Global agriculture and carbon trade-offs

By 2050, the United Nations estimates the global population will exceed 9 billion people and world food demand will grow by about 70% from 2000. Agricultural production can be increased through intensification, which reduces the spread of agriculture to new land through increased use of fertilizer, pesticide and water inputs, shorter fallow periods, and improved seed varieties, or through extensification, which expands the number of hectares used for crop production. While intensification of existing crop lands is an important future strategy, it is likely that extensification will also be necessary to meet the increased demand for food.  And, as agriculture production expands, it often means the conversion of grasslands and forests, which decreases their ability to provide essential ecosystem services like carbon storage. How can we balance these competing needs? Where should we cultivate to increase the amount of calories produced and decrease the amount of carbon lost in the process?

How can agriculture expand while maximizing calorie production and minimizing carbon loss? Photo: PL Tandon on Flickr

I had the opportunity to attend an interesting briefing session at the Woodrow Wilson Institute on a newly released paper by Johnson et al., Global agriculture and carbon trade-offs, which tries to answer some of these complex questions. The authors offer a unique solution which combines both intensification and extensification based on a global geospatial analysis. They argue that extensification should be targeted to the areas that will minimize carbon storage loss. Through this tactic, the world can meet the growing demand for agricultural output while minimizing the impact on essential ecosystem processes.

In order to determine the optimal places for extensification to occur, they calculated the comparative advantage of a grid cell based on its potential for food production vs. the amount of carbon that would be released into the atmosphere if that cell were converted to full food production. They call this the “crop advantage” (CA), or the ratio of the caloric yield of the land to its potential carbon loss.  The grid cells were then ranked by CA to determine which regions would be most suitable for crop extensification and which should be reserved for carbon storage.

The result: to minimize carbon loss while maximizing calorie production, we should extensify the edges of places that are already intensively cultivated, like the US Corn Belt, the Nile River Valley, and eastern China, while minimizing further expansion of agriculture in most other areas and especially the tropical forests, which have a very high potential for carbon storage. By focusing the increased cultivation on sites with the highest CA, the value of the additional carbon stored, when compared to a baseline scenario, ranges from $0.44 trillion to $1.30 trillion in 2012 US dollars.

While an interesting result, this analysis neglects to consider some other important factors, including the effects of climate change on agriculture in particular locations. Additionally, there are important methods of increasing carbon storage along with agriculture (i.e. climate smart agriculture and landscapes) that this model does not consider. Finally, it seems unlikely that this result could be implemented at a world-wide scale where economic and political factors, such as trade barriers, infrastructure gaps, and concerns over food sovereignty will likely determine where food is grown and how it is distributed. Thus, while the principles of this optimization process are interesting in theory, I can’t help but wonder if a more nuanced view of the relationship between agriculture and carbon storage as well as agriculture production and global food security would give a different result.