7 x edible shrubs for improving urban biodiversity

In these blog posts, Maike van Stiphout (landscape architect and author of First Guide to Nature Inclusive Design) and Jeanne Tan (architecture writer and content editor) delve into the world of shrubs, sharing the beauty of this under appreciated group of plants which are ideal for urban nature, urban biodiversity and urban food forests. First up is Sloe famed for its ethereal white blossoms and its plum-like fruit. Supporting a wide variety of wildlife, the low maintenance Sloe shrub or hedge is a firm favourite for improving urban biodiversity all year round.

  1. Sloe or Blackthorn (Prunus spinosa)

Native to the Netherlands, Sloe is an ancient shrub that supports a wide variety of wildlife, making it one of our favourites to plant in urban landscapes to improve biodiversity all year round. It’s famed for its delicate white blossoms and edible dark purple fruit called sloes. Low maintenance Sloe shrubs suit rather wild landscapes and gardens and are excellent as hedges. It thrives in full sun but can tolerate some shade.

After long Dutch winters, a blossoming Sloe in March is a spectacle to celebrate – spring is on the way! They transform in early spring from a thick mass of thorny branches into ephemeral clouds of delicate white blossoms. Importantly, at this time when there’s little food available, Sloe blossoms provide precious nectar and pollen for bees, bumblebees and butterflies. After the blossoms have been pollinated, the fruit appears. 

Later in the season Sloe becomes a favourite foodplant for the caterpillars of moths and butterflies, in particular the black hairstreak (Satyrium pruni) which lay their eggs almost exclusively here. This butterflie is extremely rare in The Netherlands.

Sloe provides an ideal nesting habitat for birds – especially with caterpillars, an important food source, within easy reach. Although Sloe is deciduous, its dense, thorny branches offer shelter to birds and other wildlife against urban predators all year round.

Come autumn, the small oval leaves turn orange and the clusters of fruit ripen into a rich dark purple – a beautiful sight. Resembling mini plums, sloes are the predecessor of our cultivated plums. Try to spot birds such as thrushes feasting on them. If you’re going to harvest some, don’t be tempted to eat them straight away – they’re astringent and tart. Traditionally sloes are prized for making jam and wine and infusing liqueur such as Slivovitsj.

Trees, Urban Ecosystem Services and the ‘Internet of Nature’

In the 2020 virtual tour on her city’s Arboreal Wonders Amsterdam based researcher Nadina Galle lines up a variety of beneficial ecosystem services of city trees as key ingredients for a biodiverse city.

Already when planted the service expected by the elm trees in Amsterdam was to strengthen the canal quay sides with their vertical roots. Today there are 400.000 trees along streets and canals, and more than one million trees in the entire city offering many services. Software like iTree helps quantify these value of trees. Next to cooling and a pleasant soundscape these values include the increase of property value, and safety by lowering traffic speed and decreasing crime. In addition, trees help to buffer storm waters, store carbon dioxide and improve health by lowering stress and blood pressure, says Galle.

The Amsterdam Urban Nature Map (also available for Breda) shows all the green and blue public spaces, and how to better use urban nature. More information on trees and their benefits can be seen on the Interactive Amsterdam Tree Map, and MIT’s Treepedia. Or use an identification app such as PlantSnap, iNaturalist or PictureThis. Speaking with Nadine get one and have ‘a botanist in your pocket!’

© Still by Nadina Galle, video by Christiaan Kanis

Building with Nature perspectives

A new publication about Building with nature is published by Rius (Research in Urbanism Series), TU Delft. This publication offers an overview of the latest cross-disciplinary developments in the field of Building with Nature for the protection of coastal regions.

Drawing from the experience of DS landscape architects, four actualized projects and two student master theses of the Academy of Architecture illustrate the challenges, opportunities and benefits that building with nature presents. These cases highlight four important lessons for designing with nature in rural and urban landscapes

Publication: https://www.rius.ac/index.php/rius/issue/view/10/10

The Nature of Cities Festival 22-26 February 2021

“The 2021 TNOC Festival pushes boundaries to radically imagine our cities for the future. Join a diverse international community of urban thinkers to re-imagine our cities today, to build the cities of tomorrow.

This virtual festival spans 5 days with programming across all regional time zones and provided in multiple languages. TNOC Festival “offers the ability to truly connect local place and ideas on a global scale for a much broader perspective and participation than any one physical meeting in any one city could ever have achieved.

Look at the program and register (100 USD for Global North).

Green ‘city skin’ delivers many ecosystem services

Protecting the ‘skin’ of the city with all forms of greenery delivers a wide array of ecosystem services, as Nicole Pfoser shows in her research already in 2012. While the unprotected skin leads to noisy, hot and flooded cities, the ‘city skin’ composed of roofs, facades and public space surfaces delivers sound absorption, water buffering, reduction of urban heat islands – and an increase in urban biodiversity, when protected with urban flora.

Download the full (and free) report of Mrs. Pfoser at the German Fraunhofer Insitute.

Viennese public transport company contributes to biodiversity

There is also positive news from Vienna these days: Because securing biodiversity on public green spaces is important – they are not only attractive areas to be used by people and animals and help cooling down the city in the summer – the University of Natural Resources and Life Sciences Vienna (Boku) was asked by the metropolitan public transport company (Wiener Linien) how to preserve and maintain these spaces appropriately. A large scale investigation into insect and plant species on 20+ green spaces along the public transport network has shown surprising results.

In the only 3.7 hectares studied 378 species of plants and a third of all 460 bee species in Vienna could be found. This is remarkable, given the more than 200 km2 of green space in the entire metropole, and stresses the importance of transport infrastructure for green-blue urban networks in the city, and Quality of Life.

Read more on the still ongoing research of Bärbel Pachinger and Sophie Kratschmer at Wiener Linien or Der Standard. Final results will be published in 2021, see the university website for details. Image is (c) Boku.

Porosity for closed buildings and a park instead of parked cars: the new BUas campus in Breda contributes to quality of life in the city

The city of Breda has formulated the ambition to become the first ‘City in the Park’ and has been working consequently on improving biodiversity and nature-inclusive building. Recently the Breda Architecture Award 2020 (BLASt Prize) was awarded to the new Breda University of Applied Sciences Campus, a design by Inbo and Culd. In the heart of the project a formerly car-lined road was transferred into a new park. The courtyard of the adjacent cloister was opened up towards the new green campus. Even when the university buildings might be closed due to covid-19, the new campus space is open to the public and contributes to quality of life in the city.

Stichting BLASt
Inbo architects
Culd landscape architects

The end of the stone gardens in Baden-Würthemberg

The stone garden increases the climat problems such as heatstress and stormwater floods in the neighbourhoods. Since a few days a stone garden is forbidden in Baden-Würthemberg. Their garden-legislation (1995) prescribed that paving is only allowed where it is really needed. The recent garden trend to replace plants by small pebbles was not foreseen and not stopped. The film explains to the inhabitants why the new law is made and how to change the garden.

film in: https://www.swr.de/swraktuell/baden-wuerttemberg/schottergaerten-ministerien-uneins-100.html

“A leafy neighbourhood feels 15°C cooler than areas with no trees.” TU Delft now has a test set up with 75 tree species to check what is the coolest tree.

Trees provide all kinds of ecosystem services, such as converting CO2 into carbohydrates, producing oxygen, and purifying the air by trapping particulates. They provide habitats for fungi, mosses, insects, mammals and birds and so form the basis of all ecosystems, including in urban areas. But trees also help to keep city squares, streets and buildings cooler. Their leaves absorb solar radiation, transpire water and create shade, so lowering the temperature in their immediate environment. During a heat wave, a dense foliage provides much-needed shelter and a park or public garden with lots of trees quickly feels like an oasis in the urban desert. On a hot, windless day, a leafy neighbourhood may well feel 10 to 15°C cooler than an urban area that is more exposed to the sun, which can be enough to prevent heat stress. Trees thus play a key role in the design of climate-proof and healthier cities.

To determine the cooling performance of various species of trees, in 2018 TU Delft’s Faculty of Architecture and the Built Environment and the Dutch Association of Landscape Gardeners (VHG) formed the Urban Forestry joint research programme to support fundamental research into the relationship between tree architecture and the urban microclimate. Urban landscape specialist René van der Velde, who is affiliated with the Faculty’s Chair of Landscape Architecture, is leading the programme. Lotte Dijkstra joined the programme as a researcher. “Although gardeners and other ‘green’ professionals already understand a great deal about the performance of tree species in the built environment, there is very little empirical knowledge about their cooling capacity.”

In order to determine how physical properties such as the trunk and crown shape, the branch structure, and the leaf characteristics influence the local air temperature and the apparent temperature, this spring the research team designed and built special ‘climate arboreta’, experimental plots containing tree species that are common in Dutch parks and gardens.

Read more