The World Health Organization (WHO) has warned that climate change will lead to a series of significant health impacts including higher levels of some air pollutants and concomitant increased respiratory disease.

It predicts the spread of malaria, dengue and other infectious diseases as a serious health risk for the whole world and stresses that the compromising of food production and food security in some of the poorer countries will lead to greater malnutrition. And it warns of an increase in extreme weather events such as floods and droughts, with dramatic impacts on the health of people living in coastal communities.

But it’s not just those poorer parts of the world that are at risk.

Depression – which currently costs UK employers something close to £30 billion a year in lost workdays – is also cited by the WHO as the condition that is fast becoming the single biggest threat to human health.

Mental health, says the WHO, can be defined as “a state of well-being enabling individuals to realize their abilities, cope with the normal stresses of life, work productively and fruitfully, and make a contribution to their communities”.

Interesting, then, that those whose definition of good health relates most closely to this one are the tribal peoples whose immense botanical knowledge may also hold the key to surviving the spread of those infectious diseases across the globe.

In Sustaining Life, our special feature on how human health depends on biodiversity, we investigate the forgotten links and discover how we urgently need a brand new definition of health (ecological medicine); how the health sector itself could prove the driving force that shifts the entire economy towards sustainable products and practices; how we will need to protect the land rights of tribal peoples to preserve their knowledge of medicinal plants and how Nature, not antidepressants, may hold the key to tackling the root cause of depression.

Susan Clark is the editor of Resurgence.