Climate change as a result of human activity represents a huge threat to population health and to the planet and a huge opportunity to improve health – both human and planetary – if we act together.

Most people do not think about climate change and human health as being related, unless it is in the most obvious, linear sense – for example, the injuries and illnesses which invariably follow after a Category Six hurricane makes landfall and stays there. We, as a society, need to accept that this linear connection is only one facet of what is in fact a complex and intersectional relationship between interdependent variables – health and the planet.

We cannot have human health if we do not have a healthy planet. Planet Earth has been sending us increasingly strong signals for decades. We must open our eyes, minds and hearts to the signs – climate change, unprecedented heat and fires, epidemic zoonotic diseases like Ebola, Zika and COVID, mega hurricanes, floods, ocean acidification, and de-speciation – to name a few. It is clear that these phenomena can all directly and negatively affect human health, but what has yet to be considered is that it is our lack of care for our health – and thereby the planet’s health – that has led to some of these phenomena happening in the first place.

The continuous pumping of the by-products of ‘civilisation’ into the atmosphere have led not only to an increase in global temperatures, but also to human illness and death. Once temperatures have increased, climate change follows, bringing with it the threats of rising sea levels, bomb cyclones and uncontrollable wildfires, and as these phenomena unfold, all life on Earth will suffer.

COVID-19, NCDs and climate change are inter-linked symptoms of planetary ill-health. From a planetary health perspective, the COVID-19 pandemic is a serious wake-up call of more than one kind. The virus originated from a forest animal – as have other viruses – exposed and forced into areas it would naturally avoid, by deforestation, human encroachment and environmental degradation. If we continue to treat our forests and wildlife in this way, more viruses will emerge and cause further havoc so that surveillance and rapid, coordinated responses to new diseases become necessary, as well as the regulation of deforestation, and wildlife/wildmeat sales and trade. We may even end up with diseases more devastating to human health than COVID-19.

COVID-19 is having such a severe impact on population health because the current human population – a product of our genetics and how our societies are fed and organised – is ‘unfit’ to face the virus, given widespread inactivity, obesity, noncommunicable diseases (NCDs), hypertension, diabetes, air pollution, tobacco use, and lack of access to quality health care. Unsurprisingly, having pre-existing health conditions including those mentioned previously makes the risk of having serious complications associated with COVD-19 much more likely. As the disease continues to spread around the globe, it is becoming clearer that even those who are young with no pre-existing conditions can experience life-threatening cases of the virus. The rapid and devastating spread of COVID-19 has revealed that we need a healthy planet to have healthy societies and healthy populations.

Human disregard for their own health is also a disregard for the health of their planet, and that disregard is the first step in a vicious, self-perpetuating cycle.