Carbon sink

from Wikipedia, the free encyclopedia
This article needs to be revised: Carbon sinks, as elements of the carbon cycle, have played a role in the earth's climate since ancient times. This article, however, has an extreme tunnel vision of anthropogenic climate change.
Please help to improve it , and then remove this flag.

In the geosciences, a natural reservoir is referred to as a carbon sink (also known as a carbon dioxide sink or CO 2 sink ) which - viewed in geological time scales - temporarily absorbs and stores carbon . Carbon sinks are of great importance for the global climate because they absorb the greenhouse gas carbon dioxide (CO 2 ) from the atmosphere and thus weaken the greenhouse effect . Therefore, they currently play an important role in connection with global warming .

Important carbon sinks

Terrestrial ecosystems

Terrestrial ecosystems contain carbon in organic compounds both in their living biomass and in the humus of their soils . If the carbon stocks increase in an ecosystem (i.e. the sum of the carbon stocks in biomass and soil), this ecosystem is a carbon sink.

By photosynthesis pick plants (and in lesser amount, some types of bacteria ) carbon dioxide from the atmosphere and build the carbon in organic material a. Some of these organic substances serve as food for animals and microorganisms . Organic substances that are no longer part of living beings are added to the soil as litter and form the humus there. In addition to dead creatures, litter includes z. B. also fallen leaves and needles, root exudates ( exudates ) and animal excrement. The majority of the litter is mineralized by bacteria and fungi after a short time , with the carbon from the organic compounds being converted back into carbon dioxide and released into the atmosphere. Also fire converts to organic bound carbon into carbon dioxide. If an ecosystem is to serve as a carbon sink, two goals must be pursued: more biomass and more humus (more litter, less mineralization). As the diagram below shows, more than twice as much carbon is stored in the soil worldwide as in living biomass, although this diagram only shows the carbon stocks of the top meter for the soil.

Carbon cycle diagram . The black numbers indicate how many billions of tons of carbon (Gt C) are in the various reservoirs. The blue numbers show how much carbon is exchanged between the individual storage facilities per year.

In the carbon cycle , carbon is exchanged between carbon sinks and carbon sources. The most important source of carbon is currently the steadily growing consumption of fossil fuels such as crude oil , natural gas or coal . In addition, the above processes release carbon from ecosystems.

Forests have high carbon stocks, both in their biomass and in their soils. Afforestation is therefore very effective for the climate, but only if the carbon bound in the process cannot get back into the atmosphere as carbon dioxide. The tropical rainforests were previously considered to be particularly large carbon sinks. However, according to a study published in 2020, this effect appears to be weakening or reversing as a result of global warming.

Scientific studies with CO 2 -fertilized forests indicate that they release additional CO 2 through soil respiration . An outdoor experiment by the University of Basel and the Paul Scherrer Institute found no growth promotion in the trees examined despite the CO 2 fertilization.

Even Moore bind carbon dioxide while they grow.

Grasslands, so z. B. steppes and savannahs also have a high potential as a carbon sink. As scientists from Lund University have established, the carbon dioxide bound by their annual photosynthetic activity corresponds to about a third of the annual anthropogenic carbon dioxide emissions. There are many fires in savannahs, most of which are man-made. It is therefore particularly important to offset the bound carbon dioxide against the carbon dioxide that is released back into the atmosphere through mineralization or fire.

Aquatic systems

Oceans play the most important role. They hardly take up carbon dioxide from the air, but get their main carbon supply from flooded biomass and from the respiratory carbonic acid of the soil and water organisms contained in the tributaries.

According to a 2017 projection by researchers at Lanzhou University , endorheic waters are another important sink that could store amounts of carbon on a scale like the deep sea.

The lithosphere as a carbon store

In geological time, the most important carbon reservoir is the lithosphere , which contains 99.8% of the carbon found on earth; mainly as a carbonate like lime . From the lithosphere, no significant amounts of carbon get back into the biological carbon cycle.

In the earth's crust there are very large amounts of suitable silicate minerals which , in the long term, will permanently remove large amounts of CO 2 from the atmosphere through conversion into carbonates . However, the corresponding chemical reactions take place so slowly that the lithosphere cannot function as a sink in a carbon dioxide removal process for the current emissions of carbon dioxide, at least in the short to medium term . An artificial acceleration of these processes through mining and crushing of corresponding silicates as well as the use of acids is theoretically possible, but not realistic on a world scale due to the associated consumption of materials, energy and landscape. For example, more than eight tons of what are probably the most suitable minerals of the serpentine group would be required to permanently remove one ton of CO 2 from the atmosphere.

Individual evidence

  1. ↑ Wannes Hubau, Simon L. Lewis, Oliver L. Phillips, Kofi Affum-Baffoe, Hans Beeckman: Asynchronous carbon sink saturation in African and Amazonian tropical forests . In: Nature . tape 579 , no. 7797 , March 2020, ISSN  1476-4687 , p. 80–87 , doi : 10.1038 / s41586-020-2035-0 ( nature.com [accessed March 8, 2020]).
  2. ↑ DER SPIEGEL: Climate change: Rainforests store up to 30 percent less CO2 - DER SPIEGEL - Wissenschaft. Retrieved March 8, 2020 .
  3. ^ AS Allen, JA Andrews, AC Finzi, R. Matamala, DD Richter and WH Schlesinger (1999): Effects of Free Air CO 2 -Enrichment (FACE) on Belowground Processes in a PINUS TAEDA Forest , in: Ecological Applications, Vol. 10, No. 2, pp. 437-448, abstract online
  4. ↑ a b Christian Körner : Forest trees in a world rich in CO 2 (PDF; 39 kB)
  5. ↑ L. Bergmann, M. Drösler: The importance of moors as CO2 sinks, 2009
  6. ↑ Viktiga savanner . In: Sveriges Natur , No. 106 - 415, Member magazine of the Swedish Nature Conservation Association, Stockholm, September 2015, ISSN  0039-6974 , p. 16.
  7. ↑ Yu Li et al. a .: Substantial inorganic carbon sink in closed drainage basins globally . In: Nature Geoscience . June 2017, doi : 10.1038 / ngeo2972 . Report on this: Bobby Magill: Desert Basins Could Hold 'Missing' Carbon Sinks. In: climate central. June 20, 2017. Retrieved June 26, 2017 .

Web links