| 英文摘要: | Future food production is highly vulnerable to both climate change and air pollution with implications for global food security1, 2, 3, 4. Climate change adaptation and ozone regulation have been identified as important strategies to safeguard food production5, 6, but little is known about how climate and ozone pollution interact to affect agriculture, nor the relative effectiveness of these two strategies for different crops and regions. Here we present an integrated analysis of the individual and combined effects of 2000–2050 climate change and ozone trends on the production of four major crops (wheat, rice, maize and soybean) worldwide based on historical observations and model projections, specifically accounting for ozone–temperature co-variation. The projections exclude the effect of rising CO2, which has complex and potentially offsetting impacts on global food supply7, 8, 9, 10. We show that warming reduces global crop production by >10% by 2050 with a potential to substantially worsen global malnutrition in all scenarios considered. Ozone trends either exacerbate or offset a substantial fraction of climate impacts depending on the scenario, suggesting the importance of air quality management in agricultural planning. Furthermore, we find that depending on region some crops are primarily sensitive to either ozone (for example, wheat) or heat (for example, maize) alone, providing a measure of relative benefits of climate adaptation versus ozone regulation for food security in different regions. Global demand for food is expected to increase by at least 50% from 2010 to 2050 mainly as a result of population growth and a shift towards a more ‘westernized’ diet in developing regions11. Assuming that agricultural production is able to meet the growing demand through a combination of economic growth and agricultural advancements, undernourishment rates in developing countries are projected to decline substantially11. Future production is, however, sensitive to both climate change and air pollution. Temperature extremes are highly damaging to various major crops1, 2, 5. Surface ozone, formed through the photochemistry of precursor gases mainly arising from human activities, is phytotoxic and detrimental to crop yields4, 12, 13. Climate adaptation and ozone regulation have thus been identified as important measures to tackle food insecurity, but their relative benefits for different crops and regions remain largely uncertain. In this study, we quantify the individual and combined effects of 2000–2050 mean temperature and ozone pollution trends on the global production of wheat, rice, maize and soybean and then on undernourishment rates in developing countries as a necessary input to policy formulation for food security. Figure 1 illustrates a roadmap for our methodology and summarizes our results. First, we use the Community Earth System Model (CESM) to simulate present-day (2000) and derive future (2050) projections of hourly temperature and ozone concentration consistent with the representative concentration pathways (RCPs) represented in the Intergovernmental Panel on Climate Change Fifth Assessment Report14, 15 (AR5). Our future ozone projections not only follow trends in anthropogenic emissions of precursor gases but also include the effects of climate and land use changes; these confounding factors are known to significantly impact future ozone projections16, 17 but are not considered in previous crop impact studies. We consider two scenarios: RCP4.5, representing an intermediate pathway with a global reduction in surface ozone due to pollution control measures worldwide (except in South Asia)14; and RCP8.5, representing a more ‘pessimistic’, energy-intensive pathway with a worldwide increase in ozone except in the US and around Japan18 (Supplementary Fig. 1). The two scenarios represent a range of policy options regarding ozone regulation. Both scenarios project a global increase in surface temperature (Supplementary Fig. 1), with similar effects on crop production as discussed below. Previous historical crop–temperature impact analyses5, 19 suggest a substantial potential for crop-level adaptation to avoid losses from warming, but they do not consider the concurrent impacts of changing ozone levels that may offset the benefits of adaptation12. We therefore exclude adaptation in our projections, and focus on the potential of ozone regulation to combat the warming impacts. Other environmental factors such as water scarcity and land degradation may influence future food production but are outside the scope of this study.
| http://www.nature.com/nclimate/journal/v4/n9/full/nclimate2317.html
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