Reducing pavements and improving the ground: patios out, green in
Urban agriculture: 1
Air quality: 1
Multifunctional space usage: 2
Construction costs: 2
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Less paving in the garden and in urban areas has many advantages: the rainwater is absorbed into the ground, supplementing the groundwater.
Paved surfaces get warmer in the summer than green space; removing paving creates more room for plantings and the plants keep the area cooler on hot summer days. Removing paving offers animals, plants and soil life more space.
Indigenous perennials suited for the particular type of ground need less water. Ground coverings protect the soil from drying out and offer food for birds, butterflies, bees and insects for a better biodiversity.
In urban areas many surfaces are paved unnecessarily, often with the argument of lower maintenance costs. But unused paved surfaces must also be maintained: they must be swept and pesticides to fight weeds are often used. So the question is whether a low-maintenance field of wild grass that needs to be mowed only twice a year needs more maintenance.
Unplanted surfaces dry out quickly and have little cooling capacity. The capacity to absorb water also diminishes if the ground is dry. More water runs off from dried-out surfaces during heavy rainfall than from wet surfaces. Vegetation improves the surface’s infiltration capacity. Taller vegetation such as shrubberies increase the ground’s absorption capacity by a factor of three, since the larger presence of roots in the soil makes the ground more porous. [Ministerium für Klimaschutz NRW, 2011]
Adding organic material stimulates soil life. Materials that can be used include compost, grass clippings, woodchips, cocoa shells, humus-rich soil and fertilizer. More expensive conditioners include bentonite, biochar and lava rock. The ground quality must of course be considered when choosing conditioners.
Not only horizontal surfaces such as paving at ground level and roofs, but also vertical surfaces (facades, noise barriers) can be made permeable. In general, the following rule applies: the rougher the surface, the greater the effect. A field of flowers does more than a grass lawn, and bushes have a greater effect than a stand of herbaceous plants. The biggest effect on air quality is most likely through the reduction in the disturbance of precipitated particle matter. If there is a lack of space at ground level, green facades can be used. These contribute to the capture of particle matter, though mainly to the lowering of the atmospheric temperature.
See also the measure: Creating, maintaining and improving green areas and unhardening surfaces.