The East Africa study area – including Ethiopia, Kenya, Tanzania and Uganda – has experienced deforestation and also contains many large-scale land restoration and land-based climate mitigation programs, but lacks systems for quantifying regional carbon stocks and fluxes.
Organic carbon stored in the soil equals roughly three times the amount found in living plants and twice that found in the atmosphere, where carbon dioxide (CO2) acts as a heat-trapping greenhouse gas. However, measuring and monitoring the capacity of soil carbon sequestration remains a challenge.
Stemming from the 2015 Paris climate agreement, these East African countries have ambitious climate mitigation programs to sequester carbon in soils. Since the countries don’t produce a lot of energy that emits carbon, their mitigation measures rely on putting carbon into ecosystems such as soils.
A rigorous, accurate and low-cost carbon monitoring system will therefore help policymakers verify the effectiveness of their efforts when they seek international climate financing. The data will also inform food-security policies, as more soil carbon provides crop resilience to climate change. Carbon helps store more water in soils, making crops more tolerant and resistant to droughts, which increases yields, especially in drier regions and during dry years.
“There is a really high demand now for using modern technologies to quantify carbon stocks and fluxes on regional and global scales, so that we can reduce the costs and maintain accuracy and rigor,” said Ying Sun, assistant professor of geospatial sciences in the School of Integrative Plant Science (SIPS) Soil and Crop Sciences Section (SCSS), and principal investigator (PI) of the grant, which began on July 1.
“If we’re going to invest in storing carbon in soils and vegetation for climate-change mitigation and soil health, we need to be able to monitor the impact and how effective the interventions actually are,” Woolf said. “We need to have large scale systems of what’s happening below ground,” he added.
Current methods of monitoring soil carbon over large scales are unfeasible in terms of effort and cost, as they rely on taking individual core soil samples, which must be repeated every few years for long-term datasets.
The new system will combine observable ground data, real time satellite measurements of CO2 in the atmosphere, and next-generation microbial soil modeling, which incorporate information on land-cover changes, moisture, vegetation and photosynthesis, harvesting and crop management, to provide below-ground soil carbon data. Incorporating satellite measurements of CO2 concentrations in the air to optimize the computer simulations is an important and novel approach that will improve confidence in using models to predict soil changes over large geographical areas. These CO2 measurements will be added to atmospheric transport models that include what is already known about CO2 sources and sinks, and how CO2 is circulating and mixing in the global atmosphere.
“The discrepancy between what we observe in the atmosphere and what ought to be there, given everything we know about the sources and sinks of CO2, should total what’s going below ground, and we use that to better constrain our below-ground estimates,” Woolf said.
The study will improve below-ground soil carbon modeling, partly by adding soil microbial processes; assimilating observations from multiple NASA Earth-observing satellite instruments; developing a platform to estimate regional-scale carbon exchange between the ground and air; optimizing the system and quantifying uncertainties; and engaging government and nonprofit stakeholders to use the developed products in their land management programs.
“We hope that this will really expand the capacity at state, county, national and global scales by providing an accounting of carbon in a way that’s just not possible at the moment,” Sun said.
Partner stakeholders include the Ethiopian Ministry of Agriculture and the Consultative Group on International Agricultural Research (CGIAR) Research Program on Climate Change and Food Security.
Header image: A 2014 false-color Pleiades satellite image of a land restoration project at Weira Amba in Ethiopia, with green areas showing reforestation. Photo provided.
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