Changing Food Systems

Fishery CatchGlobal environmental change – particularly climate change, pollinator declines, fishery and wildlife declines, water shortages, and other forms of environmental processes – will pervasively affect our food systems and the ability to provide a growing human population with enough quality nutrition. Research is needed to understand how multiple interacting types of environmental change impact the quantity and quality of food available to different populations around the world. Another important priority is to understand how accelerating changes and losses to many wild and indigenous foods are likely to alter nutritional intake for different populations and affect their health.

Learning Objectives

  • L1: Identify the direct and indirect drivers of changes in food systems.
  • L2: Evaluate systems of food production in the context of accelerating environmental change.
  • L3: Identify factors in the food system that influence upstream and downstream outcomes in food production, distribution, consumption, and human health.
  • L4: Consider the impacts of changes in food systems on human health and how this may change over time.



Branch TA, DeJoseph BM, Ray LJ, Wagner CA. Impacts of ocean acidification on marine seafood. Trends in Ecology and Evolution [Internet]. 2013;28 (3) :178-186. Publisher's VersionAbstract

Ocean acidification is a series of chemical reactions due to increased CO2 emissions. The resulting lower pH impairs the senses of reef fishes and reduces their survival, and might similarly impact commercially targeted fishes that produce most of the seafood eaten by humans. Shelled molluscs will also be negatively affected, whereas cephalopods and crustaceans will remain largely unscathed. Habitat changes will reduce seafood production from coral reefs, but increase production from seagrass and seaweed. Overall effects of ocean acidification on primary productivity and, hence, on food webs will result in hard-to-predict winners and losers. Although adaptation, parental effects, and evolution can mitigate some effects of ocean acidification, future seafood platters will look rather different unless CO2 emissions are curbed.


Avnery S, Mauzerall DL, Liu JF, Horowitz LW. Global crop yield reductions due to surface ozone exposure: 1 year 2000 crop production losses and economic damage. Atmospheric Environment [Internet]. 2011;45 :2284-2296. Publisher's VersionAbstract

Exposure to elevated concentrations of surface ozone (O3) causes substantial reductions in the agricultural yields of many crops. As emissions of O3 precursors rise in many parts of the world over the next few decades, yield reductions from O3 exposure appear likely to increase the challenges of feeding a global population projected to grow from 6 to 9 billion between 2000 and 2050. This study estimates year 2000 global yield reductions of three key staple crops (soybean, maize, and wheat) due to surface ozone exposure using hourly O3 concentrations simulated by the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2). We calculate crop losses according to two metrics of ozone exposure e seasonal daytime (08:00e19:59) mean O3 (M12) and accumulated O3 above a threshold of 40 ppbv (AOT40) e and predict crop yield losses using crop-specific O3 concentration:response functions established by field studies. Our results indicate that year 2000 O3-induced global yield reductions ranged, depending on the metric used, from 8.5e14% for soybean, 3.9e15% for wheat, and 2.2e5.5% for maize. Global crop production losses totaled 79e121 million metric tons, worth $11e18 billion annually (USD2000). Our calculated yield reductions agree well with previous estimates, providing further evidence that yields of major crops across the globe are already being substantially reduced by exposure to surface ozone e a risk that will grow unless O3-precursor emissions are curbed in the future or crop cultivars are developed and utilized that are resistant to O3.

Fangmeier A, Grüters U, Högy P, Vermehren B, Jäger H-J. Effects of elevated CO2, nitrogen supply and tropospheric ozone on spring wheat – II. Nutrients (N, P, K, S, Ca, Mg, Fe, Mn, Zn). Environmental Pollution [Internet]. 1997;96 :43-59. Publisher's VersionAbstract

CO(2) enrichment is expected to alter leaf demand for nitrogen and phosphorus in plant species with C(3) carbon dioxide fixation pathway, thus possibly causing nutrient imbalances in the tissues and disturbance of distribution and redistribution patterns within the plants. To test the influence of CO(2) enrichment and elevated tropospheric ozone in combination with different nitrogen supply, spring wheat (Tritium aestivum L. cv. Minaret) was exposed to three levels of CO(2) (361, 523, and 639 microl litre(-1), 24 h mean from sowing to final harvest), two levels of ozone (28.4 and 51.3 nl litre(-1)) and two levels of nitrogen supply (150 and 270 kg ha(-1)) in a full-factorial design in open-top field chambers. Additional fertilization experiments (120, 210, and 330 kg N ha(-1)) were carried out at low and high CO(2) levels. Macronutrients (N, P, K, S, Ca, Mg) and three micronutrients (Mn, Fe, Zn) were analysed in samples obtained at three different developmental stages: beginning of shoot elongation, anthesis, and ripening. At each harvest, plant samples were separated into different organs (green and senescent leaves, stem sections, ears, grains). According to analyses of tissue concentrations at the beginning of shoot elongation, the plants were sufficiently equipped with nutrients. Elevated ozone levels neither affected tissue concentrations nor shoot uptake of the nutrients. CO(2) and nitrogen treatments affected nutrient uptake, distribution and redistribution in a complex manner. CO(2) enrichment increased nitrogen-use efficiency and caused a lower demand for nitrogen in green tissues which was reflected in a decrease of critical nitrogen concentrations, lower leaf nitrogen concentrations and lower nitrogen pools in the leaves. Since grain nitrogen uptake during grain filling depended completely on redistribution from vegetative pools in green tissues, grain nitrogen concentrations fell considerably with severe implications for grain quality. Ca, S, Mg and Zn in green tissues were influenced by CO(2) enrichment in a similar manner to nitrogen. Phosphorus concentrations in green tissues, on the other hand, were not, or only slightly, affected by elevated CO(2). In stems, 'dilution' of all nutrients except manganese was observed, caused by the huge accumulation of water soluble carbohydrates, mainly fructans, in these tissues under CO(2) enrichment. Whole shoot uptake was either remarkably increased (K, Mn, P, Mg), nearly unaffected (N, S, Fe, Zn) or decreased (Ca) under CO(2) enrichment. Thus, nutrient cycling in plant-soil systems is expected to be altered under CO(2) enrichment.

Lever JJ, van Nes EH, Scheffer M, Bascompte J. The sudden collapse of pollinator communities. Ecology Letters [Internet]. 2014;17 :350-359. Publisher's VersionAbstract

Declines in pollinator populations may harm biodiversity and agricultural productivity. Little attention has, however, been paid to the systemic response of mutualistic communities to global environmental change. Using a modelling approach and merging network theory with theory on critical transitions, we show that the scale and nature of critical transitions is likely to be influenced by the architecture of mutualistic networks. Specifically, we show that pollinator populations may collapse suddenly once drivers of pollinator decline reach a critical point. A high connectance and/or nestedness of the mutualistic network increases the capacity of pollinator populations to persist under harsh conditions. However, once a tipping point is reached, pollinator populations collapse simultaneously. Recovering from this single community-wide collapse requires a relatively large improvement of conditions. These findings may have large implications for our view on the sustainability of pollinator communities and the services they provide.

Schneider SH, Semenov S, Patwardhan A. Assessing key vulnerabilities and the risk from climate change. In: Parry, M L, Canziani, O F, Palutikof, J P, Van der Linden, P J, Hanson, C E Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press ; 2007. Publisher's Version
Davis DR, Epp MD, Riordan HD. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. Journal Of The American College Of Nutrition [Internet]. 2004;23 :669-682. Publisher's VersionAbstract


To evaluate possible changes in USDA nutrient content data for 43 garden crops between 1950 and 1999 and consider their potential causes.


We compare USDA nutrient content data published in 1950 and 1999 for 13 nutrients and water in 43 garden crops, mostly vegetables. After adjusting for differences in moisture content, we calculate ratios of nutrient contents, R (1999/1950), for each food and nutrient. To evaluate the foods as a group, we calculate median and geometric mean R-values for the 13 nutrients and water. To evaluate R-values for individual foods and nutrients, with hypothetical confidence intervals, we use USDA's standard errors (SEs) of the 1999 values, from which we generate 2 estimates for the SEs of the 1950 values.


As a group, the 43 foods show apparent, statistically reliable declines (R < 1) for 6 nutrients (protein, Ca, P, Fe, riboflavin and ascorbic acid), but no statistically reliable changes for 7 other nutrients. Declines in the medians range from 6% for protein to 38% for riboflavin. When evaluated for individual foods and nutrients, R-values are usually not distinguishable from 1 with current data. Depending on whether we use low or high estimates of the 1950 SEs, respectively 33% or 20% of the apparent R-values differ reliably from 1. Significantly, about 28% of these R-values exceed 1.


We suggest that any real declines are generally most easily explained by changes in cultivated varieties between 1950 and 1999, in which there may be trade-offs between yield and nutrient content.