From the TECHNICAL UNIVERSITY OF MUNICH (TUM) and the “cities have greater CO2 and greater warmth” department, comes this verification of Liebigs Law of the Minimum and a follow on to a story we covered on the same subject a few years back.
International study on the impact of climate change on tree growth
Trees in metropolitan areas have been growing faster than trees in rural areas worldwide since the 1960s. This has been confirmed for the first time by a study on the impact of the urban heat island effect on tree growth headed by the Technical University of Munich (TUM). The analysis conducted by the international research team also shows that the growth of urban trees has already been exposed to changing climatic conditions for a long period of time, which is only just beginning to happen for trees in rural areas.
“While the effects of climate change on tree growth in forests have been extensively studied, there is little information available so far for urban trees”, said Professor Hans Pretzsch from the Chair for Forest Growth and Yield Science at TUM. The study supported by the Bavarian State Ministry for Environment and Consumer Protection as well as by the Audi Foundation for the Environment, which was published in the journal Scientific Reports, for the first time systematically examined the growth of urban trees worldwide for trends resulting from changing environmental conditions.
A central motivation for Professor Pretzsch’s team is the prevailing trend towards global urbanization: According to calculations by the United Nations, the urban population worldwide is expected to increase by more than 60 percent by 2030 – with a continuing upward trend. Urban trees already improve the climate in cities and contribute to the well-being and health of city dwellers, and these forecasts show that their significance for the quality of life in cities will increase even further in the future.
Heartwood samples from the metropolises of Berlin, Brisbane, Cape Town, Hanoi, Houston, Munich, Paris, Prince George, Santiago de Chile, and Sapporo were collected and analyzed. The cities were selected to cover different climate zones. The spectrum ranged from boreal to temperate, Mediterranean, and subtropical climates. In total, the TUM research team focused on almost 1400 mostly mature trees. A typical and predominant tree species was selected for each city and examined in both the city center and surrounding rural areas.
Urban Trees Grow One Quarter Faster than Rural Trees
“We can show that urban trees of the same age are larger on average than rural trees because urban trees grow faster”, said Professor Pretzsch. Further observation showed that the relative difference in size between urban and rural trees decreases with increasing age, but still remains relevant. „While the difference amounts to about a quarter at the age of 50, it is still just under 20 percent at a hundred years of age.”
The researchers believe that the growth acceleration of urban trees is due to the so-called heat island effect. This effect leads to a stronger heating-up and thus higher temperatures in urban centers. Compared to the surrounding rural area, this increase in temperature can amount to between three and ten degrees Celsius. Higher temperatures can increase the growth of trees in two ways: On the one hand, they stimulate photosynthetic activity. On the other hand, they prolong the vegetation period, which extends the time of the year during which trees can grow.
However, the initial positive effect is also accompanied by accelerated aging of the trees. According to Pretzsch, accelerating the life cycle may mean that city administrations will have to replace aging and dying trees sooner.
Climate Change Accelerates Growth in General
Regardless of the growth advantage of urban trees, the study conducted by Prof. Pretzsch’s team also shows that both urban and rural trees have been growing faster since the 1960s as a result of climate change. This observation reflects a pattern that has already been reported for forest trees in comparable international studies.
“The general acceleration of growth in all trees by about 20 percent, which we report in the current study, is comparable to previous findings on forests. This effect has also been observed in agricultural production”, forest growth expert Pretzsch explained. Evidently, there have been and still are changes in environmental conditions that promote accelerated tree growth across different climate zones. „In this context, in addition to global warming, fertilization effects due to the rising atmospheric CO2 concentration and increased nitrogen depositions are discussed as potential driving forces.”
Despite the potential growth-inhibiting effects of global climate change on trees – such as drought events that can limit growth or even lead to the death of trees – the observed trees seem to have benefited so far. This was a uniform pattern: Both urban and rural trees across all the climate zones studied have exhibited significantly accelerated growth in recent decades.
However, as urban and rural tree growth converges more and more, this could indicate an imminent limit. „We believe this to be the case because urban trees experience a kind of early-onset climate change brought forward by the heat island effect,” said Professor Pretzsch – „In a current study, we are trying to uncover these mechanisms in order to identify problematic side effects.”
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The paper: https://www.nature.com/articles/s41598-017-14831-w
Hans Pretzsch, Peter Biber, Enno Uhl, Jens Dahlhausen, Gerhard Schuetze, Diana Perkins, Thomas Roetzer, Juan Caldentey, Takayoshi Koike, Tran van Con, Aurélia Chavanne, Ben du Toit, Keith Foster, Barry Lefer: Climate change accelerates growth of urban trees in metropolises worldwide, Scientific Reports 11/2017. DOI: 10.1038/s41598-017-14831-w
Abstract
Despite the importance of urban trees, their growth reaction to climate change and to the urban heat island effect has not yet been investigated with an international scope. While we are well informed about forest growth under recent conditions, it is unclear if this knowledge can be simply transferred to urban environments. Based on tree ring analyses in ten metropolises worldwide, we show that, in general, urban trees have undergone accelerated growth since the 1960s. In addition, urban trees tend to grow more quickly than their counterparts in the rural surroundings. However, our analysis shows that climate change seems to enhance the growth of rural trees more than that of urban trees. The benefits of growing in an urban environment seem to outweigh known negative effects, however, accelerated growth may also mean more rapid ageing and shortened lifetime. Thus, city planners should adapt to the changed dynamics in order to secure the ecosystem services provided by urban trees.
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Not all trees are equal. Trees in the country may very well be multiple generations along, one generation dropping seeds to create the next. Trees in cities are planted. If you go to all the work of planting a tree, you are likely to plant a healthy sapling from vigorous stock, with proper fertilization. On average, city trees have a better start-off. There are other factors, of course, but a head start could account for a lot.
(As a side note, I have used weasel-words like “may very well be”, “likely”, and “could”. I’ve been trained as a physical scientist, and I’d want to know a lot more about trees before I’d have the hubris to say anything more definite. Many people here have snickered at warmists’ use of such unfalsifiable terms, but sometimes they’re warranted.)
Good point. Most if not all cityscape trees came from tree farms and nurseries, and you can be 100% sure that the grower selected particularly vigorous strains and varieties, culled out weaklings, gave them everything they needed for optimum growth when on the farm, selected for disease and pest resistance if possible…
Seeds are cheap, and it takes a long time to grow a tree.
The usual process is to plant a bunch and to progressively thin out all but the healthiest one at the proper spacing.
It is making me sad to imagine that the nearly 1400 trees studied probably did not survive the sampling. Hugs.
Taking a core from a large healthy tree is unlikely to kill it, particularly if it was done carefully and sealed up afterward, and the equipment was sterilized between uses, etc.
Large old trees often have huge hidden voids and such.
In Florida, we just got a lesson in what makes some trees blow over more easily that others.
Part of it is random luck…but at the limit of what can be withstood, trees with damage, even if hidden underground or inside the trunk, will be the first to go over.
I have a lot of trees get knocked over, shredded, break in half, etc.
But most did not do so.
The damaged ones, on close inspection, frequently had ant nests in and around the base of the tree trunk, a unseen diseased section inside, may have been deficient in some micronutrient and were more brittle…etc.
Very interesting. Am escaping the mess from Harvey in Rockport this week where most native trees (live oaks) appear to have survived severe winds, probably the worst many ever faced. They are hard to age but are very old on a Pleistocene barrier island where some blew over intact from shallow roots and wind exposure. It is an unusual association of trees and understory much being either modified or destroyed by development, now on hold. A large right of way and highway through the peninsula visible on Google Earth (view shortly after storm available) probably took out a lot more than the storm. Advice to plant different species because of potential disease for the “monoculture” live oaks was just proven wrong as they held up much better than exotics, except for the palms.
The expanded right of way south of town, possible for a future exchange, is now the location fora huge collection of damaged materials and wood which is being incinerated. Survivors put on leaves rapidly and we hope somebody is studying hurricane effects as the importance of the trees as a buffer seemed evident. Much of Texas has more trees in the last half century or so, but rainfall has increased some.
“Photosynthesis Photosynthesis Photosynthesis!”
Saying the ph word is like saying “Jehovah” among pharisees in the Life of Brian movie.
“Jehovah Jehovah Jehovah!”
https://youtu.be/FQ5YU_spBw0
Just proves that trees like people and urban environments.
Think of the trees, and stop trying to restrict development in the rural areas.
(I didn’t read the paper … did they include this in the summary?)
alternate headline:
“AGW causes shorter lifespan in urban trees, stresses on urban budgets”
alternate headline
“scientists find no significant growth differences between plants supportively talked to versus trees cussed at”
Objective of study: to show that UHI is a proxy for expectations for trees experiencing future global warming by showing urban trees are growing faster because of UHI temperature rise than rural because of current lower global warming temperatures.
They reluctantly mention CO2’s role as a driver, because of a pact among alarmists to give zero benefits to it because this would reduce the “cost of carbon”. They couldn’t decently ignore it all together so that they hey marginalized it and threw in the old “temporary” effect but reckoning it will eventually harm growth.
Let a mining industry engineer /geologist correct the study: UHI may have an effect but it must be discounted by the effect of care, pruning, fertilization, watering, pest control, no competition for nutrients and sunshine.
Moreover, warming over the past century in urban areas where trees grow has been very slight (globally, 0.8C but mostly in Arctic Amplification if ~2.5-3C). However, CO2 has been credited with fattening existing trees but also expanding forest cover (rural areas) by 14% over 30yrs (NASA). Therefore, UHI must be further discounted at least 14% and more because urban environments also have higher CO2. It would seem that UHI is a very minor player, like marginal global warming in expanded agriculture harvests.
http://cosy.com/Science/CO2-pineGrowth100120half.jpg
“they’ll call out the Handicapper General … ” [h/t gnomish above]
The HG is still very active here … mandatory rules on the spacing of “shade trees” in retail/commercial parking areas. Bit of a boost from the nutrients dumped in the hole, then gradual decline as the irrigation systems get bunged up due to fine clay particles entering the lines or roots getting in or squeezing them tight, etc. The ideal car park tree would grow straight up for 3m, then outwards min 3m radius horizontal, doesn’t attract birds, doesn’t drop leaves, fruit or big bits of itself, needs minimal water/nutrients. Tut tut … God/Gaia/Intelligent Design has so far failed to provide such a tree.
Remember that episode 9 of the BBC’s TV Life Series titled “Plants” narrated by David Attenborough, made not a single reference to photosynthesis.
Clearly even mentioning this word is politically awkward as it points to the beneficial life-giving nature of CO2.
Can you imagine the BBC suits siting down with the old man and actually arriving at verbal consensus to not mention photosynthesis, for reasons of political mood music, to the huge damage and impoverishment of the scientific value of the program?
The worst aspect of humanity is what we are able to justify to ourselves. Our inward facing mental theater in which we are always the hero.
I’ve always noticed that plants seem to grow in great abundance and density on the verges of main roads and highways / motorways, where CO2 is locally elevated. These long verges are important wildlife refuges.
Comparing trees growing outside in different places means you are comparing a large number of variables that have varied in ways that are impossible to ever know.
Are these city trees growing on a concrete sidewalk with a small opening, a large opening, a grassy strip, bricks pavers nearby or surrounding the tree, etc.
Trees in cities are widely spaced…no competition in the root zone for moisture and nutrients…or did they correct for this by choosing equally spaced trees in each location?
It is warmer in cities, and most especially it is less cold at night and in Winter.
Few sewer systems in old cities are watertight. Most large cities are near water. Older cities likely have thousands of buried privies and old cemeteries, etc.
Depends on the city, the street, the tree…
There are a lot of variables and confounding factors.
But, we can notice a few things that are for sure: Being hotter is not killing trees; trees are growing faster now than before; it is not a little but a lot hotter in cities and it is not having the effects the panic-mongers would have us believe; and when they find good news, they do not trumpet it like when the find bad news…in fact they try to minimize it, explain how it is temporary, anything but admit that adding CO2 and other changes caused by man could be highly beneficial rather than a catastrophe.
No trees haven’t been growing faster due to ‘climate change’. They’ve been growing faster due to significantly more C02 in the atmosphere. At least in rural areas. It’s interesting the way that scientists lie without lying. Their papers are accurate but the narrative around them assumes things that haven’t been proven.
One would think that such a study would seriously evaluate each growing area along with the studied tree.
Nope, all that is needed are some tree samples; all the rest is assumption.
Which is it Prof. Pretzsch?
Urban tree far outgrow forest trees or all tree are growing approximately 20% faster?
The sentence in the abstract, quote, “However, our analysis shows that climate change seems to enhance the growth of rural trees more than that of urban trees.” end quote, contradicts the conclusions of the main body of the paper. Confusing rubbish.
Silicate weathering gradually removes CO2 from the atmosphere over billions of years.
It came close to causing a mass extinction in the last glacial maximum with CO2 levels well below 200ppm.
Hominid fossil fuel burning is a Gaia response of the biosphere to survive.
Fossil fuel burning and CO2 enrichment of the atmosphere is the only sensible geoengineering.
Attempts to stop it are genocidal.
We just replaced a section of plastic water main at a tee near a hydrant that had probably developed a tiny leak years ago, and caught the attention of a nearby tree. It took several hours to cut and tear away the root nest away because we were afraid of damaging the pipes further. All the time the tree trying to wave us away and the leaves were murmuring “It wasn’t me!” When irrefutable evidence was uncovered the tree turned its back to us in a petulant manner. Not content to sip, it had become greedy and strangled the pipe until the joint buckled and the gasket blew out.
If trees would just drink responsibly… or evolve the ability to plug small leaks entirely then we could have a nice symbiotic arrangement. But they’re only human, I guess. Watch out for those California trees, a lawyer fungus attaches to them and they attempt to secure water table rights in neighboring states.
There has to be a “however”. Every piece of good news about warming/CO2 has to be neutralized by an equivalent negative. Got to keep the peasants worried.