Healthier Diets Needed to Avert Climate Change

by Adin Bonapart

Using global datasets, the Bajželj et al. (2014) study models different agriculture-based climate mitigation scenarios that minimize the expansion of cropland while insuring global food security. The business-as-usual (BAU) projections for 2050 result in a scenario in which global agriculture alone produces ~21 gigatons of CO2 every year, almost the full 2 °C global target emissions allowance in 2050. The study quantifies the loss of Net Primary Production potential along the agricultural biomass flow, and identifies areas of significant food waste and inefficient farming practices for improvement. The researchers then examine the effects of different “demand-side” or “supply-side” agricultural efficiency measures and solutions.

Supply-side management changes include what the study identifies as yield-gap closures, which behave as if agricultural land is intensively farmed in ways that improve yields as well as reducing environmental impacts (i.e. improved irrigation efficiency and eliminating over-fertilization). According to the models, if sustainable intensification of agriculture were implemented worldwide, about 20% additional crop and pasturelands would still be required to feed the global human population in 2050 and GHG emissions would increase by 42% (from 2009 levels). As such, supply-side measures alone are not sufficient, nor will they provide sufficient agricultural GHG reductions and avoid dangerous levels of climate change.

Primary demand-side measures include food waste reductions and alterations in diet of peoples from richer countries. Wasted food is costly because it has accumulated previous transformation stages that required numerous inputs of resources and energy. Improving crop storage and implementing waste reductions programs are one conceivable way of reducing emissions from agriculture worldwide. Models show that, by reducing food agricultural waste by half, the area of cropland required is reduced by about 14% and GHG emissions are reduced by 22-28% (compared with their respective baseline scenarios for 2050).

The Bajželj et al. study introduces the concept of dietary adaptation, or “Healthy Diets,” as a demand-side measure for mitigating emissions and re-allocating resources. Healthy Diets, as a reduction in the consumption of livestock products (meat and dairy) and other energy-rich food commodities by the industrialized nations, is considered an essential facet of climate mitigation via the agricultural sector. Scenarios including Healthy Diets significantly reduced the area for cropping/pasture and GHG emissions by ~45%, with almost all of the large GHG emissions associated with livestock reductions. There is a tiny amount of food delivered compared with the overall productivity associated with livestock systems, with energy losses at every step of production; making animal agriculture a very inefficient form of land usage. Additionally, allowing retired crop/pasture lands return to more natural states of vegetation allows for CO2 sequestration and encourages better health by removing the overabundance of energy rich foods from the diets of people from the richer countries. Demand-side reductions in this area can be best attained with economic incentives (i.e. a carbon tax), and that the livestock sector should enter a comprehensive climate mitigation policy.

A combination of supply and demand-side solutions are required to avoid dangerous climate change and ensuring global food security. Studies like this thus challenge the foundations of the modern industrialized food system, demanding that health requirements dictate agricultural priorities, and not the other way around.

Bajželj, B., Richards, K., Allwood, J., Smith, P., et al., 2014. Importance of Food-Demand Management for Climate Mitigation. Nature Climate Change 4, 924-29.

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