09/04/2009

News / NASA Researcher Fights Loss of Africas Coastal Forests

Threatened mangroves affect climate, play vital role in ecosystem

Washington — The decline of swampy mangrove forests — essential habitats for fish and shellfish in tropical African countries like Mozambique and Madagascar — is threatening the livelihood of already impoverished fishermen, but a NASA researcher is on a mission to reverse that decline.

Environmental scientist Lola Fatoyinbo of NASA’s Jet Propulsion Laboratory (JPL) began a project while still in graduate school in the United States to gain more information about mangroves and develop insight into their role in the environment, according to NASA.

Fatoyinbo grew up in Cotonou, Benin, where she saw mangroves being poisoned by pollution and leveled by real estate development. Such destruction not only threatens African food supplies and economies, but also can contribute to global warming and reduce the planet’s biodiversity.

Mangroves, the most common ecosystem in coastal areas of the tropics and subtropics, are essential — especially in densely populated developing countries — to rice farming, fishing and aquaculture, timber, firewood and, increasingly, ecotourism. Mangroves defend against storm damage by tempering the effects of strong winds and floods, and their large, dense root systems help protect shorelines against debris and erosion.

These coastal woodlands also have a direct link to climate because they sequester carbon dioxide from the atmosphere at a rate of about 112 kilograms per hectare per day — comparable to the intake of tropical rain forests.

Mangroves are hardy, adaptable trees that can thrive in extreme heat, high salt levels and swampy soil. Rampant clearing of these forests for agriculture and construction, soil toxicity and long-term oil and sewage pollution threaten their survival and that of more than 1,300 animal species that make their homes in mangroves.

RETURNING TO HER ROOTS

Fatoyinbo’s studies brought her back to Africa to test a new satellite technique for measuring the area, height and biomass of mangrove forests. Her method, which can be used across the continent to replace expensive and inconsistent modes of ground-based measurement, recently produced what she believes is the first full assessment of the continent’s mangrove forests.

With colleague Marc Simard of JPL, Fatoyinbo used satellite images from the NASA-built Landsat and a complex software-based color classification system to distinguish areas of coastal forest from other types of forests, urban areas and agricultural fields. They also integrated data from NASA’s Shuttle Radar Topography Mission to create relief maps of the height of the forest canopy. Finally, they merged the radar maps with high-accuracy observations from a light detection and ranging (commonly called lidar) instrument aboard NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) to obtain accurate height estimates.

Fatoyinbo’s measurements yielded three new kinds of mangrove maps: continental maps showing how much land the mangroves cover; a three-dimensional map of the height of forest canopies across the continent; and biomass maps that allow researchers to assess how much carbon dioxide the forests store.

“To my knowledge, this study is the first complete mapping of Africa’s mangroves, a comprehensive, historic baseline enabling us to truly begin monitoring the welfare of these forests,” said Assaf Anyamba, a University of Maryland-Baltimore County specialist in vegetation mapping, who is based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Fatoyinbo checked the accuracy of her satellite measurements by traveling to Africa to measure tree heights and trunk diameters. In Mozambique, she confirmed she had extremely accurate measurements of the forests.

“Beyond density or geographical size of the forests, the measurements get to the heart of the structure, or type, of mangroves,” Fatoyinbo explained. “It’s that trait — forest type — that drives which forests land managers target for agriculture, conservation and habitat suitability for animals and people.”

In North America, the densest concentration of mangrove forests is found in the Florida Everglades, much of which has been federally protected and managed since 1947 as part of the Everglades National Park. The park, also designated an International Biosphere Preserve, is home to more than 300 species of birds as well as alligators, manatees and Florida panthers.

“The United States’ largest mangrove forests, Florida’s Everglades, are largely protected now and recognized as an endangered natural resource,” Fatoyinbo said. “But in many other places, resource managers lack solid monitoring capabilities to counter mangrove exploitation. Better mangrove monitoring will, I hope, mean better management and preservation.”

Free satellite data could help ease the problems presented by funding, logistics and political instability that can prevent mangrove preservation. For that reason, Anyamba and Fatoyinbo are working to convince the U.N. Environment Programme and the U.N. Educational, Scientific and Cultural Organization (UNESCO) to include the study’s data in their environmental assessments.

The new technique also distinguishes itself, added Anyamba, “as an excellent example of how we can use different remote-sensing technologies together to address science questions and global social issues.”

http://www.america.gov/st/scitech-english/2009/September/20090904120559abretnuh0.7119104.html?CP.rss=true

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