Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Climate change: Urban trees are growing faster worldwide

13.11.2017

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.


For the study, samples of heartwood from trees in major cities such as here in Vietnam's capital Hanoi were taken and analyzed.

Photo: 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 „Nature 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.“

Publication:
Hans Pretzsch, Peter Biber, Enno Uhl, Jens Dahlhausen, Gerhard Schütze, Diana
Perkins, Thomas Rötzer, 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, Nature Scientific Reports 11/2017. DOI: 10.1038/s41598-017-14831-w

Contact:
Prof. Dr. Hans Pretzsch
Technical University of Munich
Chair for Forest Growth
Phone: +49 (8161) 71 - 4710
Mail: hans.pretzsch@tum.de

Weitere Informationen:

https://www.tum.de/en/about-tum/news/press-releases/detail/article/34305/ the article

Dr. Ulrich Marsch | Technische Universität München

More articles from Ecology, The Environment and Conservation:

nachricht Despite government claims, orangutan populations have not increased. Call for better monitoring
06.11.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Increasing frequency of ocean storms could alter kelp forest ecosystems
30.10.2018 | University of Virginia

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

NASA keeps watch over space explosions

16.11.2018 | Physics and Astronomy

UNH scientists help provide first-ever views of elusive energy explosion

16.11.2018 | Physics and Astronomy

How the gut ‘talks’ to brown fat

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>