Felling of tropical trees has soared, satellite shows, not slowed as UN study found

The Democratic Republic of Congo contains half of Africa's tropical forest and the second largest continuous tropical forest in the world. This animation of Landsat images from 1999 and 2008 shows how much deforestation has occurred between those years -- impinging even on Virunga National Park. These images are from the same Landsat datasets used by researchers at the University of Maryland to study the 34 countries -- including the Democratic Republic of the Congo -- that contain 80 percent of the forested tropical lands. The rate at which tropical forests were cut, burned or otherwise lost from the 1990s through the 2000s accelerated by 62 percent, according to a new study which dramatically reverses a previous estimate of a 25 percent slowdown over the same period. That previous estimate, from the U.N.'s Food and Agriculture Organization's (FAO) Forest Resource Assessment, was based on a collection of reports from dozens of countries. The new estimate, in contrast, is based on vast amounts of Landsat image data which directly record the changes to forests over 20 years. "Several satellite-based local and regional studies have been made for changing rates of deforestation [during] the 1990s and 2000s, but our study is the first pan-tropical scale analysis," explains University of Maryland, College Park, geographer Do-Hyung Kim, lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. Kim and his University of Maryland colleagues Joseph Sexton and John Townshend looked at 34 forested countries which comprise 80 percent of forested tropical lands. They analyzed 5,444 Landsat scenes from 1990, 2000, 2005 and 2010 with a hectare-scale (100 by 100 meter) resolution to determine how much forest was lost and gained. Their procedure was fully automated and computerized both to make the huge datasets manageable and to minimize human error. They found that during the 1990-2000 period the annual net forest loss across all the countries was 4 million hectares (15,000 square miles) per year. During the 2000-2010 period, the net forest loss rose to 6.5 million hectares (25,000 square miles) per year -- a 62 percent increase is the rate of deforestation. That last rate is the equivalent to clear cutting an area the size of West Virginia or Sri Lanka each year, or deforesting an area the size of Norway every five years. In terms of where the deforestation was happening, they found that tropical Latin America showed the largest increase of annual net loss of 1.4 million hectares (5,400 square miles) per year from the 1990s to the 2000s, with Brazil topping the list at 0.6 million hectares (2,300 square miles) per year. Tropical Asia showed the second largest increase at 0.8 million hectares (3,100 square miles) per year, with similar trends across the countries of Indonesia, Malaysia, Cambodia, Thailand and the Philippines. Tropical Africa showed the least amount of annual net forest area loss. Still, there was a steady increase of net forest loss in tropical Africa due to cutting primarily in Democratic Republic of Congo and Madagascar. The new, satellite-based study "really provides a benchmark of tropical forest clearing not provided by other means," said geographer Douglas Morton, who studies forest cover by satellite sensing at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and was not a coauthor on the GRL paper. However, the U.N. agency's report is not as flawed as it may seem, argues Rodney Keenan, a University of Melbourne, Australia, forest science researcher who participated in the agency's last forest assessment. Unlike the satellite evaluation, he explained, other deforestation estimates, such as the FAO's 2010 assessment, are based on ground based surveys of trees, often supplemented by imagery. "Both approaches are useful and people need to understand the distinctions and implications of different approaches," he said. While the new study is "an important contribution to the overall picture," Keenan added, it "should not be seen as contradicting the FAO figures." Not so, say Kim and his colleagues. "We made it very clear in our paper where the FAO missed deforestation that is obvious in satellite images," Kim said, noting that, for example, the FAO reported no change of deforestation rate for 16 of 34 countries from 1990 through 2010, whereas Landsat images show otherwise. Morton notes that the new, satellite-based estimates are particularly important for those trying to understand the global amounts of carbon being released into the air (primarily in the forms of the climate-warming gases carbon dioxide and methane) or being taken up by plants, soils and waters. "Tropical deforestation plays a big role in global climate cycles," he explained, pointing out that the cutting and burning of forests accounted for 20 percent of greenhouse gas emissions in 1990s. It's not really a surprise that the new research shows dramatically higher deforestation rates although "without the transparency of Landsat satellite data is difficult to put your finger on changing trends," Morton added. "Tropical deforestation has become increasingly more mechanized," he observed. "In the 60s, it was axes; in the 70s, chainsaws; and in the 2000s, it was tractors." For him, he explained, an increase in deforestation rates makes technological sense. Story Source: The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length. Journal Reference: Do-Hyung Kim, Joseph O. Sexton, John R. Townshend. Accelerated Deforestation in the Humid Tropics from the 1990s to the 2000s. Geophysical Research Letters, 2015; DOI: 10.1002/2014GL062777

Deforestation remedies can have unintended consequences

 

July 2, 2014

University of Florida

When it comes to fixing deforestation and forest degradation, good intentions can lead to bad outcomes. Among other points, researchers note that even when there’s technically no net deforestation, tropical forests can still suffer. For example, if degraded natural forests are replaced by plantations of invasive exotic trees or low water-use efficiency trees, biodiversity will diminish, wildlife could suffer and soil erosion could render streams unusable by local villagers.

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That’s the take-away from a new study by two University of Florida researchers who say efforts to restore damaged and destroyed tropical forests can go awry if the people making the plans of action don’t choose wisely.

“We need to be careful about what is it we’re losing and gaining,” UF biology professor Francis E. “Jack” Putz said. Putz worked with UF biology professor Claudia Romero on the paper, which will appear in the July issue of Biotropica.

Deforestation continues at a rapid pace in much of South America, Southeast Asia and the Congo Basin. Similarly, escaped agricultural fires and uncontrolled logging harm huge areas of tropical forest around the world. That destruction is linked to loss of habitat for wildlife, soil erosion and even accelerated climate change. Estimates of how much land is deforested run as high as 18 million acres a year – an area nearly as large as South Carolina – and a similarly large area is degraded.

The people deciding what to do in those areas range from villagers to large landowners to global stakeholders. Options include letting the forests recover naturally, assisting natural regeneration, or planting new trees so as to make the areas more wildlife-friendly and biodiversity-rich – but each comes at a cost, Putz said.

So, when developing forest access and use policies, people need to consider several factors, including short- and long-term financial profits, biodiversity and local needs for timber and non-timber forest products such as medicinal plants. The authors say it’s possible to minimize environmental impacts if decision-makers pay attention to ecosystem structure, composition and dynamics. They shouldn’t base everything on a single statistic, such as the total land area occupied by forest, especially if the state of that forest is not specified.

The authors point out that even when there’s technically no net deforestation, tropical forests can still suffer. For example, if degraded natural forests are replaced by plantations of invasive exotic trees or low water-use efficiency trees, biodiversity will diminish, wildlife could suffer and soil erosion could render streams unusable by local villagers.

“When you save a forest from deforestation, it’s great, but you might not have gotten the full package of what you wanted,” he said.

The discussion, Putz said, needs to center on the definition of “forest.” The Food and Agricultural Organization of the United Nations describes it as an area of more than 0.5 hectares, or a little more than an acre, with trees taller than about 16 feet and more than 10 percent canopy cover. Using that definition could obscure great losses of forest values, he said.

In general, the benefits of a forest are jeopardized when land-use decisions are based on that overly loose classification, according to the paper.

Under that designation, for example, tree plantations qualify as forests. Although plantations can supply services to society such as slope stabilization, firewood and carbon, they can also result in avoidable losses of biodiversity. They have less value in some ways, Putz said, and more value in others.

But once people differentiate among types of forests, alternatives to environmentally destructive management will become real options. Then, decision-makers can fully examine the local, regional and global benefits of natural forests versus their economic priorities.

“We need to demand clarity about what’s meant by ‘forest’ and what the full range of costs are of different interventions,” Putz said. “Then we need to figure out the mechanism to get decision-makers to employ the interventions that are least damaging to naturalness but that still satisfy their other desires.”

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Story Source:

The above story is based on materials provided by University of Florida. Note: Materials may be edited for content and length.

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Journal Reference:

1. Francis E. Putz, Claudia Romero. Futures of Tropical Forests (sensu lato). Biotropica, 2014; 46 (4): 495 DOI: 10.1111/btp.12124

Saving trees in tropics could cut emissions by one-fifth, study shows

 

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Reducing deforestation in the tropics would significantly cut the amount of carbon dioxide emitted into the atmosphere -- by as much as one-fifth -- research shows.

In the first study of its kind, scientists have calculated the amount of carbon absorbed by the world's tropical forests and the amounts of greenhouse gas emissions created by loss of trees, as a result of human activity.

They found that tropical forests absorb almost two billion tonnes of carbon each year, equivalent to one-fifth of the world's carbon emissions, by storing it in their bark, leaves and soil. However, an equivalent amount is lost through logging, clearing of land for grazing, and growing biofuel crops such as palm oil, soya bean and sugar. Peat fires in forests add significantly to the greenhouse gas emissions.

Researchers estimate that if all human-related deforestation of the tropics were to stop, the forests could absorb more carbon than at present, equivalent to one-fifth of global emissions.

Researchers say carbon emissions from tropical forests will increase as the climate warms, as rising temperatures accelerate the decay of dead plants and trees, giving off more CO2. Global temperatures are forecast to rise by two degrees by the year 2099, which is predicted to increase annual carbon emissions from the forest by three-quarters of a billion tonnes.

Scientists from the Universities of Edinburgh and Leeds analysed data from multiple previous studies, including satellite studies, to determine the amount of carbon absorbed and emitted by the world's tropical forests in South and Central America, equatorial Africa and Asia.

Their study, published in Global Change Biology, was supported by the Natural Environment Research Council.

Professor John Grace of the University of Edinburgh's School of GeoSciences, who led the study, said: "If we limit human activity in the tropical forests of the world, this could play a valuable role in helping to curb the rise in carbon dioxide in the atmosphere. Preventing further losses of carbon from our tropical forests must remain a high priority."

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Story Source:

The above story is based on materials provided by University of Edinburgh. Note: Materials may be edited for content and length.

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Journal Reference:

1. John Grace, Edward Mitchard, Emanuel Gloor. Perturbations in the carbon budget of the tropics. Global Change Biology, 2014; DOI: 10.1111/gcb.12600