It’s important to recognize the connection between rainforest destruction and the increase in viral diseases like COVID-19 over the past two decades. Viruses have evolved and continue to evolve in many rainforest species such as bats, birds, pangolins, and primates. Such animals serve as reservoirs for viruses. Through natural selection, they come to live in harmony with them.
If the animals stay in the forest performing their ecological services (such as pollination, seed dispersal, nutrient cycling), the forests remain healthy and we all benefit through rainfall, carbon sequestration, and abundant oxygen. If the forests are degraded, fragmented, and transformed by humans for roads and new communities, the animals that serve as reservoirs of pathogenic viruses increasingly come into contact with human populations. This relationship has been known for many years.
Humans have been accelerating even closer contact by handling animals as part of the illegal pet trade, wildlife trade, and bushmeat trade. These animals end up in “wet markets” where they are slaughtered and consumed. Evidence suggests that stressed bats being sold and handled shed a larger "viral load" as a physiological response. Inevitably, a mutated form of a virus will make the leap from the reservoir species to that first human host. And if the virus is novel, it may be highly virulent and contagious before the person feels ill, making a pandemic a real possibility.
So those of us who are supporting wildlife and rainforest conservation are also helping to keep novel viruses exactly where they belong—within the biodiversity in the rainforest.