Millions of years before it can turn into coal, dead and decaying organic matter exists as a dark, spongy, carbon-rich material called peat. When layers of peat become saturated with water and sink lower into the earth, they create a type of wetland called a peatland. Peatlands sequester a sizable fraction of the world’s carbon, including 95% of all wetland stores.
Although many scientific studies have investigated vast peatlands found in northern forests and the sub-Arctic, smaller, freshwater peatlands in tropical and temperate regions remain comparatively unexamined. Peatlands in these lower regions could play an important role in global carbon storage if adequately protected. Although land use changes, such as agricultural and urban expansion, threaten the existence of these peatlands, researchers estimate that temperate climates contain at least 20% of all peatland carbon.
Past studies using coring and probing methods (extracting narrow cylinders, or cores, of earth) to determine depth do not account for the uneven depth distribution of most peatlands, which could be providing inaccurate estimates of carbon storage since about 95% of a peatland’s total carbon storage is held underground. Generally speaking, coring requires a lot of time and effort, provides an incomplete picture of peatland depth, and can disrupt or damage habitats.
Here, instead of coring, McClellan et al. employ a technology called ground-penetrating radar (GPR), which uses high-frequency radar pulses to quickly and noninvasively create below-the-surface images. The team used GPR to determine the volume of peat in several depressional wetlands in the Disney Wilderness Preserve in Florida. They also took some direct measurements (cores) to calculate the amount of stored carbon and used aerial photographs to develop a relationship between carbon stock and surface area in order to find out how much these sites were contributing to the overall carbon storage in the area. This approach shows the potential of the method for estimating regional inventories of peat carbon stocks with minimal cost and labor.
The researchers found that the peatlands they studied play a critical role in sequestering carbon across the landscape—more so than previously thought. By imaging the collapse structures underneath the depressions, they could spot the geologic controls in their formation. The team believes that if it is implemented in larger boreal systems, this method could be used to study the formation and structure of underground peat deposits in tropical and subtropical systems both quickly and noninvasively. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1002/2016JG003573, 2017)
—Sarah Witman, Freelance Writer