‘Unprecedented’ emissions maps will hone mitigation

To lower agricultural emissions, policymakers and communities first need to pinpoint the sources. Not just by country but crop by crop, field by field. In other words, they need maps. Detailed maps.

In a study published Feb. 13 in Nature Climate Change , researchers have synthesized data from multiple ground sources and models to map global cropland emissions at high resolution - down to about 10 kilometers - while breaking down emissions by crop and source and identifying regions for more precise mitigation.

"This is an absolute global synthesis of all the information you need, by country, by production system, for calculating greenhouse gas emissions - it's been a significant undertaking," said senior author Mario Herrero , the Nancy and Peter Meinig Family Investigator in the Life Sciences and professor of global development in the College of Agriculture and Life Sciences (CALS). "This enormous update will now be used by all sorts of groups for targeting and understanding much better the emissions sources and developing precision mitigation strategies to address them."

Croplands constitute 12% of land use globally and account for 25% of greenhouse gas emissions within the agricultural sector. But the last effort to actually map global cropland emissions dates to 2000. Since then, the sector has grown, management practices have changed, and researchers have many more tools to model complex systems.

The new and improved maps incorporate historical data and models, ground and remote sensing, inventory surveys, hydrological information and more. With this integrated data set, the researchers calculated that croplands emitted the greenhouse gas equivalent of 2.5 gigatons of carbon dioxide in 2020, with East Asia and Pacific contributing about half of the total, followed by South Asia, Europe and Central Asia, which collectively contributed 30%.

The data captured emissions across 46 crop classes, but four crops - rice, maize, oil palm and wheat - accounted for nearly three-quarters of cropland emissions, with rice leading at 43%. The source of the emissions differed depending on the crop; the main culprits were drained peatlands for palm oil production (35%), flooded rice paddies (35%) and synthetic fertilizer used in high-production areas (23%).