At AAAS-Hitachi Lecture, Ecologist Thomas Lovejoy Offers a Climate Change Rescue Plan

Thomas E. Lovejoy

While societies face a daunting challenge trying to reverse the impact of human-induced climate change, the living planet itself offers one means for a rescue plan, according to a prominent ecologist who delivered the inaugural AAAS-Hitachi Lecture on Science and Society.

In the 6 November lecture, Thomas E. Lovejoy, the president of the Washington, D.C.-based H. John Heinz III Center for Science, Economics and the Environment, traced the predicament in stark terms, noting that "nature is now on the move in response to climate change" as both plant and animal species change their historic ranges in response to warming temperatures.

But he also said there are steps, including restoration of degraded grazing lands and devastated forests, that would allow the planet to absorb more heat-trapping carbon dioxide from the atmosphere while also providing lasting environmental benefit.

Lovejoy's lecture was the first in what will be an annual series at AAAS sponsored by Hitachi, Ltd. In introductory remarks, Alan I. Leshner, the chief executive officer of AAAS, noted Hitachi's history of science and technology development as well as its sense of environmental responsibility. He said there is a "wonderful intersection between their interest in business, science and society" and AAAS's similar interests. Kazuo Furukawa, the president and chief executive officer of Hitachi, said he hopes the lectures "will contribute in some small way to public understanding of the excitement of science and technology" and encourage younger people to pursue science-related careers.

Lovejoy, who was chief biodiversity adviser at the World Bank before taking his current position in 2002, told his audience that it is time to take a larger planetary view, both of the impacts of climate change—which are unlikely to be linear or gradual—and of possible solutions.

The underlying problem is well-known: Burning of fossil fuels releases solar energy captured by ancient green plants, but it also releases carbon into the atmosphere as heat-trapping carbon dioxide gas. And when today's green plants and forests are burned, they too release carbon dioxide.

The average global temperature is now three-quarters of a degree Celsius warmer than in pre-industrial times, and is expected to rise another 0.5 to 0.6 degree even if greenhouse gas concentrations were to be capped at current levels, Lovejoy said.

While abrupt climate changes have been normal over many thousands of years, he said, the last 10,000 years, encompassing all of recorded human history, have been marked by a period of unusual climate stability. "The entire human enterprise is based on the assumption of a stable climate," he said. That is now changing, and diverse signals of trouble are being found in the natural world.

Many species of flowers are blooming earlier in the spring; swallows are nesting nine days earlier than they did four decades ago; species such as the Edith's Checkerspot butterfly are moving their range northward and to higher elevations; longer summers have allowed bark beetles to prosper in the evergreen forests of North America and Europe, killing huge numbers of trees.

The list goes on. Lakes are freezing later in the autumn, ice packs are melting sooner in the spring. Glaciers on the high mountains of the tropics could be gone in 15 years. The most dramatic changes involving water and ice are the annual advance and retreat of the ice cap over the Arctic Ocean, Lovejoy said. "The ultimate date at which a first ice-free summer will be seen in the Arctic has been advanced from 2100 to 2050," he said, "and now people talk about 15 years and even shorter periods of time" until that event.

Lovejoy focused primarily on the biological changes afoot, some of which already have proved to be abrupt. Tropical reefs are particularly sensitive. With even small temperature increases, the coral organisms expel the symbiotic algae that live with them, leading to a bleaching of the reef. "Basically the entire Technicolor world goes black and white," Lovejoy said. "Much of the diversity and productivity is lost."

There are other critical thresholds that may be crossed as global average temperatures continue to rise. Lovejoy noted a scientific paper in January 2004 that predicted 20% to 30% of the world's species could be lost if pre-industrial levels of greenhouse gases were to double, a prediction that was echoed in last year's report of the Intergovernmental Panel on Climate Change.

There are multiple examples of "decoupling," in which a species adapted to normal seasonal variation is affected by changing temperatures. The snowshoe hare, for example, has adapted to have white fur in the winter and dark in summer. The hare is "now being found in the springtime, bright and white as can be, against dark backgrounds," Lovejoy said.

He also noted that the human-dominated landscape has made it more difficult for species to adapt to the climate-related changes. Natural corridors between areas of biodiversity have been disrupted by development, making it an obstacle course for species to congregate. Moreover, species seldom move in concert in response to disruptions in their habitat, Lovejoy said. "Ecosystems as we now know them will disassemble," he said, "and novel ecosystems will arise."

There is little scientific debate on the need to reduce the level of greenhouse gas emissions. The pre-industrial concentration of carbon dioxide in the atmosphere was 280 parts per million (ppm). The concentration today is 389 ppm, well above the 350 ppm that influential NASA climate scientist James Hansen has suggested is a "safe" level. Once a carbon dioxide molecule is in the atmosphere, it will stay there for 100 to 1,000 years.

How to start bringing those worrisome carbon dioxide levels down? One answer rests with the stressed planet itself, Lovejoy said. Deforestation accounts for 20% of global greenhouse emissions each year, with carbon dioxide released to the atmosphere as the living matter is burned or degraded.

Reducing destruction of forests is an important step in controlling greenhouse emissions. At the same time, efforts to restore forests and vegetation already lost will provide new areas to absorb carbon dioxide from the atmosphere through photosynthesis. Lovejoy cited a study which estimated that restoring Australia's degraded grazing lands would produce enough vegetation to take up half a billion tons of carbon each year from the atmosphere. Each time roughly two billion tons of carbon are absorbed, the atmospheric concentration of carbon dioxide would be reduced by about 1 part per million, Lovejoy said. Aggressive steps to restore degraded grazing lands worldwide could restore billions of tons of atmospheric carbon to the ecosystem, he said.

That would help roll back carbon concentrations in the atmosphere to safer levels. But there are complications, particularly if more forests are leveled to meet demands for crops and biofuels production. "We're going to have to figure out the best combination of land use to maximize those societal goals, and that's going to be complicated," Lovejoy said.

Still, he was reasonably optimistic that societies will find ways to use the Earth's natural restorative processes to help combat climate change. Such steps must be accompanied, of course, by wiser use of energy and natural resources. Amid talk of measures such as seeding the oceans with iron particles to foster carbon-absorbing plankton blooms, the restoration of forests and grazing lands is a more environmentally benign approach, Lovejoy said.

"The living planet, if worked with in a thoughtful way, and brought back to the extent that we can," he said, could benefit the whole climate change picture. "Sort of think of it as the living planet to the rescue," he said, "and perhaps the only form of planetary engineering that is without any immediate or hard-to-see environmental downside."

Earl Lane

18 November 2008