Feed the Future
This project is part of the U.S. Government's global hunger and food security initiative.

What the World Eats and How It’s Grown

This post was originally published on Climatelinks and was authored by Noel Gurwick and Dr. David Miller. Here, Gurwick and Miller share findings from a research paper by Michael Clark and David Tilman reviewing the life cycle analyses of various foods.

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.

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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.

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