WASHINGTON – We are using the Earth to improve our lives, but our children and grandchildren will be forced to live in a worsening environment that endangers their existence, more than 1,300 scientists warn.

In a report to be released Wednesday, a team of international experts concluded that the world is at risk on a variety of fronts, including a skyrocketing runoff of nutrient-rich farm waste that’s killing swaths of the world’s oceans, a massive wave of animal and plant extinctions and a planet that’s growing warmer.

But it’s not hopeless, they said.

The five-year study, commissioned by the United Nations and a number of businesses and independent groups, arrived at a mixed prognosis for planet Earth: Its deteriorating environmental health is still treatable, but only with aggressive and expensive corrective measures.

In the 219-page report, scientists looked at 24 different “services” the Earth’s ecosystem provided people and found that 15 of them are in trouble.

“At the heart of this assessment is a stark warning,” the board overseeing the report wrote. “Human activity is putting such a strain on the natural functions of Earth that the ability of the planet’s ecosystem to sustain future generations can no longer be taken for granted.”

Increased demand for food, fresh water, energy and raw materials is weakening the delicate but complex systems of plants, animals and biological processes that make Earth livable, the report warned.

What makes this study – called the Millennium Ecosystem Assessment – different from other reports is that it’s based on evidence that’s generally agreed upon by the consensus of scientists, rather than facts of the “he-said, she-said” variety, said study executive director Walt Reid, an ecologist.

Aimed at business and government leaders, the report is often written not in the scary language of an environmental polemic, but as a financial ledger for Earth.

The scientists reiterate the analogy of a person overspending his resources.

“What we’ve been doing now is running down the account, if you will,” said Oregon State University zoology professor Jane Lubchenco, president of the International Council for Science. “We’ve been utilizing services assuming that they were free and would always be available.”

World Bank chief scientist and study co-chair Bob Watson said unless mankind changes its ways, our consumption will “undermine the very ability for these ecosystems to provide the goods and services we need.”

Poorer countries will pay the steepest price, Watson said. Much of the problems surround water or the lack of it, a problem that’s particularly acute for poor countries.

Nitrogen and phosphate farm runoff is creating “dead zones” in oceans around the world and the problem is likely to increase by two-thirds by 2050, the report found. There are already more than 50 dead zones – including in the Gulf of Mexico, Chesapeake Bay and Puget Sound – caused by an abundance of nutrients choking off oxygen, Lubchenco said.

More than one-quarter of the world’s wild fish stocks are overharvested. For example, the number of Atlantic cod caught off Newfoundland’s east coast went from more than 800,000 tons a year in the 1960s to none now. Cod fishing was halted after the stock of fish collapsed.

More than 2 billion people live in “dryland ecosystems,” which hold a third of the world’s population but only 8 percent of the renewable water supply. Unable to keep up with the demand for water, these regions will become poorer and its political institutions will become more unstable.

A majority of different types of species are seeing their populations drop. The report said 32 percent of amphibian species, 25 percent of mammals and 12 percent of birds are threatened with extinction over the next century.

And by 2050, the world won’t be able to feed everyone living, despite better farming, the report predicted.

Add to that the prospect that global warming will worsen, making it harder for some species to survive.

“If we continue the way we’re behaving today, it’s a very pessimistic outlook,” said the World Bank’s Watson. “But the future is in our hands. We can do something about it.”

Some of the recommended changes:

• Remove subsidies to agriculture, fisheries and energy sources (such as fossil fuels) that harm the environment.

• Pay landowners to manage property in ways that help the environment, such as storing carbon dioxide, which causes global warming.

• Use free-market incentives to reduce farm pollution and global-warming gas emissions.

• Protect more areas from development, especially in the oceans.

• Invest in better and cleaner technology for agriculture and energy use.

Computer models showed that these solutions fixed some problems, said University of Wisconsin-Madison zoology professor Stephen Carpenter, a co-author.

“There are quite a few things that we could be doing to make things better, but we’re not doing any of them,” Carpenter said.

For a copy of the Millennium Ecosystem Assessment, go to: http://www.millenniumassessment.org.

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.