Carbon Sequestration Across Biomes: Characteristics and Strategies

By: Fadi Abdulghani

The past few decades of climate research have identified that the Earth is warming at an accelerated rate due to human activity. Since the industrial revolution, humans have extracted fuel from long-term carbon sinks like oil, natural gas, and coal, resulting in the emission of trillions of tons of carbon that would not have been released otherwise. But what exactly does this suggest? Well, when fuel commodities like gasoline and oil are combusted, they emit carbon dioxide (CO₂₎ that enters the atmosphere, and when excited by radiation, absorb and radiate heat. This phenomenon, known as the greenhouse effect, while beneficial for keeping the surface of the Earth at a relatively constant, warm temperature has been exacerbated by the excess carbon dioxide emitted by human activity. As shown in Figure 1, CO₂ levels have risen dramatically since 1960 (by R. Lindsey, H. Diamond, 2022). Such abnormally levels of CO₂ can radically change observed climate patterns, disrupting industrial agriculture, increasing the frequency and severity of weather events, and creating environmental conditions that may be intolerant for plant and animal life.

So, how do we collectively solve an existential issue that appears to be insurmountable at times? Knowing what we know about climate change, if we can decrease the amount of carbon in the atmosphere, then we can the solve issue at hand. Many private companies and researchers are creating new technologies that can capture carbon and store it on a long-term basis using processes and characteristics from biomes and ecosystems. This process is known as carbon sequestration. Therefore, we should make land-use decisions that are effective and efficient for storing atmospheric CO_2. Biomes such as forests, grasslands, wetlands, croplands, and urban environments can be managed in ways that promote carbon sequestration to reduce the impacts of climate change, but how does each biome compare to one another? Through what mechanisms and properties make these biomes valuable and effective for carbon sequestration? Through research and extensive study, society can utilize and manage different biomes in order to promote carbon sequestration, mitigating the effects of climate change.

FORESTS

So, how do we collectively solve an existential issue that appears to be insurmountable at times? Knowing what we know about climate change, if we can decrease the amount of carbon in the atmosphere, then we can the solve issue at hand. Many private companies and researchers are creating new technologies that can capture carbon and store it on a long-term basis using processes and characteristics from biomes and ecosystems. This process is known as carbon sequestration. Therefore, we should make land-use decisions that are effective and efficient for storing atmospheric CO_2. Biomes such as forests, grasslands, wetlands, croplands, and urban environments can be managed in ways that promote carbon sequestration to reduce the impacts of climate change, but how does each biome compare to one another? Through what mechanisms and properties make these biomes valuable and effective for carbon sequestration? Through research and extensive study, society can utilize and manage different biomes in order to promote carbon sequestration, mitigating the effects of climate change.

GRASSLANDS

The vast variety of vegetation grasses, sedges, and even plants with beautiful flowers have dominated the grassland landscape. The root systems of grassland plants tend to be long, fibrous root systems that prevent soil erosion, contribute positively to soil structure, and most importantly, effectively contribute to sequestering carbon. Soil organic carbon in grasslands is typically brought into the soil through the excrement of herbivores, decomposition of plant parts, and exudates from roots. This SOC can be conceptualized as “pools” in the soil with different pools possessing different characteristics and residence times as shown in Figure 2 (Jones and Donnelly, 2004).  It is important to clarify that this process of aggregate organization is present in many biomes, not just grasslands.

WETLANDS

Wetlands are a unique type of biome that have little oxygen in the soil layers due to prolonged saturation by water. Low oxygen levels in soil lowers decomposition rates of organic materials significantly, resulting in the accumulation of organic matter, and in turn, carbon. Nahlik, and Fennessy found that despite making up 5-8% of total land mass, wetlands store 40% of soil carbon in the world (p. 2). Since wetlands store nearly a majority of the Earths soil carbon, they must be managed properly so that the carbon can be stored for long periods of time. In fact, freshwater, inland wetlands store similar quantities of carbon to saline wetlands (Nahlik, & Fennessy, 2016). However, saline wetlands tend to have a more uniform distribution of carbon in the soil layers. Inland wetlands tend to have more soil carbon present in the upper layers, making them prone to loss of soil carbon when disturbed compare to saline wetlands. Villa and Bernal (2017) found that saline wetlands, unlike inland wetlands, emit negligible amounts of methane and are more efficient at sequestering carbon because of the abundance of sulfates; these sulfates act as electron acceptors in some metabolic pathways which prevent soil organic matter from being decomposed.  Wetlands must be preserved and protected from degradation and conversion as these processes were found to release 175-500 years’ worth of carbon in the form of methane in a specific type of wetlands called peatlands (Nahlik, & Fennessy, 2016).

CROPLANDS

Although the proper management of croplands is and will be important to ensure that the nutritional needs of people are met, there are ways in which we can maximize carbon sequestration and storage in these soils too. The topsoil is most sensitive to disturbances as extensive use of farm machinery may compact soils destroying macro and microaggregates that protect SOM—and in turn carbon—from being decomposed by microorganisms. Potential management strategies that may prove effective in sequestering carbon in croplands can be anything from agroforestry, crop rotations, and incorporation of crop residues. Many management strategies rely on increasing carbon inputs and reducing SOC losses. In a comparative study analyzing the effects of compost of SOC in the topsoil, they found that composting regularly may have a carbon sequestration potential of 714 ± 404 kg C ha⁻¹ y⁻¹ which, compared to many management practices, is massive (Tiefenbacher et al., 2021). Figure 3 illustrates the carbon sequestration potential in topsoil with various management practices (Tiefenbacher et al., 2021).

URBAN LANDS

The world is becoming increasingly urbanized with more and more people flocking to urban areas. As a result of urbanization, the land area used to expand cities to build infrastructure is being covered by impermeable surfaces like concrete and other hard materials, making the soil highly compacted, less nutrient dense, and dry (Brown et al., 2011). These characteristics of urban soils that are poorly managed lead to low concentrations of SOC; however, urban soils that are managed properly have the potential to store more carbon than soils outside the urban boundary (Brown et al., 2011). Some potential management practices that could increase the amount of sequestered carbon in urban areas is the proliferation of green spaces such as parks, community gardens, and bio-swales. Also, city wide initiatives that manage food and fecal waste effectively could sequester carbon in urban areas and promote the growth of vegetation. These practices, while increasing carbon in urban soils, help to combat negative effects of cities like the urban heat island effect. Ultimately, proper management of urban soils that promotes the sequestration of SOC leads to healthy, sustainable cities.

FINAL THOUGHTS:

As society continues to combust fossil fuels and release more and more CO₂ into the atmosphere, climate change will accelerate and worsen in a variety of ways, disrupting many ecosystems and much of life as we know it. Only through the implementation of management practices and policies can carbon storage and sequestration be maximized in the various biomes that cover our Earth. Composting, promoting the proliferation of native vegetation, and the restructuring of our cities are all great starting points; what matters is that we should begin to use these practices now, rather than later. From the rolling prairies of Oklahoma to the wetlands of South Asia, nations must unite under a shared love of Earth and all its life and properly manage soils to combat climate change.

References:

Brown, S., Miltner, E., & Cogger, C. (2011). Carbon sequestration potential in urban soils. Carbon Sequestration in Urban Ecosystems, 173–196. https://doi.org/10.1007/978-94-007-2366-5_9

Dixon, R. K., Brown, S., Houghton, R. A., Solomon, A. M., Trexler, M. C., & Wisniewski, J. (1994). Carbon Pools and Flux of Global Forest Ecosystems. Science, 263(5144), 185–190. http://www.jstor.org/stable/2882371

Edwards, T. (2022, June 28). What is Soil Organic Carbon? Agriculture and Food. Retrieved March 4, 2023, from https://www.agric.wa.gov.au/measuring-and-assessing-soils/what-soil-organic-carbon

Jones, M.B. and Donnelly, A. (2004). Carbon sequestration in temperate grassland ecosystems and the influence of management, climate and elevated CO₂. New Phytologist, 164: 423-439. https://doi.org/10.1111/j.1469-8137.2004.01201.x

Lindsey, R. and H. Diamond (2022, June 22). Climate change: Atmospheric carbon dioxide. NOAA Climate.gov. Retrieved March 4, 2023, from https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide#:~:text=Carbon%20dioxide%20is%20Earth%27s%20most,including%20back%20toward%20Earth%27s%20surface

Nahlik, A. M., & Fennessy, M. S. (2016). Carbon storage in US wetlands. Nature Communications, 7(1). https://doi.org/10.1038/ncomms13835

Tiefenbacher, A., Sandén, T., Haslmayr, H.-P., Miloczki, J., Wenzel, W., & Spiegel, H. (2021). Optimizing carbon sequestration in croplands: A synthesis. Agronomy, 11(5), 882. https://doi.org/10.3390/agronomy11050882

Villa, J. A., & Bernal, B. (2018). Carbon sequestration in wetlands, from science to practice: An overview of the biogeochemical process, measurement methods, and Policy Framework. Ecological Engineering, 114, 115–128. https://doi.org/10.1016/j.ecoleng.2017.06.037