Video Transcript:
Global agriculture is a leading cause of environmental degradation, emitting ~25% of GHGs, occupying 40% of Earth’s land surface, and accounting for >70% of freshwater withdrawals.

Understanding the linkages between agriculture and environment is necessary if we are to reduce agriculture’s environmental impact. We performed a meta-analysis of life cycle assessments to examine three aspects of agriculture that could be leveraged to reduce its environmental impact. The aspects we examined are how production systems, for example organic and conventional systems, differ in their environmental impact, how input use efficiency influences agriculture’s environmental impact, and how foods differ in their environmental impact. 

We found that agricultural production systems often differ in their environmental impact. Organic systems, for example, required 25 – 110% more land and caused almost 40% more eutrophication, but emitted the same amount of GHGs as conventional systems per unit of food produced. In addition, grass-fed beef occupied 25% more land than grain fed beef but did not offer benefits for the other environmental indicators included in the analysis. However, organic and grass-fed systems may offer environmental benefits that we could not examine. On and near-farm biodiversity, for example, is often higher in organic and grass-fed systems, while pesticide inputs are often lower.

Our results thus contradict the commonly held perception that organic foods and grass-fed beef have lower environmental impacts than their more common alternatives. However, this should not be taken as an indication that current agricultural practices are sustainable as current practices have large environmental and health impacts. A new agricultural system that combines the benefits of organic systems and grass-fed beef, for example their reduced reliance on synthetic inputs, with the benefits of conventional production practices, such as its reduced land use, would result in a more sustainable agricultural future.

We also examined how agricultural input efficiency, or the amount of food produced per unit of input, affects its environmental impact. We found that the environmental impact of cereals and of non-ruminant animal-based foods was negatively correlated with their fertilizer and feed efficiency – that is, increasing the amount of food produced per unit of input would decrease its environmental impact. The potential environmental benefits of increasing input efficiency are greatest in the least efficient systems. 

Increasing input efficiency is possible with current technology. Precision agriculture, for instance, has been an effective method of increasing input efficiency across a variety of crops. Implementing policies designed to improve input efficiency would offer large environmental benefits.

The third part of our research focused on the environmental impact of different foods. We found that plant-based foods consistently had the lowest environmental impact for all environmental indicators examined; that dairy, eggs, pork, poultry, and some fish had impacts 5 – 20 times those of plant-based foods; and that ruminant meats such as beef had impacts approximately 100 times greater than those of plant-based foods. 

Dietary shifts from high-impact to low-impact foods would thus offer substantial environmental benefits. In addition, many recent analyses have shown that similar dietary shifts, especially in nations with a history of high meat consumption, would improve health outcomes.

In sum, our research indicates that there are many avenues to reduce agriculture’s environmental impact. Dietary shifts away from animal-based foods, and especially ruminant meat, would offer the largest benefit. However, this would necessitate dietary shifts that may go against cultural or social values, as well as taste preferences. Increasing agricultural input efficiency through improved management techniques would reduce agriculture’s environmental impact without requiring a dietary shift. In contrast, switches to organic agriculture or grass-fed beef, would often increase agriculture’s environmental impact unless there was a simultaneous dietary shift to lower-impact foods.

Several recent analyses have shown that agriculture’s global environmental impact will substantially increase by 2050 as populations grow and diets shift to include more meat. Implementing policy and educational initiatives designed to reduce consumption of high-impact foods, to increase adoption of lower impact production systems, and to shift to systems with high input efficiency is necessary before agriculture causes substantial, and potentially irreversible, environmental damage.