Latest World News

Mini forests in cities: air conditioning for the district


In summer it often gets hot in densely built-up cities. Fast-growing mini-forests are said to improve and cool the air. An idea from Japan – does it work here too?

By Niklas Schenck, NDR

It’s a hustle and bustle: On a small plot of land next to a high-rise building, around 50 people are digging their spades into the ground at the same time. They plant young trees. Oaks, beeches and native shrubs. They are to be used to create a new 300 square meter mini forest. In the middle of a residential area in Hamburg’s Altona district.

Neighbors and a few families are helping to plant around 1,000 seedlings. She thinks it’s great to be able to plant lots of trees in a short space of time, which will store CO2, explains Nina Schumann, while her son is digging in a root.

In Altona, a mini forest is to be created in the middle of the city.

Image: Niklas Schenk

Urban oases for biodiversity

The idea of ​​the Tiny Forest came from the Japanese forest researcher Akira Miyawaki. He also studied and taught in Germany. As early as the 1970s, Miyawaki was thinking about how to improve the climate in big cities through reforestation. His answer: create small, green islands of nature. They provide shade, support biodiversity and clean the air of pollutants.

Because the trees are planted in a very small space, they should grow particularly quickly. Because they compete for light. The soil is also enriched with natural nutrients – again to accelerate growth. The organisms feed each other. After only three years of care and watering, a Tiny Forest in the city is left to its own devices.

More planting campaigns

Such mini forests, for which an area of ​​just 100 square meters is sufficient, are now found in India, the USA and Europe, for example in London and Vienna. In Germany, Boris Kohnke and his association “Citizens Forests” have already planted 19 Miyawaki areas, the first in Schleswig-Holstein. “They don’t heat up the city as much and they also offer a retreat for endangered animals that otherwise have no place to stay,” says Kohnke.

He stands in the midst of the newly planted trees in Hamburg. His club has a mission. As with the authorities in northern Germany, thousands of other cities and communities will soon be approached to find unused areas for tiny forests. “The question is whether a small forest can make a difference. But many small forests can make a difference and that is exactly our goal.”

Forest expert takes a critical view of the climate effect

Such a mini forest cannot be compared with a real forest. The biologist Ernst-Detlef Schulze is correspondingly critical of the effect of the new urban greenery on the climate as a whole. “The extent of these activities is minimal and hardly measurable,” says the professor at the Max Planck Institute in Jena.

Of course, every tree in a residential area has a beneficial effect. It reduces dust pollution and provides shade. From the researcher’s point of view, however, the Tiny Forests are not large CO2 stores, even if many were created. Further measures such as green facades and roof gardens as well as a sustainable timber industry are needed.

Mini-forests break up sealing

For Gesche Jürgens, this is not an argument against the idea from Japan. Greenpeace’s forest expert believes that real forests are allies in climate protection. They looked like giant air conditioners. “Without the Amazon rainforest and the Nordic forests, we have no chance of getting climate change under control.”

But in addition to forest preservation, it is also important to create more greenery in the cities. “Because there is a lot of concrete and sealed areas here. And mini forests like this are simply an important contribution to more cooling,” says the environmentalist.

That is exactly what Kohnke and the volunteers from “Cititzens Forests” are all about: They want to improve the quality of life in neighborhoods. In Hamburg and other German cities, more trees are currently being felled than are being planted. That’s why every piece of nature counts, every tree. They want to plant a total of 100,000 in Hamburg alone over the next few years.