- CRITTER TALK
Climate change is ecosystem change. And like all change, it involves myriad and complex consequences. Some consequences of climate disruption—like sea-level rise—are easily measured and readily anticipated. Other consequences will stem from a long and seemingly unrelated series of hidden but immensely consequential changes. Those hidden factors will likely blindside us with increasing frequency as humans further disrupt the climate. This is sometimes known as the increasing prevalence of Black Swan events. The Covid-19 pandemic is one such event. It is the culmination of many ecosystem disruptions.
By tracing those disruptions we can find the origins of the pandemic. One easily observable outcome of climate disruption—even if its effects remain unknowable—is the global redistribution of species. As humans alter the makeup of environments, their biotic communities will change. In general, flora and fauna are moving higher in both altitude and latitude, searching for climates similar to the ones for which they are adapted. Some species are expanding their ranges, bringing competition to the endemic life forms in their new territories. Others are finding the amount of livable habitat greatly reduced; climate disruption is directly linked to the extinction crisis. One recent study found that one-third of the planet Earth’s flora and fauna are at near-term risk of extinction.
As life forms decline in some areas and thrive in others, they will alter not just the large, visible makeup of species diversity, but the distribution of microbiological life as well. When animals migrate into new territories, they will bring microbiological hitchhikers with them. This will affect human life in many ways, some easy to see, others of the sudden Black Swan variety. Recent research has uncovered one chain of effects that likely gave rise to the most widely felt disaster of the past year: the global Covid-19 pandemic. What is not immediately seen is that the pandemic may have come about because a heated planet is redistributing mammal populations across the globe. Welcome to a climate-changed world, one in which new zoonoses—diseases shared between humans and animals—emerge with newly heated environments.
Among those migrating animals are bats. Bats are particularly salient for human health. They are the source of two previously well-publicized coronaviruses (CoV): the Middle East respiratory syndrome (MERS), and severe acute respiratory syndrome (SARS). Other well-known zoonotic diseases are swine flu, transmitted to humans by pigs, and HIV, transmitted to humans via chimpanzee. But bats are a singularly important source of viruses. Flying foxes are the likely source of the Nipah and Hendra virus infections. Other bat species house Marburg virus disease, and, along with wild birds, the Influenza A virus. Bats are also famous as carriers of rabies. That viral diseases emerge from bats is not surprising. Bats are vast reservoirs of viral diversity; they host by far the highest percentage of zoonotic viruses among all mammalian orders. Indeed, bats may carry up to 3000 coronavirus varieties alone.
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