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Estimation of CO2 uptake in TreeSisters' reforestation projects

TreeSisters calculated the emission reduction potential across our reforestation project portfolio as of August 2019 - across eight projects located in various locations in the tropics.

We're offering this estimate to help increase understanding about the vast capacity that tropical forests and trees have to help cool our world as they draw carbon out of the atmosphere. Tropical forests are the largest terrestrial carbon reservoirs on our planet.

Before we get to the calculation, it feels important to share that, as an organisation, we have chosen a different route than the carbon offset path for various reasons (and then we will give you a calculation to make!)

Firstly, TreeSisters looks through the multifaceted lens of living systems (of which carbon is one facet), which are complex, interdependent, multi-species communities that provide vital ecosystem services that have foundational importance to the whole web of life. To measure carbon without looking at water, soil, biodiversity, oxygen etc., is like looking at the bones of a human and ignoring the rest. Looking at carbon offsets, we 'lose' what a forest is and completely miss the subtle and the sacred.

Secondly, calculating carbon tends to be reductionist rather than generative or generous. It can steer towards the least that can be done to feel good rather than the most that can be done to do good. Forest plantations are preferred for offsetting carbon, but they provide relatively few benefits to native biodiversity and watershed health.

If your house was on fire, would you expect your neighbours to stand by trying to assess how much of it they might have been responsible for before getting a watering can and watering a few flames? Or would you want them to give it all they'd got to put out the fire? Because our world is on fire, TreeSisters has chosen the latter rather than the former position.

Having said that, we are not ‘against’ the offsetting activity, and it needs to happen. It's just that wildly more than that needs to happen for us to touch the edges of this fire. TreeSisters will always be a call for the most that you are able to do in terms of radical generosity. We will plant trees for you if you figure out the most you can do.

The Carbon Sequestration Potential of the TreeSisters Portfolio as of August 2019:

We estimate that nearly 800,000 tonnes of carbon dioxide (CO2) will be sequestered over 20 years from the 6 million trees funded (1) by TreeSisters. These numbers are our best estimation.

We estimate that for every £3 or USD$ 4 donated, 1 tonne of carbon dioxide is drawn down over 20 years. This is equivalent to the CO2 emitted for a round trip when one person is flying from London Heathrow to New York John F. Kennedy and back. (2)

At £0.40 per tree, a donor who gives £10 per month for one year funds approximately 300 trees per year and sequesters 40 tonnes of carbon dioxide, which will be drawn out of the atmosphere over 20 years. As a comparison, 40 tonnes of carbon dioxide is equivalent to what's emitted when charging your smartphone 5 million times or 8.5 passenger vehicles driven for one year in the United States. (3)

Note: these estimates should be used with caution bearing in mind the limitations discussed here.

TreeSisters is not a carbon offset provider. We do not issue carbon-certified units or credits, and none of our current projects is carbon certified. We can't lead complex experimental work and research that's required (4) to reach the accuracy needed to issue valid carbon credits ‒ we focus our finances and energy on ethical and effective reforestation.

Nevertheless, if you decide to address your carbon footprint, we can offer a quick and easy way for you to compensate for your carbon emissions by running a simple calculation and donating to our reforestation projects.

This is a quick method to compute how many trees to fund to help offset your carbon footprint:

  1. Calculate your footprint at a site like

  2. For every tonne of carbon dioxide you have emitted, allocate £3 or USD$ 4 to plant trees.

  3. Understand that these trees will sequester that carbon over 20 years.

  4. Donate here, and your account will show your number of trees.

Note: adding/removing reforestation projects to our portfolio may slightly change the estimates, and thus the amount to donate per 1 tonne of carbon emitted may vary


1. Trees funded have been either planted, are being planted within a year, or are assisted to naturally regenerate and thus would emerge progressively over 20 years.

2. Figures from published by the Guardian Newspaper 19th July 2019.

3. US EPA, OAR. “Greenhouse Gases Equivalencies Calculator - Calculations and References.” Data and Tools. US EPA, August 10, 2015. Available here.

4. They require the collection of field data and make use of complex model simulations and remote sensing data that is complex and costly to acquire.

5. In 2019, TreeSisters started funding new reforestation projects in Mozambique, in West Papua and in the Brazilian Amazon, which are not accounted for here.


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How Your Mangrove Trees are Saving Lives and Landscapes

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