Trees are nature’s lungs. While we enjoy their beauty, shade and fruits of their existence, they are silently working to clean the air. The natural process of all plants taking in carbon and releasing oxygen not only gives us clean air to breathe but also stores carbon that otherwise contributes to global warming.

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Two large trees with bending branches.

Countries around the world are in a race to find solutions for these types of greenhouse gases, which are a result of human activities like driving cars and manufacturing goods. While the push for electric vehicles and renewable energy through solar panels, wind power and hydroelectricity takes the spotlight, another part of the solution equation is growing all around us in the form of trees.

Related: Three Americans’ lifetime emissions enough to kill one person

The simple fact is, planting trees is an exceptional tool in the fight against climate change. With this in mind, Compare The Market has presented its most recent research on the number of trees capital cities around the world would need to plant annually to offset the carbon emissions they contribute to the atmosphere. The study is based on information available through the Global Carbon Atlas Global City Emissions dataset, which measures emissions levels.

An overhead view of a fourway highway surrounded by trees.

While major cities work to reverse, slow down and stop the creation of these carbon emissions, what is the estimated number of trees it would take to counterbalance them? Which countries are the highest contributors and which have the lowest environmental impact?

According to the data, Asia has some work to do. Five of the ten top carbon-emitting capital cities are in Asia. Note that for comparative purposes, the dataset measures transport, industrial, waste and local power plants emissions within city boundaries. The report combined data to show the total amount of carbon produced alongside the number of trees it would take to offset it. For example, the five cities in Asia, which include Beijing, Singapore, Hong Kong, Tokyo and Seoul, release a combined 219,506,539 tCO2 annually. The cities would have to plant 43,901,308 trees each year to offset those emissions.

Beijing's city skyline.

Individually, Beijing would need to plant 15,020,976 trees, followed by Singapore with 9,366,336 and Hong Kong with 8,975,292. Tokyo needs a 5,522,200-plant offset and Seoul 5,016,504. Other cities in the top 10 were Istanbul, Lagos, Santiago, London and Mexico City. 

An energy spokesperson at Compare The Market comments, “Becoming carbon neutral is an essential goal for countries around the world, and as pledges roll in to reach this target by 2050 and beyond, immediate action is needed. One way we have studied is to offset emissions by planting trees which is great for absorbing CO2, with added benefits of supporting the ecosystem and wildlife.”

The tree offset calculation is based on information sourced from’s carbon dioxide emissions calculator. The estimates are based on the assumption that five trees planted can clean up each ton of carbon dioxide produced. 

A city highway with trees off to the side.

The study stated, “A tree planted in the humid tropics absorbs on average 50 pounds (22 kg) of carbon dioxide annually over 40 years – each tree will absorb 1 ton of CO2 over its lifetime; but as trees grow, they compete for resources and some may die or be destroyed – not all will achieve their full carbon sequestration potential.”

On the other end of the data spectrum are the countries performing better in the battle of low carbon emissions. For these results, a few substitutions were made in the face of missing data. Toronto, Milan and Basel were substituted to include Canada, Italy and Switzerland in the study.

Reykjavik, Iceland was the least carbon-emitting capital in the study with total emissions of 346,630 tCO2 per year. The city would still have some work to do, planting 69,326 trees annually to offset its footprint. Of all the cities in the study, Reykjavik was the only one to come in below the 500,000 tCO2-produced mark. Even though nearly 70,000 is still a lot of trees, it was also the only city to have an estimate below 100,000 trees per year to offset carbon emissions.

A grassy lane with trees in the background.

New Zealand took second place for carbon control with annual emissions of 621,179 tCO2. For Wellington to neutralize this, it will have to plant 124,236 trees a year. Basel, Switzerland, had the third-lowest number to plant at 156,786 trees to offset its 783,932 tCO2 footprint. Every other city in the study came in at over 200,000 trees a year.

The study provides one tool in an array of options to reduce carbon release. Planting trees alone isn’t a sustainable solution, but neither is focusing solely on renewable energy or recycling. To achieve goals set by world leaders, it will take a combination of actions across a range of environmental fields. 

“The number of trees required may seem very high in cities like Beijing which would need to plant over 15 million trees, but this is if we only used plant power alone. There are many other initiatives and technologies in place, like the government incentives, which present lots of opportunities to offset carbon emissions on a small and large scale,” the spokesman said.

+ Compare The Market

Images via Pixabay