Smallholder farms have and can store more carbon than previously estimated

Patrick M. Ewing, Xinyi Tu, Bryan C. Runck, Alison Nord, Regis Chikowo, Sieglinde S. Snapp

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Increasing soil organic carbon (SOC) stocks is increasingly targeted as a key strategy in climate change mitigation and improved ecosystem resiliency. Agricultural land, a dominant global land use, provides substantial challenges and opportunities for global carbon sequestration. Despite this, global estimates of soil carbon sequestration potential often exclude agricultural land and estimates are coarse for regions in the Global South. To address these discrepancies and improve estimates, we develop a hybrid, data-augmented database approach to better estimate the magnitude of SOC sequestration potential of agricultural soils. With high-resolution (30 m) soil maps of Africa developed by the International Soils Database (iSDA) and Malawi as a case study, we create a national adjustment using site-specific soil data retrieved from 1160 agricultural fields. We use a benchmark approach to estimate the amount of SOC Malawian agricultural soils can sequester, accounting for edaphic and climatic conditions, and calculate the resulting carbon gap. Field measurements of SOC stocks and sequestration potentials were consistently larger than iSDA predictions, with an average carbon gap of 4.42 ± 0.23 Mg C ha−1 to a depth of 20 cm, with some areas exceeding 10 Mg C ha−1. Augmenting iSDA predictions with field data also improved sensitivity to identify areas with high SOC sequestration potential by 6%—areas that may benefit from improved management practices. Overall, we estimate that 6.8 million ha of surface soil suitable for agriculture in Malawi has the potential to store 274 ± 14 Tg SOC. Our approach illustrates how ground truthing efforts remain essential to reduce errors in continent-wide soil carbon predictions for local and regional use. This work begins efforts needed across regions to develop soil carbon benchmarks that inform policies and identify high-impact areas in the effort to increase SOC globally.

Original languageEnglish (US)
Pages (from-to)1471-1483
Number of pages13
JournalGlobal change biology
Volume29
Issue number6
DOIs
StatePublished - Mar 2023

Bibliographical note

Funding Information:
We thank many team members for their dedication in collecting field data, including Emmanuel Jambo, Hannah Livuza, and Edward Mzumara. We thank Dr. Dan TerAvest and Dr. Sharon Schneider for comments on earlier drafts. This study was funded by the United States Agency for International Development Grant AID-OAA-A-13-00006, as part of the Feed the Future Initiative project Africa Research in Sustainable Intensification for the Next Generation with support from the International Institute of Tropical Agriculture. The research was also supported through a Michigan State University contract under International Fertilizer Development Center and USAID under the Prime Agreement No. AID-BFS-IO-15-00001. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. The USDA is an equal opportunity provider and employer.

Funding Information:
We thank many team members for their dedication in collecting field data, including Emmanuel Jambo, Hannah Livuza, and Edward Mzumara. We thank Dr. Dan TerAvest and Dr. Sharon Schneider for comments on earlier drafts. This study was funded by the United States Agency for International Development Grant AID‐OAA‐A‐13‐00006, as part of the Feed the Future Initiative project Africa Research in Sustainable Intensification for the Next Generation with support from the International Institute of Tropical Agriculture. The research was also supported through a Michigan State University contract under International Fertilizer Development Center and USAID under the Prime Agreement No. AID‐BFS‐IO‐15‐00001. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. The USDA is an equal opportunity provider and employer.

Publisher Copyright:
© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Keywords

  • carbon sequestration
  • climate change mitigation
  • geographically weighted regression
  • iSDA
  • smallholder agriculture
  • soil carbon
  • sub-Saharan Africa

PubMed: MeSH publication types

  • Journal Article

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