The Intergovernmental Panel on Climate Change has determined that agricultural activities directly account for about one-seventh of greenhouse gas (G.H.G.) emissions. If indirect effects from land conversion are added in, the contribution approaches one-third.

Yet, people need to eat, and national governments — especially in developing countries — understandably place food security ahead of climate change concerns. The result has been a tension between food security and climate change advocates that often appears to reflect deep-seated value differences.

Wealthier, more well-fed countries and consumers increasingly are stressing the need to protect the planet and to conserve resources. At the extreme, this view argues for producing and consuming less, but even supporters of continued economic growth want to “put a price” on carbon as a means of attacking emissions.

Leaders in developing countries may acknowledge the importance of dealing with G.H.G. emissions, but their priorities are elsewhere. One billion people are hungry, hundreds of millions more are malnourished and the majority of the world’s people — those living on incomes below $3,000 per person per year — are extremely sensitive to food price increases. Both periodic food price spikes and any reversal of the long-term trend of declining real food prices are problematic.

This tension may be easing as the terms of the debate change. New tools and new understanding may help bring food security and agricultural sustainability closer together.

Eat local to save on food miles

Early on, agriculture’s G.H.G. emissions and their potential effects on climate produced a call to “eat local” in order to save on “food miles.” Locavores (and some agricultural protectionists) seized on this notion to urge consumers to buy locally produced foods rather than imports.

Soon, the idea of doing a “life cycle analysis” of a product’s G.H.G. emissions exposed some of the fallacies in such thinking. “Food miles” ignore the form of transport, which has a larger effect on G.H.G. emissions than distance: bulk shipment by rail or ocean vessel emits much less G.H.G.s per calorie than hauling goods to market in the back of a pickup truck. It also ignores production

emissions: growing food in climatically-favored regions causes fewer emissions than production in less favored regions, even after transport emissions are included.

Supply chain carbon footprints

“Food miles” arguments have given way to a more sophisticated examination of G.H.G. emissions “from farm to fork.” Life cycle analyses of food-product supply chains is a much more comprehensive and useful idea. It also is a challenging and still developing methodology for defining the “carbon footprint” of a food product.

There are many interpolations that have to be made in carbon footprinting: different input configurations yield disparate emissions profiles; calculating the “CO2 equivalent” of non-carbon emissions like methane and nitrous oxide requires sensitive adjustments for their different periods of persistence in the atmosphere; dealing with potential indirect emissions from land-use changes involves controversial judgments about causes of such shifts; and accommodating technological innovation as producers attempt to reduce their carbon footprints requires regular revisions of the calculations. As well, there are other environmental issues affecting sustainability that are not necessarily well-captured by a carbon focus, such as erosion or water usage.

As a result, the idea of a product’s carbon footprint is a useful one, but it also is less precise than its quantitative representation might suggest. It is an indicative measure that helps producers, processors and handlers identify processes that may be improved from a carbon-emissions standpoint. But it is not a definitive gauge of sustainability.

Nevertheless, carbon footprints have entered every day language. Food manufacturers and retailers are measuring them, and some are

putting the data on posters or packages to help inform consumer choices.

Sustainability as efficiency

What may be emerging now is a growing recognition of a closer alignment between efficiency and sustainability than previously acknowledged. The basic idea is that more efficient use of land, water and purchased inputs contributes to reduced G.H.G. emissions and a more sustainable food system in a variety of ways.

It lowers the energy intensity of producing each calorie. It captures the intrinsic emissions savings of trade, revealing an environmental comparative advantage embedded within the traditional idea of economic comparative advantage. And it highlights the G.H.G. emissions advantages of intensifying production on good lands versus either inefficient use of marginal lands or, worst of all, conversion of natural habitat to food production.

Similarly, it helps direct research and innovation in animal husbandry. Variations in genetics, feeds and management practices may signal pathways toward lower G.H.G. emissions. Breeding, formulating feeds and managing animals against such goals also may lead to lower costs or better yields.

Aligning efficiency with emission-reduction strategies may prove helpful in resolving another tension around sustainability. Mandating sustainable practices to “save the planet” may push up costs for all and be trumped by overriding food security concerns. Letting consumers choose more sustainably-produced foods implicitly suggests that such choices are likely to be more costly, raising the risk that consumers may not choose that option. Pursuing emissions reductions as an efficiency- or productivity-enhancing strategy helps direct technological innovations toward a truly sweet spot — lower emissions and lower costs.

Of course, not every productivity gain is an emissions reduction, nor do emissions reductions always lead to lower costs. The alignment is not perfect, but it is closer than sometimes thought. Focusing on such alignments points the way to feeding more people better … and more sustainably.