Human Impact Triggers Massive Extinctions

ST. LOUIS, Missouri, August 2, 1999 (ENS) - Humanity's impact on the earth has increased extinction rates to levels rivaling the five mass extinctions of past geologic history, transformed nearly half of Earth’s land and created 50 dead zones in the world’s oceans, according to research being presented this week at the 16th International Botanical Congress.

Delegates at the world's largest gathering of plant scientists, which opened Friday, heard a seven point plan to slow the extinction rates of plants around the world. The Congress has brought together some 5,000 scientists from more than 100 countries to discuss the importance of plants for human survival and improved quality of life, and to announce breakthrough research in the field of plant science.

Two studies being discussed find that humans have gravely altered the chemistry, biology and physical structure of the Earth's land and water. What scientists are calling the "human footprint on Earth" is increasingly impairing the planet’s ability to maintain the quality of human life, and may lead to the loss of up to two-thirds of all plant and animal species during the second half of the 21st century.

Earth's Water Resources in Trouble

"We're degrading the water, changing our coastlines, filling in our estuaries, and changing our rivers," says Dr. Jane Lubchenco of Oregon State University, author of "Environmental Science and Engineering for the Twenty-First Century: The Role of the National Science Foundation." Lubchenko specializes in marine biology and zoology and their relation to climate change. Lubchenco

Dr. Jane Lubchenco (Photo courtesy the White House)
Dr. Lubchenco, past president of both the American Association for the Advancement of Science and the Ecological Society of America, warns, "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."

Lubchenko and coauthors Harold Mooney and Peter Vitousek of Stanford University found that close to 50 percent of the land surface of the planet has been transformed by humans through actions such as filling in wetlands, converting tall grass prairies into cornfields, or converting forests into urban areas. Humans have also more than doubled the amount of available nitrogen in the environment because of excess fertilizer use and burning of fossil fuel.

Lubchenco points 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 says. 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. But the massive human-wrought changes in our oceans are impairing their ability to function as we assume they will," says Lubchenco.

Lubchenco lists problems facing the world’s waterways, including loss of mangrove forests and invasive marine species carried in ships' ballast waters. About 3,000 species of marine life are in transit in ballast water of ships around the world, Lubchenco says.

The changes humans have set in motion on a global scale 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 says.


Erosion caused by deforestation sends a stain of sediment into the sea off the Mekong Delta in Vietnam (Photo courtesy National Aeronautic and Space Administration)
Forests, grasslands 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 and spawning habitat for economically important species.

Massive environmental changes also have far reaching implications for peace and political boundaries. "Scarce resources such as water or fishing rights lead to battles between states and nations. Environmental degradation resulting in food shortages lead to civil unrest and migration into neighboring countries," Lubchenco explains.

Massive Species Loss Predicted

Meanwhile, "Plants in Peril: What Should We Do?" a report by the president of the International Botanical Congress, Dr. Peter Raven, predicts massive losses of plant and animal species, most in the tropics, during the second half of the next century.

"Human efforts have been notable for their lack of attention to the living world that supports us all," said Raven, who is also director of the Missouri Botanical Garden, which is hosting the conference. "In the face of the worldwide extinction crisis, we should redouble our efforts to learn about life on Earth while it is still relatively well represented."

Raven's paper says that if current trends continue, within 50 years only five percent of tropical forests will remain in protected areas. Extinction rates will then be three or four orders of magnitude higher than those prevailing between mass extinctions.


In the Nafud Desert of Saudi Arabia, irrigation turns small patches of desert into monoculture cropland, pushing aside native plants (Photo courtesy National Aeronautic and Space Administration)
Mass extinctions are events where the rate of species extinctions becomes much higher than the background rate, and large percentages of species are lost.

There have been five major extinction events in Earth history, including the one in which dinosaurs disappeared. At that time, two thirds of all land organisms disappeared and the character of life changed permanently.

The current extinction rate is now approaching 1,000 times the background rate and may climb to 10,000 times the background rate during the next century, if present trends continue. At this rate, one-third to two-thirds of all species of plants, animals, and other organisms would be lost during the second half of the next century, a loss that would easily equal those of past extinctions.

Raven’s paper also states that vast numbers of unknown plants, animals, and other organisms are currently being lost before they have even been recognized. Only about 1.6 million organisms out of a conservative estimate of between seven and 10 million have been recognized scientifically. A great majority of these are poorly known, often from a single specimen, a brief description, a locality, and nothing more, according to the paper. Some 250,000 of 300,000 species of plants have been identified, leaving some 50,000 completely unknown.

Dr. Raven's Seven Point Plan to Slow the Extinction of Plants

  1. Establish a new coordinating body, possibly connected with the United Nations, to monitor the status of plants throughout the world, detect those most in danger, and take steps to conserve them.

  2. Increase financial support for the study of plants throughout the world both by strengthening the major museums and other institutions that have holdings of specimens and literature on plants and by building capacity in developing countries with scarce resources. Currently, 80 percent of the world's scientists live in industrialized countries, which have about 20 percent of the world's population and only 20 percent of the world's biodiversity.

  3. Make information on plants accessible on the Internet to people throughout the world, especially to the poor "who truly need it."

  4. Place more emphasis on alien-introduced plants and animals as a major cause of biodiversity losses. Studies of aliens and of the ways of controlling them should be taken into account in evaluating the status of species in nature.

  5. At the national level in every country around the world, maintain an active census of the condition of the country's plants, so that it will always be obvious which are well protected in nature and which are rare and endangered.

  6. Place special attention on conserving medicinal plants.

  7. Internationally fund an ongoing program of research on plant population biology and reproductive characteristics so that these areas can be used as part of the world's overall preservation scheme.
"Although this expenditure may seem high, we are living in an era when our great-grandchildren may live in a world in which more than half of the plant species that exist now will be known only as specimens," said Raven. "All plants are important in one way or another and this comprehensive plan seeks to save them all - a priceless gift to future generations."

The International Botanical Congress is held once every six years. It last met in the U.S. in 1969, when it was convened in Seattle, Washington.