The discussion talks explicitly about
how diminishing terrestrial and ocean
carbon sinks over time require reduced CO2 emissions from fossil fuels /
land use to achieve stabilization goals at various levels (e.g. 550 ppmv of CO2 in the atmosphere).
Land - use change, e.g., the clearing of forests for agricultural use, can affect the concentration of greenhouse gases in the atmosphere by altering
how much
carbon flows out of the atmosphere into
carbon sinks.