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II.
Forest ecosystems are important components of the globalcarbon cycle in at least two ways. First, terrestrial ecosystemsremove nearly 3 billion tons of anthropogenic carbon every year (3Pg C year–1) through net growth, absorbing about 30% of allCO2 emissions from fossil fuel burning and net deforestation.Forests are major contributors to this terrestrial carbon sink andits associated economic benefits. Second, 4 billion hectares offorest ecosystems (4 × 103 Mha; about 30% of the global landarea) store large reservoirs of carbon, together holding more thandouble the amount of carbon in the atmosphere. Although theclimate protection role of forests is in no doubt, it is complex todetermine how much of the forest carbon sink and reservoir can bemanaged to mitigate atmospheric CO2 buildup, and in what way.