Commonly Used Methods for Estimating Agricultural Emissions Are Only 60% Accurate in Tropical Developing Countries. What Now?.

Commonly used methods for estimating agricultural emissions are only 60% accurate in tropical developing countries. What now?

Demand for tools to rapidly assess greenhouse gas (GHG) impacts from policy and technological change in the agricultural sector has catalyzed the development of ‘GHG calculators’— simple accounting approaches that use a mix of emission factors and empirical models to calculate GHG emissions with minimal input data. GHG calculators, however, rely on models calibrated from measurements conducted overwhelmingly under temperate, developed country conditions and their precision and accuracy in tropical developing countries is unknown.

We found that GHG calculators may poorly estimate emissions in tropical developing countries by comparing calculator predictions against measurements from Africa, Asia, and Latin America. Estimates based on GHG calculators were greater than measurements in 70% of the cases, exceeding twice the measured flux nearly half the time. For 41% of the comparisons, calculators incorrectly predicted whether emissions would increase or decrease with a change in management.

These results raise concerns not only about applying GHG calculators to tropical farming systems, but about the methods used by most tropical developing countries countries to report their emissions to the UN Framework Convention on Climate Change (UNFCCC), which are the same as those used by GHG calculators. Improving estimates of GHG emissions from the tropics depends on calibration of the underlying factors and models to the environmental conditions and systems common in agriculture in tropical developing countries. In the short term, IPCC-approved Tier 2 emission factors based on currently available data may help provide a more reasonable picture of both current fluxes and mitigation potential. In the long term, more data is needed.

To support this data collection effort, we have published GHG measurement guidelines that address some of the constraints common in developing countries, such as highly heterogeneous agricultural landscapes and resource limitations. The methods provide a standard for consistent, robust data that can be collected at reasonable cost with equipment often available in developing countries. A database of emission factors and measured data from the tropics is also available to support wider use of available data. Both resources are freely available at samples.ccafs.cgiar.org.