Trees are essential for maintaining ecosystem balance and provide countless services to both people and wildlife. One of their most important functions is carbon storage (carbon dioxide, or CO₂). Carbon storage is crucial in slowing climate change. If CO₂ levels in the atmosphere continue to rise, so will global temperatures—leading to devastating consequences such as melting glaciers and Arctic ice, rising sea levels, and extreme weather events, as we’ve witnessed in recent years. Trees store carbon by absorbing CO₂ during photosynthesis, which they use to grow their trunks, roots, branches, and leaves. In this article, we take a closer look at how CO₂ uptake works and why it matters.
How Trees Store CO₂
The amount of carbon trees can store depends on species, age, size, and location. Tropical rainforest trees, for example, can store significantly more carbon than trees in temperate zones, due to their rapid growth and year-round activity. Large, old trees with abundant wood hold far more carbon than young ones—highlighting the importance of conserving old-growth forests.
That said, tree felling is not always negative. Cutting can make space for younger trees that absorb more CO₂ during their growth phase. As long as felled trees are not burned or left to rot, their carbon remains stored. Much harvested wood is used in construction, which preserves stored carbon. If discarded, however, the wood will eventually release its carbon as it decomposes—and burning releases large amounts of CO₂ all at once, along with other harmful gases.
It is not just trees that store carbon: soil, groundwater, surface water (such as ditches and rivers), and especially oceans also play a critical role in carbon storage.
Greater Storage Through Strong Root Systems
Trees are capable of sending their roots deep into the soil, locking away carbon for hundreds or even thousands of years, depending on the species, soil type, and groundwater depth. Carbon storage is strongly linked to rooting capacity, tree health, and soil conditions.
In forests, root systems are often no larger than the tree’s crown spread. But solitary trees need stronger, wider root systems to withstand wind, meaning they can store more carbon. Root systems are therefore crucial not only for tree stability and growth, but also for carbon storage potential.
The Role of Vegetation Types
Among all vegetation types, wetlands are by far the most important carbon sinks—storing more carbon than all other vegetation types combined. Forests rank second. Large-scale wetland drainage, deforestation, and wildfires have released vast amounts of carbon, accelerating climate change. Protecting wetlands and forests is therefore critical.
To fight climate change, it is essential to both protect existing forests and plant new trees. But planting only works if healthy, resilient trees are used. Poor-quality or stressed trees cannot effectively fulfill their ecosystem services. Alongside planting, knowledge and innovation are key. In urban areas, the greatest short-term gains can be achieved by greening rooftops, paved squares, and infrastructure corridors, as well as reforesting degraded lands.
Do Young or Old Trees Store More CO₂?
A common question is how much CO₂ a single tree can absorb. The answer depends on many factors. On average, one cubic meter of wood stores just under one ton of CO₂. One study (source: 8billiontrees.com) found that a mature tree can absorb about 48 tons of carbon dioxide per year—the equivalent of emissions from a car driving 25,000 km. Other studies show that increasing the number of trees in cities also significantly reduces other types of air pollution.
While exact values per species are difficult to define, evergreen trees store CO₂ year-round, unlike deciduous species. Young trees, with their rapid growth, absorb carbon more quickly in the short term, while older trees—with denser wood mass and larger crowns—store more in the long term.
Examples of good carbon-storing tree genera include:
Acer, Aesculus, Carpinus, Fagus, Gymnocladus, Koelreuteria, Liquidambar, Quercus, Taxodium, and Tilia.
Using Wood in Construction to Fight Climate Change
Wood in construction not only locks away carbon but also replaces carbon-intensive materials like cement, concrete, glass, and bricks. The building industry accounts for about 11% of global carbon emissions, largely from the production and transport of these materials. Using timber and wood fiber for insulation and building materials can dramatically reduce emissions.
In this way, cities themselves can become long-term carbon storage systems, with buildings serving as reservoirs of sequestered carbon.
Conclusion
Trees that live long and produce valuable timber for durable use are especially effective for carbon compensation and long-term storage. By planting, protecting, and using trees wisely, we can reduce atmospheric CO₂ and make real progress in combating climate change.
*1 Source: Hiemstra et al. 2008, Bomen een verademing voor de stad.
*2 Source: Hiemstra, 2022, Groen in de Stad, Soortentabel
