Tracking Down Carbon in Water-Soaked Forests

Mangrove forests or grow at tropical and subtropical latitudes near the equator and line about two-thirds of the coastlines in tropical areas of the world. Photo by NOAA.
Mangrove forests grow at tropical and subtropical latitudes near the equator and line about two-thirds of the coastlines in tropical areas of the world. Photo by NOAA.

C-28: Methods for Assessing Carbon Stocks in Mangrove and Coastal Wetland Systems


In this session, presenters explored different techniques used to estimate the amount of carbon stored in mangrove forests, coastal wetlands, and peatlands. Research suggests that these systems have the potential to stock enormous amounts of carbon, both in the above ground biomass and in the soil, but so far there are few studies that provide estimates of this variable (C stock) and the methods for making these estimates are not as well documented as those for other forest ecosystems.

Boone Kauffmann of Oregon State University and CIFOR set the stage, providing background information about the extent of mangrove forests globally, their importance, and the threats facing them, including those attributed to climate change. Kauffmann emphasized the need for researchers to devise reliable methodologies to quantify carbon-related parameters such as the carbon emissions associated with land use and rates of intake from different systems. Knowing this, he said, would enable the implementation of some of the guidelines associated with REDD+, allowing member countries to participate in carbon trading markets.

Each of the presentations that followed delved into the actual methodologies adopted to quantify the C stocks within their respective areas of study. For example, Kristel Hergoualc’h of Peru provided a comparative study between peatlands of Indonesia and Peru using remote sensing technology, specifically Landsat and radar data (ALOS-PALSAR). Using these techniques, she was able to distinguish flooded and non-flooded areas. More importantly, she separated dense peatlands from other types of vegetation, because the former had a very distinct spectral signature. Using this method, she was able to provide the total area of these systems (in sq. km) in both countries.

Similarly Steve Frolking and John Hribljan, working on peatlands in Indonesia and South America, respectively, presented somewhat new methods of estimating carbon that captivated the attention of the audience. Frolking introduced a model called the Holocene Peat Model (HPM) that uses different data inputs such as bulk density, water content, and water table depth, among others, to build a peat profile. The profile simulates peat development over time. Tweaking the model a little (because he had developed it for specifically for the conditions in the Northern Hemisphere), he produced results showing peat profiles for Indonesia. Coastal peats developed faster than inland ones, indicating that carbon stocks in coastal peatlands are much higher than in their inland counterparts.

On his part, Hribljan showed that mountain peatlands (of Peru) developed much faster (2mm/year) and were thicker (av. ≈ 4.5 meters) than lowland ones, and hence had a much higher potential to store a lot more carbon. He was looking forward to using ground penetrating radar (GPR) data to give countrywide and regional spatial estimates of peat development and their associated carbon storage potential.

Related to this was the talk by Erik Lilleskov of the U.S. Forest Service, who speculated on the possibility of also using PALSAR and Landsat data coupled with doming analysis (analysis of structure of dome topography in peatlands) to estimate areas of peat formation (and hence carbon accumulation) in South America.

Rich MacKenzie, also of the Forest Service, used a very novel method called Lead 210 (210Pb) to measure carbon accumulation rates in Palau and Indonesia, and in both cases, the method proved to be very promising in providing sedimentation data at land/water interfaces and in inland locations. He explained that sedimentation data correlates well with carbon accumulation, and his method could complement other more traditional methods of carbon inventory in mangrove forests, peatlands, and other water-inundated systems.

Clearly, this session provided a wealth of data collection techniques that could no doubt revolutionize the way scientists in different parts of the world appraise carbon stocks. But as Carl Trettin cautioned while presenting on estimating carbon stocks within the Zambezi region of Mazimbique, researchers need to stay cognizant of the principles of sound data collection so as to obtain data that are accurate and reliable.

Written by: Humphrey Kalimbo


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