WETLAND RESTORATION & BLUE CARBON
An eddy covariance tower in the Sacramento San Joaquin Delta continuously measures the exchange of greenhouse gases, energy, and water to understand the climatic benefit of these restored, managed wetlands. Photo: Kyle Hemes
In dissertation work, I found that restored freshwater deltaic wetlands were highly productive, sequestering carbon in the soil as productivity outpaced ecosystem respiration. This productivity came at the cost of substantial methane emissions, however, making these wetlands greenhouse gas neutral to sources over a century. Despite this fact, transitions from high-emission degraded peat soil agricultural land uses to restored deltaic wetlands often reduced greenhouse gas emissions overall.
Restoration of coastal and deltaic wetlands, with their often carbon-rich organic soils and high productivity, presents an attractive but largely untested land-based climate mitigation strategy. The benefits associated with wetland restoration stem from two key areas. First, drained agricultural peat soils can be large greenhouse gas sources. Second, the slow decomposition rates of inundated wetland soil organic matter along with high productivity leads to soil carbon accumulation and protection. While these tenets are generally widely appreciated, they have rarely been tested and measured at the ecosystem scale, over multiple years.
Figure from Hemes et al., 2018 Geophysical Research Letters
I analyzed how the biophysical impacts of this restoration activity – the changes to the way the ecosystems exchange heat and water – affect the surface temperature and boundary layer. I found that along with potential biogeochemical benefits, restored deltaic wetlands have an evaporative cooling effect due to rougher, wetter canopies.