The rate of build-up of CO2 in the atmosphere can be reduced by taking advantage of the fact that
atmospheric CO2 can accumulate as carbon in vegetation and soils in terrestrial ecosystems. Under
the United Nations Framework Convention on Climate Change any process, activity or mechanism which removes a
greenhouse gas from the atmosphere is referred to as a
"sink". Human activities impact terrestrial sinks, through land use, land-use change and
forestry (LULUCF) activities, consequently, the exchange of CO2 (carbon cycle) between the
terrestrial biosphere system and the atmosphere is altered.
The role of LULUCF activities in the mitigation of climate change has long been recognized. Mitigation can be
achieved through activities in the LULUCF sector that increase the removals of greenhouse gases (GHGs) from
the atmosphere or decrease emissions by sources leading to an accumulation of carbon stocks. An important
feature of LULUCF activities in this context is their potential reversibility hence, non-permanence of the
accumulated carbon stocks.
Forests present a significant global carbon stock accumulated through growth of trees and an increase in soil
carbon. Estimates made for Global Forest Resources Assessment 2010 (FRA 2010) show that the world’s forests store more
than 650 gigatonnes (1 Gt=1 billion tonnes) of carbon, 289 Gt in the biomass (44 percent), 72 Gt in dead wood
and litter (11 percent) and 292 Gt in soil (45 percent). While sustainable management, planting and
rehabilitation of forests can conserve or increase forest carbon stocks, deforestation, degradation and poor
forest management do reduce carbon stocks. For the world as a whole, carbon stocks in forest biomass
decreased by an estimated 0.5 Gt annually during the period 2005–2010. This was mainly because of a
reduction in the global forest area.
Croplands and grasslands also play an important role in the global carbon cycle, however, most of the carbon
stocks of these lands are found in the below-ground plant organic matter and soil.