"Natural sinks" refers to natural processes or environments that can absorb or store something, such as carbon dioxide or pollutants, and help mitigate their impact on the environment. Full definition
During the last century or so, over half of the CO2 emissions from fossil fuel burning, industry, and deforestation have been absorbed by natural sinks such as the forests and oceans. (iiasa.ac.at)
CO2 emissions rise as natural sinks slow, but how can scientists precisely track this greenhouse gas, especially in advance of a potential global treaty to reduce its emissions? (scientificamerican.com)
In 1959, natural sinks removed just over 50 % of the carbon dioxide man emitted. (blogs.nature.com)