The establishment of ecological public health as crucial to modern public health is overdue. While the basic concepts have been gestating for decades, receptivity within broader public health has been limited. This position is changing, not least as the population-level impacts of climate change and, more broadly, of limits to growth are emerging from theory and forecasting into daily reality. This paper describes several key elements of ecological public health thinking. These include the 'environmental' risks to human health (often systemic and disruptive, rather than local and toxic) posed by climate change and other forms of adverse global environmental change. Closer recognition of the links between social and environmental factors has been urged--an 'eco-social' approach--and, relatedly, for greater co-operation between social and natural sciences. The authors revisit critics of capitalism who foresaw the global capture and transformation of ecosystems for material human ends, and their resultant despoliation. The perennial call within public health to reduce vulnerability by lessening poverty is more important than ever, given the multifactored threat to the health of the poor which is anticipated, assuming no radical strategies to alleviate these pressures. But enhanced health security for the poor requires more than the reconfiguring of social determinants; it also requires, as the overarching frame, ecological public health.