the true value of trees
We believe that trees are the beating heart of villages and cities, making them more sustainable, resilient and beautiful. Trees offer us coolness on hot days, retain water when it rains hard and the sewers fill up, store CO2 and capture particulate matter.
As a green professional, it is our job to make the true value of trees transparent! With the Eco Impact report we offer a great tool for that. In this document, we will go into how we do this.
Eco Impact with i-Tree Eco
The true value of a tree can be found in the ecosystem services it contributes to: for example CO2 storage, air filtering, water retention and cooling. At TreeTracker we call this the Eco Impact. With the TreeTracker tree detection we can calculate the Eco Impact very accurately, because we visualize the tree very accurately. To calculate the Eco Impact of each tree, we use the internationally accepted i-Tree Eco model.
i-Tree is a model that provides insight into the ecosystem services that trees provide for their environment. An ecosystem service is a service or function that nature provides to society. Specifically, TreeTracker uses the i-Tree Eco calculation. This model goes into detail about ecosystem services and also expresses the benefits in money. In short: i-Tree makes it possible to convert tree information into a detailed insight into the benefits of trees!
The model was developed in the United States in 2006 by the USDA Forest Service, which manages several national forests. For the Netherlands, the American i-Tree calculation was translated for the Dutch situation back in 2019, with a unique collaboration between government, education and the business community.
By using i-Tree Eco we can currently calculate six values:
- CO2 storage (in kg)
- CO2 capture (in kg per year)
- Filtering of pollutants from the air (in grams per year)
- Water retention (in m3 per year)
- Structural value expressed in money (in euros)
- Income expressed in money (euros per year)
Ecosystem services we calculate
CO2 storage and sequestration
An important objective of the national climate policy is to reduce greenhouse gas emissions, in which CO2 has a large share. Because trees capture CO2 (or in full: carbon dioxide) from the atmosphere in their wood tissue, the emission of CO2 is compensated naturally. About 50% of the dry weight of a tree consists of carbon and trees can store CO2 for a long period of time.
We calculate both how much CO2 the trees capture annually and the amount of CO2 that is already stored in the trees.
Filtering of pollutants
Poor air quality in the city is caused by industry and traffic. This has all kinds of adverse effects as a result, for example negative impact on our health or damage to buildings.
Trees contribute by improving air quality in the urban environment. Trees either directly remove air pollution by absorption it through the leaves, or capture pollutants such as particulate matter through the leaf surface.
The air pollutants included in the calculation are carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM2.5) and sulphur dioxide (SO2).
Heavy rainfall is becoming more and more common in our changing climate. Especially in the cities, where a large part of the space is covered by buildings or pavement, this increasingly leads to flooding. The water that is not absorbed into the soil or through the trees must be discharged through the sewer. More and more often we see that the sewer system cannot handle this properly.
Trees can lighten the pressure on the sewerage during heavy rains. Rainwater is captured in the tree crown, after which it either evaporates or is released slowly to the soil.
We calculate with i-Tree Eco how much water the trees capture in their crown. This water does not flow directly into the sewer.
Incidentally, it is also known that water around trees can sink more easily into the ground anyway, which also ensures that the sewer is spared. This effect is not yet calculated in i-Tree Eco.
Value expressed in monetary terms
The mentioned ecosystem services ensure that fewer actions need to be taken and therefore less costs are incurred to generate the benefits in a different way. This could include savings on sewer costs, air treatment plants and the compensation of CO2 emissions in order to achieve certain climate goals. i-Tree Eco calculates what the benefits delivered by the trees are in euros, both the value per year and the structural value.
Impact of measured values
Each tree species has its own characteristics, which translate into specific ecosystem services. For example, a birch tree has hairy leaves where fine dust sticks well to. Birch trees therefore score high on filtering pollutants. Horsechestnuts have a dense foliage and therefore a high score for water retention.
Thickness of the trunk
The thickness of the trunk is important because it stores the CO2 to a large extent. This is therefore decisive for the CO2 storage, but also for the structural value.
The leaf surface is determined as precisely as possible. CO2 capture, filtering, water retention and annual benefits are largely determined by the surface of leaves. On the one hand, the dimensions are important here, with which the crown volume can be determined very accurately. On the other hand, the condition of a tree plays a role, because this affects the leaf cover.