Carbon Pools in African Mangrove Forests

Partnership with NASA and universities to estimate carbon in African mangroves and coastal wetlands

by Zoё Hoyle, SRS Science Delivery Group
Measuring tree diameter in the mangrove swamps of the Zambezi Delta. Photo by Carl Trettin.

Measuring tree diameter in the mangrove swamps of the Zambezi Delta. Photo by Carl Trettin.

The National Aeronautics and Space Administration (NASA) recently announced funding for a proposal that involves the U.S. Forest Service, NASA, Duke University, and the University of Maryland in using field-based research as the basis for developing remote sensing tools to assess and monitor carbon pools in African mangrove forests. The project will use advanced 3-D remote sensing technology to map forest structure and extent as well as change over time.

Even though they represent only three percent of the world’s total forest area, mangrove forests sequester higher levels of carbon than all other forest ecosystems. If mangrove destruction continues at current rates, carbon emissions from these forests alone could make up 10 percent of carbon emissions from deforestation worldwide.

The high level of carbon sequestration coupled with the high risk of destruction make mangroves a prime target for mitigation for programs such as the United Nations Collaborative on Reducing Emissions from Deforestation and Degradation in Developing Countries (UN-REDD and REDD+).

The partners on the new project, with Temilola Fatoyinbo from NASA’s Goddard Space Flight Center as principal investigator, propose to develop a Mangrove Total Monitoring system for Africa using  Gabon, Tanzania, and Mozambique for field validation. The researchers selected these countries because of their investment in the on-the-ground monitoring, reporting, and verification activities needed to relate data collected by remote sensing to field measurements. The project will build on work in Mozambique by U.S. Forest Service researcher Carl Trettin and collaborators developing the carbon estimations needed for REDD+ carbon incentive programs and will develop a timeseries of mangrove change in the three countries from 1990 to the present.

Establishing plots and taking measurements in mangrove forests is very difficult because of the swampy terrain, the tangled forests, and the remoteness of many remaining mangrove forests. Over the past three years, Trettin, team leader of the Forest Service Southern Research Station Center for Forested Wetland Research, and collaborators have worked in the Zambezi Delta of Mozambique to set up monitoring plots and develop methods for taking inventory in other African locations. “This new remote sensing project, with the protocols we’ve developed in the Zambezi Delta, will lay the foundation for monitoring change in carbon pools in mangrove forests in Africa and the world,” said Trettin.

Access more information about the NASA Carbon Monitoring project.

 For more information, email Carl Trettin at ctrettin@fs.fed.us.

Read about Forest Service research in the Zambezi Delta of Mozambique.

 Access the latest publications by SRS scientists .

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Posted in Climate Change, Economics & Policy, Forest Inventory & Analysis, Forest Watersheds

A City’s Dynamic Mangrove Forest

Inventory and monitoring of the urban forest in the San Juan Bay Estuary watershed, Puerto Rico

by Zoё Hoyle, SRS Science Delivery Group
The southern part of the San Juan Bay Estuary, a hilly area with soils derived from volcanic soils, is less densely developed and has higher tree cover than other parts of the watershed. Photo by Tom Brandeis.

The southern part of the San Juan Bay Estuary, a hilly area with soils derived from volcanic soils, is less densely developed and has higher tree cover than other parts of the watershed. Photo by Tom Brandeis.

A recent report by U.S. Forest Service researchers on the forests of the San Juan Bay Estuary watershed provides details about a highly dynamic urban forest that provides important benefits for its residents. Tom Brandeis, supervisory research forester with the Forest Service Southern Research Station (SRS) Forest Inventory and Analysis unit, worked with other Forest Service and university researchers to complete the first decade of a study started in 2001 of the watershed of Puerto Rico’s San Juan Bay Estuary.

Lying along the northeast coast of Puerto Rico, the 53,500-acre San Juan Bay Estuary watershed is the heart of the expanding and densely populated San Juan metropolitan area. The 2010 U.S. Census estimated the population of the area at 2,478,905, with a population density of 3,215 people a square kilometer (about half a square mile), and in some places over 8,300 people a square kilometer.

Forests once covered most of the estuary’s watershed, with mangroves circling the bays and lagoons and a diverse mix of species in the coastal plains and further inland. Human activities and development greatly reduced forest cover over the last century, with losses to mangrove forests ranging from 28 to 67 percent. Reduction in forest cover in such a dense urban area has far-ranging consequences, from the loss of biodiversity to increases in air and water pollution, to higher temperatures (the urban “heat island” effect) for people to endure.

In addition to providing data on the forests in the estuary’s watershed—including forest structure, tree and shrub species present, insects and diseases—the report estimates the value of the ecosystem services provided by the forests, including carbon sequestration, which reduces the carbon dioxide in the atmosphere that pushes climate change. Findings include:

  • Half the trees sampled in 2001 were gone by 2011, either removed or dead. In general, however, new growth exceeded mortality, with an average increase of 40 trees per acre. Natural regeneration in upland and mangrove forests accounted for most of the new trees added.
  • Species richness (the number of different species present) increased from 75 tree and shrub species in 2001 to 86 in 2011.
  • Red, black, and white mangrove made up the most common tree species. The occurrence of tree pests, diseases, and natural or human-caused damage was relatively low.
  • Mangrove and subtropical moist secondary forest covered 12 percent of the area. The estimated 10.1 million total of all trees stored 352,450 tons of carbon and sequestered carbon at a rate of 31,288 tons a year.
  • The estimated value of carbon storage by trees in the San Juan Bay Estuary watershed was $8.1 million, with an annual carbon sequestration value of $718,113 in 2011.

In 2011, shade from trees helped save approximately 19,000 megawatts of energy for cooling buildings in commercial and residential areas of the San Juan Bay Estuary, equating to 1986 metric tons of avoided carbon emissions due to building energy effects.

The 2001 and 2011 urban forest inventories were integrated with island-wide inventories of Puerto Rico carried out at the same times. The primary goal of these and other FIA surveys is to develop and maintain the information needed to support sound forest policies and programs.

“Urban forest benefits can be lost in the future due to development and other activities,” said Brandeis. “But benefits can also be increased by tree establishment and protection programs. We found that 16.8 percent of the estuary could be planted. Proper planning and management can sustain or enhance existing urban forest to increase the environmental and social benefits from trees in the San Juan Bay estuary watershed.”

For more information, email Tom Brandeis at tbrandeis@fs.fed.us

Additional authors for the report are Francisco Escobedo, University of Florida; Christina Staudhammer, University of Alabama; David Nowak, Forest Service Northern Research Station; and and Wayne Zipperer, research forester with the SRS Integrating Human and Natural Systems unit.

Access the full text of the report.

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Posted in Ethics & Values, Forest Inventory & Analysis, Forest Watersheds, Urban Forests

Guide to Prescribed Fire in Southern Ecosystems

by Zoё Hoyle, SRS Science Delivery Group

Prescribed burning is FIRE “applied in a skillful manner, under exacting weather conditions, in a definite place, to achieve specific results.”

Printed on the inside cover of the Introduction to Prescribed Fire in Southern Ecosystems, the sentence above sets the tone for the revised guide developed by Southern Research Station (SRS) scientists Tom Waldrop and Scott Goodrick and published last year.

The guide is designed to help resource managers plan and execute prescribed burns in southern forests and grasslands. Originally written in 1966 by Merlin Dixon from the Forest Service Southern Region, the guide has seen numerous revisions, the last in 1988 by Southern Region fire manager James Lunsford and SRS research forester Dale Wade, who also worked as a forester for the Region.

Our goal was to update this extensively used resource to include the best available research and current management practices,” says Waldrop, Fire Ecology Team leader for the SRS Center for Forest Disturbance Science led by Goodrick. “The previous versions emphasized prescribed burning on the Coastal Plain. This version adds information on burning in grasslands and on steep terrain.”

The publication opens with an overview of the history and ecology of fire and reasons for using prescribed fire to manage forests and grasslands in the South, with an emphasis on environmental effects. Using numerous photographs and illustrations, the guide first introduces the reader to the weather and fuel condition choices key to controlling the fire and meeting the objectives of the burn.

Managers can choose weather conditions that will give them the fire intensity they want in relation to topography and fuel conditions,” says Goodrick. “We added information from the latest research on smoke modeling to help with more precise smoke management, which is of increasing importance as human populations expand into areas where prescribed burning is needed.”

Following chapters include detailed information on firing techniques, preparing and implementing a written plan, evaluating the burn, and setting up coordination. The guide features sample plans, checklists, single page overviews of general rules and red flag situations, a glossary, and an extensive bibliography of suggested readings, many new to this version of the guide.

Access the guide online.

For more information, email Tom Waldrop at twaldrop@fs.fed.us.

Access the latest publications by SRS scientists.

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Posted in Fire, Restoration