Lester R. Brown
Chapter 8. Restoring the Earth: Planting Trees to Sequester Carbon
As of 2007, the shrinking forests in the tropical regions were releasing 2.2 billion tons of carbon per year. Meanwhile, expanding forests in the temperate regions were absorbing 0.7 billion tons of carbon annually. On balance, a net of some 1.5 billion tons of carbon were being released into the atmosphere each year, contributing to global warming. 47
The tropical deforestation in Asia is driven primarily by the fast-growing demand for timber. In Latin America, by contrast, it is the growing demand for soybeans and beef that is deforesting the Amazon. In Africa, it is mostly the gathering of fuelwood and the clearing of new land for agriculture as existing cropland is degraded and abandoned. Two countries, Indonesia and Brazil, account for more than half of all deforestation. The Democratic Republic of the Congo, also high on the list, is a failing state, making forest management difficult. 48
The Plan B goals are to end net deforestation worldwide and to sequester carbon through a variety of tree planting initiatives and the adoption of improved agricultural land management practices. Today, because the earth’s forests are shrinking, they are a major source of CO2. The goal is to expand the earth’s tree cover, growing more trees to soak up CO2.
Although banning deforestation may seem farfetched, environmental reasons have pushed three countries— Thailand, the Philippines, and China—to implement complete or partial bans on logging. All three bans were imposed following devastating floods and mudslides resulting from the loss of forest cover. After suffering record losses from several weeks of nonstop flooding in the Yangtze River basin, Beijing noted that when forest policy was viewed not through the eyes of the individual logger but through those of society as a whole, it simply did not make economic sense to continue deforesting. The flood control service of trees standing, they said, was three times as valuable as the timber from trees cut. With this in mind, Beijing then took the unusual step of paying the loggers to become tree planters—to reforest instead of deforest. 49
Other countries cutting down large areas of trees will also face the environmental effects of deforestation, including flooding. If Brazil’s Amazon rainforest continues to shrink, it may also continue to dry out, becoming vulnerable to fire. If the Amazon rainforest disappears, it would be replaced largely by desert and scrub forestland. The capacity of the rainforest to cycle water to the interior, including to the agricultural areas to the south, would be lost. At this point, a fast-unfolding local environmental calamity would become an economic disaster, and because the burning Amazon would release billions of tons of carbon into the atmosphere, it would accelerate global warming. 50
Just as national concerns about the effects of continuing deforestation eventually eclipsed local interests, now global interests are beginning to eclipse national ones as deforestation has become a major driver of global warming. Deforestation is no longer just a matter of local flooding, but also rising seas worldwide and the many other effects of climate change. Nature has just raised the ante on protecting forests.
Reaching a goal of zero net deforestation will require reducing the pressures to deforest that come from population growth, rising affluence, the construction of ethanol distilleries and biodiesel refineries, and the fast-growing use of paper. Protecting the earth’s forests means halting population growth as soon as possible, and, for the earth’s affluent residents who are responsible for the growing demand for beef and soybeans that is deforesting the Amazon basin, it means moving down the food chain. A successful deforestation ban may require a ban on the construction of additional biodiesel refineries and ethanol distilleries.
Against this backdrop of growing concern about the forest-climate relationship, a leading Swedish energy firm, Vattenfall, has examined the large-scale potential for foresting wasteland to sequester carbon dioxide. They begin by noting that there are 1.86 billion hectares of degraded land in the world—land that was once forestland, cropland, or grassland—and that half of this, or 930 million hectares, has a decent chance of being profitably reclaimed. Some 840 million hectares of this total are in the tropical regions, where reclamation would mean much higher rates of carbon sequestration. (Every newly planted tree seedling in the tropics removes an average of 50 kilograms of CO2 from the atmosphere each year during its growth period of 20–50 years, compared with 13 kilograms of CO2 per year for a tree in the temperate regions.) 51
Vattenfall estimates that the maximum technical potential of these 930 million hectares is to absorb roughly 21.6 billion tons of CO2 per year. If, as part of a global climate stabilization strategy, carbon sequestration were valued at $210 per ton of carbon, the company believes that 18 percent of this technical potential could be realized. If so, this would mean planting 171 million hectares of land to trees. This area—larger than that planted to grain in India—would sequester 3.5 billion tons of CO2 per year, or over 950 million tons of carbon. The total cost of sequestering carbon at $210 per ton would be $200 billion. Spread over a decade, this would mean investing $20 billion a year to give climate stabilization a large and potentially decisive boost. This global forestation plan to remove atmospheric CO2, most of it put there by industrial countries, would be funded by them. An independent body would be set up to administer, fund, and monitor the vast tree planting initiative. 52
Aside from the Vattenfall forestation idea, there are already many tree planting initiatives under way that are driven by a range of concerns, from climate change to desert expansion, to soil conservation, to making cities more habitable. These include the worldwide Billion Tree Campaign launched in 2007, urban tree planting initiatives in many cities, the Great Green Wall being planted in China, and the Saharan Green Wall of Africa, as well as a big push to expand tree plantations within a number of countries.
The Billion Tree Campaign was inspired by Kenyan Nobel laureate Wangari Maathai, who had earlier organized women in Kenya and several nearby countries to plant 30 million trees. The United Nations Environment Programme, which is administering the Billion Tree Campaign, reported as of October 2007 that it had received pledges to plant a total of 1.2 billion trees by year end. Of that total, 431 million already had been planted. Among the leaders are Mexico, which pledged to plant 250 million trees, and Ethiopia, which promised to plant 60 million trees to commemorate its millennium celebration. Senegal signed up for 20 million trees. 53
Some state and provincial governments have also joined in. In Brazil, the state of Paraná, which launched an effort to plant 90 million trees in 2003 to restore its riparian zones, committed to planting 20 million trees in 2007. Uttar Pradesh, India’s most populous state, mobilized 600,000 people to plant 10.5 million trees in a single day in July 2007, planting the trees on farmland, in state forests, and on school grounds. If the goal of 1 billion trees is reached and half of them survive, these trees would sequester 5.6 million tons of carbon per year. 54
Independent of the Billion Tree Campaign, in September 2007 New Zealand Prime Minister Helen Clark announced an impressive package of steps to cut carbon emissions, including expanding forested area by 250,000 hectares (617,000 acres) by 2020. This would roughly total some 125 million trees, or 30 for each New Zealander. 55
Many of the world’s cities are planting trees. Tokyo, for example, has been planting trees and shrubs on the rooftops of buildings to help offset the urban heat island effect and cool the city. Washington, D.C., is in the early stages of a campaign to greatly restore its tree canopy. 56
An analysis of the value of planting trees on the streets and in the parks of five western U.S. cities—from Cheyenne, Wyoming, to Berkeley, California—concluded that for every dollar spent on planting and caring for trees, the benefits to the community exceeded two dollars. A mature tree canopy in a city shades buildings and can reduce air temperatures by 5–10 degrees Fahrenheit, thus reducing the energy needed for air conditioning. In cities with severe winters like Cheyenne, the reduction of winter wind speed by evergreen trees cuts heating costs. Real estate values on tree-lined streets are typically 3–6 percent higher than where there are few or no trees. 57
Planting trees is just one of many activities that will remove meaningful quantities of carbon from the atmosphere. One activity that involves a good use of wasteland is the planting in Africa and Asia of jatropha, a four-foot perennial shrub that produces seeds that can be used to produce biodiesel. This covers wasteland and sequesters carbon. 58
A number of agricultural practices can also increase the carbon stored as organic matter in soils. Farming practices that reduce soil erosion and raise cropland productivity usually also lead to higher carbon content in the soil. Among these are shifting from conventional tillage to minimum-till and no-till, the more extensive use of cover crops, the return of all livestock and poultry manure to the land, expansion of irrigated area, a return to more mixed crop-livestock farming, and the forestation of marginal farmlands.
Rattan Lal, a Senior Agronomist with the Carbon Management and Sequestration Center at Ohio State University, has calculated the range of potential carbon sequestration for each of many practices, such as those just cited. For example, expanding the use of cover crops to protect soil during the off-season can store from 68 million to 338 million tons of carbon worldwide each year. Calculating the total carbon sequestration for the practices he cites, using the low end of the range for each, shows a potential for sequestering 400 million tons of carbon each year. Aggregating the numbers from the more optimistic high end of the range for each practice yields a total of 1.2 billion tons of carbon per year. For our carbon budget we are assuming, perhaps conservatively, that 600 million tons of carbon can be sequestered as a result of adopting these carbon-sensitive farming and land management practices. 59
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