The right tree in the right place, for the right reason!

I know I haven't been as active with writing blogs lately. In the past period, I've been mainly focused on building a new house, and I had my reasons for that. Nevertheless, I saw an opportunity to give a presentation at the Barcham Tree Tour event. Barcham is a high-quality English tree nursery that had asked me to give an introduction at the beautiful Bedgebury National Pinetum on how people are programmed in relation to tree diseases. I met my good friend Tony Kirkham there, the former head gardener of Kew Gardens. Tony was also one of the speakers, and at Bedgebury, he introduced: 'The right tree in the right place for the right reason'. I realized how much we are kindred spirits, because Tony thought the term "Treeguests" (source: Bomenbieb)I used was absolutely brilliant to use to describe everything we now mainly consider as pests in trees. So, plenty of inspiration to fill a blog!

Esthetically, it's old school
Tree species selection is often made by designers. A designer is spatially trained and will want to fill that space with the desired appearance of a tree: a transparent crown, blossoms, autumn color, just to name a few esthetic considerations. But designers are also people and are therefore, by definition, fashion-conscious. That means we might even be able to place species choices in time. For example: the designs from the 1970s and 1980s primarily led to an overabundance of Rosaceae, as Prunus, Malus, Pyrus, and Crataegus were chosen en masse for their blossoms. In the cramped residential areas, the trees of the third size also fit better with the image of 'a tree in the sidewalk for every three parking spaces'.

Monoculture of silver linden in a street in Rotterdam, Netherlands

Nowadays, transparency and minimal nuisance are still a fad, resulting in too many Gleditsia and silver linden. In my opinion, the choice of how to fill a space is often esthetically driven. In fact, it's hardly considered, especially by private individuals, that trees grow. The desired end result is primarily attempted to be achieved directly with far too many planted trees. But what is the reason for planting?

Ecosystem services
By now, we know better that trees are much more than their outward appearance. Over the years, we have gained increasing scientific evidence for various functions of trees that we call ecosystem services. Americans realized decades ago that trees are much more than just beautiful. This led to the I-tree model: a calculation model that allows you to calculate a number of ecosystem services provided by trees in hard numbers. In 2019, I helped introduce the model in the Netherlands. The publication "Baten van Bomen" is still a valuable resource. This allows you to calculate how much CO2 a tree sequesters per year thru its growth. Additionally, how much carbon the tree already contains, how much water the tree retains and thus doesn't flow into the sewer, and the amount of fine dust it captures. The positive thing is that you no longer have to talk about your feeling that trees are important. You can back it up with hard numbers. Many people, and especially administrators, find that pleasant.
Ecosystem services provide a number of very good reasons to maintain or plant trees. Carbon sequestration is a hot political topic and a great motivation for administrators to plant trees. Furthermore, you can translate the hard data on ecosystem services into hard euros, which people find even more appealing! That's where the risk lies immediately, because now you get the poison of our society: economic systems. If we can degrade trees to representatives of euros, then it's simple to buy them off, you can be motivated to fell trees, and you bypass a lot of values, soft values.

Soft values
We all know that trees are important. But if a tree only yields €10.00 per year in current calculable ecosystem services (note, this is just an example here!), then you're better off cutting it down. While we all know this isn't true, we still can't substantiate it strongly enough.
Let's analyze the term ecosystem services. A human-centered term in which we calculate everything that trees do for us, humans. By doing so, we are going beyond those values that we as humans might not think we directly benefit from, but which are essential in the chain we call nature. A tree is a home for many organisms, tree guests, which are essential for the tree's functioning and its environment.

There are also plenty of people-oriented soft values.
Trees provide essential shade on a hot day. A prime example is the anniversary event in Amsterdam, where I recently became involved as a project manager. The Municipality of Amsterdam has received 750 trees as a gift in honor of its 750th anniversary. These trees were placed in containers and set up on the A10 highway on the longest day of the year, June 21, 2025, as part of the anniversary celebrations.
People might be critical of this, but I'm convinced these trees were the best promotion for themselves. June 21, 2025 couldn't have been better: a scorching day with a forecast of 32 degrees Celsius was predicted. The 750 jubilee trees were all located on both outer edges of the highway, partly on the hard shoulder and partly on the lanes, with a tree-free safety strip of about 8 meters in between.

Pleasant stay among the trees during festival at the A10 highway in Amsterdam, Netherlands

Rene van der Velde from Delft University of Technology conducted temperature measurements based on radiant heat. Radiant heat is the surface heat measured between the trees and in the strip between them, excluding the trees themselves. I'm basing this on the radiation temperature I read myself, but on the highway it was 44°C, which is 12°C higher than between the trees, where it was only 32°C!
There were more than 200,000 people on the highway, and I saw them almost jogging across the hot asphalt, including from the Rabobank's steel and sail stand, and visibly slowing down, step by step between the trees. People stayed between the trees and enjoyed the benefit of the shade. Planting trees along the highway was a great and valid reason to make even a highway more livable and to lower the temperature. A soft value, still people-centered, but tell me: how much is that worth compared to all the natural values?

The Power of Numbers
It's already getting better, but many political forces still think they can score points by mentioning large numbers of trees being planted. It's quite easy to score points by planting thousands of trees on a few hectares, or by cramming them into unsuitable growing sites. This is completely contrary to the interest of achieving sufficient crown volume to improve the quality of the living environment. That's why I'm much more enthusiastic about the 3+30+300 rule by Ceciel Konijnendijk. Specifically, you can only achieve a 30% crown volume in an area with good site quality. Another approach is the tree crown volume from the Dutch Tree Institute, introduced as the national tree standard. That Tree Standard can only be achieved thru quality as well. The tree standard aims for 2.2 cubic meters of tree crown volume per square meter, and this is primarily about growing sites: the right place. Trees are like pizzas: it's all about the base. If politics continues to focus on tree numbers, they actually understand nothing about the real reason: quality of life!

It's about the trees that establish
What matters is not the number of trees planted, but the number of trees that establish. I see this go wrong too often in frequency contracts, where the specifications prescribe a number of trees to be planted, but do not regulate aftercare.

It's not about the numbers you plant but about those who establish, Warwick United Kingdom

With the current climate, after planted you can't rely on a tree to survive on its own at all anymore. Outcome-based contracts, where the result is a healthy, vital tree that is delivered, are much more meaningful. Deliver everything in a vital state after a minimum of three years, or preferably after five years, and you can be sure you'll get what you're asking for. And what is vital then? 'From the moment of planting, an increasing average shoot length including the tip.' A simple, testable standard that works on any soil and for any species. Because wasn't planting trees, I hope, the right reason to plant them?

In short, there are many reasons to plant trees. Thanks to Tony Kirkham, we can look forward to many more years with the completed slogan:

The right tree in the right place, for the right reason!