Quantifying the recarbonization of post-agricultural landscapes
| Nature Communications | 2023 | Peer Reviewed | Communication | nature.com/articles/s41467-023-37907-wAbstract
Despite worldwide prevalence, post-agricultural landscapes remain one of the least constrained human-induced land carbon sinks. To appraise their role in rebuilding the planet’s natural carbon stocks through ecosystem restoration, we need to better understand their spatial and temporal legacies.
In provisioning human civilization with food, fuel, and fiber for millennia, agriculture has drastically depleted terrestrial carbon stocks at the expense of natural ecosystems. Our challenge today is to use more sustainable practices to recapture some of the 116 Pg of soil organic carbon (SOC) lost since agriculture began, while simultaneously ensuring global food security1,2. That being said, the cessation of agriculture altogether is still the most efficient way to increase carbon stocks and restore ecosystems in tandem and at large scales.
Consider the vast expanses of forests that regrew over the 60 Mha of cropland abandoned following the collapse of the Soviet Union3. It has been called the world’s largest human-made carbon sink attributed to a single event;4 a title challenged by the climatic consequences of the ‘Great Dying in the Americas’ and its 56 Mha abandoned following the arrival of Europeans5. At more practical scales, intentional efforts to restore agricultural land such as the Grain-for-Green program in China and the Conservation Reserve Program in the USA have demonstrated that carbon sequestration is far from being the only advantage6,7. Ecological co-benefits include reduced soil erosion and water run-off, reduced flooding and drought, and improved soil health, water quality, and biodiversity indicators.
These post-agricultural landscapes (PALs) often signify the return of ecosystem properties, such as carbon, towards pre-disturbance states or new equilibria through secondary succession. Whether planned or unplanned, they appear in every agricultural region of the world and they can drawdown carbon with or without human involvement. If commitments to halt gross forest area loss by 2030 succeed, recarbonizing PALs will play a key role in reversing global land use change from being a net carbon source to a net sink8.
Unfortunately, PALs are insufficiently represented in terrestrial carbon models, both spatially (as a poorly mapped land cover class) and temporally (as uncertain carbon sinks). This hinders our ability to monitor, quantify, and leverage them strategically. We discuss here some of the reasons behind these issues and what can be done to address them so that we can properly evaluate the role of PALs.