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Urban private gardens promote biodiversity

Helena Hanson. Photo.
Helena Hanson, researcher. Photo: Anna Maria Erling.

They become smaller as urbanisation increases. Troublesome, according to researcher Helena Hanson, because urban private gardens affect both cities’ biodiversity and human wellbeing by functioning as social green spaces. Now she strikes a blow for gardens in the urban planning.

Green spaces, such as parks and allotment gardens, have a major impact on our physical and mental health and wellbeing – not at least in densely populated areas, where people may have to travel far to experience ‘true’ nature. In addition, urban green spaces are important islands of biodiversity that enables life for others then just humans.

Important bird song

In a newly published study, Helena Hanson, environmental scientist at the Centre for Environmental and Climate science (CEC), Lund University, states that urban private gardens are as important as public green spaces. She has studied how private gardens affect urban biodiversity and garden owners’ wellbeing.

– We discovered a knowledge gap. Previous studies had mainly looked at public green space and overlocked the importance of private green space, such as private gardens. We wanted to find out what functions they have for those who own them as well as for the whole city, says Helena Hanson.

The researchers visited 35 gardens in the centre of Lund and interviewed the garden owners. Those who used their gardens for socialising, recreation and relaxation were clearly predominant.

– Almost all the interviewees thought that it was important with nature experiences, such as bird song and fragrant flowers. People also seemed to value seeing the seasons sweeping by, and some expressed that nature were a part of them. Many also replied that they had wanted a house with a garden for the sake of their children.

Small gardens lack biodiversity

How valuable the garden is, for both animals and humans, however, depends on the size, age (for both owners and the garden) and design. The bigger, the better according to Helena Hanson. But the trend seems to be going in the opposite direction. New residential areas often have small gardens with little or no space for trees that can provide shade when the climate gets warmer. According to Helena Hanson, this is partly because it is expensive to build houses with large gardens in many urban areas. There is also a political will to save valuable agricultural land and forested areas from exploitation. The consequence is less space for trees, shrubs and flowers, and hence important structures for biodiversity.

– Large trees are especially important for biodiversity, but there is no room for them in new small gardens. If you want the private land to contribute to biodiversity and societal wellbeing, you have to create space for larger structures, says Helena Hanson.

Older gardens are generally larger and therefore have more space for trees and shrubs. However, in their study, the researchers found that large gardens often consist of large areas of lawns, which have limited contribution to biodiversity. Nor did the majority of the garden owners, regardless of size, seem to choose garden plants to benefit wildlife.

– Most of the interviewees chose plants based mainly on aesthetic preferences such as colour and form. The most important thing for them was that it should be beautiful. However, there may be indirect effects as a varied garden with different types of flowers can benefit pollinating insects.

Green spaces over cars

The researchers’ conclusion is that urban gardens have the potential to function as multifunctional urban green spaces, but in order to reach their full potential; both garden owners and the municipality must change how they plan, develop and manage gardens. According to Helena Hanson, garden owners need to get more and better information about what they can do to contribute to biodiversity and the municipality must be aware that when they build new houses with small gardens, these will not contribute much to biodiversity and the society.

– Like so much else, it is ultimately about cars. Cars occupy large areas in cities, but we must ask ourselves if we want roads or green spaces. Is it necessary to be able to drive all the way to your home, or is it possible to park the car further away so that you can make the gardens larger?

She also mentions trampolines, which have become very popular in families with children.

– Trampolines are tremendously fun, but they are sometime the only thing that can fit in the garden. Maybe there should be common green areas where you can put them instead? The same goes for swimming pools that are becoming increasingly popular. Small gardens already have limited opportunities to contribute, so you should try to make the best of them.

The article is published in the scientific journal Urban forestry & Urban greening.

Gardens’ contribution to people and urban green space - ScienceDirect