The German “Nature & Biodiversity Conservation Union” (NABU) periodically organises streamlet – renaturations, so-called “Bach-Aktionstage”. A good chance for us to turn into practice, what we have learned during our studies in Prof. Wolfgang Dickhaut`s classes at HafenCity University Hamburg.
On the first weekend of June 2015, we participated on the renaturation of the streamlet Tarpenbek, Hamburg. Together with other volunteers, we regenerated a part of the streamlet in such a way, that it will (re)transform into a vivid water body with manifold habitats for flora and fauna. After a quick introduction by Andreas Lampe (NABU), the necessary equipment – wheelbarrows, spades, shovels, loppers, sledgehammers and wading boots – was allocated. Currently, the Tarpenbek is a rather featureless streamlet with a low range of habitats. Hence, today’s tasks mainly involved the integration of absent materials:
INTEGRATION OF DEADWOOD // branches:
On various spots we integrated woodpiles of deadwood. These piles – below & above the water surface – create a habitat for the fish fauna (hiding spots, …). Furthermore, they represent a habitat and food source for many macrozoobenthos.
These deadwood piles retain organic material, such as other branches or foliage. Hence, after a while they will be overgrown by native riparian flora
INTEGRATION OF WOOD // tree trunks:
Trunks from fallen over trees were used to build dams. These dams create areas with different flow velocities. One part of the streamlet is now a stagnant water zone, which is particularly liked by juvenile fishes. The remaining part features a higher grade of turbulence, and increased the water`s oxygen content.
INTEGRATION OF GRAVEL:
Fishes depend on gravel beds as spawning grounds. By integrating gravel on both watersides, areas with different flow velocities were created. Due to the higher grade of turbulence, the water`s oxygen content can be increased.
WEEDING A NEOPHYTE // Himalayan balsam:
Many years back, the Himalayan balsam (Impatiens Glandulifera) was brought to Germany. Due to its above-average nectar production – according to Ingo Kowarik it produces 40 times more nectar than a comparable native plant (2003) – it was considered to be excellent for bee pastures. In the meantime, it threatens the local flora and is seen as neophyte. We weeded solitary plants and mowed larger quantities. Where possible, seeds of riparian plants were spread.
It was a great day – we did not only learn much more about the renaturation of flowing waters but also met many pleasant “Hamburgers”. Furthermore, it was fascinating to experience such an advanced level of teamwork – all kinds of human beings participated as best as they could and spent a lovely day with each other.
Photos: All rights reserved.
Photographs: All rights reserved