This Wednesday, most of us will commemorate the 50th Earth Day not by frolicking in nature but by hunkering down in the comforts of our built environment. That’s a pity, because it’s pretty out there. Suddenly blue skies and cleaner water are showing us what a healthier environment might look like, if only our governments took decisive action to decarbonize the global economy and if we stopped running down the natural capital assets upon which our prosperity and indeed survival depend. Beyond a chance to daydream of a greener future, our current quarantine provides an apt moment to reflect on how intimately our own health is connected to that of the planet. COVID-19, which likely originated in bats, is a reminder that we are part of the biosphere, no matter how much we pretend otherwise. It also reveals how far out of balance we have gotten in our relationship with nature. When we despoil Earth’s ecosystems and disturb the organisms that inhabit them, we put our own health in jeopardy.
It is tempting to treat a pandemic as an unpredictable and unprovoked assault on humanity, akin to an earthquake or a tidal wave. In fact, human activity is the main driving force behind the recent emergence of dangerous new pathogens, particularly what are called zoonoses that jump from one animal reservoir to another. Since the first Earth Day in 1970, the number of identified zoonoses has surged, with many becoming household names. They include HIV/AIDS (chimpanzees and sooty mangabeys), Nipah virus (fruit bats), hantavirus (mice, other rodents), herpes B (macaques), Ebola (fruit and insect bats, forest mammals), Marburg (bats), SARS (horsehoe bats, palm civets), H1N1 (swine), H5N1 (wild birds), MERS (camels), West Nile virus (wild birds), Zika (monkeys and rodents) and now COVID-19 (bats).
Those seeking a culprit need only look in the mirror. Scientists attribute the explosion of zoonoses to three interlinked factors: massive population growth, accelerating climate change and rampant environmental degradation. Since 1970, our own species has more than doubled from 3.7 billion to 7.8 billion, placing unprecedented strains on the biosphere. We have altered the composition of Earth’s atmosphere through unchecked greenhouse gas emissions, while transforming three quarters of its terrestrial surface through logging, farming, ranching, mining and the building of new human settlements. In the process, we have encroached upon and degraded once pristine ecosystems and come into closer proximity with previously isolated species and their pathogens. A booming international trade in wild animals offers opportunities for new infections, even as global warming continues to alter the ranges of vector-borne diseases, from malaria to Zika.