TreeScore provides insight into the value of urban trees |
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A tool to better weigh the importance of trees in projects
In highly paved environments, it becomes most apparent: trees have value. Exactly how much depends on the tree. TreeScore brings those differences to light.
| Trees contribute to the urban living environment |
For arborist Marnix de Croock of the municipality of Haarlem, it is essential that trees contribute as much as possible to the quality of the urban environment. The TreeScore method has proven to be a welcome aid in this regard. "A tree with a large crown volume, for instance, will offer more to the living environment than a row of smaller trees. That's why crown volume carries significant weight in the score."
Haarlem is the cradle of this new assessment method. In collaboration with Investree, the municipality applied the method. 46,000 trees received a score. "These are all our street and square trees. Trees in parks and woodlands were not included. Projects are unlikely to be carried out in those areas, and without pavement, the growing conditions are generally already good."
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"Preserving an old tree with a large crown volume can be worth the extra maintenance effort due to its high value for the environment."
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 | | Marnix de Croock |
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Enthusiastic
The value of trees is most recognized where they are scarce—typically in paved areas. The ecosystem services that trees provide are especially valuable there. Urban residents highly appreciate their presence, and De Croock finds that gaining public support for more greenery in Haarlem's historic neighborhoods is not difficult. Even when the proposed changes involve reducing parking space.
"Often, in narrow streets, utilities are located everywhere except under parking strips. That's the only place where we can improve soil conditions."
The result is a totally different type of street. Residents now look out on greenery and blooming plants instead of parked cars. They also experience less heat stress.
Together with Floris van Imhoff of Investree, De Croock explains the TreeScore approach. The best way to understand it is in practice—hence a walk through part of the city center undergoing redevelopment. This shows how new greening opportunities arise and how TreeScore helps. Many new trees are planned, but whether existing ones stay depends on their score. Mature trees that can remain are especially appreciated next to newly planted young ones.
Method
TreeScore ratings range from 1 to 6, where 1 indicates the most valuable specimens and 6 indicates trees beyond saving. Crown volume weighs most heavily, but other factors also count, such as growth potential, presence of disease, life expectancy, and manageability.
"The system builds on the W (Value) score from the Tree Handbook," explains Van Imhoff, "which laid the foundation for tree valuation. TreeScore also aligns with NEN standard 2767, a widely used rating method among public space stakeholders."
TreeScore emphasizes a tree's added value for the environment. "From a management perspective, a large old tree might seem unfavorable," Van Imhoff says. "It may require a lot of care. But the ecosystem services it provides through its large crown are substantial. The W score doesn't reflect that, leading to lower ratings that might result in such trees being removed during projects. A few years ago, in the Spaarneboog area development in Haarlem, we ran into this limitation. That's when we decided to upgrade the W score."
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"You don't want to damage valuable trees. It's possible to take them into account during excavation work."
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 | | Weathered, but worth it here |
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 | | Floris van Imhoff |
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Redevelopment
On the walk, a healthy honey locust tree on the corner of Zijlstraat and Nieuwe Groenmarkt catches the eye. Such a tree will likely be included in the redevelopment plan for Nieuwe Groenmarkt. Zijlstraat has already been revamped, with young linden trees given carefully constructed planting pits. Nieuwe Groenmarkt is next.
Here, the saying "hunger is the best sauce" rings true—enough to consider preserving two struggling silver maples that currently dominate the view. "This first one is debatable," says Van Imhoff. "It's in moderate condition, not growing anymore, but because of its visual contribution, you might keep it." The second one looks worse. De Croock adds, "This one's really not much. You can see right through the crown. And yet, it might also stay for now, simply because it's a large tree."
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"If trees in a project area are unlikely to respond to soil improvements, their time is up. It's often better to replace them with a new tree."
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Planning
TreeScore enables the value of tree stock to be considered early in spatial projects. Van Imhoff explains: "You don't want to damage valuable trees during excavation. With the scores in hand, you can make better decisions from the design stage. For instance, you might decide to protect certain trees by placing new sewer lines farther away."
Numerous aging trees have also been assessed and may be less likely to be spared when the excavators arrive. De Croock adds, "If they're unlikely to benefit from better growing conditions, it's often better to replace them with a new, thriving tree—one that will quickly surpass the old in value."
 | | Young linden trees in Zijlstraat |
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Replacement Program
Other municipalities have also started using TreeScore. For example, Almere has based a large-scale study on it to develop a multi-year replacement plan. This was necessary due to soil subsidence and its impact on the tree population.
TreeScore, the duo concludes, does not provide a ready-made answer. Van Imhoff: "It's more of a traffic-light method. You see whether it's red, orange, or green. You don't need to examine all trees in detail—just investigate the ones that fall in the grey zone." Based on the context and guiding principles, the best decision can be made.
De Croock adds: "Thanks to this method, we work more efficiently and manage to retain more trees in our projects."
This article was originally published on 21 February 2025 on the website of Stad + Groen.
Dit artikel werd eerder gepubliceerd op 21 februari 2025 op de website van GreenInside.
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