Howy, this is the second time I've noticed you ask this question. I thought you weren't serious the first time, but seeing that you are, I'll try and answer.
Another way of looking at CO2 is to measure its ratio to all other gases, as in CO2 is X parts per million. There is a range within which our species has made its home. We are now outside that range and climbing at an extremely fast pace.
Essentially there are two different systems we are talking about: the biologic system and the geologic system. There is a cyle in both systems: CO2 is released into the air and it is removed from the air. The the model of interdependence between plants and animals you have in mind is based on the biological cycle. Then there is the geological cycle where things like volcanoes and naturally dissolving deposits of exposed calcium based rock release CO2 that is "new" into the biosphere. This is also an ongoing process. Acting to achieve a balance to this is, for example, CO2 that is absorbed by the ocean where through various mechanisms it ends up getting buried in the seabed for millions of years. (The oceans, you should recall, are part of our bioshpere, so until it is removed from the ocean and permanently buried, it really isn't geologically sequestered.)
What has gone wrong is that our presence has changed the balance that existed before we became so able to manipulate our environment. The rate we are digging up and consuming fossil fuels has taken us out of that range were we (and most other life on the planet) have developed.
There is zero chance that through carbon sequestration efforts we will move back down into that "safe zone" and then through it and come out the other side. You don't need to worry about that particular problem.
However, what you might want to consider to put on your schedule to contemplate worrying about is that rising greenhouse gas concentrations will start a cascade of changes that we have no hope of controlling. This cascade has happened a couple of times before and both times a very large percentage (95% at the Permian Triassic boundary) of life on this planet died off because the planet got so hot. Now, of course that isn't an overnight event, so if you are only concerned about what happens in your lifetime, perhaps you'll want to look into the effects that "minor" warming is expected to have on war, famine, drought and competition for resources.
Some good links to reputable climate science information are included for your convenience:
http://www.earthportal.org/http://www.ucsusa.org/http://www.realclimate.org/