Environment and development. Earth system science for global sustainability: grand challenges.

916 POLICYFORUM T remendous progress has been made in understanding the functioning of the Earth system and, in particular, the impact of human actions (1). Although this knowledge can inform management of spe-cifi c features of our world in transition, societies need knowledge that will allow them to simultaneously reduce global environmental risks while also meeting economic development goals. For example, how can we advance science and technology, change human behavior, and infl uence political will to enable societies to meet targets for reductions in greenhouse gas emissions to avoid dangerous climate change? At the same time, how can we meet needs for food, water, improved health and human security, and enhanced energy security? Can this be done while also meeting the United Nations Millennium Development Goals of eradicating extreme poverty and hunger and ensuring ecosystem integrity? Answering these questions will require reorientation toward new research that better allows science and society to address the needs of decision-makers and citizens at global, regional, national, and local scales (2). We will have to meet a twofold challenge: (i) develop strategies to respond to ongoing global change while meeting development goals and (ii) deepen knowledge of the functioning of the Earth system and its critical thresholds (3). Promoting sustainable development requires research on a wide range of social, economic, cultural, institutional, and environmental issues (4). Given that sustainable development is no longer possible without addressing interactions with global change dynamics (5), we focus here on an important dimension of this larger sustainability agenda: the need to broaden and deepen Earth system research to encompass the intersection of global environmental change and sustainable development. A great deal of collaborative international research on global environmental change is coordinated through four Global Environmental Change Research Programmes (6) and the Earth System Science Partnership. In light of the need for an overarching set of solution-focused and integrated research priorities for these institutions, the International Council for Science (ICSU) and the International Social Science Council (ISSC) carried out a consultative process to rethink the focus and framework of Earth system research (7, 8). Efforts were made to obtain balanced input from developed and developing country experts, young and senior scientists, social and natural sciences, and both researchers and those using the fi ndings of research. This process resulted in fi ve " Grand Challenges " (listed below in italics), a consensus list of the highest priorities for …