An experiment was set up in Rotterdam to find the optimal mowing method for the municipality to enhance biodiversity. Urban ecologists have called this ‘mosaic mowing’. This type of mowing is used for broader roadside verges with nutrient-rich soil. With mosaic mowing, there are three rounds of mowing, whereby one part is done in the first round and another part in the next. The vegetation is never completely mowed in one go and one part is always left untouched during the winter. This is especially beneficial for insects, which use the vegetation throughout the year in all their life stages (egg, larva, pupa and imago). By removing the cuttings, the soil is prevented from becoming too rich in nutrients. The first round is scheduled early in the year (in May), so the herbs in one third of the area have the chance to bloom at the end of the summer. Verges at crossings and the first 50 centimetres along the roads are always kept short for safety reasons. Already within a year, measurements indicated that biodiversity was significantly higher than in similar parts with traditional management. Many grasses and herbs completed their entire flowering cycle, thus increasing the wealth of insects, especially butterflies. Not only the species that live in these grass strips benefit from this mosaic mowing, but perhaps these strips also serve as a refugium for the more picky species from the surrounding areas. In 2017, the survey will be extended with an inventory of bees.
Philips Healthcare in Best has reserved a building site for future company expansions. For the meantime, a butterfly garden was realized at this location. This temporary nature will sooner or later make way for future developments. That this phenomenon is becoming increasingly popular is due to the Dutch state regulation ‘Temporary Nature’, which was implemented in 2015. Where previously owners of such areas were very reluctant because of the risk that future building plans could be blocked because of protected plant or animal species, they are now guaranteed free use of their land at locations this state regulation applies to. The terrain in Best is not only a rich biotope for plants and animals, but it is also good for the company. Dedicated employees helped sow the native flowers and plants that are attractive to butterflies. The Dwaaltuin (cottage garden), as the area is now being called, is a place they go to during their lunch breaks. Above all, the collaboration with the Vlinderstichting (Dutch Butterfly Conservation) has made the people working for the company aware of the power of nature and the biodiversity that can arise even in a short amount of time. This is important, because the biodiversity of butterflies has nearly been halved in Europe since 1990.
Located in the Thames corridor in London, the Deptford Creek area now has several brown roofs. The first and most famous of these is the roof of the Laban Dance Centre by Herzog & de Meuron. Before the redevelopment of the area, the brownfields with a lot of debris and bricks had become the habitat of various rare plants, insects and birds, including the black redstart. When the declined area was redeveloped and new buildings were constructed, the roofs were covered with crushed concrete and loose bricks from the demolished buildings that once stood there. Between this substrate and the waterproofing layer, there is only a 10-milimetre water storage membrane without drainage. The resulting biotope has characteristics similar to those of the original ‘brown’ terrains. The vegetation was not sown, but has gradually taken over the roofs. By now, more than a hundred plant species have colonized the roof and some rare insect species are found there. The black redstart is doing well in its new rooftop habitat.
An edible forest garden is a forest ecosystem related to permaculture gardening, in which a wealth of edible or otherwise usefull species is laid out. Although the principle is ancient and can be found in many cultures, it was reintroduced in our temperate climate zone by Robert Hart with his book Forest Gardening, Rediscovering Nature and Community in a Post-Industrial Age (1997) and further developed by Martin Crawford. Compared to most permaculture gardens and smaller vegetable or plant gardens, a forest garden is generally larger and contains mostly perennial plant species. The principle is the same, though: creating a closed and resilient ecosystem of mutually cooperating species. Diversity in types of microclimates (shaded and sunny, and everything in between) and gradients (taller and lower plants and trees) are important design principles for an edible forest garden. The local conditions, namely the climate, the soil and native species, form the basis for the design. More so than in a permaculture vegetable garden, the various horizontal layers, from the canopy to the deeper soil layers, play a role in the structure of a forest garden. In a well-laidout edible forest garden, every niche is filled and there are no empty spots in the system. Edible species can be taken up in all layers of the system: trees bearing nuts or fruit; berry bushes; rubus species; ground covers, such as strawberries; climbers, such as Indian cress and hardy kiwi; a multitude of herbs and edible tuber and root species.
A crinkle crankle wall is a winding masonry wall that used to be placed in orchards to protect the trees. The wall provides sheltered spots in the bends where wind-sensitive species and those that require a slightly higher temperature can thrive. At the southern edge of an industrial estate along the motorway, artist Krijn Giezen and landscape architect Roel Bakker laid out an enormous (300 metres long, 6 metres high and 3.5 metres thick) crinkle crankle wall in 1991, made from construction debris from the area and held together by steel nets. The wall serves as a noise barrier that protects the quiet pasturelands behind it, but because of the debris, it has ecological significance as well: plants grow on it and animals like to hide between the boulders.
Vegetated roofs can play an important role as oases where plants and animals (especially birds and insects) feel at home. By now, many versions have been developed, each with its own specific merits. In Wageningen, there is an experiment with a green-blue version, focusing on water storage in addition to ecological values. A roof package was placed, providing space for grasses and larger plants with water storage underneath. This in contrast to the many green roofs with a relatively thin substrate layer and sedum vegetation. Sedum is drought-resistant, but when it rains, the water runs off rapidly. So the roof can survive dry periods, but is much less useful when it comes to reducing the growing problems with water due to climate change. Vegetation with many grasses is much better at retaining water. Hence, scientists are experimenting with a so-called polder roof at the roof of the NIOO (Netherlands Institute of Ecology) building, a wet version of the green roof. The field of many kinds of roof packages is part of a research programme on the specific qualities and limitations of each system. One of the aims is to find vegetation that can survive periods of drought and at the same time retain water longer. In addition to the green roof, the building has ecologically rich ponds right next to its entrance. The gardens behind the complex are also used for experiments. There is a large insect wall, for example, to study what choices work best in terms of biodiversity, just like the experiments on the roof.