Tree Planting: Why Is It So Important?

December 2016, the Australian government were the first in the world to declare a climate emergency.¹ In the same year, the Paris Climate Agreement, adopted by 196 International Parties, entered into force.² Its goal is to keep global warming well below 2°C, preferably limiting it to 1.5°C above pre-industrial levels.³

Climate change and trees

Tree planting is one essential component to achieving this objective and preventing an environmental catastrophe, as predicted by the Intergovernmental Panel on Climate Change.⁴

The best way to plant trees and protect their root ball

Tree planting is the process of planting trees, starting with seedlings, seeds or cuttings. It typically involves digging a planting hole, placing seeds or cuttings or transplanting a seedling into the ground. The root ball is subsequently covered with soil or compost. The root ball is particularly important if a tree is transplanted. To optimize the health of the plant and to help endemic insects and animals to thrive, it is always best to plant a native tree.⁵

How does planting trees affect climate change?

The effects of climate change can be mitigated by planting trees. Global warming is caused by humans burning fossil fuels, cutting down forests, and farming livestock.⁶ These activities increase the number of greenhouse gases in the Earth’s atmosphere.⁷

Gases such as CO2, methane, and nitrous oxide prevent heat from escaping the planet. This causes the greenhouse effect, which increases the planet’s overall temperature.⁸ Trees help to reduce the number of greenhouse gases in the atmosphere through photosynthesis.⁹

Trees and photosynthesis reduce CO2

Photosynthesis is the method by which all plants create glucose. Glucose is a type of sugar that plants require to grow. It involves combining water from the ground with CO2 from the air and using sunlight to provide energy for the reaction. In the process, they sequester carbon and release oxygen.¹⁰ This reduces the amount of CO2 in the air, thereby alleviating the effects of climate change.

Trees store CO2

Tree planting is a powerful tool in the fight against climate change for this reason. Planting trees can decrease the amount of CO2 in the Earth’s atmosphere. ¹¹ Trees store carbon in their trunk, roots, leaves, and the surrounding soil.¹²

A UK native broadleaf tree is estimated to take up one tonne of carbon dioxide during its full lifetime of approximately 100 years.¹³ There is no technology that can reduce the amount of CO2 in the atmosphere as cheaply and efficiently as a tree.¹⁴

Which trees absorb the most CO2?

Older and larger trees

Planting trees that are older and larger soak up the most carbon. ¹⁵ A mature tree captures on average about 22 kilograms of CO2 per year through photosynthesis.¹⁶ The amount increases according to the size and the age of the tree. For example, large-diameter trees account for just three percent of total stems in the forests of the Pacific Northwest region of the US.¹⁷ Nevertheless, they are responsible for 42 percent of the total carbon storage of the area’s forest ecosystems.¹⁸

Trees that have been preserved

This highlights the importance of leaving old-growth forests standing. It takes a long time for a sapling to capture and store significant amounts of carbon.¹⁹ Meanwhile, chopping trees down and burning them or leaving them to rot releases any carbon they have stored.²⁰

Deforestation produces at least 10 percent of all anthropogenic emissions annually for this reason.²¹. Tree planting is an important component of climate change mitigation, as the trees will eventually pull large quantities of carbon from the air. However, as a short-term solution, it has limitations.

Planting Trees: Their age and CO2

an effect on the CO2 in the atmosphere, and we need to reduce the amount now. The best way to achieve this is to prevent deforestation and stop producing fossil fuels.

Consequences of tree planting for biodiversity

Tree planting also has enormous benefits for biodiversity. Trees create habitats for diverse wildlife, offering them shelter and food, which they could not survive without. For instance, the two native species of an oak tree in the UK support 2,300 species of mammals, birds, invertebrates, fungi, and mosses. 326 species are highly specialized and rely solely on oak.²²

A mature oak tree in the UK will typically support over 280 different species of insects alone.²³ However, introduced species of tree will attract far fewer animals as their biomass is often unpalatable to native species.²⁴ For example, non-native horse chestnut trees in the UK typically yield just four insect species.²⁵

Scientists have found that in Costa Rica, adding a single indigenous tree to pasture could boost the number of bird species from nearly zero to 80.²⁶ The same study saw a significant increase in four out of six plant and animal species analyzed wherever tree cover increased.²⁷ Though they cover just six percent of the planet’s land surface, forests are home to about 80 percent of all terrestrial biodiversity.²⁸

Earth’s land-based biodiversity relies on the protection and enhancement of forests. If a tree species is lost, other organisms that are specifically associated with that species will disappear too. This can leave a forest’s entire ecosystem biologically impoverished.²⁹

Can tree planting solve climate change?

Tree planting alone cannot solve the climate issue. A drastic reduction in greenhouse gas emissions is also required. It is the greenhouse gases trapping heat in our atmosphere that are driving global warming. Trees can help by soaking up CO2. But climate change cannot be addressed until we leave fossil fuels in the ground and stop destroying the forests.

How planting trees can help other existing efforts

Careful management, restoration, and protection of all of our extant nature-based solutions to climate change is needed. These solutions include global forests, wetlands, grasslands, and agricultural lands. Between now and 2030, they could collectively provide more than one-third of the cost-effective climate mitigation needed to limit warming to below 2°C.³⁰ Enhancing many of these areas would involve large-scale tree planting operations. However, it would still leave two-thirds of the necessary climate mitigation unaccounted for.

We, therefore, need to stop producing and burning fossil fuels if we are to meet the objectives of the Paris Agreement. Coal, oil, and natural gas all release large quantities of carbon through combustion.³¹ In 2018, fossil fuels and industry caused 89 per cent of global CO2 emissions.³² Global greenhouse gas emissions need to be about 55 percent lower in 2030 than in 2017 to limit global warming to 1.5°C.³³ This will not happen without a seismic shift in energy production and consumption.

A dual approach to climate change

Tree planting is an important element in combatting climate change. It can help provide as much as one-third of the global warming mitigation needed by 2030. By planting the right trees in the right places, trees can also support myriad species worldwide.

But, we cannot hope to save our planet whilst relying on fossil fuels for our energy needs. The science is clear: a dual approach must be taken to transition to clean, renewable energy. This must happen whilst also investing in the nature-based solutions we already have.

If we do not act now, it will be too late.

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