Summary written and edited by New Harvest Journal Club’s Jack Davis and Hanna Tuomisto, respectively.
Abstract: Worldwide demand for crops is increasing rapidly due to global population growth, increased biofuel production, and changing dietary preferences. Meeting these growing demands will be a substantial challenge that will tax the capability of our food system and prompt calls to dramatically boost global crop production. However, to increase food availability, we may also consider how the world’s crops are allocated to different uses and whether it is possible to feed more people with current levels of crop production. Of particular interest are the uses of crops as animal feed and as biofuel feedstocks. Currently, 36% of the calories produced by the world’s crops are being used for animal feed, and only 12% of those feed calories ultimately contribute to the human diet (as meat and other animal products). Additionally, human-edible calories used for biofuel production increased fourfold between the years 2000 and 2010, from 1% to 4%, representing a net reduction of available food globally. In this study, we re-examine agricultural productivity, going from using the standard definition of yield (in tonnes per hectare, or similar units) to using the number of people actually fed per hectare of cropland. We find that, given the current mix of crop uses, growing food exclusively for direct human consumption could, in principle, increase available food calories by as much as 70%, which could feed an additional 4 billion people (more than the projected 2–3 billion people arriving through population growth). Even small shifts in our allocation of crops to animal feed and biofuels could significantly increase global food availability, and could be an instrumental tool in meeting the challenges of ensuring global food security.
Summary: This article addresses the emergent schism between the implications of increasing crop yields (e.g. from better farming techniques and technology) and increasing demand for crops – as a large proportion of crops are going towards biofuel and feeding livestock. Rather than defining crop yields as ‘the mass of the plant matter coming out of the ground’, this article defines the agricultural output as ‘how many people are fed by a unit of land’.
Globally, the most commonly cultivated crops are maize, wheat and rice. When considering the 41 major crops suitable for human-consumption, only 67% of the crop output (by weight) directly feeds humans, whereas 24% of the crops are used for livestock feed and 9% for industrial processes, including but not limited to biofuel. However, the variation within different regions is wide. In the United States only 37% of the crops are used directly for food, whereas in India the share is 92%.
As livestock can convert only 3-40% of feed calories to food, only 60% of the produced human-consumable crop calories are delivered to the world food system. The paper estimates that shifting the crop calories used for feed and other uses to direct human consumption could potentially feed an additional ~4 billion people (at 2700 calories per day per person). For example, a hectare (100m x 100m) of cropland in India feeds 5.9 people, but could feed 6.4 ha without loss to animal conversion. By contrast, in the United States a hectare of cropland feeds 5.4 people, but it could be feeding 16 people. Partial gains could be made with reductions rather than outright eliminations of animal products in diets.
The estimates of the food availability presented in the paper do not include food waste. According to recent studies, food waste can account for up to third of crop production. This study also excluded food calories that are produced elsewhere than on croplands, e.g. grasslands and marine systems. Ruminants are able to convert grass to food, and therefore, enable food production in the areas that are not suitable for human-edible crop production.
The authors also admit the simplified assumption made in the paper that treats crop and livestock calories equally, even though the nutritional compositions are different. A crop based diet can provide all essential amino acids only when both cereal and legume crops are included in the diet. Therefore, the proportion of legume crops would most likely need to increase if the world was fed solely by crops.
It is concluded that while shifting larger share of the produced crop output to direct human consumption would have tremendous benefits to global food security and environment, there are many political and cultural obstacles to implement the shift.
