Healthy planet, healthy people? The intersection between biodiversity and human health
Hilary Allison, head of our Ecosystem Assessment and Policy Support Programme, walks us through how we rely upon, and are affected by, the natural world.
When we think of improving human health we tend to think of improved access to medical services, the development of new drugs, and improved diets — not the quality of the natural world around us and the biodiversity it contains.
This is in part because while biodiversity has been in decline for decades, global measures of human health such as life expectancy and child mortality have been steadily improving. There’s also the fact that many of the health issues that increasingly blight the developed and developing world are non-communicable diseases such as coronary heart disease, born from increasingly sedentary lifestyles, obesity and diet, rather than vector-borne diseases from the natural environment. So, no link, right?
Well, the truth is it’s all a bit more complicated. Two landmark reports in 2015, The Lancet Commission on Planetary Health and the Convention on Biological Diversity/World Health Organisation State of Knowledge Review on Biodiversity and Health, showed that the natural world impacts on our health in many and often complex ways. No one is immune from its effects, both positive and negative.
Let’s take a look at some of the positives. The Japanese have long practised “shinrun-yoku,” an immersive experience of being in and at one with nature that literally translates as ‘forest bathing,’ as a form of relaxation and relieving stress. There are also many recently published reviews of literature summarising how the quality of urban environments, including the existence of green spaces as places for physical recreation and the role of urban trees as air filters, can improve both physical health but also mental wellbeing.
A more directly obvious benefit of biodiversity for human health is the role of plants for medicinal use — more than 28,000 species of plants have medicinal properties. Even the diversity of our own human microbial gut and skin flora plays a role in our health; changes and reductions to these have been associated with various inflammatory conditions.
But there are also more complex relationships between human health and wildlife. Some emerging infectious diseases, called ‘zoonotic diseases,’ are passed to humans from animals or insects, and these may be made even worse by human-induced changes in land use. Many of these, such as Ebola or bird flu, have made global headlines.
Direct infection from wildlife, however, excluding vectors such as mosquitoes, ticks, is still thankfully relatively rare (though that may well change as climate change makes more places suitable breeding grounds). At the moment domesticated animals not only carry more zoonotic pathogens than wildlife, but they also potentially transmit pathogens to a greater diversity of other host species.
It is of course possible to control some diseases, but these control measures can often themselves harm biodiversity through drastic ecosystem modification. Malaria, for example, can be reduced by draining water bodies where mosquitoes and other disease vectors breed. Similarly, application of insecticides can have adverse effects on local biodiversity.
So the picture is complex — biodiversity affects human health both positively and negatively and may itself be affected by disease control measures. But these relationships are becoming increasingly clear — and the emerging planetary health movement recognises that:
“the continuing degradation of natural systems threatens to reverse the health gains seen over the last century. In short, we have mortgaged the health of future generations to realise economic and development gains in the present.”
Discussions about the development of a post-2020 framework for biodiversity are now beginning to call for the recognition of this interdependency, and in fact I was lucky enough to be on a panel on that very subject at the recent UN Biodiversity Conference’s Health Day.
For this to happen it will be crucial to create meaningful measures which can expressly show how human health and biodiversity relate to each other as recommended by a UN Interagency Group on Biodiversity and Health. We at UNEP-WCMC, with our experience in the creation and development of biodiversity indicators are keen to take a leading role in this work. We look forward to this challenge.
