Climate change is expected to affect water resources, with implications for both natural ecosystems and human food security. Nature Climate Change and Nature Geoscience are jointly presenting 'Water in a warming world', a collection of articles highlighting many of the key issues in this important area of climate change research; the focus will be available from Monday 3 December at http://www.nature.com/nclimate/focus/water-warm-world/index.html. Here we highlight some of the new content to be included from this journal.

Complacency over water availability is misguided. We need hardly emphasize the primary importance of water for life, including our own, but in addition to drinking water and other domestic requirements vast amounts of freshwater are needed for agriculture and industry, as well as in power generation, so disruptions to supply can be economically crippling. At an international level, disputes over water resources are likely to intensify with human population growth — and climate change could exacerbate such tensions.

Among the most damaging natural disasters are droughts. Aiguo Dai of the United States' National Center for Atmospheric Research in Boulder, Colorado, shows that observed changes in global aridity since 1923 are broadly consistent with Earth-system model simulations (http://go.nature.com/dQEws7). These models suggest that widespread droughts will increase in the coming decades over many land areas.

North America's Rocky Mountains are a source-water region for over 60 million people. They are also famous for their lodgepole pine forests. However, climate change has made these forests more prone to pest outbreak, and around four million acres of forest have been affected by an ongoing bark-beetle epidemic. Kristen Mikkelson of the Colorado School of Mines and her collaborators report that large-scale tree die-off can detrimentally affect water quality (http://go.nature.com/oQbE3w), potentially affecting water availability to millions.

Groundwater represents the largest source of distributed freshwater on Earth. International scientists led by Richard Taylor of University College London, UK, review recent research assessing climate impacts on groundwater as well as groundwater–climate feedbacks (http://go.nature.com/uKsxFF). Based on their analysis, they identify the need for systematic groundwater observations, and emphasize both the importance of managing groundwater sustainably and its strategic significance for climate adaptation.

Meanwhile, a team led by Quentin Grafton of The Australian National University examines the health of four major world rivers — the Colorado River in the United States, the Murray River in Australia, the Orange River in South Africa and the Yellow River in China (http://go.nature.com/qHyryL). All have suffered as a result of water use, climate variability and change. The researchers find that increased water extraction has severely compromised environmental flows and ecological function for all four rivers, and consider changes in management thinking aimed at achieving a better balance between water consumption and river health.

Finally, in an interview (http://go.nature.com/uGOqYC) Pavel Kabat, Director of the Austria-based International Institute of Applied System Analysis, explains the importance of the system analysis approach for identifying potential synergies among different water users, as is necessary for improved water management in the context of climate change adaptation.