Upwithclimate teammember Brian Machovina has just pulled off a rare scientific trifecta: over the last month has published letters in PNAS, Science and Nature. All three letters address the need for reducing human consumption of meat in order to minimize habitat loss and anthropogenic impacts on biodiversity. The Science and PNAS letters were previously posted to upwithclimate here and here. I now post the new letter from Nature (a response to a previous comment article in Nature Eisler et al.). The Nature editors cruelly “butchered” the article to fit space constraints so I am posting the original, unedited (but still super short), version.
Livestock: Need for Global Limits
Brian Machovina & Kenneth J. Feeley
In “Agriculture: steps to sustainable livestock,” (see Eisler et al. Nature 507:32; 2014), the authors argue for improved breeding and cultivation of ruminants to provide better food sources. They mention a need to focus “on eating less, better quality meat,” and advocate for a diet containing only 300g of red meat (approximately the size of 3 decks of cards) per week. This is approximately 3.5-7% of a 2000 calorie-a-day diet depending on species and cut of meat. We strongly support the push to reduce consumption of ruminants, especially within a larger context of reducing overall meat consumption to a global average of 10% or less and with preferential use of meat sources with higher energy conversion efficiencies (i.e. chickens > pigs > ruminants). Globally, the average contribution of meat to the human diet is now approximately 30%. This varies greatly between countries, ranging from ~50% in the United States to ~5% for some developing countries. As such, reaching the proposed goal should ideally be achieved not only through an overall reduction in meat consumption, but also through a more equitable redistribution of consumption. A global maximum of 5% red meat in diets within a 10% maximum for all animal-based products would enable more people to be fed on less land (e.g., eliminating livestock and growing crops only for direct human consumption could feed an additional 4 billion people on extant agricultural lands1), thereby reducing or eliminating greenhouse gas emissions associated with conversion of natural habitats and biodiversity loss. The many other environmental impacts of agriculture related to use of water, fertilizer and fossil fuels, would also be reduced. Furthermore, a move towards more plant-based diets would result in many potential health benefits.2,3 Global meat consumption is increasing; this increase is not inevitable, nor is it beneficial to the planet or even human well-being.
1 Cassidy, E., West, P. C., Gerber, J. S. & Foley, J. A. Redefining agricultural yields: from tonnes to people nourished per hectare. Environmental Research Letters 8, 8 (2013).
2 Campbell, T. C. & Campbell, T. M. The China study: the most comprehensive study of nutrition ever conducted and the startling implications for diet, weight loss and long-term health. (Wakefield Press, 2007).
3 Levine, Morgan E. et al. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell metabolism 19, 407-417 (2014).