Only half of anthropogenic CO2 emissions remain in the atmosphere. This is easy to check by comparing the rate of emissions against the rate of increase in atmospheric CO2. I have read from various sources that the remainder is absorbed - roughly in equal proportions - by two sinks, namely the ocean and the biosphere (some sources just say "woodland"). However, the total area of woodland globally has been shrinking for many decades. My question is: how can woodland be a carbon sink when it is shrinking?
I agree that this kind of source and sink budgeting is a little bit misleading. The answer to your question is that the land use change you mentioned to be a source of CO2 is added to the anthropogenic CO2 emissions. And indeed it is about as large as the sink effect of the biosphere (check out the figure I found in a WMO article).