Canopy Volume (BKV)

Greening is playing an increasingly important role in both urban and rural areas. With the introduction of the European Nature Restoration Law in 2030, governments and project developers will be required to create more space for green. In the Netherlands, this takes shape in the National Tree Standard, which comes into force in May 2024. Where the number of trees used to be the benchmark, the focus is now on canopy volume (BKV).

BKV refers to the total volume of tree canopies that contributes to a healthy, liveable climate. This is not determined by the number of trees, but by their combined effect on shade, cooling and biodiversity. Scientific research, including work by Professor Cecil Konijnendijk, supports this approach with the 3-30-300 rule:

At least 3 trees must be visible from a home.
A neighbourhood must have at least 30% tree canopy cover.
Everyone should have access to a green space within 300 metres.

Studies show that 30% canopy cover is a threshold at which the positive effects of green on health, cooling and biodiversity become measurable. Many Dutch cities have not yet reached this standard, which means there is still a lot of ground to make up.

BKV in practice: a more efficient approach to greening

For a long time, the focus was on the number of trees planted, but the National Tree Standard introduces a different approach: steering greening by canopy volume. The larger the BKV, the sooner a tree delivers functional value to its surroundings.

An example:

A Platanus hispanica that is eight metres tall with a trunk girth of 30 to 35 centimetres at planting already has a canopy volume of 35 cubic metres. To achieve the same volume, eight young trees with a trunk girth of 14 to 16 centimetres are needed.

So larger trees deliver returns more quickly: more shade and faster CO₂ storage. It also turns out that young trees, although they may seem cheaper to buy, require more maintenance in the long run. Mature trees are more robust and need less management, which saves costs over time.

For a site of five thousand square metres, the National Tree Standard calls for a total canopy volume of eleven thousand cubic metres. That means:

With young trees (fourteen to sixteen centimetres trunk girth, BKV: five cubic metres per tree), two thousand two hundred trees are needed.
With mature trees (thirty to thirty-five centimetres trunk girth, BKV: thirty-five cubic metres per tree), three hundred and fifteen trees are enough.

Alongside the numbers, space and cost savings also play a role. Young trees take up a lot of space and require intensive maintenance. Larger trees deliver the desired effect from day one and need less management, which means maintenance and replacement costs are significantly lower in the long term.

Choose balance

Large trees provide cooling and air purification quickly, but smaller species are important too. A healthy mix creates a tree population that is resilient and ecologically valuable for the future.

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Balancing large and smaller tree species

The National Tree Standard emphasises canopy volume because larger trees contribute directly to cooling, water retention and air purification. Even so, smaller tree species also have an important role to play. Greening that is fit for the future calls for a varied tree population, in which both large and smaller species have their place. The right balance is crucial: choose trees with a large canopy volume wherever possible, but also take into account sites where smaller species are a better fit and ecologically valuable. First-size trees deliver a high BKV more quickly, but second- and third-size trees contribute as well, especially when planted at a semi-mature size. It is also important to choose a mixed planting of both native and non-native species that will remain resilient in the changing Dutch climate.

How Van den Berk Boomkwekerijen helps deliver BKV

Successful greening is about more than planting trees. The right tree selection and growing-site design determine long-term success. At Van den Berk Boomkwekerijen, we help with:

BKV calculations based on project requirements, so it is clear how much canopy volume is needed and how this can be achieved efficiently.
Supplying large-sized trees that contribute immediately to a greener environment.
Advice on growing sites, tailored to soil, rooting space and water management.

By working together early in the design process, the available space is used to best effect and the result is a green scheme that meets the standard straight away and remains effective in the long term.

Need tailored advice? Get in touch for personal guidance or a custom calculation. Together, we can create greening that is ready for the future.