It’s one of the first questions people ask when they look into tree planting for climate action – how much carbon does a tree absorb?
The long answer is – it depends.
The short answer is – A mangrove tree sequesters an estimated 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.
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 powerful tool for carbon sequestration and the fight against climate change.
Is carbon dioxide a bad thing? Not always.
However, if you’re planting trees to help in the fight against climate change, 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 estimate the future CO2 sequestration via MoreTrees.
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 perThis figure was divided by the number of trees planted in a hectare of mangrove forest (1,000), which comes to 0.3.They’re also working hard to increase nursery capacity by hundreds of thousands and establish a new agroforestry nursery.
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,
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 capturing CO2?
We, along with our tree planting partners, believe that mangrove trees are one of the best trees for sequestering 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 absorbing CO2 and, studies have shown that each additional tree species introduced to a plantation can add 6% to its carbon sequestration 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 CO2 that tree could go on to sequester. 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.
What’s the difference between CO2 sequestration and carbon offsetting?
It’s a great question. A newly planted tree will go on to sequester (or absorb) CO2 emissions over its growth life, which we hope will be many, many years.
A carbon offset comes from CO2 avoidance or capture that has already taken place – i.e. a completed wind turbine project or a 15-year-old tree.
Both are important – carbon offsets allow businesses to attribute existing offsets again business emissions, while tree planting allows us to protect our planet’s future.
Want to put this average figure to work?
Enough about the science and mathematics behind how much carbon a tree sequesters – let’s put these figures into action by planting more trees in forests across the world.
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