HARVARD GAZETTE ARCHIVES

At the Kennedy School of Government's 2005 Gustav Pollak lecture on March 3, botanist Peter Raven sketched out a statistical portrait of a world heedlessly stampeding toward ecological disaster. (Staff photo Justin Ide/Harvard News Office)

Raven, the Engelmann Professor of Botany at Washington University in St. Louis and director of the Missouri Botanical Garden, delivered the Kennedy School of Government's 2005 Gustav Pollak lecture on March 3. His topic: "Biodiversity and Sustainability: How to Forge the Link."

Speaking in an energetic, rapid-fire style, Raven sketched in a statistical portrait of a world heedlessly stampeding toward ecological disaster. In 10,000 years, or, to put it in more comprehensible terms, about 400 generations, the human race has gone from 3 or 4 million, living in small scattered bands of hunters and gatherers, to its present population of 6.3 billion and rising.

In the past 50 years alone, the population has more than doubled, while soil erosion has increased by 20 percent, agricultural land has decreased by 20 percent, one-third of the world's forests have been chopped down, carbon dioxide has increased by one-sixth, and there's been 7 percent loss of the stratospheric ozone layer.

If the Earth's carrying capacity were a checking account, we'd be overdrawn. Based on calculations by ecologists William Rees and Hans Wackernagel, it would take 1.2 Earths to support our current population. The fact that we have only one planet at our disposal means that large portions of humanity are undernourished.

Some look to development to correct the problem of unequal distribution, assuming that in time the developing world will reach the standard of living that the developed world already enjoys, but Rees and Wackernagel's calculations demonstrate the folly of such belief.

"To support everyone at the standard of the developed countries, we would need three Earths," Raven said. "To support everyone at current standards if the population doubled [a milestone we are likely to reach by the mid-21st century] we would need six Earths. To support double the current population at the standards of the developed countries would take 12 Earths."

The stress that billions of hungry humans exert on the environment is driving plant and animal species to extinction at a rate unprecedented since Earth's collision with a giant asteroid wiped out the dinosaurs. Over Earth's history, the average extinction rate has been 10 species per year, said Raven. But between 1600 and 1950, it has averaged 100 per year. "Currently, we are losing thousands of species every year and soon it will be tens of thousands. At this rate, two-thirds of Earth's species will be gone by the year 2100."

Most of these extinctions are the result of habitat destruction, but there are other factors as well. Overfishing, overgathering of wild herbs for the natural medicine market, the introduction of alien invasive species, and changes in habitat due to global warming are all taking their toll.

What makes it worse is that the majority of the species being lost are still unknown to us. Raven said that of the estimated 7 million to 13 million species on Earth, only about 1.6 million have been identified, and of those, only 100,000 are known to any degree.

Since biodiversity "supports life on Earth and makes it possible," this loss is a serious matter. "But by losing biodiversity, we could also be losing a substantial number of species that could help us develop a truly sustainable Earth," Raven said.

For example, genes from plant species yet unknown might help breeders develop hardier, more productive food plants that could help alleviate hunger and lead to more sustainable agricultural policies. Medicines from plants could lead to breakthroughs in the treatment of diseases that afflict people in less developed parts of the world.

Because there is such disparity in the level of consumption between the rich and poor nations, the developed world bears a disproportionate responsibility for curbing its appetites. Those who live in the United States, Canada, Great Britain, and the other developed countries - which together account for only 23 percent of the world's population - use about 80 to 90 percent of the Earth's resources. And when it comes to wasting energy, the United States outstrips all rivals.

"We use twice as much energy as Germany, France, England, Switzerland, and the other developed countries, and it's hard to demonstrate that we get anything for it," Raven said.

What can be done to stave off what appears to be a rapidly approaching catastrophe? Establishing parks and protected areas, fighting invasive species, using seed banks to preserve threatened plant species - all of these measures will help and are important. But the key to altering the situation is a change in attitude, Raven said.

"The only way is to forge a world that is equitable and just. If poverty continues, there is no real hope of preserving biodiversity. In a high-consumption society like the United States, we can't solve the problem from the top down. Sustainability has to come from the bottom up."

Raven warned against relying too much on technology to cure our environmental ills.

"So far, technological advances have left us with a world where many people are starving. Technology is extremely important, but it would be a mistake to assume that it can solve everything."

Raven, a scientific prodigy who became a member of the California Academy of Sciences at age 8 and at 15 discovered a subspecies of the heather family that had not been seen for 50 years, puts a great deal of stress on education, particularly about the local environment.

"I think if you imbue children with a love of nature, they will want to do the right thing."

But the most important change in attitude for Raven is the realization that we do not have multiple Earths to sustain our growing population, and the fact that we are all inhabitants of this one precious planet unites us in a way that we have yet to fully realize.

"People are not yet willing to regard their destiny as shared and to take actions for the common good. We can only hope that in time a change in our attitude will become inevitable."