One Health Week: One Earth, the impacts of climate change

The UK Health Alliance on Climate Change represents over 600,000 health professionals across the UK and advocates for responses to climate change that protect and promote public health.

In September, the UK One Health Co-ordination Group invited Laurie Laybourn-Langton from the Alliance to their meeting. He gave a stimulating talk on the impacts of climate change on human and animal health, and he tells us more about the issue and solutions here.

The issue

Headlines like “We have only twelve years to save the world” appeared across the globe in early October, in the wake of a new report from the United Nations underlining the scale of the challenge posed by climate change.

This wasn’t fake news.

The world has already warmed by around 1°C since large-scale industrialisation began, and at current rates is set to breach a 1.5°C rise by as early as 2030.

The UN Intergovernmental Panel on Climate Change (IPCC) report warns that additional warming could lead to catastrophe, with temperature rises stressing food and water systems, leading to mass migration, social collapse, and conflict. In light of this, it has been argued that ‘climate breakdown’ is a better phrase than climate change.

How does this affect us and our animals?

All health professionals - whether working in human or animal health - should be mindful of the health consequences of reaching a 1.5°C temperature rise.

Climate breakdown impacts health directly and indirectly: directly through, for example, the physical and mental harm inflicted by storms and extreme temperature fluctuations; and indirectly, by eroding the conditions upon which good health can occur, including through increases in malnutrition resulting from crop failure. These negative health impacts will increase in frequency and severity if the temperature rise exceeds 1.5°C.

In addition, we are using up resources at 1.5 times the Earth's capacity to regenerate them. As much as a third of arable land has been lost globally, and rates of soil degradation have reached critical levels, with the UK government warning that parts of the British Isles may only have 30-40 years of soil fertility remaining. 

According to the WWF's last bi-annual Living Planet Index there has been a 58% overall decline in the numbers of fish, mammals, birds and reptiles worldwide since 1970. This extrapolates to a global loss of wildlife at a rate of 2% a year, described by the WWF as the ‘sixth mass extinction’ and is ‘the result of human over-exploitation of resources, pollution and climate change’, all resulting in habitat loss.

A 1.5°C warmer world, also experiencing wider conditions of environmental breakdown, will inevitably place new stresses on relationships between animals and between animals and humans.

Environmental breakdown adds complexity and uncertainty to both human and animal health issues, by impacting upon the emergence or increase of infectious diseases, food and water security and, in the case of animals, the consequences of species loss from food chains resulting in dramatic changes in ecosystem structure.

Long before pathogens were discovered late in the nineteenth century, humans have known that climatic conditions affect epidemic diseases. Roman aristocrats would quite literally run for the hills each summer, retreating to higher resorts to escape the seasonal influx of disease spreading mosquitos.

The effect of climate change globally on zoonotic disease epidemiology - the incidence of diseases that spread from animal to human – is apparent, and animal-human interactions are increasingly considered as potential sources for the emergence of new pathogens and as potential sources of epidemics.

Climate change is likely to be the reason for current changes in infectious disease transmission patterns. Some diseases, such as malaria that were restricted to just tropical areas are now spreading to other once-cooler areas. Pathogens whose migration and habitats are limited by seasonal weather can now, as winters get warmer, annex new places, and affect new vulnerable species.

Species react in different ways to environmental changes. To predict and manage the movement of disease through ecosystems as the Earth’s climate changes, we will require the expertise and knowledge from the fields of veterinary, medical, and public health.

What can we do to help?

Human and animal health professionals will need to encourage and contribute to the achievement of two concurrent objectives.

The first is to stop the problem, by bringing human (and related animal) activity to within sustainable limits in the shortest time possible.

The UN report sets a clear timeline for the climate system. Global carbon emissions must be nearly halved by 2030, reaching net zero by 2050 - net zero being the state of equilibrium where, although there may be a small amount of carbon dioxide being emitted each year to the atmosphere, an equivalent amount is also absorbed and stored.

The voice of the agricultural experts will be important.

A recent report describes livestock consumption and production to be ‘out of balance’, and suggests that farmed livestock numbers already fall outside sustainable limits for Greenhouse Gas (GHG) emissions, nutrient flows and genetic biodiversity loss. At the same time, results of a study reported in Nature have concluded that dietary changes towards healthier diets could reduce the environmental impacts of the food system, if environmentally intensive foods - in particular animal products - were replaced by less intensive plant-based food types.

With many of us consuming far more than the recommended amount of meat advised for good cardiovascular and overall health, the  argument for the adoption of a flexitarian diet is growing – a change that could stem environmental breakdown while making us healthier.

In addition, overuse of fertilisers and antibiotics present additional risks to the health of humans and animals and to the health of the planet. Excess fertiliser can deplete soil quality and result in eutrophication, where nitrates and phosphates enter natural aquatic environments, killing aquatic life forms and enabling over colonisation of oxygen depleting algae. Overuse of antibiotics is thought to be contributing to growing drug resistance in humans and animals with serious health implications.

The second objective human and animal health professionals will need to contribute toward is ensuring continued resilience against climate change. This is because there is a time delay between when humans negatively impact the environment and the consequences of those impacts. Even if it were possible to decarbonise the entire world tomorrow, the Earth’s temperature will still continue to rise.

By supporting the continuation of practices that safeguard our planet, researching and developing new ones and educating those who have the power to implement them, health professionals will be pivotal to this too.

A strong response

In the UK and globally, protecting human and non-human animals and their environments from the effects of climate change, and protecting the very foundations upon which societies can flourish, will need to involve those who understand the biological mechanisms and systems that underpin life.

This approach will not only enable a stronger response to climate change but will also maximise the health co-benefits to all species.

Over the coming years, the Alliance will work closely with colleagues across human and animal health to argue that what’s good for the planet is good for health.

More information

• BVA guidance on AMR
• UK Health Alliance on Climate Change