Using computer simulations, scientists have predicted that the release of only 1 per cent of dormant pathogens could cause major global environmental damage.
These pathogens have been frozen in ice and permafrost for millennia. However, rising global temperatures could cause these materials to melt, releasing the microbes.
To better understand this hypothetical scenario, researchers have simulated experiments where digital pathogens from the past invade communities of bacteria-like hosts. They then compared the effects of the invading pathogens on the diversity of host bacteria to those in communities where no invasions occurred.
The results of the study showed that the ancient invading pathogens could often survive and evolve in the modern world, with about 3 per cent becoming dominant in their new environment.
However, about 1 per cent of those invaders caused up to one-third of the host species to die out, while others increased diversity by up to 12 per cent compared to the simulations where escape was not permitted in the simulations.
The risks posed by this 1 per cent of released pathogens might seem small, but given the sheer number of ancient microbes regularly released into modern communities, the researchers said these outbreaks represent a substantial danger.
"We found that invading pathogens could often survive, evolve and – in a few cases – become exceptionally persistent and dominant in the community, causing either substantial losses or changes in the number of living species," said Dr Giovanni Strona of the European Commission Joint Research Centre.
"Our findings therefore suggest that unpredictable threats so far confined to science fiction could, in reality, pose a serious risk as powerful drivers of ecological damage."
Professor Corey Bradshaw of Flinders University said the new findings show that the risk of invasion of unknown 'black swan' pathogens that can cause irreversible damage is not negligible.
"In the worst but still entirely plausible case, the invasion of a single ancient pathogen reduced the size of its host community by 30 per cent when compared to our non-invasive controls," he said.
"As a society, we need to understand the potential risk posed by these ancient microbes so we can prepare for any unintended consequences of their release into the modern world. The results tell us that the risk is no longer simply a fantasy that we shouldn't be prepared to defend against."
The findings have been published in the journal PLOS Computational Biology.
