What are the environmental origins of pandemics such as COVID-19? Why are they going to become more and more frequent? In this first article of a series devoted to the links between COVID-19 and the environment, agronomists Julien Calas and Léa Lugassy, together with economist Étienne Espagne, take us back to the environmental origins of the current health crisis.

A jackal stands in the grass in Yarkon Park in the Israeli coastal city of Tel Aviv on April 13, 2020. – The jackals of Yarkon Park took the paths of the park with greater confidence in search of food during the coronavirus COVID-19 pandemic as a result of the lockdown imposed by Israeli authorities to curb the spread of the disease. (Photo by JACK GUEZ / AFP)

The COVID-19 pandemic has caused an economic and financial crisis that is taking on historic proportions and is currently the focus of everyone’s attention. Much of the discussion is understandably on support for the most stricken sectors or countries, on the appropriate timetable for restarting economic activities, or on the necessary boost that – this time – will preserve global equilibrium.

But it’s also urgent to review the causes of the emergence and spread of this pandemic, which can mostly be found at the border between human activities and biodiversity. In fact, in trying to get out of this current dilemma, we face the huge challenge of not aggravating the factors that have provoked it. In short, before we exit the crisis, we must define it properly.


From economist to ecologist: biodiversity as a response to pandemics

Going back over the causes will teach us operational lessons useful in building up better resilience in our societies in the short term, so that we can prepare for future pandemics. Indeed, in a future that’s already set to see significant climate change and accelerated erosion of biodiversity, pandemics are bound to be more regular and more violent. From a more structural point of view, this retrospective approach shows us that any economic or financial response to the crisis will be inadequate and would even accelerate the process of ecological collapse at the origin of the pandemic.

Here, the economist must act as an ecologist – unless it’s the other way around. In this pandemic, biodiversity (or its destruction) is in fact the alpha and omega: it determines the emergence of the pandemic, accelerates its diffusion, and imposes a response.


More frequent epidemic outbreaks

Although epidemic outbreaks are not new, they are much more numerous and frequent than before. It seems that their nature has changed, and that the root cause is human pressure on the biosphere. Between 1940 and 2008, 60% of emerging infectious diseases were zoonoses, i.e. “diseases usually transmitted between animals and humans”. Of these, 72% originated in wildlife, as several researchers have pointed out in the scientific journal Nature.

The current pandemic is a perfect example of this. It appears that bats are a natural reservoir of the SARS-Cov2 virus that causes COVID-19. While they are not affected by the virus, they can transmit it to other species, including to humans. More generally, the causes of infectious diseases involve a growing number of species due to the increased risk of pathogens crossing the barrier between animals and humans. There is a sharp increase in emergence factors, which are themselves intimately linked to types of development. Four main factors behind emergence can be identified.

Factor 1: ecosystem degradation

Humans are penetrating more than ever before into preserved natural spaces. Contact increases where deforestation occurs, leading to trade in and consumption of wildlife. This is the foremost factor in the emergence of epidemics. Contact with diseases existing in wildlife has always tended to generate infectious diseases or epidemics, but today the number of species involved in the transfer of pathogens between humans and animals is constantly on the increase.

The problem is not with pathogen-bearing species, but rather with ecosystems whose state of degradation means they can no longer dilute the chances for transmission to humans. In a rich ecosystem, a pathogen is more likely to encounter hosts that are “low-competence” (i.e. that are less likely to be vectors spreading the pathogen) or even “dead-end” species. On the other hand, in poorer ecosystems there is greater chance that a pathogen ends up in humans. Degradation of ecosystems therefore greatly increases the risk of transfer to humans.

Factor 2: ecosystem disturbances

Imbalances in an ecosystem can then lead to the emergence of viruses or pathogens that proliferate and become pandemic. This factor is different from the previous one because it specifically relates to the properties of emergence in a disturbed system. As pointed out, for example, by the researchers S. J. Ghanem and C. C. Voigt in Advances in the Study of Behavior, a decrease in predators facilitates the proliferation of mosquitoes and, with them, the diseases they can transmit.

Factor 3: the pet trade and industrial livestock production

The increase in human-animal and animal-animal promiscuity, linked to the trade in pets and to industrial livestock practices, creates perfect “incubators” for the production of pandemics. In particular, as explained by Rob Wallace in his book Big Farms Make Big Flu, this is due to selective breeding, which produces animals that are productive but – having been reared in conditions far from their natural needs – are not very resistant to diseases and thus vulnerable to them.



Under such conditions, the spread of an emerging pathogen can be very swift and difficult to control, prompting authorities to take radical and ethically questionable measures such as large-scale preventive slaughter. This is why the recent outbreaks of avian influenza, and more recently African swine fever, have led to large-scale slaughter of livestock.

Factor 4: climate change

The fourth factor behind the emergence of pandemics is climate change, which promotes vector-borne diseases. Specifically, animals (e.g. migratory birds, insects and mosquitoes) that transmit diseases to other animals shift their habitat to new areas due to climate change.

These vector-animals transmit their pathogens to pets or humans more frequently. This is what is currently happening with the West Nile virus. As C. Caminade, K. McIntyre, and A. E. Jones have reported, it crossed the United States in six years and has established itself in Southern Europe, infecting horses and humans. This is also the case with dengue, a viral disease transmitted by a tiger mosquito of the Aedes genus. For the past decade, indigenous cases have been reported in Southern Europe, where the disease had previously been unknown.

Meanwhile, the accelerated melting of permafrost is increasing the risk that viruses that have long been frozen may soon awaken to endanger human communities with no immunity to them. In 2015, for example, two giant viruses dating back over 30,000 years were identified.


Globalization of trade and the spread of pandemics

Another feature of the COVID-19 crisis is the speed with which it has traveled the planet, becoming in just a few months a global pandemic.

Denser human populations and the uncontrolled acceleration of trade are one of the major characteristics of the most recent globalization, or of what could be called the last phase of the Capitalocene. More than half of the world’s population lives in cities, a proportion expected to rise to 70% by 2050. In addition, 90% of global urban growth is taking place in Asia and Africa. Africa’s cities, now home to 472 million people, will have a total population exceeding 1.2 billion by 2050. Movement of people, animals, and goods is accelerating, and with it the occasions for spreading emerging diseases are growing hugely.

Up to now, reducing delays in trade controls has been considered as surely  beneficial to trade and growth, as reported in an article on African exports by researchers C. Freund and N. Rocha. Yet, the speed of travel and the absence of controls – especially health controls – increase the risk of global crises. The trillions of dollars in cost of our current COVID-19 crisis should sound the alarm among economists and financiers who for decades have ignored these risks of environmental externalities. It’s important to note that it is not freedom of movement or the number of people moving that are the problem, but rather the fact that the speed of these movements is out of control.


The role of comorbidity: the weakened immune systems of humans

The extreme spatial concentration of economic activities and the exponential mobility of persons and goods have an inevitable side effect: heavy pollution in the megacities of emerging and developed countries. As we saw last autumn in cities such as Delhi, this pollution sometimes even presents a mortal danger.

This heavy pollution creates conditions of comorbidity among urban populations, as the recent coronavirus crisis has shown. Such comorbidity can partially explain the especially lethal nature of the virus in northern Italy. An Italian study  has even argued that PM10 and PM 2.5 particles may have facilitated rapid movement of the virus to this region.

According to a comparative study, the intestinal flora of urban populations has been degraded compared to those of pre-industrialized populations, due to a less natural diet and to living in a more sterilized environment. This degradation probably weakens the effectiveness of the immune system of people who live in metropolitan areas.

Finally, widespread exposure to endocrine disruptors exacerbates this phenomenon. With the most recent globalization, our bodies have become less resilient than those of our forebears; when epidemics occur, we are thus more prone to disease.


Treating pandemics at the root, by protecting ecosystems

As we have seen above, the main causes of the emergence and spread of the COVID-19 pandemic – as well as the broader causes of the emergence and spread of infectious diseases – are directly linked to our approach to biodiversity. Our response must include regulating these causes and processes of propagation. And to do so we must mobilize ecologists, agronomists, veterinarians, microbiologists and epidemiologists before turning to economists.

Three focuses of regulation stand out. The first concerns how we interact with wildlife, whether it concerns protecting natural areas, protecting wildlife against poaching, or helping to build food markets that limit proximity among species. In the case of vector-borne diseases, protection should target predators of the vectors. If we look at mosquitoes, which are vectors of numerous pathogens responsible for malaria, dengue, and chikungunya, their main predators include a large number of species that are in decline or threatened: bats, insectivorous birds (swallows and swifts), amphibians, and dragonflies.


Towards value chains rooted in ecosystems

The second key regulatory focus concerns intensive livestock production. When it is subject to few regulations or is unregulated, support must be given to local veterinary services and to planning and supervision of livestock-production value chains. Intensive production of pigs and poultry is undoubtedly one of the possible sources of future pandemics, and particularly of influenza. We should promote small-scale farms with reduced herds, reasonable animal density, significant genetic diversity, and a healthy livestock-production method. This can in turn promote resistance to pathogens or, in the event of infection, contain them without transmitting them to tens of thousands of animals.

Finally, the third focus point concerns the ways infectious diseases spread. As we have seen, the weakness of controls over value chains and of customs controls will certainly be one of the major improvements to be made, in addition to strengthening the health capacities of countries suffering an epidemic. But, beyond these common-sense support measures today, transformation of value chains to maintain small and medium-sized diversified farms or agricultural value chains will, more broadly, require protecting those value chains from competition from imports of heavily subsidized livestock products.

In short, farming and livestock production must be once again rooted into ecosystems. In controling infectious diseases, agriculture – as a bridge between ecosystems and humans – is both the main risk (in its financialized market form) and the main ally (in its re-rooted form). If this transformation (as Polanyi defined it) is to be achieved, the economy must be able to offer prospects for our future.


Read the second part of this contribution devoted to the lessons of the COVID-19 on the climate.



The opinions expressed on this blog are those of the authors and do not necessarily reflect the official position of their institutions or of AFD.

Partager cet article :

I subscribe to the ID4D newsletter

Once a week, I receive the latest blog posts!