China’s Forests Combat the Greenhouse Effect

Chinese scientists have made the significant discovery that Chinese forests planted some 20 years ago are now absorbing large amounts of carbon dioxide – some 5 to 8 percent or 26 million tons of all the industrial emissions in China in an average year during the mid-1990s.

“We hadn’t realized that China’s reforestation had been contributing so much to improving the environment of the country and, indeed, the whole world,” Professor Fang Jingyun of Peking University’s Department of Urban and Environmental Science who led the research team said last week in a telephone interview.

Science magazine called the Chinese research which it published in its June 22, 2001 issue “a significant milestone.” It was the first time the US-based magazine has carried the results of independent research by Chinese scientists.

Carbon dioxide is produced during respiration by living organisms, but also through the burning of fossil fuels (coal, natural gas and oil), which has produced the “greenhouse” effect of world-wide concern.

Professor Fang’s study was designed to analyze changes and distribution patterns in carbon dioxide produced by forests that were planted in China starting in the late 1970s to help with flood and erosion control and to protect water supplies as well as to produce wood for fuel.

"It was beyond all our expectations to discover our forest management practices had slowed the rate of carbon density in the air."

The Chinese research team began study in 1992 after carbon dioxide and the question of how it is absorbed into the air, ocean and land became a hot topic in scientific circles.

In 1977 Science magazine led the way by publishing articles on the disturbing evidence that the heightened “greenhouse” effect could be blamed on the destruction of forests all around the world, especially in the tropics. It was thought at the time that about half of the carbon dioxide produced by humans went into the air, while about one-third was absorbed by the oceans.

Meanwhile, it was also thought that the land biosphere had come to a balance in carbon dioxide absorption and emission. That left a significant amount of greenhouse gases unaccounted for.

Where did the carbon dioxide go? Scientists plunged into the study of “carbon sinks” in the forest around the world where they believed carbon could be stored the same way people deposit money in banks.

In the early 1990s US scientists discovered that the mid- and high-latitude forests in the Northern hemisphere were acting as “carbon sinks,” or areas absorbing carbon. But they also thought that because of the depletion of forests in China, Chinese forests were a source of emitting carbon dioxide, not absorbing it.

Using a 50-year Chinese national forest resource inventory as well as direct field measurements of carbon, Professor Fang and his colleagues estimated changes in the storage of carbon in the biosphere in China from 1949 to 1998. They found that before the mid-1970s, Chinese forests did emit large amounts of carbon dioxide into the air. However, over the past 20 years, they found that Chinese forests absorbed some 450 million tons of carbon, or about half of the annual emissions of Chinese industry in the mid-1990s.

By the end of 2000, forests covered 16.55 percent of the total area of China, which amounts to some 1.58 billion hectares (about 3.9 billion acres). Of that total area, newly planted forests amounted to 47 million hectares (about 116 million acres), the largest such new-growth area in the world.

The increase in forest size is a basic reason for the increase in carbon dioxide absorption in China. Another reason can be attributed to global climate change, Professor Fang said. The higher temperatures provide a better environment for forest growth, enabling more in-take of carbon dioxide.

Employing satellite remote-sensory data on climate, soil and vegetation, Professor Fang and his colleagues also plotted the changes of biological productivity in different times and places of China. They found overall Chinese land productivity increasing annually by one percent – still another factor in explaining what is happening to excess carbon dioxide in the world, Professor Fang said.

The potential international impact of the discovery was explained by Steven C. Wofsy, professor from the Department of Earth and Planetary Sciences at Harvard University, who praised the Chinese research team for helping to provide a rationale for sensible national and international policies regarding forests and the carbon dioxide cycle.

"Forests cannot miraculously stop an increase in carbon dioxide in the atmosphere, but they can significantly mitigate the rate of increase for many decades to come," Professor Wofsy said. "We need to develop a scientific basis for measuring and improving the properties of forest carbon sinks."

The Chinese scientists’ work may also impact China’s future diplomatic negotiations on the environment. For instance, it provides scientific evidence to support the Kyoto Accords proposal that reforestation can partially offset carbon dioxide emissions from industry.

The Kyoto Accords stipulate that between 2008 and 2012, some 38 industrialized countries are supposed to reduce their emissions of greenhouse gases such as carbon dioxide and methane by 5.2 percent of the 1990 level. The reduced ratios for the United States, European Union, Japan and Canada are respectively 7 percent, 8 percent, 6 percent and 6 percent.

The Accords did not call for restrictions on carbon dioxide emissions in developing countries, but calls for such countries as China and India to determine their own standards.

Under President George Bush, the United States began retreating from the Kyoto Accords, using as one of its reasons that the developing countries with large amounts of carbon dioxide emissions like China and India should also be obligated to reduce such emissions even if it means shutting down plants, slowing down economic growth and increasing unemployment.

Professor Fang’s findings on the absorption of industrial emissions in China thus may also benefit China’s social and economic development by offering more space to negotiate in international talks on the global problem.

Professor Fang and his research team are now working on a new project which they hope will be a contribution to vegetation theory on the effect of global climate change on new-growth forests and grasslands.

(CIIC by Li Jinhui 07/17/2001)

In This Series

Farmers in Northwest China Fight Desert With Clover

China’s Forests Help Clean the Air

16 National Nature Reserves Established

US Newspaper: China Sharply Reduces Greenhouse Gases

Worsening Environment, a Challenge to Chinese People



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