Forests naturally remove about 11.7 billion tons of CO2 from the atmosphere each year – roughly a third of total fossil fuel emissions.  This basic fact means that, if the world’s forests didn’t exist, there would be a lot more CO2 in the atmosphere, and the oceans would be considerably more acidified.
At the same time, land-use changes across the globe contribute, on average, about 5.5 billion tons of CO2 to the atmosphere each year. This is the net of emissions — primarily from deforestation, forest degradation (including forest fires) and peatland burning  — and removals associated with regeneration, tree planting, and forest management. The emissions are further compounded by the foregone sequestration of hundreds of millions of tons of CO2 that deforested areas would have provided each year had they been left uncleared.
Most of the emissions from land use change can be eliminated in ways that benefit the atmosphere, the forests, and people that depend upon them. That hasn’t happened by itself largely because there are powerful interests that benefit from deforestation and forest degradation while the costs are borne more broadly, primarily by those lacking such power. Nonetheless, some important progress has been made, despite setbacks, and reducing emissions from land use change remains an urgent priority.
And through improved forest management and reforestation it’s still possible to increase forest removals of CO2 from the atmosphere. By how much is a matter of some controversy, but over the next few decades billions of tons per year is feasible with proper incentives and could be broadly beneficial if proper safeguards are put in place and maintained.