Biological sequestration

ForestBiological (or terrestrial) sequestration involves the net removal of CO2 from the atmosphere by plants and micro-organisms and its storage in vegetative biomass and in soils.

On this page, we deal with the main natural carbon dioxide sinks in Manitoba:

Click a link in the list above to jump to that topic on this page. Biological sequestration offers many potential advantages: (1)

  • could sequester relatively large volumes of carbon at comparatively low cost
  • protecting or improving soils, water resources, habitat, and biodiversity
  • generate rural income
  • promotes more sustainable agriculture and forestry practices

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Soils contain more carbon than is contained in vegetation and the atmosphere combined. (2) Agricultural carbon sequestration has the potential to substantially mitigate global warming impacts. At the same time, employing methods to enhance carbon sequestration in soil will increase soil quality. Carbon is stored within soil organic matter (SOM). SOM is a complex mixture of carbon compounds, consisting of decomposing plant and animal tissue, microbes (protozoa, nematodes, fungi, and bacteria), and carbon associated with soil minerals. (3) Methods that significantly enhance carbon sequestration in soil include

  • conservation tillage (low till / no-till farming) – minimizing or eliminating manipulation of the soil for crop production. This includes the practice of mulch tillage, which leaves crop residues on the soil surface. These procedures generally reduce soil erosion, improve water use efficiency, and increase carbon concentrations in the topsoil. Conservation tillage can also reduce the amount of fossil fuel consumed by farm operations
  • cover cropping – the use of crops such as clover and small grains for protection and soil improvement between periods of regular crop production. Cover crops improve carbon sequestration by enhancing soil structure, and adding organic matter to the soil.
  • crop rotation – planting different crops on a rotating pattern of years (e.g. corn-oats-clover) will reduce the loss of carbon from the soil and with some additions (e.g. manure-lime-phosphorous) will add carbon to soils (4)

All of the methods above are more widely used in organic farming than in conventional farming. Carbon stored in soils oxidizes rapidly. See also Solutions / Agriculture / Soil management

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Grasslands contribute to soil organic matter, mostly in the form of their extensive fibrous root mats. Since the 1850s, a large proportion of the world’s grasslands have been tilled and converted to croplands, allowing the rapid oxidation of large quantities of soil organic carbon. Livestock producers can enhance carbon sequestration on their operations by converting from continuous grazing to rotational grazing. This keeps the plants in an actively growing state and keeps photosynthesis rates high. This improves the quality of the forage and allows the plants to sequester more carbon. (5) See also Solutions / Agriculture / Pasture management

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Canada has about 10% of the world’s forests. The boreal forest is the most extensive forest type and a large part of Manitoba is covered by boreal forest. Trees and plants in forests draw carbon dioxide out of the atmosphere when they are growing and release carbon dioxide as they decay. In general, forests store carbon (like a bank account) when they are in a stable state. Forests store carbon in the following ways:

  • Soils
  • Wood products
  • Re-growth
  • New forest (aforestation)

Forest soils

Canada’s boreal forests store as much as 80% of their total carbon in the soils as dead organic matter. (6) Therefore any erosion of forest soil (such as after clear-cutting) increases the potential for release of this stored carbon.

Wood products

Wood can be incorporated into construction material for houses, for furniture, or for other durable products, thus sequestering forest carbon over years or even centuries. (until the houses are torn down and the wood burned or sent to landfills) Paper products, however, may be disposed of quickly (e.g. fliers, newspapers) and decompose in landfills or may last a much longer time period (e.g. books)

Re-growth of harvested forests

According to Natural Resources Canada, reducing timber harvesting in Canada would have very little impact on carbon dioxide emissions. With sustainable forest management, less than 0.5% of the managed forest is harvested in any given year in Canada. These harvested areas regenerate to become forests again, so there is substantial new storage of carbon occurring in the areas previously harvested. Additionally, the amount of carbon released from each year to forest fires and other natural disturbances is about 2.5 times the amount of carbon lost in harvesting.

New forest (aforestation)

Because growing vegetation absorbs carbon dioxide, the UN Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol both recognize the importance of forests for addressing climate change. However, Article 3.3 of the Kyoto Protocol calls for the maintenance of forests by afforestation, reforestation, and controlling deforestation (ARD). Afforestation and reforestation credits are obtained, while deforestation is associated with debits. Article 3.4 provides credits for increases in the carbon sequestered by managed forests. Thus, there is a role for forest sequestration under these agreements. Although a role for sustainable forest management (SFM) is not explicitly articulated in the Kyoto Protocol, SFM is recognized in the UNFCCC. The Manitoba Hydro Forest Enhancement Program has been in operation since 1995, funding hundreds of community tree planting projects throughout the province. Thousands of trees have been planted at schools, churches, boulevards, parks and recreation centres, memorials and campsites all over Manitoba. These trees serve to educate, beautify, and to provide erosion control, shade and windbreaks. The Forest Enhancement Program provides a way for people to become involved in their communities and create beautiful and useful green spaces for future generations. The program delivers real greenhouse gas benefits through the biological sequestration of carbon but it was not specifically designed as a carbon sequestration program.

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Figure 1: Carbon storage in Peatlands in the Prairies

Over long periods of time, great amounts of carbon have accumulated in peatlands. Since bogs and fens are waterlogged, there isn’t enough oxygen for decomposition and the carbon of dead plant matter remains trapped. (i.e. sequestered) Manitoba has the largest carbon storage in peat bogs of the three Prairie Provinces. (7) Figure 1 shows the amount of carbon stored in Prairie Province peatlands. Values are in kg/m2 (8) There is a danger that much of the carbon that is currently trapped in peatlands will be released due to global warming. It is estimated that “a warming of 4 degrees C will cause a 40 percent loss of soil organic carbon from the shallow peat and 86 percent from the deep peat” of Northern peatlands. (9) This will greatly increase the amount of greenhouse gases in the atmosphere and will amplify the global warming effect. This is dangerous for three reasons:

  • The northern peatlands store a lot of carbon – They are believed to store some 320 (+/- 140) billion metric tons of carbon, roughly half of what the atmosphere contains
  • Peatlands tend to emit much of their carbon in the form of methane, which is more than 20 times as powerful a greenhouse gas as carbon dioxide
  • A warming of 4 degrees C this century is all but inevitable if we don’t sharply reverse emissions trends quickly (10)

Can we save our peatlands?

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