Ever noticed that grey green crusty stuff on rocks and trees? I've seen it all my life but never thought much of it. I now know that it is not just one organism but a symbiosis of photosynthetic algae or bacteria and fungus. I probably wouldn't know this if what happened had not happened.
There have been many concerns about what global warming would bring - rising seas, acidification, famine, extreme weather, drought but the most dangerous result we never saw coming.
Throughout the arctic circle there are many permafrost regions, land that has been frozen solid or covered in ice for centuries or even millennia. As global temperatures increased these regions began to thaw. Scientists were concerned about the trapped methane being released into the atmosphere, how it would accelerate the warming effect but they could not foresee what ancient life that was also lying dormant.
Perhaps it was alien in origin or maybe just so old that it was forgotten in time but the lichen was unlike any we had ever seen. Within a few years it began to be seen in cities around the world. It flourished in the environments that we had built, asphalt, concrete, even steel and glass skyscrapers. Scientists studying the phenomenon confirmed that it was lichen, a symbiosis between two previously unknown species.
Every attempt to remove it only helped it spread faster, the spores or whatever, spread on the wind. Dusty fragments floating like snowflakes, carried by storms to every corner of the world until every place you went looked like it was covered in frost.
If it were only the surfaces effected we might be fine, able to adapt but it turned out much more dangerous than that. Humans had never coexisted with this organism and it turns out to be quite toxic for us.
The takeover was very quick. We spent more time arguing amongst ourselves over petty issues than preparing for the future. I laugh when I think of the politicians mummified by lichen flakes in their mansions clutching the cash that they worked so hard to embezzle.
It was the tech giants that quietly retreated from the stage and made things happen. I am one of a few thousand in bunkers scattered across the Pacific Northwest. Not sure how many have survived in other areas. We have been working on vehicles to begin exploration but most of our efforts are just making sure everything works and we have food, water and fresh air.
The good news is that it seems that very few other species experience the toxic effects the way humans do, so nature is doing just fine without us.
At least there is that.
Photograph by Tanya Kusova; Modified by @Schemataobscura