Skip to Content

What are carbon sinks?

A carbon sink is anything that absorbs more carbon that it releases, whilst a carbon source is anything that releases more carbon than is absorb. Forests, soils, oceans and the atmosphere all store carbon and this carbon moves between them in a continuous cycle. This constant movement of carbon means that forests act as sources or sinks at different times.

Not all stores of carbon are naturally cursed with such fluctuations however. In the context of climate change, the most important carbon stores are fossil fuel deposits as they have the unique benefit of being buried deep inside the earth, naturally separated from the carbon cycling in the atmosphere. This separation ends when humans burn coal, oil and natural gas, turning fossil carbon stores into atmospheric carbon. This release of carbon from fossil fuel has caused greenhouse gas (GHG) concentrations in the atmosphere to soar to levels more than 30 per cent higher than at the beginning of the industrial revolution. We are still adding roughly 6 billion tonnes of carbon per year to the atmospheric carbon cycle, significantly altering the intricate web of carbon fluxes, and as a consequence, altering the global climate.

Because of this increase in atmospheric carbon, a lot of emphasis and hope has been put into the ability of trees, other plants and the soil to temporarily sink the carbon that fossil fuel burning releases into the atmosphere. Indeed, the Kyoto Protocol, the international communities’ main instrument for halting global warming suggests that the absorption of carbon dioxide by trees and the soil is just as valid a means to achieve emission reduction commitments as cutting carbon dioxide emissions from fossil fuels.

The fatal flaw of carbon sinks

FERN profoundly disagrees with the assumption that planting trees or reducing deforestation is just as good as reducing emissions from burning fossil fuel. Such an assumption overlooks some important facts:

  • There is general agreement about the need to halt fossil fuel emissions, particularly inindustrialised countries. However instead of moving ahead with drastic reductions of energy use and initiating a tranistion towards low-carbon economies, forests' ability to (temporarily) sinks carbon is being used to justify continued fossil fuel use. Companies who have had their emissions capped are going beyond that cap by claiming sinks offset their above cap emissions. This means that carbon sinks are being used to justify an emission that would not otherwise have happened and the result is a furtehr rise in global greenhouse gas concentrations.
  • All carbon is not the same. Fossil carbon is generally static, whereas that which is in the active carbon pool, (the atmosphere and the biosphere) can be easily released through activities beyond government control such as forest fires, insect outbreaks, decay, logging, land use changes or even the decline of forest ecosystems as a result of climate change. Storing your carbon in a tree rather than a fossil fuel deposit is analogous to betting your money on a horse rather than storing it in a bank.
  • Afforestation - especially afforestation in northern tundra regions - may accelerate global warming. Climate change is expected to shift e.g. Canada's boreal forest borders northward and boreal forests are expected to expand into the southern parts of the tundra. While this will mean that carbon is removed from the atmosphere as trees grow, it may not benefit the climate: One of the key factors affecting the global climate is the 'albedo effect', a process which determines how much sunlight is reflected back into space and how much warms the Earth's surface. Dark green forests absorb more sunlight than tundra or farmland, adding to the warming trend in the boreal if large non-forested areas that are now covered in highly reflective snow were planted with trees.
  • It is not possible to accurately measure the “sink” effect of a forest (trees will take in different amounts of carbon depending on the weather and very little is known about the movemetn of carbon in forest soils).

Carbon offsets' negative effects on forest dependent communities

Besides the major shortcomings of the concept of carbon sinks from a scientific perspective, FERN’s analysis has shown that many tree planting offset projects have had, and continue to have, servere impacts on forests and forest peoples:

  • The Kyoto Protocol does not differentiate between forests and plantations, meaning that a substantial percentage of afforestation and reforestation offset projects will result in large-scale tree plantations. The first carbon sinks project seeking registration with the Kyoto Protocol’s Clean Development Mechanism (CDM) was a plantation in Brazil.
  • Many forest carbon offset projects are, or will be, located on lands where forest peoples' rights to customary land use have not been recognised or have been violated (see Forests of Fear). The Kyoto Protocol cannot hope to improve this situation as it includes no reference to the rights of indigenous peoples or forest dwellers.
  • Lands dedicated to carbon sink projects require contractual agreements that lock the land up for years, often decades. This means carbon sink offsets are effectively grabbing the best land to generate emission rights that allow the most polluting countries and industries to continue polluting while the needs of forest dependent communities in the Global South are curtailed.

For more information on any of these issues please see the SinksWatch and REDD-Monitor websites.



Most recent publications

Will carbon markets ever deliver for southern government, forests and people?

This statement, endorsed by 57 prominent human rights and environmental organisations from Europe, Africa, Asia,and North America, argues that carbon markets will never deliver for southern governments, forests or people.

PDF iconWill carbon markets deliver?931.71 KB

Comment on the COP21 - a forest perspective

Forests barely feature in the draft text, but runaway climate change could devastate the forests which more than a billion people directly rely on for their survival. Forests also play a crucial role in regulating the climate. Whichever way you look at it, the outcome of the Paris agreement is also an outcome for forests.
Kate Dooley  is in Paris, tracking the developments in the UN climate summit. She has written this overview of the talks from a forests perspective for Fern. Check back later in the  week for  further perspectives from Kate and other contributors.

New research shows risk of including land use and forests in EU’s emissions target

Two days before the European Union closes its consultation on the role that land use, land use change and forestry (LULUCF) should play in EU climate effort, new research reveals that including this sector in emissions reductions plans would cause havo

Impacts on the EU 2030 climate target of including LULUCF in the climate and energy policy framework

The European Union (EU) has a target to reduce emissions by at least 40 per cent by 2030. This is an economy-wide target and therefore includes the Land Use, Land Use Change and Forestry (LULUCF) sector. This study looks at how to integrate LULUCF into the EU’s 2030 Climate and Energy Framework.

PDF iconLULUCF_2030_revised_b696.06 KB

Fern’s response to EU LULUCF Consultation

Fern's response to this consultation concludes that the challenge of limiting global warming to two degrees is so great that effort should be made in all sectors. By maintaining Land Use, Land Use Change and Forestry (LULUCF) separately, the EU avoids reducing its ambition and gives itself the opportunity to create real ambition to maintain carbon stocks and reduce emissions in LULUCF.

PDF iconLULUCF consultation_Fern.pdf243.17 KB