The COVID pandemic and climate change are underpinned by international trade and travel that is powered by fossil fuels and the drastic changes in land use, where complex and varied habitats are razed to make way for the monocultures that feed the world. 

Addressing the land use change and our food system could offer a win-win solution that helps to reduce greenhouse gas emissions while preventing new and re-emerging viruses from spiralling into global pandemics, argues ecological pioneer Serge Morand. Morand is currently a research director at the French National Centre for Scientific Research (CNRS) and an associate researcher at the French Agricultural Research Centre for International Development (CIRAD) at Montpellier University as well as a member of the One Health High-Level Expert Panel set up by a quadripartite alliance formed by the Food and Agriculture Organisation, United Nations (UN) Environment Programme, World Health Organisation and World Organisation for Animal Health. Morand, who has a special interest in Southeast Asia where he holds several adjunct and consulting appointments, investigates the connections between biodiversity and health in the face of planetary changes.

MEDICUS speaks with him about the solutions ecologists can contribute to help prevent the next outbreak from spiralling into a pandemic while combatting the effects of global warming and climate change.

Here are the highlights from our extensive conversation:

MEDICUS: Thank you for joining us. It’s been nearly three years since COVID erupted. While it was the most recent and acutely felt pandemic, it is by far not the only one. From your perspective as an ecologist, what are some of the drivers behind the rise in outbreaks?

Serge Morand: When we look at the relationship between biodiversity and the diversity of infectious diseases in the world, including parasitic diseases, we see a clear positive correlation between the number of known infectious diseases in a country and its biodiversity. And this is to be expected because infectious and parasitic diseases are caused by microbes and parasites that are hosted in reservoirs which are most of the time wild animals and vectors like mosquitoes, that are all part of the biodiversity.

But as we all know, we are rapidly losing biodiversity. Indicators like the IUCN Red List demonstrate a clear increase in the number of species listed as at risk of extinction. So you could assume that as we lose species, we’d have fewer infectious diseases. Yet, when we look at the data for the last 20 years or so, we observe an increasing number of outbreaks of zoonotic diseases, of vector-borne diseases and even outbreaks in domestic animals and wildlife.

So rather than looking at the diversity of the diseases, we need to look at the number of outbreaks and how that is related not to biodiversity itself, but to the biodiversity at risk of extinction. After controlling for the known diseases and known biodiversity in a country, the relative number of outbreaks nicely correlates with the relative number of wildlife species at risk. When we lose biodiversity then, we are losing something like the regulation of the transmission of diseases. So that’s why we are starting to see this abnormal, enhanced transmission, especially transmission to humans but also domestic animals. Of course, this is only a correlation. So what are the ecological mechanisms at play?

When you lose biodiversity, when you lose species, usually you start by losing predators, especially the big predators. And the predators control the reservoirs, they control the vectors.

Secondly, we see a simplification of habitats largely due to land use change. When that happens, you lose the specialist species from those habitats that are very competitive against the generalist species. So you are starting to increase the generalist species and these species are what we call syntrophic species, and are the ones that thrive around humans. For example, rodents like rats and vectors like Anopheles and Aedes mosquitoes. They increase in density, in abundance and, of course, they are very good reservoirs or vectors for infectious diseases and can spread them to humans.

Some people call this the dilution effect, but I don’t like this term because it doesn’t explain the mechanism behind the pattern. The most important aspect of biodiversity is regulation. It is this loss of regulation—that means some species grow out of control and with them, the pathogen transmission also goes out of control.

MEDICUS: But you could also argue that what has made outbreaks so deadly is the rise in international trade and travel, which have turned outbreaks that could have remained isolated into global pandemics within weeks.

Serge Morand: You’re right. In addition to the factors that drive outbreaks at the source, we’re also seeing an increasing spread of outbreaks among countries. This trend really started in the 1960s and is related to the increase in the global transportation of people and goods. Using the database from the World Bank, we see that there is a more than 1,200 per cent increase in travel of people and goods between 1970 and 2017 and a good correlation between this increased travel of people and goods and the globalisation of epidemics worldwide.

And this connectedness also impacts the speed of the spread. For example, when you look at the flight connections from Wuhan and compared them to the time since COVID was first declared, let’s say December or November 2019, there is a broad connection. A country that is a hub for international travel was much faster at reporting its first case.

In 2022, when travel resumed, it was the same for mpox. The more connected countries were also the countries that were quicker at reporting mpox cases.

So, countries like Singapore that are highly connected need to be informed very fast of new outbreaks. They need to know what is going on everywhere.

MEDICUS: If transport hubs need to know what is going on everywhere, then extensive global biosurveillance will be key. Will that be enough to better protect us from the next outbreak?

Serge Morand: I am quite confident that we can do this because quite a lot of people are starting to think about how to reshape surveillance, response and preparedness.

But we should also invest in prevention at the source, so we can reduce spillover events. It will be less costly and avoid some surprises. It will also offer some win-win solutions, particularly as we also have to address the climate crisis. One driver of outbreaks is the land use change and farming system. And this we know is also very important for climate change. Working on this, we can really have some win-win solutions.

But for this, we need more people engaged in ecological research. Because in terms of science-based evidence, we are short right now. We know that degradation of the environment has an impact on climate, is bad for health, and possibly promotes spillover events. But what we have absolutely no scientific evidence for right now is whether stopping this and replacing it with efforts to increase reforestation, ecological restoration, better land use, or even rewilding, works. So especially in Thailand, we’re starting projects to study how we can prevent outbreaks at the source.

Field studies like this will help to determine the impact on ecological interventions on the health of local communities, domestic animals, wildlife and the environment // Credit: Serge Morand

 
For example, we are working on a reforestation project with a national park and local communities in Thailand that also involves virologists and public health experts. Together, we are looking at the potential transmission of viruses between bats, rodents, dogs and humans. We are doing this by monitoring the kind of wildlife that lives in different areas—the villages, the reforested area and the croplands—and what viruses they carry. And I was amazed by some of the early results in the reforested areas, where we have seen an amazing return of wildlife, including mongooses, civet cats, pangolins, deer and even Asian bears that come close to the villages. But whether this resurgence in biodiversity is good for public health, we don’t know yet. And that’s what we are trying to find out because we need good studies that can really assess the protective effect of biodiversity.

MEDICUS: This will need to be balanced against the increased danger to human life, right?

Serge Morand: Yes. We have found that when it comes to rewilding, people are OK at the very beginning. But when they start to see big animals in their backyard, they are afraid. Or when deer come back and start to eat the crops, then that causes conflict. That’s why you need to keep this context in mind. That’s what we are studying with the project in Thailand. To understand how people are responding to this. Not only the local farmers but also the national park people, what the benefits, risks, dangers and costs are. Because the benefits may come with conflict. And that is a question which requires all sectors to come together to discuss how to address it. And so far, the national parks are very interested, they are already actively engaging the local community in occupations such as park rangers to better control and live with the wildlife.

And using health as the common outcome is a good way to bring people together because everyone wants good health. That way, we can really work to create a solution that is innovative in terms of biodiversity, ecological restoration, surveillance and reducing the risk of spillover on the spread of disease.

MEDICUS: And work like this really falls into the realm of One Health. So what impact has the pandemic had on the One Health agenda?

Serge Morand: One Health was really a concern of the public health and the animal health sectors, which were focused on how to avoid diseases from emerging and spreading from wildlife, like avian flu. It was really focused on livestock.

In the wake of COVID, we now have a quadripartite alliance, which brings together three organisations and one programme: the Food and Agriculture Organisation, World Health Organisation, World Organisation for Animal Health and the UN Environment Programme.

And it really looks like this will work. Because the one thing COVID has done is it has really forced us ecologists to work more closely with specialists in virology and infectious diseases, so that we can better impact public health, and improve the prevention, preparation and response to the next outbreak.

And I was amazed and happy to see that the World Organisation for Animal Health has added the environment to the list of domains it supports and promotes right alongside wildlife health and disease.

MEDICUS: Why do you think it took so long for ecologists to get a seat at the table?

Serge Morand: Oh, for several reasons. First, I would say because of the ecologists themselves. I think most of the time, we tend to present things in a complex way. Of course, things are complicated but we should avoid presenting them in such a way, especially when we present to non-ecologists. So, we need to communicate better. The second thing is the decrease in emphasis on prevention. We’ve moved from a prevention perspective that focuses on community health to a more individualistic health perspective that is focused on treatment.

MEDICUS: Looking to the future then, what is one thing we need to change to have the biggest impact when it comes to advancing the One Health agenda?

Serge Morand: We need to work on the underlying drivers, and key among them is the food system, which is also a key contributor in terms of climate change. That will be the most impactful and will create those win-win solutions I talked about. So, working globally and locally on the food system, putting agriculture not only at the centre of the problem but at the centre of the solution. Working with this, we can deliver better health for everyone—humans and animals.

MEDICUS: What are your hopes for the One Health joint plan of action that was launched last year?

Serge Morand: The joint plan was a really important task and what is nice is that it not only includes zoonotic and emerging diseases but has a much broader focus, including pollution, neglected tropical diseases and antimicrobial resistance. But the problem with big is that it touches everything. Now, we really need to focus on how to implement this at the country or even local level. How to help countries to prioritise and implement locally.

MEDICUS: Do you think it can be done?

Serge Morand: For Southeast Asia, I’m quite confident because One Health is not new here, many already have action plans that just need to be updated. And we have many regional organisations that have been conducting such activities. And what we need is to innovate and this innovation has to come from local experience and experiments—the successes and the failures.

Of course, financial resources will be important but I think there will be donors including the World Bank.

And the second thing is capacity building. We need to work on the different levels and we really need to support the environmental sectors, where not everyone is convinced or understands how One Health concerns them. So, we need to do a little more advocacy and help with the implementation.

MEDICUS: What solutions can you see that help us protect nature, reduce the risk of outbreaks, mitigate climate change and feed the world?

Serge Morand: We are working now with UNESCO and the implementation of One Health territorial implementation using UNESCO’s biosphere reserves as a platform. The biosphere reserve, which can even include cities, is quite interesting because it focuses on sustainable development, conservation of biodiversity, education and science. It is a good way to work because it involves the local government and communities, who are key to successful implementation.

Such an approach will contribute to the health and wellbeing of population while preserving biodiversity, driving innovation and supporting the livelihood of local communities.

MEDICUS: Thank you for your time and insights.

The interview was conducted and edited by Nicole Lim, Senior editor