Reply to Van Meerbeek and Svenning, Emery, and Springmann et al.: Clarifying assumptions and objectives in evaluating effects of food system shifts on human diets.

Authors: WHITE, ROBIN - Virginia Polytechnic Institution & State University; Hall, Mary Beth

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Other
Publication Acceptance Date: 1/30/2018
Publication Date: 2/20/2018
Citation: White, R.R., Hall, M. 2018. Reply to Van Meerbeek and Svenning, Emery, and Springmann et al.: Clarifying assumptions and objectives in evaluating effects of food system shifts on human diets.. Proceedings of the National Academy of Sciences. Proc. National Academy of Sci. 115(8):E1706-E1708.

Interpretive Summary:

Technical Abstract: Letters by Van Meerbeek and Svenning (1), Emery (2), and Springmann et al. (3), regarding the study by White and Hall (4), expressed concerns regarding assumptions of land allocation, and proposed dietary characteristics. The authors also present individual, diverse concerns. We attempt to address each concern below. Land Allocation In our paper (4) we allocated tillable land used for animal feed to food production assuming crops in the same proportions as currently grown. If it was economically desirable to grow higher value crops, it is unlikely that the U.S. would be importing 51% and 39% of the fruits and vegetables we consume. All authors (1, 2, 3) posited that this assumption led to underestimation of land for fruit and vegetable production, citing agricultural policy as an inhibitor of expansion despite societal demand. Suggesting that demand or policy alone can dramatically shift land use is a limited view of cropping choice drivers. In (2), Balagtas et al. is cited as evidence for the impact of policy-driven changes; however, Balagtas et al. indicates impact of U.S. policy on fruit and vegetable acreage varied by area, with no appreciable impact in the upper Midwest, and reduced acreage in the Sun Belt. Perhaps a major reason why policy-driven changes are not the sole driver of land use is that sensitivity to climate, soil, and management make fruit and vegetable production an economically risky endeavor. As described by one author: “farmers may generate higher marketplace revenue from fresh produce” but such farming is “an already risky industry.” The food waste during production, handling, and storage is 22.6% for fruits and vegetables, and 25.1% for roots and tubers, with both values greater than all other food sources, and representing a risk of lost income. The simplistic representation made in the popular press article cited by (3) on the substantially greater per acre value of fruit production vs. grain production does not reflect the complex conclusions drawn by the crop analyst cited, who indicated that potential economic returns “should not be viewed as the amount of income that would be returned to anyone that was growing or raising the particular product”, and that “management ability, product variety and quality, product yield, marketing outlet, labor ef'ciency and wage rate, and a host of other factors” would affect outcomes. In addition to economic risk, fruit and vegetables are challenging to grow and some land is not suitable for their production. Factors like rainfall, temperature, and elevation affect entry or exit in fruit and vegetable acreage. More than 70% of the fruits and vegetables grown in the U.S. are irrigated, and concerns regarding availability of water to support this irrigation are increasing. Impact and uncertainty of climate, soils, water availability, harvest reliability, etc. make fruits and vegetables more risky to produce than grains, and this is likely a significant expansion barrier. Feasibility challenges aside, we updated our analysis to calculate conversion of all tillable forage land to fruits and vegetables: the food supply was still insufficient to meet domestic requirements for Vitamins D and B12, and specific fatty acids. In this updated scenario, greenhouse gas emissions (GHGE) increased 13% above current GHGE even without including GHGE from replacing fertilizer and disposing of byproducts. This additional scenario and the amassed literature data collectively suggest that not only would expanding fruit and vegetable production be a notable political, economic, and biological challenge, it would fail to generate a food supply capable of meeting the U.S. populations needs and fail to reduce GHGE. Diet Formulation Additional concerns were raised about failure to consider a variety of diets (1) and continuing “to grow animal feed and incorporate it into human diets” (2