The Millions of Species We Ignore at our Peril

Wastewater, tourism and trade are moving microbes around the globe at an unprecedented scale, a group of international researchers have argued. 

An editorial article, published in the journal Science, voices the concerns of the scientists who warn that as people travel the modern world they leave billions of bacteria along the way, with potentially hazardous consequences for human health.

For several billion years, microorganisms and the genes they carry have mainly been moved by physical forces such as air and water currents. These forces generated biogeographic patterns for microorganisms that are similar to those of animals and plants. In the past 100 years, humans have changed these dynamics by transporting large numbers of cells to new locations and by modifying selection pressures at those locations. 

As a consequence, the Earth is in the midst of a substantial alteration to microbial biogeography. This has the potential to change ecosystem services and biogeochemistry in unpredictable ways.

As with rats, foxes, tigers and pandas – all species whose survival has greatly benefited from the actions of humans – some microbes are winners, spreading around the world into new ecological niches. Others are losing, and might face extinction. These changes are invisible, but, according to the article, “our survival may depend on these microbial winner and losers.”

The problem lies not only in the unprecedented amount of travel by humans this century, but also in modern agricultural practices, transport systems and other trade practices.

“The oxygen we breathe is largely made by photosynthetic bacteria in the oceans and not by rainforests, as is commonly believed,” says Professor Michael Gillings from Australia's Macquarie University. “Over 95 percent of the feces in the world comes from humans and the animals we farm, And our poo is traveling around the world with a billion tourists, spreading microbes and antibiotic resistance genes.

“Until 100 years ago all the nitrogen in our food came from bacteria we nurtured in our crops. Now more than half comes from artificial fertilizers,” says Gillings.

“We’re moving trillions of ocean microbes around the world in ballast water. Some one hundred million tons of ballast water is dumped in U.S. waters each year. We know they’re introducing foreign starfish, sea snails and seaweed. But we don’t know what invisible changes they’re making to ocean microbes as well.”

The team of researchers is calling for urgent action to help monitor and model changes in the microbial world and to improve waste water and manure treatments to reduce the spread of microbes and resistance genes.

“Microbes usually perform their essential ecosystem services invisibly, but we ignore them at our peril. Current models which track the movement of genes through microbial communities are unable to do this with an overarching global perspective, leaving us open to potentially dangerous microbes that could impact human health – an issue that molecular and environmental scientists need to keenly focus on in the near future,” says Gillings.

The international team who authored the article consists of researchers from Macquarie University, Australia; the Chinese Academy of Sciences, China; Universite de Lyon, France; University of Nottingham and University of Leeds, U.K. and CSIC/CREAF, Barcelona, Spain.