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Humankind's Grave Impacts on the Natural World Human activity has altered almost 50 percent of the Earth's total land area and now threatens to cause the greatest extinction of species seen in the last 65 million years. By GSReport Start Date: 8/10/99 More than 4,000 scientists from 100 countries, meeting at the Sixteenth International Botanical Congress in St. Louis, Missouri in late July, have sounded an urgent warning: Human activity is gravely impacting the natural world, leading toward a mass extinction of plant and animal species that will rival the greatest extinction events of geological history. According to papers issued by Congress participants on August 2, the "human footprint on Earth" has gravely altered the chemistry, biology and physical structure of the planet's land and water. Data show that nearly half of the Earth's total land surface has been changed by human activity, and some 50 "dead zones" (areas with little or no oxygen) have developed in the Earth's coastal waters. The latest findings, analyzed by Drs. 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." At the same time, between one-third and two-thirds of all plant and animal species now living will become extinct during the second half of the next century if current trends continue, according to a paper released by International Botanical Congress president Dr. Peter Raven, a world leader in plant conservation. "Human efforts have been notable for their lack of attention to the living world that supports us all," said Raven. "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." Scientists believe there have been five great extinction episodes since life first appeared on the Earth more than 3.5 billion years ago. In each case, as much as 80 percent of all then-living species were wiped out within a few decades or centuries. In the most recent case, 65 million years ago, it is believed a giant asteroid slammed into the Earth, causing one of the greatest of all extinction events including the disappearance of the dinosaurs. But, according to Raven, the present extinction episode -- entirely induced by human activity -- could be similar in scope. The current extinction rate is now approaching 1,000 times the background ("normal") rate and may climb to 10,000 times the background rate during the next century if present trends continue, he said. Among the chief causes of species extinction is forest loss, particularly the destruction of tropical forests in South America and Africa. If the world only manages to retain five percent of tropical forests in protected areas, which will be true within 50 years at present rates of destruction, then 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, the Congress paper said. Thus far, scientists say, only about 1.6 million organisms out of a conservative estimate of between seven and 10 million have been identified, and vast numbers of plants, animals, and other organisms are currently being lost before they've even been discovered. Raven noted that only a coordinated international effort could slow the extinction of the world's plants and animals. Inasmuch as most of the world's threatened animals are dependent upon forests, he stressed the urgent need to monitor threats to the world's plantlife. Raven advocates establishing a new coordinating body through the United Nations or one of its constituent organizations to monitor the status of plants throughout the world, detecting those most in danger and taking steps to conserve them. Dr. Lubchenco, a Distinguished Professor of Zoology at Oregon State University, emphasized other factors that show the grave impacts of human activity. Close to 50 percent of the land surface of the planet has been transformed by humans, such as filling in wetlands, converting tall grass prairies into cornfields, or 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. 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. But the massive human-wrought changes in our oceans are impairing their ability to function as we assume they will," stated Lubchenco. "We're degrading the water, changing our coastlines, filling in our estuaries, and changing our rivers," she said. "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." The global-scale changes that human beings have set in motion will impair the Earth's ability to provide a wide range of services to human life, 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 also result in human conflicts across 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 said. "The dramatic rise in [human] population simply exacerbates the problems," she added, noting that the number of people on Earth has doubled from 3 to 6 billion in less than 40 years. Lubchenco did see some hope in the fact 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," she 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."
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