Ecosia has planted over 100 million trees on over 30 thousand hectares of land in over 10 thousand locations in 25 countries.

At the moment, we predict the carbon sequestration of our trees with **the Forest Landscape Restoration (FLR) carbon storage model **developed by Win Rock. As you can see on their online calculator, you have to select the jurisdiction where your trees are growing and the restoration technique (is it a plantation, natural regeneration, mangrove). The model then gives you the carbon sequestration per hectare per year.

This way of calculating the CO2 reduction of a forest, sits somewhere between a Tier 1 and a Tier 2 calculation of carbon reduction. The UN’s international panel on climate change (the IPCC) has defined 3 levels on which CO2 absorption of forests can be calculated:

- Tier 1: Uses default factors and parameters. It can be combined with remote sensing information.
- Tier 2: Is like Tier 1, but uses country specific factors.
- Tier 3: Uses even more detailed models and uses GIS based differences on age and classes within forests.

As with every model that goes from a broader to a more detailed calculation, the conservatism of assumptions reduces with granularity. In other words, this Tier 1 calculation of carbon is largely underestimating how much carbon has really been stored - the real number is probably higher. That is why we said that our 100 million trees sequestrate between 1 million and 3.5 million tonnes of CO2 at the moment, because other models actually give us a higher estimation than the Winrock calculator.

You have probably noticed that these models look at how much carbon is sequestrated per hectare, not per tree. This is the correct way of doing it. In a forest system, you have trees of all different ages, shares, volumes, species etc. What matters for the CO2, is how much biomass they have in total - it doesn't matter whether this biomass comes from 1000 or 4000 trees. So, although we can give a range of how much CO2 different trees can absorb, the total carbon stored by our trees cannot be calculated by multiplying that number with our number of trees.

By the way, the Winrock calculator is not integrated in our restoration database. So, if we want to know how much carbon our trees have likely absorbed, we have to manually do this calculation. To do it properly, a single person needs around half a day for that.

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