It’s one of the first questions people ask when they look into tree planting to offset their carbon – how much carbon does a tree absorb?
The long answer is – it depends.
The short answer is – A mangrove tree offsets 0.3 tonnes of CO2 over its growth life. How do we know this? Well, let’s delve into the long answer.
Back to basics: how do trees absorb carbon?
To explain how much carbon a tree sequesters, let’s first recover how a tree absorbs carbon in the first place.
Trees sequester carbon through the process of photosynthesis.
Photosynthesis is where plants take energy from sunlight and turn it into energy for respiration, growth and reproduction – allowing them to stay alive.
To do this, trees absorb CO2 from the air, water from the soil and light from the sun, and turn these into glucose and energy.
And, since trees are known for being pretty big and having an enviable lifespan, trees absorb a lot of carbon dioxide, which is why they’re a popular method for offsetting carbon dioxide.
Learn more in our guide on tree planting to offset carbon
How much CO2 does a tree offset?
The amount of carbon dioxide a tree absorbs varies tremendously, depending on:
- The age of the tree
- The lifetime of the tree
- The size of the tree
- The health of the tree
- The location of the tree.
A small tree in your back garden absorbs a lot less carbon dioxide than a deep-rooted, broadleaf tree in a perfect climate. But it’s still absorbing carbon dioxide, and that’s important to remember.
However, if you’re planting trees to offset your business carbon footprint or to make a dent in your personal carbon footprint, you want a tree that’s going to sequester a lot of CO2.
Scientific studies have found that Mangroves sequester carbon 2 – 4 times greater than mature tropical forests and contain the highest carbon density of all terrestrial ecosystems (Fatoyinbo et al, 2017). How much carbon dioxide is that?
Our tree planting partner, Eden, has worked hard to establish the average amount of CO2 absorbed by a mangrove forest as 308kg (0.3 tonnes) of CO2 per tree.
With an average tree grow life of 25 years, a hectare of mature mangrove forest absorbs 840 metric tonnes. This means that one mangrove tree removes 308kg (0.3 tonnes) of CO2 from the atmosphere over its growth life, which is 12.3kg per year.
And that’s the figure we use to calculate the carbon offset via MoreTrees.
What does 0.3 tonnes per tree mean in actual life?
Well, 0.3 tonnes per tree is the same as:
- Driving 732.9 miles in a standard car
- Flying from London to Monaco
- Riding a motorbike from Brighton to Inverness
Calculating how much carbon a tree absorbs
How did Eden get to this calculation?
First, they calculated the ratio of CO2 to carbon, based on the atomic weights of each molecule, which comes to 3.67.
This ratio was multiplied by the amount of carbon per hectare of mangrove forest to come to the amount of CO2 absorbed per hectare of mangrove forest, which comes to 308kg.
This figure was divided by the number of trees planted in a hectare of mangrove forest (1,000), which comes to 0.3.
Is this figure a little conservative?
We’ve researched many sources on how much carbon a tree sequesters and the figures vary, a lot. This is understandable because different trees sequester different amounts.
Some scientists might believe this figure should be higher, others might think it should be lower, but we felt believe it’s a valid figure, and an average is better than no average at all. Our key priority is to help the planet by planting more trees.
It’s also important to remember that tree planting brings tonnes of other benefits too, including:
- Extreme poverty alleviation
- Reversing the effects of deforestation
- Helping local communities
- Regulating rainfall
- Preventing flooding.
Why are mangrove trees the best at offsetting carbon?
We, along with our tree planting partners, believe that mangrove trees are one of the best trees for offsetting carbon emissions. This is because they sequester a large amount of carbon, they have an extensive root system that allows them to thrive in muddy coastal areas (Komiyama et al, 2008), and they’re also cost-effective to grow and maintain – making them more likely to survive and people more likely to plant them, which is what we all want.
What about other trees?
Of course, there are many different trees good at offsetting carbon and, studies have shown that each additional tree species introduced to a plantation can add 6% to its carbon offsetting figures.
We adopted an average figure of 0.3 tonnes of carbon per tree to make it easier for businesses and people to put a figure on how much carbon they’re offsetting. We could get into the ifs and buts of how much carbon a tree sequesters, but we believe the easier it is for people to understand the benefits of tree planting and do it themselves, the better.
Relevant reading: The business guide to offsetting carbon
Want to put this average figure to work?
Enough about the science and mathematics behind how much carbon a tree offsets – let’s put these figures into action by planting more trees in forests across the world.
To find out how easy it is to plant trees, sign up to the platform to see for yourself.
MoreTrees makes it easy and affordable for businesses and individuals to offset their carbon transparently.
Our platform lets you pick the project and trees you want to plant and, once you’ve done so, you’ll get a certificate showing the positive impact you (or your customers) are making.