What Role Do Trees Play in Today’s Global Warming?

Global warming is caused by greenhouse gases, namely carbon dioxide (CO2), in the Earth’s atmosphere, preventing heat from escaping.¹ In the past 200 years, humans have increased the atmospheric CO2 concentration by 47 percent by burning fossil fuels.² Trees play a very important role, as they absorb carbon and store the surplus in their biomass.³ They are, therefore, essential for combatting climate change.

How do trees affect global warming?

Our planet’s atmosphere naturally contains a small proportion of carbon. The element is constantly transferred between different reservoirs, such as the oceans, vegetation, and rock formations.⁴ This process is known as the carbon cycle.

For instance, trees pull CO2 out of the atmosphere through photosynthesis and use it to create wood.⁵ This reduces the quantity of carbon in the atmosphere, as it is transferred to the trees’ vegetation and surrounding soil. Planting trees can decrease the amount of CO2 in this reservoir.

However, by burning fossil fuels like coal and oil and deforesting the land to convert it to agriculture, humans have significantly raised the amount of carbon dioxide in the atmosphere.⁶ It is now at its highest point for at least 800,000 years.⁷

Combustion of fossil fuels produces carbon which combines with oxygen in the air to form CO2.⁸ Fossil fuels and industry together are responsible for 89 percent of all CO2 emissions.⁹ Cutting down trees releases the carbon they had stored in their trunks, branches, roots or surrounding soil.¹⁰ As a result, deforestation accounts for at least 10 percent of all anthropogenic emissions.¹¹  Planting trees can be a huge help in this regard.

How does planting trees help global warming?

Planting trees helps to prevent global warming by removing CO2 from the atmosphere. ¹² Tree cover is the best carbon capture and storage technology in existence.¹³ Some trees could live for centuries, pulling large quantities of carbon from the air and sequestering it.¹⁴ Forests act as carbon sinks, helping to offset the emissions we produce in our daily lives.

The power of forests to reduce and stop climate change should not be underestimated. For example, the biomass of forests in the European Union contains an estimated 9.8 billion tons of carbon. Total CO2 emissions from the EU were 1.4 billion tons of carbon in 2004. In other words, forests in Europe store about seven years’ worth of the EU’s emissions.¹⁵ Planting trees is pivotal.

How does cutting trees affect global warming?

Cutting down trees releases the carbon they have stored and also prevents them from absorbing any further CO2. Burning trees or leaving them to rot releases the carbon in their wood.¹⁶ It reenters the atmosphere and contributes to the greenhouse effect.

Moreover, 80 percent of deforestation occurs to convert the land to agriculture.¹⁷ Replacing forests with either arable land or grazing fields hugely curtails carbon absorption. Agriculture also releases greenhouse gases. Between 2001 and 2011, the global emissions of crops and livestock production increased by 14 percent.¹⁸ Raising livestock is particularly harmful. It produces significant amounts of CO2, plus two other greenhouse gases: methane and nitrous oxide.¹⁹

Organic and mineral nitrogen fertilizers indirectly produce nitrous oxide emissions.²⁰ Livestock produce methane during digestion and release it by belching.²¹ Methane is a far more active greenhouse gas than CO2.²² 1.5 billion cows and one billion sheep are reared for consumption, and these numbers are projected to grow. The amount of methane produced is a serious facilitator of climate change.²³ We urgently need to adapt our diets and lifestyles to ensure forests are left standing and land use for food production is minimized.

Can planting strategies make a difference?

It is impossible to estimate exactly how many trees are necessary to stop global warming. One estimate suggests that current nature-based solutions to climate change, including the existing three trillion trees we have²⁴, can “provide over one-third of the cost-effective climate mitigation needed between now and 2030 to stabilize warming to below 2°C”.²⁵ This figure depends on the highly sensitive management of these ecosystems to function.²⁶ However, to successfully tackle climate change, tree planting and enhancing existing forests must be combined with a huge reduction in fossil fuel usage.²⁷

Is it feasible to plant a trillion trees?

It is also important to note that there is not enough time to plant trees to prevent climate change. The Intergovernmental Panel on Climate Change (IPCC) has cautioned that the global temperature rise should be limited to 2°C above pre-industrial levels.²⁸ Almost every nation on Earth has agreed that there is a climate emergency by signing the Paris Climate Agreement.²⁹ They acknowledge that global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate.³⁰ Trees can take decades to absorb and store large quantities of carbon. There is simply not enough time to rely on tree planting alone.

How does global warming affect trees?

Climate change affects trees in several ways. One positive outcome is that planting trees in many temperate and boreal forests, such as those found in North America, Europe, and parts of Eurasia, means they grow faster. ³¹ Since 1870, the growth rate of beech and spruce has sped up by almost 77 percent.³² This is because warmer temperatures make more nitrogen available in the soil.³³ It is also due to a longer growing season thanks to longer and hotter summers.³⁴

However, the temperature rise, combined with pollution from vehicles and farms, makes trees’ wood weaker. This may also mean that forests are less efficient at soaking up CO2. Faster growing trees in temperate regions have a wood density 8 to 12 percent weaker as a result. At a practical level, it means lumber is less durable and breaks easier. With regards to climate change, it suggests that some trees are losing their ability to absorb CO2 from the atmosphere and store it for long periods of time.³⁵

Climate change solutions

Trees play a crucial role in the carbon cycle in part due to their capacity for carbon sequestration. This links them intricately with global warming. We cannot prevent a disastrous increase in planetary temperatures unless we protect our current forests and make more tree planting and forest restoration efforts. After all, trees are the most powerful method of removing carbon from the atmosphere, and we should all make an effort to plant trees.³⁶

How can we fight climate change?

Nevertheless, we cannot rely exclusively on nature-based solutions and planting trees to combat climate change. At the root of the problem lies greenhouse gases, which we continue to emit. Until we change our approach to energy production, food production, and transportation, we will be unable to meet the Paris Climate Agreement’s goals, and we are on course for an environmental catastrophe.

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