How plants in your garden remove carbon dioxide from the atmosphere

Analysis: They're up there with forests, bogs and oceans as serious players in the business of taking and storing carbon from the atmosphere.

Plants are nature's unsung heroes when it comes to combating climate change. You often hear about carbon emissions and how rising carbon dioxide (CO₂) levels are wreaking havoc on our climate, but did you know that plants play a crucial role in removing (sequestering) CO₂ from our atmosphere?

CO₂ is a colourless, odourless gas that is naturally present in our atmosphere. Whilst it is necessary for life on Earth, excessive amounts of CO₂ are causing the planet's temperature to rise, leading to climate change. Human activities like burning fossil fuels, deforestation and heavy industrial processes release enormous quantities of CO₂ into the atmosphere which are disrupting the delicate balance of the Earth's ecosystem.

You might not have to look much further that your back garden to find a solution that can help capture and store this excess CO₂ - plants. They do this through a remarkable ability that they possess called photosynthesis. From the tiny Irish Shamrock to the Giant Redwood Sequoia, all plants photosynthesize. This process allows them to harness energy from the sun. With this energy, along with water and CO₂ from the air, the plant can produce glucose (a type of sugar) and oxygen. The oxygen is released back into the atmosphere, allowing us to breathe.

Photosynthesis serves a dual purpose: it provides food for the plant and acts as a natural carbon capture mechanism. The carbon from the CO₂ that a plant absorbs is a vital part of the chemical structure of the glucose. The plant uses this glucose to grow aboveground biomass such as leaves, stems, fruit or flowers and belowground biomass such as roots.

As the plant grows, it accumulates carbon within its tissue. Just like our own cells, plants shed their leaves and roots regularly. When this tissue is shed, it decomposes. When the tissue becomes highly decomposed, the carbon which was once part of the tissue forms particles small enough to chemically bond to the clay in soils. At this point, the carbon now has the potential to stay trapped (sequestered) in the soil for hundreds, even thousands of years if left undisturbed. 80% of all carbon on Earth is found in soil.

Trees, in particular, are remarkable carbon sequesters due to their size and longevity. As they age and become more substantial, they store more carbon over time. Forests play a vital role in carbon sequestration as they act as huge carbon sinks. A carbon sink is a natural reservoir that takes in more carbon than it releases. Forests, with their lush green canopies, soak up significant amounts of CO₂ during photosynthesis. The timber they provide can also store carbon in our buildings and furniture.

Despite the importance of forests in combating climate change, deforestation is an alarming global issue. Activities such as clearing forests for agriculture, logging, and urban development are significantly reducing the number of trees that can sequester carbon. When trees are cut down or burned, the carbon they stored over their lifetime is released back into the atmosphere as CO₂, contributing to the greenhouse gas effect. This exacerbates climate change and further disrupts the Earth's delicate balance.

Bogs and peatlands are often overlooked, but they also play a pivotal role in carbon sequestration and storage. These unique ecosystems are adept at capturing atmospheric carbon dioxide through the slow decomposition of organic matter in waterlogged conditions.

As plant material accumulates over centuries, bogs act as carbon sinks, locking away substantial amounts of carbon. Distinct from other landscapes, they store carbon more effectively due to waterlogged environments that hinder decomposition. However, human activities like drainage and development disrupt this balance, releasing stored carbon into the atmosphere as greenhouse gases. Recognising bogs' significance underscores the urgency of their conservation, offering a natural solution to mitigate climate change and its impacts.

While forests are critical, all types of vegetation, including crops, grasslands, and wetlands play a significant role in sequestering carbon. Sustainable agricultural practices, such as maintaining permanent grasslands, no-till farming, good hedgerow management, cover cropping and planting multi-species grass swards can enhance the soil's ability to capture and retain carbon. By implementing and adopting these sustainable practices en masse across the agricultural sector, farmers can significantly contribute to reducing Ireland's carbon emissions, while maintaining soil fertility and overall productivity.

Interestingly, oceans are also crucial players in the carbon sequestration game. Phytoplankton, tiny marine organisms, are underwater plants that photosynthesize. They absorb CO₂ from the atmosphere and serve as an essential carbon sink. Additionally, when marine animals like molluscs and corals build their shells and skeletons, they use carbon dissolved in the seawater. This process removes carbon from the water and stores it in the ocean sediments, further contributing to carbon sequestration.

Plants are more than just green ornaments dotting the landscape. They are a serious weapon in our arsenal in the battle against climate change, working silently but efficiently to sequester carbon dioxide from the atmosphere. Whether you're looking after a forest, a farmer with hectares of land or a home owner with a small back garden, we can all play our part in helping to remove carbon dioxide from the atmosphere. The message is simple; plant more plants and disturb the soil less.

This article by James Rambaud, a Carbon Emissions & Sequestration Technologist at Teagasc's Environment Research Centre, was first published recently on RTÉ Brainstorm, where you can read it here.