Dr. Lei Ma, along with a team of researchers, has published a paper in the journal Global Change Biology about the use of spaceborne lidar data in global forest carbon modeling and monitoring.

Titled “Spatial heterogeneity of global forest aboveground carbon stocks and fluxes constrained by spaceborne lidar data and mechanistic modeling,” the paper results from Dr. Ma's collaboration with GEOG researchers George Hurtt, Rachel Lamb, Louise Chini, Ralph Dubayah, John Armston, Laura Duncanson and Quan Shen, and researchers from the U.S. Forest Service, Goddard Space Flight Center, University of Vermont, Maryland Department of Natural Resources and Maryland Department of the Environment.

The study addresses a key challenge in global carbon cycle modeling: how to characterize forest carbon dynamics accurately. This is partly due to uncertainties related to the representation of contemporary forest conditions in Earth system models and ecosystem models. Current carbon modeling has been limited to coarse scales due to a lack of direct observations and effective methods for incorporating them.

The paper proposes to advance global carbon modeling by incorporating state-of-the-art spaceborne lidar observations from NASA's GEDI and ICESat-2 missions into a newly developed global Ecosystem Demography model. 

The researchers demonstrate that, with the aid of over 3.77 billion lidar samples on vegetation structure, process-based ecosystem models can now capture the spatial heterogeneity of forest vertical structure and carbon dynamics at a resolution of 0.01°, which is nearly 50 times finer than standard global carbon cycle modeling approaches at 0.5°. At this resolution, models can track spatial heterogeneity of carbon stocks and fluxes as the result of deforestation, cropland and urban expansions, and natural disturbance and recovery.

The study bridges the gap between existing empirically-based remote sensing approaches and process-based modeling approaches. It can also address one of the key scientific questions of NASA's GEDI mission: "What is the carbon balance of the Earth's forests?" 

This research is a crucial step toward the development of a global forest carbon modeling and monitoring system, which is supported by NASA's Carbon Monitoring System. This system will help predict short-term carbon fluxes and project long-term carbon sequestration under alternative climate and land-use change scenarios. Ultimately, it will provide valuable support to policymaking on climate change mitigation.