Trees are CO2 sequestration machines

Carbon dioxide is the most produced greenhouse gas. Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide.

It is one method of reducing the amount of carbon dioxide in the atmosphere with the goal of reducing the impact on nature.

Carbon monoxide and carbon dioxide are both very important atmospheric contaminants. Atmospheric carbon dioxide comes from two primary sources natural and human activities.

Natural sources of carbon dioxide include most animals, which exhale carbon dioxide as a waste product.

Human activities are responsible for the introduction of increasing quantities of these gases to the atmosphere.

Human activities that lead to carbon dioxide emissions come primarily from energy production, including burning coal, oil, or natural gas.

Carbon monoxide is particularly important because of its potent mammalian toxicity, while carbon dioxide is most significant because of its ability to regulate global temperature.

Neither gas is thought to cause direct damage to vegetation at ambient concentrations presently monitored.^[1] 

On the other side, Geologic carbon sequestration is the process of storing carbon dioxide (CO2) in underground geologic formations.

The CO₂ is usually pressurized until it becomes a liquid, and then it is injected into porous rock formations in geologic basins. This method of carbon storage is also sometimes a part of enhanced oil recovery.

All-you-can-eat buffet for trees

Atmospheric carbon dioxide (CO₂) concentrations are rapidly increasing, having risen by about 100 ppm over the last century.

Atmospheric CO₂ is the basic photosynthetic building block of plants and is respired to generate the plant’s energy.

Atmospheric CO₂ in enhanced conditions is like an “all-you-can-eat buffet” for trees. Planting billions of trees across the world is one of the biggest and cheapest ways of taking CO₂ out of the atmosphere.

Photosynthetic carbon capture by trees is likely to be among the most effective ways to limit the rise of CO₂ concentrations across the globe.

Forests constitute from approximately 60% to 90% of the total terrestrial carbon pool. The natural net input of carbon dioxide to the atmosphere from vegetative systems is close to zero (equilibrium) when the systems exist in natural, undisturbed states.

Under conditions of widespread and rapid forest destruction, however, equilibrium conditions, or near equilibrium conditions may be lost.

Several researches address the potential of afforestation, reforestation, agroforestry and forest management for increasing carbon sequestration.

However, it should be noted that the C sink strength of forests is highly variable depending on forest types, forest age, moisture availability, local climate, and soil carrying capacity.

The C sequestration potential of various afforestation/reforestation activities also depends on the site and forest management practices and forest type.

Clearly, better-managed and fully stocked forests and forests established with genetically superior selections offer considerable opportunities for increasing the C sink strength of the world’s forests.^[2]

^{Trees store carbon}

The sequestration and storage of carbon is one of the many ecosystem services supported by biodiversity.

Carbon is initially sequestered through photosynthesis before being transferred to one of several terrestrial pools including above-ground biomass, dead wood, litter, roots (below-ground biomass) and soil.

These pools are then subject to gains and losses depending on rates of growth, mortality and decomposition that are in turn affected by varying human and natural disturbances.

Species can affect the long-term balance of carbon gains and losses in ecosystems through different components of the carbon cycle, including the magnitude, turnover and longevity of carbon stocks in soils and vegetation.

Experiments with tree plantations of native and introduced species have often found significant and positive effects of species richness on different components of the carbon cycle, including productivity, decomposition, soil respiration and plant mortality.

Additionally, Forest loss is the second largest anthropogenic source of carbon dioxide emissions to the atmosphere, contributing the equivalent of about 12 percent of fossil fuel emissions.

Deforestation results in immediate CO₂ emissions (with small amounts of CO, CH4 and N2O) when biomass and dead organic matter is burned, and in slower releases when biomass and dead organic matter decay.

^{Planting trees against carbon emissions}

Tree planting remains a viable option for carbon sequestration. As a tree matures, it can consume 48 lbs. of carbon dioxide per year (among other greenhouse gases like ozone) and releases enough oxygen for you to breathe for two years. 

Also, urban trees help ameliorate the microclimate, provide wildlife habitat, increase property values, impact human moods, absorb air pollutants, conserve water, reduce soil erosion, and decrease noise pollution^[6]

References 

1. Smith, W.H., Air pollution and forests: interactions between air contaminants and forest ecosystems. 2012: Springer Science & Business Media.
2. Karnosky, D.F., et al., Changing atmospheric carbon dioxide: A threat or benefit? Developments in Environmental Science, 2003. 3: p. 57-84.
3. Griscom, B.W., et al., Natural climate solutions. Proceedings of the National Academy of Sciences, 2017. 114(44): p. 11645-11650.
4. Lloyd, J., The CO2 dependence of photosynthesis, plant growth responses to elevated CO2 concentrations and their interaction with soil nutrient status, II. Temperate and boreal forest productivity and the combined effects of increasing CO2 concentrations and increased nitrogen deposition at a global scale. Functional Ecology, 1999. 13(4): p. 439-459.
5. Parrotta, J., C. Wildburger, and S. Mansourian, Understanding relationships between biodiversity, carbon, forests and people: The key to achieving REDD+ objectives. A global assessment report prepared by the Global Forest Expert Panel on Biodiversity, Forest Management, and REDD+. IUFRO World Series, 2012. 31: p. 1-161.
6. Karnosky, D.F., Urban forestry comes of age. Orion Nature Quart., 1984. 3 (4),: p. 46–53.