residential houses, office buildings, cars, houses, sidewalk cafes, bus stops, cycle lanes In cities have only a little space for nature remains often. So city of trees lived in the constant fight for enough space, says Sonja dümpel man, landscape historian at the University of Pennsylvania. And, although in the cities anywhere in the world, a vital role to play.

Already, more than half of the world's population lives in cities. By 2050, another 2.5 billion people will come to this - the competition for space in the cities will increase. Just in front of this Background, but it is not according to the experts crucial to consider trees only as a purely aesthetic enrichment in cities.

The cooling power of trees

this is Because trees are real power plants, when it comes to the regulation of the urban micro-climate: they filter the air and absorb CO2, they provide shade and suck on their thick root system, a lot of water, what is the danger of flash floods after heavy rain reduce. But above all, they seem to have a cooling effect and mitigate the urban heat-island effect. Because stone and concrete heat up particularly strong and the heat only slowly release it again, it is in cities, usually much hotter than in the surrounding rural areas.

"trees can affect the temperature of a city is enormous," says Tobi Morakinyo. The urban climatologist studies the cooling effect of trees in Akure, in southwest Nigeria. His studies show that trees used for shading of buildings, to cool this by up to five degrees Celsius.

Just for African cities such as Akure, South of the Sahara, and in which the average maximum temperatures in summer rarely below 38 degrees, this cooling effect of trees is an important and, above all, inexpensive means of combating heat stress.

trees provide traction in growing cities,

And city trees would have to offer far more than these "ecological services," added Cris Brack, forest ecologist at the Australian National University and Director of the National Arboretum in Canberra. "They provide biodiversity, Aesthetics, and satisfy our deep-seated need, natural to us," said Brack in an interview with DW. He refers to the concept of "Biophilia" - the innate desire of people to connect with nature. In fact, more and more studies show that people who live in places with more trees experience less Stress and less frequently suffer from mental illness than people who live in a treeless environment.

Our need for trees in towns and cities increases. But city trees are "in a constant fight" for space, says Brack. Water pipes, roads and underground Parking garages affect the Grow of your root, above ground, exposed to dust and fumes. Mechanical vibrations come through the traffic, increasingly extreme weather and damage to the Root system by construction sites.

Massive Tree due to lack of water

perhaps The most pernicious threat to city trees, however, says Somidh Saha, urban forest ecologist at the Institute of technology in Karlsruhe, is the drought. After the unprecedented heat wave in Europe in the year 2018, noted by Saha participated in the drafting of biggest study that a third of all in the last four years in Karlsruhe, planted trees received due to lack of water.

"Without enough water, trees are weak, and this makes them susceptible to diseases," explains Saha in the DW-Interview. At the same time, the decline of birds and bats lead to the fact that pests spread and the infested, in turn, then the trees and weakened them.

In a number of mega-cities around the globe in the past few years, ambitious greening projects have been built - New York City planted between 2007 and 2015, one Million trees; London mayor Sadiq Khan wants to be more than green half of the British capital up to the year 2050, as the world's first "National Park City" in the books, and Paris wants to have built by the end of 2020 four inner-city urban forests.

Outside of the global North but for instance in India, the home of the forest ecologist Saha or in Nigeria, where urban climatologist Tobi Morakinyo lives, we see only rare trees in the city. Here the money is missing, the municipalities often simply to be able to more urban Green care.

a plea for alien tree species

Also, rising temperatures and heavy rain cases require, as a consequences of climate change, an increasingly greater resistance the city of trees. In the view of Ecologists, cities must put the world on such tree species that are better adapted to heat, and the artificial environment of a city. However, these are often species that are not in the respective regions at all, and how about the dreizähnige maple is originally native to China, Korea and Japan.

Although a lot of people Balk against the idea of plants not eimische types. However, the Ecologists brackish and Saha see this as a great opportunity. An important difference between "non-native" trees and "invasive" trees for the native Flora is harmful, it is argued, because they spread in the absence of predators quickly and the home could symbolically displace species.

to see how the local wildlife comes with non-native tree species to cope, the Team of forest ecologist Sahas currently studies in Germany. His fellow Australian, Brack reported that in his home town of Canberra, almost all of the city of trees "exotics" are - however, their fruits of domestic birds would eat the tree of mammals settled in them.

citizens for trees

A solution for the preservation of city trees, which have gained in recent years in popularity, is the participation of citizens in urban tree care. In New York City about city residents courses to become an official City arborist. In Berlin, where you had excluded the citizens from the care of the urban Flora, as yet, always, called on the city administration, the residents, to pour in the summer, the trees outside your doorstep. In addition, citizens may request, in the meantime, permits for the maintenance of tree beds.

such involvement of the citizens to have advantages and disadvantages, says landscape historian dümpel man. How effective it was, hanging often from the culture of the city. But the casting of trees "has proven to be really relevant to the care measure". Although the plants and the care of city trees could not solve the causes of climate change, yet it is an effective and relatively simple way cities better adapt to climate change. "It is something that we should work while we should at the same time tackle the causes", so dümpel man.

Beyond the climatic benefits could residents manage trees in city a greater understanding of the nature. "That means, to see trees as living, growing beings that are not immune to the stressors of city life, like the people," hopes the forest ecologist brackish.

nature as a part of the city life instead of "the city" and "nature".

author: Charli Shield (jc) saw-tooth-the summer is coming to a head: Only 36 degrees - then the drop in temperature PCP sawtooth follows-the summer is coming to a head: Only 36 degrees - the temperature fall

*the following in The article "climate change makes our cities to-heat-Hotspots - more trees could alleviate" is published by Deutsche Welle. Contact with the executives here.

Deutsche Welle

Date Of Update: 27 July 2020, 16:27