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Mangrove forest in the Pacific coast of Panama. This forest is dominated by Pelliciera rhizophoreae, a species endemic to the region. (Ivan Valiela)

Studying the Effects of Deforestation on Mangrove Estuaries in Panama

Ecosystems Center senior research scientist Ivan Valiela and his colleagues have spent much of their careers studying land-sea couplings and water quality in temperate coastal areas like Waquoit Bay on Cape Cod. Now they have added Panama’s tropical ecosystem to the center’s research portfolio.

Valiela, and Anne Giblin, Jane Tucker, Rich McHorney, Rita Oliveira Monteiro and Sarah Wilkins from the Ecosystems Center along with colleagues from the U. S. Geological Service, Woods Hole Research Center, Woods Hole Oceanographic Institution, Universidad Nacional de Mar de Plata, and students from Universidad Nacional de Mar del Plata and Universidad de Panama are studying how deforestation affects the flow of precipitation from land into mangrove estuaries. Mangroves are ecosystems that constitute a fringe between land and sea, similar to salt marshes in temperate zones.

The research, funded by the National Science Foundation, is being conducted at the Liquid Jungle Laboratory (LJL), a modern field station on a small island off the western coast of Panama. Built by European businessman Jean Pigozzi, the LJL operates under the scientific guidance of WHOI and the Smithsonian Tropical Research Institute.

Tropical forests are being logged or cleared at a rate of up to 2 percent per year worldwide, Valiela says. Besides releasing large amounts of greenhouse gases into the atmosphere, burning tropical forests to clear land for other uses, such as cattle farms, has other environmental impacts.

"When you remove forest cover, you allow precipitation to go through the landscape, down slope, to the shorelines. That water, like the blood in our system, carries things—nutrients, sediments—that make a big difference to coastal environments such as mangrove forests,” Valiela says. Moreover, mangrove forests carry on a series of what have been called “ecological services” (nursery roles for coastal fish, areas for growth of commercially important fin and shellfish, stabilize sediments, intercept land-derived nutrients and sediment loads, and more). To the degree that deforestation diminishes the services furnished by mangroves, there will be further alterations to the adjoining coastal ecosystems. This change in the ecological and biogeochemical couplings of land to sea highlights the importance of the work being done in the Panama site: how do the changes brought about by deforestation of watersheds, as they cascade down-slopes to mangrove forests and adjoining reefs, alter function of tropical coastal environments, and of subsidies that mangroves provide.

The project will study several coupled watershed-mangrove-reef systems that have watersheds that have suffered different degrees of deforestation. The approach is to use these contrasting deforestation regimes to compare effects on mangrove function, exports, and services to adjoining reef and other coastal environments. The comparisons will be done by application of a number of methods, from GIS work based on satellite imagery, hydrogeological and mass balance studies, stable isotopic tracings, in situ measurements of microbial transformations, field surveys, experimental manipulations, and many other measurements.

The research team will involve colleagues and students from Latin American institutions in the work, and they also will outreach to Panamanian government and management agencies to encourage transfer and use of information to be gathered, to inform the future management of coastal resources.