Safety in Numbers | By Sydney Rudko

We live on an incredibly diverse planet; it is estimated that there are over 100 million species currently on our planet. The richness of species on our planet, while incredible, is arguably part of the problem we have in protecting it. It is hard for anyone to comprehend such an extraordinarily large number of species. Indeed, there are more than 250,000 species of beetle on earth alone, which is difficult in itself to imagine. While television programs like Planet Earth show us the amazing life in the tropical rainforest, very few of us actually get up off the couch and do something to protect these species. The World Wildlife Foundation estimates that the current rate of extinction is between 10,000-100,000 species each year. Yet once again, these numbers have very little relevance for us. As long as these species aren’t our livestock, our LOLcats, or ourselves it’s hard to care enough to really make a difference and curb this ever-growing problem. Even solutions to the issue of climate change are stalled, and we are beginning to see the effects of this everyday. But what if for every species that became extinct you become more likely of contracting a potentially deadly viral, bacterial, or parasitic infection?

Recall back to 2002 & 2003 when the SARS virus outbreak occurred. An entirely unknown virus spread from China across the world in a matter of months infecting just over 8000 people and killing 774 of them.In late 2003, scientists discovered the virus causing the mysterious ailment: a coronavirus. It took two years for scientists to ultimately trace the origin of this mysterious virus to bats. The bats passed the virus on to civet cats, which are regularly eaten in some parts of China. This was how the virus spread from its natural animal host to humans.

We live in a world where global travel can occur in a matter of hours, and therefore new pathogens can spread right across the globe in a matter of weeks. Indeed, this was the issue with SARS, it was able to spread across the globe in a matter of months, causing outbreaks in a variety of locations. Due to air travel, we are all at risk of contracting serious illnesses. Keeping ourselves healthy has suddenly become a global responsibility.

So what if the potential to prevent diseases like SARS from making the jump to humans was possible, simply by preventing extinction and increasing biodiversity?  Scientists at the University of Colorado at Boulder have modeled the spread of a parasite in a pond ecosystem under varying levels of biodiversity. The researchers added different species to an ecosystem and then tracked the spread of a disease-causing parasite transmitted to frogs through snails. The three-year study reached one striking conclusion: the greater the biodiversity of an ecosystem, the fewer successful parasitic infections occurred in the frogs.  Simply put, the more organisms a parasite encounters who are not susceptible to a disease, the fewer opportunities that parasite (or virus, or bacterium) has to spread.

While this hypothesis has not yet been applied to human populations or human disease, the core principle of this study is worth thinking about. The blanket of biodiversity that currently still surrounds us likely does protect us from a variety of new and unpleasant infections, just as it did the pond frogs of California. Any animal harbors within itself a plethora of unique microorganisms. Some of these organisms are entirely benign, while others are opportunistic organisms that when given the opportunity will become pathogenic. As more species become extinct these microorganisms will either become extinct themselves, or will go on to colonize a new host. That new host could be humans, or it could be a species we rely on heavily. As we disrupt natural ecosystems at an alarming rate in the race to cannibalize our planet, could we be inadvertently exposing ourselves to more pathogens, and could we be providing an opportunity for otherwise benign bugs to become pathogens?

Image CC desevilla on Flickr

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