Many wealthy nations are confronting the health and welfare implications of high unemployment, political instability and eroding social security. Such crises are part of our failure to move sustainability beyond rhetoric — a fact not adequately recognized by the Group of Eight (G8) community. The Rio+20 meeting in Brazil next week must accept that sustainable development and the health of populations depend on each other.

Peak global health may already be here. Low- and middle-income populations endure a double burden from communicable and non-communicable diseases, while health inequity and undernutrition persist. Social and ecological factors such as climate change, energy and food insecurity, counterfeit drugs, antimicrobial and insecticide resistance and poverty all undermine health in our interconnected world.

Many development specialists suggest that health has had its opportunity through the United Nations' Millennium Development Goals, and that the strategic imperative must shift to agriculture or energy. But these are only two legs of the stool: health remains the third.

When sustainability becomes a reality, it will reduce many risks to health. For example, clean energy will eliminate the need to clear forests and use crops for biofuel, so people will be better fed. Improved agricultural practices will reduce exposure to the animal-to-human infections that are associated with land clearing. A green revolution will protect biodiversity by producing more food on land that is already cleared. Better economic, educational and social opportunities in rural areas will slow migration and alleviate the pressure on overloaded urban health resources.