Did you also see the climate activist on Dutch Jinek TV-talkshow who glued themselves to the table during the live show? I did, and my first reaction: pull the baby from the table and shove a sweetie in his mouth, preferably a sour one, until he shuts up! Now I have had time for the dust to settle, and my petty feelings have subsided, this plaktivist also gives some insights. People are headstrong creatures.

Of course, the changing climate already has my attention and I have been seeing the impacts on trees for years. Even worse, climate change also makes me realize that my own life is passing by too quickly. Especially now I can look back on a 40 year working relationship with trees. A lot has changed in that time ‘tell us Grandpa…?’ I hear my imaginary grandchildren say.

Take the growing season…my birthday is 1st May, in my youth I asked my parents if the leaves were already on the trees, as I found it difficult to read a calendar. My birthday could never come soon enough. No they said, the first leaves come at the start of May, but the large oak here in the street won’t have any leaves for a while yet. And now? The first trees start to get leaves in March and the first oaks from the start of April. In addition the autumn and falling leaves also happens later. Oaks that keep their leaves until the end of November aren’t unusual and plane trees grow in our climate until in October. Apparently the growing season is on average a month longer than 15 years ago

damaged oak leaf by nightfrost

Nightfrost damaged oakleaf, Quercus frainetto 9 May 2017


Due to the longer growing season there are also negative repercussions thanks to the extreme weather, which you can see in the spring when we have a night frost in May. Until the ‘IJsheiligen’ that is around 11th May, I always learnt not to put frost sensitive flowers outside, night frost is normal for our climate. That is still the case. But due to the earlier developing growing season a night frost can now have much harsher effects, because the trees are much further in their development. This has strong repercussions for fruit growers who need to protect the blossom. This is becoming more difficult to do using water spray. It still protects the blossoming bud but can damage the developed fruitsetting. But also walnuts, Japanese pagoda trees and even oaks can freeze and lose their first developing leaves. This leads to less growth. During the summer we now have extreme showers and summer storms. When I started with my Tree care company on the 1990’s I had one golden rule: if I’m on holiday in the summer, then so are my employees. I didn’t want someone sticking their head through the hedge asking me if I could get someone to fix a broken tyre. Since 2000 there has been an increased demand on our workload to cope with tidying up summer storm damage. That was unusual before then. This means that a general holiday scheme was no longer possible.

Summerstorm damage

Summerstorm damage 15 July 2010


The chance of lightning has also increased. As the earth warms by 1 degree Celsius the chance of lightning increases by 12%. The chance that you are hit by lightning or experience damage due to summer storms could be greater than being hit by a dead branch. And thereby those dead branches aren’t there anymore as we have tidied them up with our excessive risk management.

flooding Nijmegen

Flooding Waalquay Nijmegen 12 February 2020, summer 2022 this place experienced the lowest level of the Waal river since many years


Other expected extremes include long periods of drought and heavy rainfall. It seems almost unthinkable after the dry and hot summers of 2019, 2020 and 2022 that the Netherlands is also getting wetter, and the periods of drought are longer. The drought has an effect on the period of care that newly planted trees need. A regular aftercare period is 3 growing seasons, where a newly planted tree requires decreasingly frequently watering. After 3 years the tree is expected to care for its own moisture intake. The summer of 2022 with temperatures in the high 30 Celsius, shows that this isn’t enough anymore. When planting trees we are looking at an after-care period of maybe 5 years. In addition to the drought there is also an increase in UV intensity. More and more trees are suffering from sunburns. Long periods of drought and a lot of rain also disturb the ground. Soil has become sensitive to erosion and slemp, but it appears that other negative effects on many tree species are due to an increase in the fungus-like pathogen Phytophthora . In the meantime Dutch sea level has risen by 20cm, the ground is silting up in coastal areas due to salt water, which is getting more chance to head inland. Trees which are dependant on groundwater, now take on brackish water and suffer from increasing growing problems as they aren’t salt tolerant, something we have already witnessed several times in Zeeland.

sunburn drought

Drought symptoms and sunburned beech, August 2020 Siebengewald the Netherlands


Still not depressed? Then I will continue... Climate change is responsible for a decline in the condition of our tree population, other factors in play include environmental effects as a consequence of our economical desire for growth. It’s a fact that trees with a weakened condition are more susceptible to attack. These attackers have evolved to sort out the weak, so secondary attacks. Beetles are designed to seek out weakened trees, but also wood parasitizing fungi are often successful.

The more monoculture woodlands we have the more the ‘tidiers’ benefit. A monoculture forest of spruce trees, weakened by drought, allows the European spruce bark beetle to be very successful is. In addition the beetle becomes supremely optimistic.

late autumn

Typical result of deferred autumn on oak, 4 November 2022


Thankfully we tree people also move with the times. Our professional knowledge has evolved enormously, personally I have evolved from tree surgeon to technical tree adviser to senior technical tree adviser. I see the word ‘senior’ as being wise and learned in the material, others may think it’s more to do with my increasing age. It makes me want to say: stop calling those newbies seniors just because they have been called technical tree adviser after receiving a 2 week European Tree Worker diploma. Sorry, that touched a nerve, where some companies have a speeded up career development throwing around ambitious titles to the detriment of actual functional titles.

Is there any hope at all? Yes! Don’t worry: everything I have summarized here, has an effect on trees, but selfish as we are it has the most far reaching effects on humans. Tree species in our climate zone will probably disappear but new species will also come. It’s really the humans that will suffer the most from the changes. We think with our egotistical tendencies that we the top of the ape pyramid. But as the climate changes, the pyramid will turn and we will succumb under the ecologically crushed mass, namely; nature.

specie diversity

Atractive example of specie diversity, Bezuidenhoutselaan Den Haag the Netherlands


Solutions still within our power? Keep and plant tree, trees and more trees. Plant trees in open growing places. Go for quality, don’t compromise. Stop with messing around on growing places with plastic, structural soils and that sort of artificial ideas. Only do this if there are no other options. Please stop counting individual trees and go for measurable surfaces of green. Ensure that urban areas have a minimum of 30% canopy cover. Ensure diversity where a tree population consists of maximum 10% of one specie, maximum 20% of one genus and a maximum of 30% from one family. Stop with excessive risk assessment dictated tree care. The safest tree is no tree. The chance that you as a 100 year old tree a ETW newbie (who wouldn’t recognize fungi between his toes) get standing at your feet, only to be condemned is increasing every year. Please stop it!



To everyone who wants to make a statement and stick themselves to a tree, do your thing. I suggest you do this somewhere visible, because there aren’t many trees on talk show tables.

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