When authorities in Yakutsk invited participants in a youth government initiative to brainstorm ideas for an empty lot in the centre last year, it seemed like a smart way to get rid of an eyesore.

But the project was held up after residents and officials raised concerns that the site could hold anthrax spores preserved in the permanently frozen soil.

Although specialists eventually said it was safe to build a skate park on the lot, which once held a laboratory making an anthrax serum, the incident raised further questions about the ancient diseases known to be lurking in the permafrost—and whether they could be unlocked by global warming.

“Anthrax spores can stay alive in the permafrost for up to 2,500 years. That's scary given the thawing of animal burial grounds from the 19th century,” said Boris Kershengolts, a Yakutsk biologist who studies northern climates. “When they are taken out of the permafrost and put into our temperatures, they revive.”

Yakutsk is the coldest city on earth with temperatures that can drop below -60C in the winter.

But it's seeing the start of warming that could lead to the destruction of infrastructure and the revival of dormant diseases across the north, even as more people arrive to man new military bases and oil and gas facilities.