[nakedneuron]

Carbon in the form of carbon dioxide as raw material is literally instantly available and the resulting "composite" is lightweight. This is not to say nature always considers recycling beforehand. Nature needed to invent fungi to break up this carbon dump. Carbon era is named thanks to this fact. And it's tempting to think nature "came up" with humankind to make the humongous carbon dump of the carbon era useful once again.

[digging]

Really, you have causation backward. Eg. the supposed Carboniferous Period was an opportunity for something to evolve which consumes wood. Many "problems" get solved by accident in this way, but many also don't - as long as they take place over a long enough timespan. If they happen too quickly, there's not enough time for living things to adapt.

Currently there is an opportunity for an industrious plastic-eating microbe to hitch a ride in every gut on the planet, deciding the winners and losers of the plastiferous period. All that means, though, is that there's a chance such a creature could appear and take advantage, not that it will happen. (Yes I know plastic-eaters have been discovered, but I'm not aware of any having an effect on the fitness of other creatures.)