A new study carried out by the Technical University of Munich (TUM) has found that metropolitan trees grow faster than rural trees.
The research team focused on almost 1400 mostly mature trees from Berlin, Brisbane, Cape Town, Hanoi, Houston, Munich, Paris, Prince George, Santiago de
Chile, and Sapporo. The cities were selected to cover different climate zones. The spectrum ranged from boreal to temperate, Mediterranean, and subtropical
climates. A typical and predominant tree species was selected for each city and examined in both the city centre and surrounding rural areas.
“Whilst the effects of climate change on rural trees has 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. “We can show that urban trees of the same age are larger on average than rural trees because urban trees grow faster. 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 centres. 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. They stimulate photosynthetic activity, and they prolong the
vegetation period, which extends the length of time of the year during which trees can grow.
Regardless of the growth advantage of urban trees, the study conducted by Professor Pretzsch’s team also shows that both urban and rural trees have been
growing faster since the 1960s – as a result of climate change.
You can read the full report here.