Roughly a billion people around the world continue to live in state of chronic hunger and food insecurity. Unfortunately, efforts to improve their livelihoods must now unfold in the context of a rapidly changing climate, in which warming temperatures and changing rainfall regimes could threaten the basic productivity of the agricultural systems on which most of the world's poor directly depend. But whether climate change represents a minor impediment or an existential threat to development is an area of substantial controversy, with different conclusions wrought from different methodologies and based on different data.

This book aims to resolve some of the controversy by exploring and comparing the different methodologies and data that scientists use to understand climate's effects on food security. It explains the nature of the climate threat, the ways in which crops and farmers might respond, and the potential role for public and private investment to help agriculture adapt to a warmer world. This broader understanding should prove useful to both scientists charged with quantifying climate threats, and policy-makers responsible for crucial decisions about how to respond. The book is especially suitable as a companion to an interdisciplinary undergraduate or graduate level class.

As efforts to mitigate climate change increase, there is a need to identify cost-effective ways to avoid emissions of greenhouse gases (GHGs). Agriculture is rightly recognized as a source of considerable emissions, with concomitant opportunities for mitigation. Although future agricultural productivity is critical, as it will shape emissions from conversion of native landscapes to food and biofuel crops, investment in agricultural research is rarely mentioned as a mitigation strategy. Here we estimate the net effect on GHG emissions of historical agricultural intensification between 1961 and 2005. We find that while emissions from factors such as fertilizer production and application have increased, the net effect of higher yields has avoided emissions of up to 161 gigatons of carbon (GtC) (590 GtCO2e) since 1961. We estimate that each dollar invested in agricultural yields has resulted in 68 fewer kgC (249 kgCO2e) emissions relative to 1961 technology ($14.74/tC, or ~$4/tCO2e), avoiding 3.6 GtC (13.1 GtCO2e) per year. Our analysis indicates that investment in yield improvements compares favorably with other commonly proposed mitigation strategies. Further yield improvements should therefore be prominent among efforts to reduce future GHG emissions.

Although China and the United States are the two largest emitters of greenhouse gases, China’s emissions on a per capita basis are significantly lower than those of the U.S.: in 2005, per capita emissions in China were 5.5 metric tons—much less than the U.S. (23.5 metric tons per capita), and also lower than the world average of 7.03 metric tons. China’s total GHG emissions were 7,234.3 million tons of CO2 equivalent (tCO2e) in 2005, 15.4 percent of which came from the agricultural sector. By comparison, total U.S. emissions were 6,931.4 million tCO2e, 6.4 percent of which were from agriculture. Within China’s agriculture sector, 54.5 percent of emissions come from nitrous oxide, and 45.5 percent come from methane, which is the opposite of the composition of global GHG emissions from agriculture.

Economic studies show that climate change will affect not only agricultural production, but also agricultural prices, trade and food self-sufficiency. The research presented here indicates that producer responses to these climate- induced shocks will lessen the impacts of climate change on agricultural production compared to the effects predicted by many natural scientists. This study projects the impacts of climate change on China’s agricultural sector under the A2 scenario developed by the Intergovernmental Panel on Climate Change (IPCC), which assumes a heterogeneous world with continuous population growth and regionally-oriented economic growth. Depending on the assumptions used related to CO2 fertilization, in 2030 the projected impacts of climate change on grain production range from -4 percent to +6 percent, and the effects on crop prices range from -12 percent to +18 percent. The change in relative prices in domestic and international markets will in turn impact trade flows of all commodities. The magnitude of the impact on grain trade in China will equal about 2 to 3 percent of domestic consumption. According to our analysis, trade can and should be used to help China mitigate the impacts of climate change; however, the overall impact on China’s grain self-sufficiency is moderate because the changes in trade account for only a small share of China’s total demand.

The effect of climate change on rural incomes in China is complicated. The analysis shows that the average impact of higher temperatures on crop net revenue is negative, but this can be partially offset by income gains resulting from an expected increase in precipitation. Moreover, the effects of climate change on farmers will vary depending on the production methods used. Rain-fed farmers will be more vulnerable to temperature increases than irrigated farmers, and the impact of climate change on crop net revenue varies by season and by region.

In recent years, China has made tangible progress on the implementation of adaptation strategies in the agricultural sector. Efforts have been made to increase public investment in climate change research, and special funding has been allocated to adaptation issues. An experiment with insurance policies and increased public investment in research are just two examples of climate adaptation measures. Beyond government initiatives, farmers have implemented their own adaptation strategies, such as changing cropping patterns, increasing investment in irrigation infrastructure, using water saving technologies and planting new crop varieties to increase resistance to climatic shocks.

China faces several challenges, however, as it seeks to reduce emissions and adapt to climate change. Fertilizers are a major component of nitrous oxide emissions, and recent studies indicate that overuse of fertilizer has become a significant contributor to water pollution. Application rates in China are well above world averages for many crops; fields are so saturated with fertilizer that nutrients are lost because crops cannot absorb any more. Changing fertilizer application practices will be no easy task. Many farmers also work outside of agriculture to supplement their income and opt for current methods because they are less time intensive.

In addition, the expansion of irrigated cropland has contributed to the depletion of China’s water table and rivers, particularly in areas of northern China. Water scarcity is increasing and will constrain climate change mitigation strategies for some farmers. One of the main policy/research issues—as well as challenges for farm households—will be to determine how to increase water use efficiency.

Despite the sizeable amount of greenhouse gases emitted by and the environmental impact of China’s agriculture sector, it also offers important and efficient mitigation opportunities. To combat low fertilizer use efficiency in China, the government in recent years has begun promoting technology aimed at calibrating fertilizer dosages according to the characteristics of soil. In addition, conservation tillage (CT) has been considered as a potential way to create carbon sinks. Over the last decade, China’s government has promoted the adoption of CT and established demonstration pilot projects in more than 10 provinces. Finally, extending intermittent irrigation and adopting new seed varieties for paddy fields are also strategies that have been supported and promoted as part of the effort to reduce GHG emissions.

In June 2009, a group of experts in climate science, crop modeling, and crop development gathered at Stanford University to discuss the major needs for successful crop adaptation to climate change. To focus discussion over the three day period, the meeting centered on just three major crops – rice, wheat, and maize – given that these provide the bulk of calories to most populations. The meeting also focused on two aspects of climate– extreme high temperatures and extreme low moisture conditions (i.e. drought) – that present substantial challenges to crops in current climate and are likely to become more prevalent through time. Other aspects of climate change such as more frequent flooding or saltwater intrusion associated with rising sea levels were not addressed, although they may also be important.

The current document is split into two sections:

• a brief summary of material presented at the meeting on the current state of climate projections, crop modeling, crop genetic resources and breeding; and
  
• the collective views of participants on major needs for future research and investment, which emerged from discussions over the three day meeting.
  

The main target audiences for the document are donor institutions seeking to invest in climate adaptation, and climate and crop scientists seeking to set research agendas. We intend the term donor institutions to include private foundations, governments, and inter‐governmental organizations such as the World Bank and United Nations. An underlying assumption of the Stanford meeting was that there is a real and growing need to identify specific investment opportunities that will improve food security in the face of climate change. This is reflected, for instance, by the recent G8 announcement of a $20B investment in food security, the expectation of additional resources for adaptation from the Copenhagen Conference in 2009, and the emphasis of the Obama administration on food and climate issues.