Environmental activists around the world are marking Earth Day Thursday, April 22. Many communities in the United States got a head start on the annual celebration this past Saturday and Sunday, with cleanups, festivals, and other events designed to promote environmental awareness.

One of America's leading environmentalists is using Earth Day 2004 to offer a mixed assessment of the state of the planet. Yale University professor Gus Speth, who founded the World Resources Institute, is the author of a new book on the environmental challenges ahead, called Red Sky at Morning.

Mr. Speth paints a somewhat contradictory picture in his assessment of environmental progress since the first Earth Day in 1970: great progress in some areas, alongside decline in others.

"On the local environmental issues, around the world, there's been tremendous progress. And these were the issues that spurred the original Earth Day in 1970," he said. "I'm talking about air and water pollution, some toxic chemicals at the local level. There's been a lot of progress in that area. But in the global scale issues, what we've seen since the period of Earth Day has been almost continuous decline. So the tropical forests have been disappearing at a rate of an acre a second globally. Buildup of climate-altering gasses in the atmosphere continues. The great predator fish of the oceans are down 90 percent. And on-and-on down this list of global environmental deterioration. So it's not a particularly happy message for earth day."

In 2001, the Bush administration rejected the United Nations-sponsored Kyoto treaty on global warming, saying it would harm the U.S. economy. The White House also objected to provisions of the treaty that would allow greenhouse gas emissions by developing countries.

Gus Speth criticized Washington's position, suggesting that faltering U.S. leadership stems from what he called a powerful domestic constituency for minimalist government. And he said it is Europe that today is providing environmental leadership.

"This is a great tragedy in my judgment. I hate to see my own country being the principal holdout, for example, on the Kyoto protocol and resisting implementing the new treaty on toxic chemicals and other things," he said. "But we have to give high marks to Europe I think right now on a lot of things - not fisheries management, where I think the Europeans are still misbehaving - but on other issues. They're definitely giving real leadership."

In his book, Mr. Speth describes a number of strategies needed to achieve a sustainable environment. He mentions population control and new technologies; pricing products so that the cost of disposing of something is included in the price that the customer pays for it. And he devotes a chapter to changing mindsets - what he calls a "transition of culture and consciousness."

"At the root of all of these things are these very bad habits of thought that focus on consumption rather than conservation, that focus on now rather than tomorrow, that focus on us rather than the whole life of the planet," he said. "Climate change, deforestation, the spread of deserts, depletion of ocean fisheries, the spread of toxic chemicals around, and on-and-on, and they are not going to be solved by some simple answer, some simple solution or any one thing. A daunting set of problems gives rise to a daunting agenda, and it's that whole agenda that we need. But the risk of not taking those steps, of not pursuing those initiatives are so much greater that the difficulty of pursuing them."

The title of Gus Speth's book refers to an old maritime couplet, "Red sky at morning/Sailors take warning." But his warning on the environment is a tempered one. Even the conservative British magazine, The Economist, welcomes the book's call for balancing environmental cleanup with the needs of the poor and even grudgingly admits that Mr. Speth makes what it calls a "semi-plausible" case for a new World Environment Organization.

Red Sky at Morning by James Gustave Speth is published by Yale University Press.