Excerpt from a lecture entitled Climate change and health: preparing for unprecedented challenges, presented by Dr. Margaret Chan, Director-General of the World Health Organization, in Bethesda, Maryland on December 10
As the climate scientists tell us, even if greenhouse gas emissions were to stop today, the consequences will be felt throughout this century. In the language of the scientists, human activities have committed this planet to climate change. The emphasis now is on the ability of our human species to adapt to changes that have become inevitable.
The warming of the planet will be gradual, but the increasing frequency and severity of extreme weather events – intense storms, heat waves, droughts, and floods – will be abrupt and the consequences will be acutely felt.
The health sector must add its voice – loud and clear – to the growing concern. Just as we fought so long to secure a high profile for health on the development agenda, we must now fight to place health issues at the centre of the climate agenda. We have compelling reasons for doing so. Climate change will affect, in profoundly adverse ways, some of the most fundamental determinants of health: food, air, water.
This is the reality that concerns me the most. Developing countries will be the first and hardest hit. Subsistence agriculture will suffer the most. Areas with weak health infrastructures will be the least able to cope.
Imagine the impact on health in areas where the food supply is already precarious, rural areas are populated with subsistence farmers and the capacity to cope with any emergency is already fragile.
Imagine the situation in cities, when water scarcity combines with heat stress and air pollution. We already have good evidence linking such conditions to increased deaths from respiratory and cardiovascular disease, especially in the elderly.
As the scientists tell us, the nature of climate change during this century is likely to go beyond human experience. But public health has abundant experience as a basis for interpreting the health consequences and understanding their impact. Public health has decades of experience in dealing with problems that will be made bigger and broader by climate change.
Ladies and gentlemen,
When I announced to my staff that I had selected climate change as the theme for next year’s World Health Day, I described climate change as the defining issue for public health during this century.
Let me take this statement one step further today. I have given my impressions about the public health landscape of today, the difficult challenges we face, but also the many reasons for unprecedented optimism.
I believe that climate change will ride across this landscape as the fifth horseman. It will increase the power of the four horsemen that rule over war, famine, pestilence, and death – those ancient adversaries that have affected health and human progress since the beginning of recorded history. Research already has a great deal to say about the impact of climate change on famine and pestilence.
Let us consider famine, hunger, food security, and malnutrition. In many parts of the world, the severe adverse effects of climate change – one could say, the catastrophic effects – are not expected to be felt until around the middle of this century or even later.
Not so for Africa. According to the latest projections, Africa will be severely affected as early as 2020. This is just a dozen years away. By that date, increased water stress is expected to affect from 75 million to 250 million Africans. A dozen years from now, crop yields in some countries are expected to drop by 50%.
Imagine the impact on food security and malnutrition. In many African countries, agriculture remains the principal economic activity, and agricultural products are the principal source of export trade. Vast rural populations survive, hand-to-mouth, on subsistence farming. There is no surplus. There is no coping capacity. Yes, as I said, these are catastrophic effects.
Concerning pestilence, abundant evidence links the distribution and behaviour of infectious diseases to climate and weather. As the scientists say, climate defines the geographical distribution of infectious diseases. Weather influences the timing and severity of epidemics.
Diseases transmitted by mosquitoes are particularly sensitive to variations in climate. Warmth accelerates the biting rate of mosquitoes and speeds up maturation of the parasites they carry. Sub-Saharan Africa is already home to the most severe form of malaria and the most efficient mosquito species. What will happen if rising temperatures accelerate the lifecycle of the malaria parasite? What if malaria spreads to new areas?
NIH funded the landmark study that demonstrated a link between climate variability and increased malaria epidemics in the highlands of East Africa. We all know about the explosive epidemic potential of malaria when this disease reaches non-immune populations. Though we are making progress, we are still not able, right now, to achieve adequate population coverage with preventive interventions in areas of stable malaria transmission.
The landmark publication on microbial threats, issued in 1992 by the Institute of Medicine, opened the eyes of the world to the growing menace of emerging diseases. It also showed how changes in the way humanity inhabits this planet have created abundant opportunities for microbes to exploit.
It is easy to see how climate change will increase these opportunities in significant ways. When we consider the effects of climate change on emerging diseases, we are looking at disruptions to intricately balanced ecological systems that reached equilibrium following centuries of evolution. Nature gives us every reason to believe that disruption of this delicate equilibrium will have profound consequences.