[waserwill]

Anything that needs carbon in its metabolism will, naturally, use what's available.

Biological systems are tricky, though. If you dump a huge amount of fruit into a forest, the animals will eat it and grow in number; then, so will their predators. Animals who don't eat the fruit but are eaten by the predators will be in a bad spot. That leads to consequences all over the food web. Plus, dumping large amounts every year also changes the soil chemistry and changes what grows there.

Similarly, higher CO2 decreases water pH (more acidic) and can cause fast-growing algae to bloom (which decreases light penetration to the water beneath, and the algae may produce toxins).

Even when high-level equilibria are reached (which they eventually would, one way or another), they won't necessarily be the same or come pleasantly.