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ST. LOUIS, Mo. - Humans have gravely altered the chemistry, biology and physical structure of the Earth's land and water, according to the latest findings on the "human footprint on Earth." The data show that nearly half of the land surface of Earth has been changed, and some 50 "dead zones" - areas with little or no oxygen - have developed in the Earth's coastal waters.

These latest findings, analyzed by Jane Lubchenco of Oregon State University and Harold A. Mooney and Peter M. Vitousek of Stanford University, show a "disturbing negative trend in the Earth's ability to maintain the quality of human life," Lubchenco said.

Lubchenco presented the findings at the 16th International Botanical Congress, where more than 4,000 scientists from 100 countries are meeting in St. Louis, Mo., to discuss the latest research on plants for human survival and improved quality of life. Among the findings:

• Close to 50 percent of the land surface of the planet has been transformed by humans - filling in wetlands, converting tall grass prairies into cornfields and converting forests into urban areas.

   

• Humans have more than doubled the amount of available nitrogen in the environment because of excess fertilizer use and burning of fossil fuel.

   

• Rates of extinction are an estimated 100 to 1,000 times what they would be without human-induced changes in the planet. On land, this is largely caused by habitat loss and species invasions that are crowding out native species. In water, overfishing also contributes.

   

• The year 1998 was Earth's hottest on record, as human activities continue to increase the concentrations of carbon dioxide and other heat-trapping gases in the atmosphere.

Lubchenco pointed out that while human domination of land masses is clear, the new data also indicates a dramatic alteration of Earth's oceans. There are now some 50 "dead zones"in the world's coastal areas, she reported. The largest in the Western Hemisphere is in the Gulf of Mexico, caused by excess nitrogen and phosphorus flowing down the Mississippi River.

"We've long thought of oceans as having an infinite ability to provide food and other goods and services to humans," said Lubchenco, the Distinguished Professor of Zoology at Oregon State University. "But the massive human-wrought changes in our oceans are impairing their ability to function as we assume they will.

"We're degrading the water, changing our coastlines, filling in our estuaries, and changing our rivers," she added. "And we're witnessing many signals of the problems that will result from these changes, including toxic algal blooms, coral bleaching and sudden disappearance of fish from key fisheries."

Lubchenco noted a number of indications of the human degradation of the Earth's waterways:

• Half of the mangrove forests, which serve as estuaries in the tropics, have been lost to a combination of coastal development and conversion to aquaculture.

   

• Global aquaculture now accounts for more than one-quarter of all fish consumed by humans. In the case of shrimp and salmon - the fastest growing segment of aquaculture - two to three pounds of fish are needed to grow one pound of the raised seafood. Thus this practice is depleting the oceans of food for wild fish, birds and marine mammals.

   

• About 3,000 species of marine life are in transit in ballast water of ships around the world, resulting in a serious invasion of non-native species in our waterways. A minor but increasing contributor to the problem is escape of non-native fish and plants from aquariums.

According to Lubchenco, these global-scale changes that have been set in motion will impair the Earth's ability to provide a wide range of services to human life.

"In addition to the direct services of food, fiber, shelter, and medicines, many other inter-dependent services are being disrupted," Lubchenco said. For example, forests, grassland and coral reefs contribute to flood control and climate regulation. Mangroves, estuaries, coral reefs and kelp forests protect shores from erosion and provide nursery areas or spawning habitat for economically important species.

Massive changes in the Earth's environment have far-reaching implications that result in conflicts across political boundaries, Lubchenco said.

"Scarce resources such as water or fishing rights lead to battles between states and nations," she pointed out. "Environmental degradation resulting in food shortages lead to civil unrest and migration into neighboring countries."

Increasing economic inequities in the world raise a host of new issues, according to the Oregon State University researcher.

"Inhabitants of poorer nations are less able to buy supplies such as bottled water if the water is polluted, less able to influence important policy decisions such as the choice of a site for a toxic waste dump," Lubchenco said.

The groundbreaking 1997 work of Lubchenco and her colleagues documented that we now live on a human-dominated planet, with the growth of the human population and the amount of resources used altering Earth in unprecedented ways. Her current analysis updates these findings.

"The dramatic rise in our population simply exacerbates the problems," Lubchenco said, noting that as of July 1999, there are reportedly six billion people on Earth, a doubling in less than 40 years.

Lubchenco said she does see hopeful signs in the increasing number of people who are concerned about the environment and are willing to take action. She noted that "it is encouraging that there is an increasing focus on the part of the private sector, religious groups, and individual citizens to take responsibility and undertake innovative action."

"As inhabitants of earth, we need to take stock of these massive changes, understand their implications, and change our direction," Lubchenco said. "We are currently inattentive stewards. It is in our best interests to be more fully engaged in ensuring our own health, prosperity and well-being."

Lubchenco strongly advocated additional research "so that we can make more informed decisions about our ecosystems." Substantial research across all disciplines is called for in a new policy report, expected to be released on July 29 from the National Science Board, "Environmental Science and Engineering for the 21st Century: the Role of the National Science Foundation."

Lubchenco, who chaired the Board's Task Force on the Environment which prepared the report, equates the need for scientists to focus on environmental research today with the nation's past decisions to invest in science to conquer disease, win the Cold War, or win the "space race."

The International Botanical Congress is held only once every six years. It last met in the United States in 1969, when it was convened in Seattle, Wash.