- Increasing total plant biomass increases the amount if carbon trapped in that portion of the cycle at any given time
- When plants decay or are eaten, some of the carbon compounds created are solids. Carbon itself is not the problem, carbon-based gases are.
- Some portion of plant biomass is harvested by humans for durable purposes, such as wood and textiles. These uses hold carbon for much longer.
I don't know what the total affect of these is, but they shouldn't be ignored.
This is a very dangerous misconception and should not be spread around. It is like saying "I don't have to worry about my emissions, because someone else will clean them up for me". Do you have/support enough plant life to clean up your own emissions?