Changes in the global production of major crops are important drivers of food prices, food security and land use decisions. Average global yields for these commodities are determined by the performance of crops in millions of fields distributed across a range of management, soil and climate regimes. Despite the complexity of global food supply, here we show that simple measures of growing season temperatures and precipitation--spatial averages based on the locations of each crop--explain about 30% or more of year-to-year variations in global average yields for the world's six most widely grown crops. For wheat, maize, and barley, there is a clearly negative response of global yields to increased temperatures. Based on these sensitivities and observed climate trends, we estimate that warming since 1981 has resulted in annual combined losses of these three crops representing roughly 40 MT or $5 billion per year, as of 2002. While these impacts are small relative to the technological yield gains over the same period, the results demonstrate already occurring negative impacts of climate trends on crop yields at the global scale.

A concept note about setting up an international program for studying the effects of the emergence of biofuels on global poverty and food security. 

The recent global expansion of biofuels production is an intense topic of discussion in both the popular and academic press. Much of the debate surrounding biofuels has focused on narrow issues of energy efficiency and fossil fuel substitution, to the exclusion of broader questions concerning the effects of large-scale biofuels development on commodity markets, land use patterns, and the global poor. There is reason to think these effects will be very large. The majority of poor people living in chronic hunger are net consumers of staple food crops; poor households spend a large share of their budget on starchy staples; and as a result, price hikes for staple agricultural commodities have the largest impact on poor consumers. For example, the rapidly growing use of corn for ethanol in the U.S. has recently sent corn prices soaring, boosting farmer incomes domestically but causing riots in the streets of Mexico City over tortilla prices. Preliminary analysis suggests that such price movements, which directly threaten hundreds of millions of households around the world, could be more than a passing phenomenon. Rapid biofuels development is occurring throughout the developed and developing world, transforming commodity markets and increasingly linking food prices to a volatile energy sector. Yet there remains little understanding of how these changes will affect global poverty and food security, and an apprehension on the part of many governments as to whether and how to participate in the biofuels revolution.

We propose an international collaborative effort to:

• Understand and quantify the effects of expanding biofuels production on agricultural commodity markets, food security, and poverty;
• Develop training programs and policy tools to harness the benefits and mitigate the damages from such expansion on both local and global scales; and
• Build an international network of scholars and government officials devoted to studying and managing biofuels development and its social consequences

In this paper we are pursuing the following objectives:

1. document the existing water management institutional forms throughout China, their evolution over time and across provinces;
2. describe the actors and their roles and other governance issues in WUAs and compare them to traditional collectively managed irrigation systems and other types of reform-oriented irrigation institutions (especially contracting);
3. analyze the determinants of the emergence of these institutions throughout China in order to understand the role of scarcity of water resources; the size of the community's irrigation system, policy and other village characteristics in their emergence.

To meet these objectives, the rest of the paper is organized as follows.

First, we will discuss the dilemma of China's surface water policy. Because of the nature of China's farming practices - since almost all of China's agriculture is based smallholders who farm small, dispersed plots, it is hard to use water pricing policy in surface water areas. This makes irrigation management reform important and it is with this motivation that we launch our study of WUAs and other water management reforms, their governance and determinants.

In the second section we discuss the data. In the following two sections, the spread of WUAs, their governance and their other characteristics are examined - first descriptively and then with multivariate analysis. The final section concludes.

The dramatic transition from Communism to market economies across Asia and Europe started in the Chinese countryside in the 1970s. Since then more than a billion of people, many of them very poor, have been affected by radical reforms in agriculture. However, there are enormous differences in the reform strategies that countries have chosen. This paper presents a set of arguments to explain why countries have chosen different reform policies.

In a book assessing the development of China during the People's Republic era, it is of interest to know how well agriculture has performed and the role that it has played in the development process. Has China produced food and other commodities that have contributed to China's growth? Has it been successful supplying labor to the off farm sector? How has agriculture contributed to the rise in rural incomes and growth, in general? In short, one of the overall goals of this chapter is to document the performance of the agricultural sector and use the criteria of Johnston and Mellor to assess how well the agricultural sector has done.

This chapter, however, seeks to go further than describing the achievements and shortfalls of China's agricultural economy; we also aim to identify the factors, both domestic policies and economic events as well as foreign initiatives, that have induced the performance that we observe. To create an agricultural economy that can feed the population, supply industry with labor and raw materials, earn foreign exchange and produce income for those the live and work in the sector and allow them to be a part of the nation's structural transformation requires a combination of massive investments and well-managed policy effort. The process can only proceed smoothly if an environment is created within which producers can generate output efficiently and earn a profit that can contribute to household income. Policies are required to facilitate the development of markets or other effective institutions of exchange. Although the sector is expected to contribute to the nation's development and allow for substantial extractions of labor and other resources, large volumes of investment also are needed. Investment in education, training, health and social services are needed to increase the productivity of the labor force when they arrive in the factories. Investment is needed in agriculture to improve productivity to keep food prices low, allow farmers to adopt new technologies and farming practice as markets change, and to raise incomes of those that are still in farming. Investment is needed in technology, land, water and other key inputs that are in short supply. In this chapter we seek to point out both policies that have facilitated the performance of the agricultural sector and those that have constrained it.