What the World Eats and How It’s Grown

Exploring Environmental Impacts of Food Choices and Food Production
By Noel Gurwick, David Miller

Agriculture occupies 40 percent of Earth’s land surface, accounts for more than 70 percent of freshwater withdrawals and emits between a quarter and a third of greenhouse gases (GHGs). The choices we make about how to feed ourselves need to protect the natural resources on which our livelihoods and health depend. It’s a challenge that attracts constant research. A new paper by Michael Clark and David Tilman is one example. They reviewed 164 published life cycle analyses of more than 90 foods to compare how different ways of growing food, and choices about which food to produce, affect five aspects of the environment: land use, fuel consumption, nutrient run-off, ecosystem acidification and GHG emissions.

Their most straight-forward finding is that ruminant livestock such as cattle impose a footprint approximately 100 times that of plant-based foods. Even shifting to fish or poultry significantly reduces the impact (see Figure 8). Large-scale adjustments in diet would dwarf the impact of changing how foods are produced.


The team’s finding that food produced with organic methods harm the environment as much as conventional methods demands more explanation and scrutiny. Synthetic fertilizer, pesticides and herbicides require energy to produce and transport; when used in excess they cause environmental and economic damage. So why don’t natural inputs lessen impacts? Clark and Tillman argue that synthetic fertilizer boosts productivity more than manure, so manure takes more land to provide the same amount of food. This reduced productivity offsets any energy and GHG emission savings organic fertilizers might confer. The study also concludes that raising cattle on pasture harms the environment as much as raising them on grain, because grass-fed cattle grow more slowly and live longer before slaughter.

However, as Clark and Tillman acknowledge, their study did not include all the potential benefits of well-managed organic systems. Avoiding agrochemicals supports human health and ecosystem biodiversity, and raising livestock on pasture can increase soil carbon, and produce beef with more micronutrients. Nor is it clear that the assessment measured the potential benefits over time of increased soil organic matter or nutrients absorbed from manure. Finally, their analysis captures a limited segment of alternative agricultural production, especially as practiced in many small-scale systems for which life-cycle assessments rarely exist.

Despite these limitations, Clark and Tillman’s conclusions underscore that improvements, especially when applied to the most wasteful, least efficient systems – whether organic or conventional – can profoundly reduce environmental impacts.

How can we apply these findings to development programming?

How is this research, which is based primarily on studies of the industrial agricultural systems of Europe and North America, relevant to development? One conclusion that stands out is the role that wise management of fertilizer plays to protect natural capital. The development community is often unable to influence whether farmers use agrochemicals or natural inputs. In many developing countries, donors must fall in line with government policies that support agrochemicals. In others, farmers use low-input systems because they lack cash or credit to adopt high-input agriculture. Clark and Tillman demonstrate the potential for impact even within these constraints.

For example, wise use of living plants throughout the year to reintroduce nutrients to the soil may be within reach for many farmers in developing countries. One 2013 study found that planting legumes as a nitrogen source led to far less nitrogen runoff than using any other nitrogen source. By promoting techniques that use plants as complimentary nitrogen sources – such as rotational farming, cover cropping, multi-cropping, and polyculture – farmers can, within their cash limits, make choices to boost productivity and mitigate overall impact by reducing the growing demand for land.

Strategic Objective
Food Security and Agriculture, Mitigation, Sustainable Landscapes
Noel Gurwick

Noel Gurwick

Noel Gurwick is the Sustainable Landscapes Team Lead in the Office of Global Climate Change at the US Agency for International Development (USAID) where he focuses on land-based solutions to mitigate climate change.

David Miller

Dr. David Miller has over 25 years of experience contributing to the fields of international agricultural development, natural resources management, and environment. Currently, Dr. Miller serves as ACDI/VOCA’s Senior Climate Change Advisor. As Technical Advisor to the African and Latin American Resilience to Climate Change (ARCC) program from 2012 to 2015, Dr. Miller lead teams of experts in the implementation of over 20 climate change vulnerability assessments in Africa. Dr. Miller also currently serves part time as the Sustainable Agriculture Intensification Specialist on the USAID ProLand project. Previously, as an international development consultant, Dr. Miller employed a variety of research methods to design, implement, and evaluate a wide range of development activities and programs.

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