Editor’s note: This post was updated on April 1, 2020, to reflect the latest information about the ongoing pandemic and to make other clarifications.
In a matter of weeks, COVID-19 has dramatically upended modern life. Almost every sector of society has been transformed, with colleges moving online while thousands of communities across the United States, urban and rural, declare states of emergency and implore residents to stay home. Seismic changes that would have been unimaginable a mere month ago have fundamentally reshaped society and politics. The world economy is getting violently rattled with stock markets tanking, growth projections shrinking, and all recovery contingent upon bringing the virus to heel. Meanwhile, shortages in ventilators and face masks, and overloaded hospitals are making the crisis more dangerous. A vaccine likely won’t be available for 18 months or more.
COVID-19’s catastrophic impact on all sectors of life critically demonstrates that the world is woefully unprepared for managing pandemics. This has dire implications for our ability to respond to emerging infectious diseases that are expected to spread more frequently due to climate change. Experts note that climate-induced changes in the movement patterns of humans, animals, and pathogens will make viral outbreaks more common. Global reactions to the COVID-19 outbreak — from failures in social distancing to rising Sinophobia — show that the world is not prepared to deal with these new health crises.
COVID-19 is a viral infectious disease whose symptoms include fever, cough, and shortness of breath. The virus that causes it, SARS-CoV-2, is primarily transmitted through respiratory droplets from sneezing and coughing, much like the flu. Unlike the flu, no one has immunity to COVID-19, which is consequently much more contagious, infecting 2.6 people on average for each unmanaged case (compared to 1.3 for the flu). It typically takes five to seven days for infected people to begin showing symptoms, versus the flu’s much shorter incubation period of two to three days, meaning people have more time to accidentally spread the infection before they know they have it. COVID-19 mortality rate estimates range from 0.1 to 3 percent, due to limited testing in many countries. Older individuals, especially those with pre-existing health conditions, including diabetes and high blood pressure, are at greater risk of death.
COVID-19 and other coronaviruses that have featured in recent epidemics — namely Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) — fall under the larger umbrella of zoonotic diseases, which are transmitted between animals and people. Other well-known zoonotic diseases include rabies, Ebola, plague, and Lyme disease. While experts are still trying to pinpoint the source of COVID-19, current prime suspects include bats and pangolins.
Zoonotic diseases already comprise roughly 70 percent of all human infections, but experts fear the climate crisis will accelerate their transmission by changing the boundaries and characteristics of existing animal habitats. Weather pattern changes and global warming are predicted to cause many wildlife species to migrate poleward (away from the equator) and toward higher altitudes, putting them in contact with new diseases to which they haven’t evolved resistance. In addition, as animals experience increased stress from these migratory changes, their immune systems may become weakened, thereby increasing both the risk of infection and amount of viral replication once infected. Deforestation and continued encroachment into animal habitats will reduce species diversity while increasing contact with humans, in turn increasing infections within host animal populations and boosting the risk of such diseases jumping to humans. In summary, the climate crisis will lower host animals’ immune responses, increase the rate of infection by crippling biodiversity, and push animals into new migration routes that will bring them into greater contact with humans — all ultimately increasing the frequency and associated risks of infectious disease outbreaks.
The climate crisis will also force humans to migrate, likely in patterns paralleling other animal species: away from extreme weather phenomena and warming regions and toward higher altitudes. The world’s poorest populations and indigenous communities, already in close contact with nature and marginalized by many societies, are the most vulnerable and will be disproportionately affected by increased disease proliferation. The climate crisis is already expected to cause an additional quarter of a million deaths per year from malnutrition, malaria, diarrhea, and heat stress, with estimates of the direct annual costs of health damage alone ranging from $2-4 billion USD by 2030. The consequences of new animal-human interactions are unpredictable; it’s still difficult to know exactly how much the spread of zoonotic diseases into new latitudes will affect our globalized economy and society. But the global response to COVID-19 suggests it could be catastrophically destabilizing.
Though the COVID-19 pandemic is still unfolding, it offers a warning of what lies in store as zoonotic diseases proliferate at greater rates due to climate change. Empty streets and upended lives could become more frequent occurrences as disease outbreaks, both life-threatening and relatively benign, swarm the globe. Or, for better or worse, the frequency of outbreaks could force people to normalize the dangers, even for emerging infectious diseases about which little is known. Regardless of which prediction reigns true, experts acknowledge that climate change will increase the frequency and severity of disease outbreaks. Linking public fear of pandemics — strong enough to shut down countries for months on end — to changing climate patterns would go a long way to overcoming inertia on fighting the climate crisis.
Views and opinions expressed here are those of the authors, and do not necessarily reflect the official position of the Columbia Climate School, Earth Institute or Columbia University.