Néolithe - blog : Everything you need to know about the carbon cycle

The carbon cycle :

The natural carbon cycle is a dynamic process in which carbon is continually exchanged, in different forms, between different reservoirs. This mechanism regulates our climate by maintaining a delicate balance.

Let’s take a look at how carbon is stored and exchanged in three main reservoirs : the atmosphere, the lithosphere and terrestrial biosphere, and the hydrosphere.

Where is natural carbon stored ?

1. The atmosphere

2. The lithosphere and terrestrial biosphere

3. The hydrosphere

1. The atmosphere

Carbon is found mainly in the form of carbon dioxide (CO2). Plants absorb this CO2 during photosynthesis, transforming the carbon into organic matter. This process not only reduces the concentration of CO2 in the air, but also produces oxygen, essential for life on Earth. Animals then consume these plants, incorporating the carbon into their own tissues.

2. The lithosphere and terrestrial biosphere

Plants, especially trees, store absorbed carbon in their biomass (trunk, branches, leaves) and in the soil. The terrestrial biosphere thus acts as a vast carbon reservoir. When plants and trees die, some of the carbon they contain is released into the atmosphere through decomposition, a process carried out by micro-organisms such as bacteria and fungi. The rest of the carbon is returned to the soil, enriching the earth.

3. The hydrosphere

The oceans absorb a large proportion of atmospheric CO2. The carbon dissolved in the water is used by phytoplankton for photosynthesis, feeding the marine food chain. When these marine organisms die, their carbon is deposited on the ocean floor, where it is stored in sediments in the form of organic and inorganic matter. This storage can last for millennia, contributing to the long-term regulation of CO2 levels in the atmosphere.

In short

In short, every year, the oceans absorb around a quarter of the world’s CO2 emissions, while forests, through photosynthesis, capture around a third.

The role of ecosystems in the carbon cycle

Ecosystems also play a role in the carbon cycle by acting as carbon sinks. They interact with reservoirs, helping to regulate the amount of CO2 in our atmosphere.

Terrestrial and aquatic ecosystems play a role in storing atmospheric carbon. Forests, for example, retain carbon in their vegetation and soils. Similarly, wetlands such as marshes and peat bogs store organic carbon in their soils.

But these ecosystems are facing increasing threats, such as deforestation, land degradation, wetland conversion, pollution and climate change, which compromise their role as carbon sinks and may even turn them into carbon sources, contributing to rising CO2 emissions into the atmosphere.

A striking example is the Centre Val-de-Loire region, where significant changes in agricultural land use over the past 40 years have resulted in a 7% reduction in available land.

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