Four years before the Covid-19 pandemic made its appearance on the world’s stage, the Lancet Commission on Health and Climate Change concluded in 2015 that

biodiversity loss may to lead to an increase in the transmission of infectious diseases such as Lyme disease, schistosomiasis, Hantavirus and West Nile virus [1]

This was in addition to the principal conclusion of the report that anthropogenic climate change threatened to undermine the past 50 years of gains in public health, and that future projections of climate change “represented an unacceptably high and potentially catastrophic risk to human health”.

By 2017, it became clear that climatic factors are routinely implicated in the epidemiology of infectious diseases, and they often interact with behavioural, demographic, socioeconomic, topographic, and other environmental factors, to influence infectious disease emergence, distribution, incidence, and burden [2]. Emerging or re­emerging arboviruses, including Yellow Fever, Chikungunya, Mayaro, and Zika viruses, all of which were important because of their effects on human populations, appeared to be responding to climate change [3].

Emerging or novel viruses are not new. The SARS epidemic of 2002-3, which infected 8,098 people worldwide, killing 774 of them, was caused by a coronavirus, and so was the MERS outbreak that began on the Arabian Peninsula in 2012 and still lingers on (2,494 people infected and 858 deaths by November 2019). The rapid spread of SARS-CoV-2 — the virus which causes Covid-19 – may have been unexpected as it occurred, but it is certainly not unsurprising or unforeseeable to anyone familiar with zoonotic diseases which spill over from animals to humans [4]. The US Centre for Disease Control and Prevention (CDC) estimates that three-quarters of new or emerging diseases that infect humans originate in animals. Some of these, for example, rabies and plague, crossed from animals to humans many centuries ago. Other diseases that have crossed into humans include Lassa fever, which was first identified in 1969 in Nigeria; Nipah from Malaysia; and SARS from China, which killed more than 700 people and travelled to 30 countries in 2002–03. Some, like Zika and West Nile virus, which emerged in Africa, have mutated and become established on other continents [5]. The SARS pathogen was one of a number of coronaviruses which normally infect bats, but which easily spread to humans and are uniquely suited to cause human pandemics. Coronaviruses have been identified in multiple individuals of four different species of bats; and the genome of that virus is 96 percent identical to the virus SARS-CoV-2 which first appeared in Wuhan, China.

One of the ways in which a novel virus strain can spread from its animal host to humans is through the killing and trading of wildlife for food. That trade was outlawed during the SARS epidemic, but was then allowed to resume — with bats, civets, porcupines, turtles, bamboo rats, many kinds of birds and other animals sold in markets such as the one in Wuhan, China, where the Covid-19 pandemic began. Viruses and other pathogens are most likely to move from animals to humans in the many informal markets that have sprung up to provide fresh meat to fast-growing urban populations around the world. Here, animals are slaughtered, cut up and sold on the spot – providing ideal locations for cross-species transmission of pathogens.

The role of biodiversity loss in the emergency and spread of the Covid-19 pandemic is less well understood, but a recent report in the Guardian newspaper strongly suggests that it is humanity’s destruction of biodiversity that creates the conditions for new viruses and diseases such as Covid-19 to arise with increasing frequency, resulting in profound health and economic impacts in rich and poor countries alike [6]. The article in the Guardian quotes Professor Kate Jones, chair of ecology and biodiversity at UCL, who states that emerging animal-borne infectious diseases are an “increasing and very significant threat to global health, security and economies.” In 2008, Jones and a team of researchers identified 335 diseases that emerged between 1960 and 2004, at least 60% of which came from non-human animals.

Professor Jones draws the further conclusion that zoonotic diseases are becoming increasingly linked to environmental change and human behaviour. The disruption of pristine forests driven by logging, mining, road building through remote places, rapid urbanisation and population growth is bringing people into closer contact with animal species they may never have been near before.

Another researcher quoted in the Guardian article is disease ecologist Thomas Gillespie, associate professor in Emory University’s department of environmental sciences. Humans, says Professor Gillespie, “are creating the conditions for the spread of diseases by reducing the natural barriers between host animals – in which the virus is naturally circulating – and themselves”. Wildlife everywhere is being put under more stress, he says. “Major landscape changes are causing animals to lose habitats, which means species become crowded together and also come into greater contact with humans. Species that survive change are now moving and mixing with different animals and with humans.”

Felicia Keesing, professor of biology at Bard College, New York, studies how environmental changes influence the probability that humans will be exposed to infectious diseases; and earlier this year she was given a $241,000 grant by the US National Science Foundation for a project to undertake further research into linkages between ecology, conservation, and health — with the aim of providing better conceptual frameworks for the study of the impact of biodiversity on plant, animal, and human health.

As the climate warms and rates of local and global extinctions accelerate, understanding connections between the environment and the health of plants, animals, and humans has become increasingly urgent. While the field of disease ecology has held great promise because of the expectation that its practitioners can facilitate predictions and guide ecological interventions to mitigate health concerns connected to the environment, Keesing says that, too frequently, predictions come too late to be useful, and plans for mitigation must await years of data collection. Her project, “A synthesis of the effects of biodiversity on plant, animal, and human health,” looks to provide predictive frameworks that allow practitioners to take advantage of the results of prior research, adapting them to new situations as these arise [7]. In the Guardian article cited above, she is quoted as saying:

When we erode biodiversity, we see a proliferation of the species most likely to transmit new diseases to us, but there’s also good evidence that those same species are the best hosts for existing diseases.

Dr Brian Bird, a research virologist at the University of California, Davis School of Veterinary Medicine One Health Institute, leads the Ebola-related surveillance activities in Sierra Leone and elsewhere; and he is quoted as saying: “The risks are greater now. We can’t predict where the next pandemic will come from, so we need mitigation plans to take into account the worst possible scenarios,” he says. “The only certain thing is that the next one will certainly come” … “We are in an era now of chronic emergency, diseases are more likely to travel further and faster than before, which means we must be faster in our responses”.
Eric Fèvre, Professor of veterinary infectious diseases at the University of Liverpool, and Cecilia Tacoli, principal researcher in IIED's Human Settlements research group, advocate rethinking urban infrastructure, particularly within low-income and informal settlements [8]. Thus he brings in the concept of environmental justice, together with urban planning – subjects close to the interests of An Taisce.

A new discipline, planetary health, is emerging that focuses on the increasingly visible connections between the wellbeing of humans, other living things and entire ecosystems. Key areas of research include more detailed investigation and greater understanding of the links between the effects of climate change, land use changes, biodiversity loss and the emergence of pandemics such as the current Covid-19 outbreak. We must also ask why an economic ideology and system which has been so damaging to the planet has been allowed to continue for so long; as the economist Manfred Max-Neef stated, “The dominant economic model is to a great degree responsible for the world’s collision course”, so that “for the first time in human history several crises converge to simultaneously reach their maximum level of tension” [9].

This link between the Covid-19 pandemic and our economic system also extends to include impacts on global energy, and it can be seen as a harbinger of crises to come as climate change intensifies. In many cases these appear as hidden risks that seem to come out of nowhere, but their consequences have long been identified by the scientific community. These other crises include deteriorating public health as a consequence of widespread industrialization, growing inequality, habitat destruction and loss of biodiversity, and ultimately an unsustainable level of consumption and associated resource constraints. “The climate crisis is a problem on its own but compounds all of these” [10].

For most of us, the World Economic Forum (WEF) is seen as a key supporter of the current economic system, and not an advocate of the necessary strong and urgent action to mitigate the impacts of climate change; but even this organisation may be changing its approach as a consequence of the Covid-19 pandemic. The WEF currently states on its website that:

An invisible virus has made our individual actions more visible than ever – and revealed our true power to face societal crises beyond COVID-19. As people around the world work together to “flatten the curve” of COVID-19, the outsize roles we play in Earth’s natural system have become clear as never before. Billions of humans can now see how they are interconnected, working together to slow the spread of a lethal virus through their individual actions. Within this experience, if we are successful, lies the potential lesson we need not just to stop the worst projections for COVID-19, but to address other pressing societal challenges, including climate change. This dawning sense of individual impact in an interconnected world – what has been called, “systems thinking” – is in many ways the true story we’ve long avoided acknowledging. We’ve gotten by for hundreds, even thousands of years, obfuscating the cost of the destruction of nature as an externality of economic progress, hardly considering the debt accruing on the system that hosts the global economy itself: Earth [11].

Could we have expressed it better ourselves? Certainly, given that the WEF has to date paid little attention to biodiversity loss and the complex interactions first identified in the Limits to Growth in 1972 and re-stated clearly by the Rocky Mountain Institute this month [10]. Climate change, biodiversity loss and the Covid-19 pandemic are interlinked components of a global “problematique” which must be addressed as potential system collapse, caused by human intervention–and it is only by our own actions can its consequences be mitigated or prevented.

by Jack O’Sullivan,An Taisce Council Member 

1 Watts N, Neil Adger W, Agnolucci P, et al. Health and climate change: policy responses to protect public health. Lancet 2015; 386: pp 1861–914 (07 November 2015).

2 Watts N, Amman M, Ayeb-Karlsson S, et al. The Lancet Countdown on health and climate change: from 25 years of inaction to a global transformation for public health. Lancet 2017; S0140-6736(17)32464-9. Published Online, October 30, 2017.

3 Hales S, de Wet N, Maindonald J, Woodward A. Potential effect of population and climate changes on global distribution of dengue fever: an empirical model. Lancet 2002; 360: pp 830–34.

4 “How Animal Infections Spill Over to Humans”. Public Health Science Talk; David Quammen and Steve Mirsky; Scientific American, March 18, 2020; and “We Made the Coronavirus Epidemic”, by David Quammen, New York Times, 28 January 2020.

5 'Tip of the iceberg': is our destruction of nature responsible for Covid-19? By John Vidal; the Guardian, 19 March 2020. Much of the information in the remainder of this research note is taken from this excellent article.

6 Smith KF, Goldberg M, Rosenthal S, Carlson L, Chen J, Chen C, Ramachandran S. 2014 Global rise in human infectious disease outbreaks. J. R. Soc. Interface 11: 20140950.


8 Coronavirus threat looms large for low-income cities. Eric Fèvre and Cecilia Tacoli; guest blog, International Institute for Environment and Development, 26 February 2020.

9 Max-Neef, M., 2010. “The World on a Collision Course and the Need for a New Economy”. Contribution to the 2009 Royal Colloquium. Ambio (2010) 39:200–210. DOI 10.1007/s13280-010-0028-1

10 COVID-19 and Climate: Risk, Mitigation, and Resilience; by Ned Harvey, Tyeler Matsuo and Christian Roselund. Rocky Mountain Institute, April 1, 2020. Accessed 03 April 2020 from