorado, questions whether a financially pressed state should spend $30 million to clean up a waste site, as Colorado did, "to save one-half of a cancer death a decade."

Another sign of receding environmental interest: the stock market. From July through the end of 1990, mutual funds that invest in environmentally related companies finished last among 27 kinds of funds, losing 21 percent of their value.

Our flagging interest will revive. There's a predictable relationship between the environment and economic cycles: In economic downturns, people think about jobs and taxes. People with full wallets turn to social issues. So late in the next business expansion, you'll hear calls for the next Earth Day, figures Washington University environmental economist Don Coursey. And we'll have more experts around to work on the problem: Tulane University law professor Oliver Hauck says his classes are crammed with students planning careers in environmental affairs.