UMD, National Researchers Publish Definitive Tropical Forest Emissions Study

Tropical forests provide global climate regulation ecosystem services, and the clearing of these forests significantly accelerates and exacerbates the dangerous effects of climate change through the forced release of anthropogenic greenhouse gas (GHG) emissions. A new study by researchers from UMD; the Woods Hole Research Center in Falmouth, Massachusetts; and the State University of New York College of Environmental Science and Forestry in Syracuse, New York; for the first time provides a definitive tropical forest emissions study offering a clear picture of pan-tropical forest carbon losses. This work is especially significant as scientific consensus on this topic was previously lacking.

“Given recent trends, natural forests will likely constitute an increasingly smaller proportion of tropical forest GHG emissions and of global emissions as fossil fuel consumption increases, with implications for the valuation of co-benefits in tropical forest conservation,” said Professor Matthew C. Hansen, a lead author on the paper and a co-creator of the world’s first high-resolution local-to-global forest mapping tool, which was used in this new research.

Among the continents, Latin America is the largest contributor to carbon emissions from forest clearing, accounting for 43% of gross aboveground carbon (AGC) loss and 54% of natural forest AGC loss. Brazil accounts for the highest AGC loss for both categories at national scales. The researchers estimate gross tropical forest AGC loss and natural forest loss to account for 11% and 6% of global year 2012 CO2 emissions, respectively.

“Compared with the previous studies, we found significantly more tropical forest carbon loss in Africa and Southeast Asia. This is partially due to the fact, that our sample-based approach allowed us to target small-scale forest disturbances in Central Africa and Mainland Southeast Asia, which are underestimated even in the 30-m resolution forest cover loss map,” said Research Associate Alexandra Yurievna Tyukavina, (Ph.D. ’15), one of the lead authors of the study.

The study, “Aboveground carbon loss in natural and managed tropical forests from 2000 to 2012” appears in Environmental Research Letters.

“The original Hansen map included any tree cover loss, regardless of its cause and nature; we have disaggregated it into the loss of natural forests—which included primary, mature secondary forests and woodlands—and human-managed forests, including tree plantations, agroforestry systems and areas of slash-and-burn agriculture with rapid tree cover rotation,” Tyukavina explained. “We found that 58% of all tropical forest carbon loss came from natural forests, and 42% of loss came from human-managed forests. The proportion of carbon emissions from natural tropical forests will likely continue to decrease over the years, which will make accounting of human-managed forest dynamics increasingly important.”

Additional key findings:

·        This is the most definitive tropical forest emissions study to date

·        Natural forests worldwide are diminishing because of human activity

·        To conserve rainforests, other ecosystem services such as biodiversity need to be emphasized in addition to GHG emissions

·        Emissions due to smallholder farming, such as in Africa, are greater than previously thought

The researchers’ new estimate employs recommended good practices to quantify gross tropical forest AGC loss from 2000 to 2012 through the integration of Landsat-derived tree canopy cover, height, intactness and forest cover loss and GLAS-lidar derived forest biomass. An unbiased estimate of forest loss area is produced using a stratified random sample with strata derived from a wall-to-wall 30 m forest cover loss map. The sample-based results separate the gross loss of forest AGC into losses from natural forests (0.59 PgC yr−1) and losses from managed forests (0.43 PgC yr−1) including plantations, agroforestry systems and subsistence agriculture.

Figure 1: Forest loss in natural and managed forests. Sample locations classified as reference loss within natural and managed forests for each of the seven forest types: 1—low cover; 2—medium cover short; 3—medium cover tall; 4—dense cover short; 5—dense cover short intact; 6—dense cover tall; 7—dense cover tall intact.

The researchers say this work is also significant in that it complies with and promotes international standards and best practices outlined by the UN’s Reducing Emissions from Deforestation and Forest Degradation (REDD) program. REDD is an effort to create a financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development; "REDD+" goes beyond deforestation and forest degradation, and includes the role of conservation, sustainable management of forests and enhancement of forest carbon stocks.

“The work reported here provides the first estimates of pantropical emissions using the Intergovernmental Panel on Climate Change good practice guidance, and it does that for a 12-year observational period. This information is key to tropical forest nations reporting their emissions in the context of REDD+,” said coauthor Scott Goetz, deputy director and senior scientist with the Woods Hole Research Center.

Forest photo from the Republic of Congo provided by Tyukavina.

Published on Thu, Jul 23, 2015 - 10:01AM