Scientists have identified five 'Grand Challenges' that the research community must address if it is to help the world move along the path towards sustainability. The challenges address the tricky question of how to tackle global environmental problems while meeting people's needs for food, water, energy and security. Details of the Grand Challenges, which are the outcome of a consultation run by the International Council for Science (ICSU) and International Social Science Council (ISSC), are published in the journal Science. According to the authors of the Science paper, the world is currently facing two challenges: as well as developing strategies that both respond to global change and meet development goals, we need to deepen our knowledge of the functioning of the Earth system and its critical thresholds, they explain. They add: 'Promoting sustainable development requires research on a wide range of social, economic, cultural, institutional and environmental issues.' To shed light on the barriers to sustainable development, the ICSU and ISSC sought the opinions of scientists young and old from around the world and from the natural and social sciences. They also quizzed people who use research findings. The five Grand Challenges identified in this exercise meet four criteria, namely scientific importance; the need for global coordination; relevance to decision-makers; and leverage (in other words, they would address many problems). The first challenge involves forecasting. Scientists need to improve their ability to anticipate the impacts of human actions on different aspects of the climate system - at both regional and global levels and on different time-scales. Similarly, research is needed to gauge the impacts of environmental changes on economies, food and water supplies, health, biodiversity and energy security. The second challenge concerns the need to improve observation systems used to assess and manage environmental change. The paper laments in particular the fact that economic and social science data are rarely gathered at scales which allow researchers to probe interlinkages between social and natural systems. According to the researchers, this 'undermines the ability of decision-makers and the public to establish appropriate responses to emerging threats and address the needs of vulnerable groups'. 'Determine how to anticipate, avoid, and manage disruptive global environmental change,' reads the third challenge. A key issue here is the identification of 'tipping points' (points beyond which changes are irreversible) in the Earth system. The fourth challenge calls on researchers to 'determine institutional, economic and behavioural changes to enable effective steps toward global sustainability', something which will require greater integration of the social and biophysical sciences. Notably, the researchers point out that, 'we must understand how more effective environmental governance can be established at a time of weakening confidence in traditional forms of governance'. Finally, the fifth challenge highlights the need for innovation in technological, policy and social efforts to achieve global sustainability. 'The challenges are a consensus list of the highest priorities for Earth system research and provide and overarching research framework. If we, the scientific community successfully address these in the next decade, we will remove critical barriers impeding progress toward sustainable development,' commented the lead author of the Science paper, Dr Walt Reid of the David and Lucile Packard Foundation in the US. 'Addressing these challenges will require new research capacity, especially the involvement of young scientists and scientists from developing countries, and a balanced mix of disciplinary and interdisciplinary research that actively involves stakeholders and decision-makers,' he added. Meanwhile the next challenge is to put together a coordinated international funding approach to address the newly identified challenges. This is already happening through the Belmont Forum, an international group of global change research funding agencies. The European Commission's Directorate-General for Research is involved in the group, as are many other national funding agencies.