If you start tinkering with things you aren't sustaining it, you're tinkering with it.

Increased in CO2 requires ecological adaptations of organisms living in the oceans, for instance. https://www.noaa.gov/education/resource-collections/ocean-co...

"Researchers have already discovered severe levels of pteropod shell dissolution in the Southern Ocean, which encircles Antarctica."

The optimal concentration for the ecology that we recently had is the CO2 concentration we had a bit before that (as it takes times for effects to be felt). Plus or minus, here or there, depending on other factors such as warming.

Forcing the rest of the ecology to try to adapt to increased CO2 levels starts to become really problematic for them when we are also forcing them to try to adapt to things like human-introduced invasives, human-caused habitat destruction and repurposing, population loss due to over-hunting and over-harvesting. It all adds up.

Good point about OA. I couldn’t find what the control was in the pteropod study. What are they comparing them against?

Also looks like OA isn’t uniformly bad. Some species seem to thrive: https://www.whoi.edu/oceanus/feature/ocean-acidification-a-r...

> Good point about OA. I couldn’t find what the control was in the pteropod study. What are they comparing them against?

No clue. I was just using it as an example.

> Also looks like OA isn’t uniformly bad. Some species seem to thrive

Sure, that's why the harm is measured in terms of entire ecologies, not individual species.

The optimal is whatever it median value was before industrialization. Not that Earth hasn't had life at a wide range of CO2 levels, but current life had a million+ years to get used to mid-200s PPM, whereas we've gone from that to over 400 in a few decades. Ecologically, that's like hitting a brick wall. The rate of change is too fast.