University of Otago urban ecologist Professor Yolanda van Heezik recently led a research team focused on the role that private gardens can play in contributing to biodiversity.
Analysing the backyards of 78 homes and five school grounds in the Otago region, the study noted what was growing where and assessed the gardens against various key criteria for biodiversity measures.
It gave the researchers data to calculate garden scores and assess how to translate those scores into a star rating.
Photo: Secret Gardens
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The research team have developed a garden biodiversity evaluation tool that they hope will support a new nationwide rating system, known as 'Garden Star,' which is modelled on the Homestar rating assessment tool for houses.
“We thought well if we want to try and motivate homeowners or households and incentivise them to improve the biodiversity in their gardens, maybe we could come up a garden start scheme where they can get their garden evaluated and that could be given say a star rating.
“But also, lots of information to show them how we got to that rating and also what they could do if they wanted to improve their rating.”
A group of 20 experts came up with more than 160 features in gardens that could be indicative of biodiversity, which the research them condensed
“We had four main categories, one was the extent of the habitat, so what proportion of your property is actually permeable.
“Then there was the quality of the habitat and that was kind of the vegetation it was supporting but there was also the management and that’s … what sort of things they do, whether they use a lot of pesticides or whether they have a free roaming cat, or whether they’ve created special things like encourage birds and lizards and invertebrates and then the fourth was kind of the landscape context.”
Using the 1000minds software, the categories were put into a ranking system and habitat quality had the biggest weighting, says prof van Heezik.
Prof van Heezik says New Zealand is not good at developing urban spaces that also allow space for biodiversity.
“The increase in hard landscaping, which is usually patios or concreted drives, it’s just ongoing all the time, it reduces habitats or all the other species that want to live in urban areas as well.”
She has looked at overseas solutions for cramped environments, which included vertical gardens and forests.
“There’s lots of different bits and pieces of the urban built environment that can play a role. The vertical forests are kind of the spectacular ones at one end of the spectrum.
Bosco Verticale (Vertical Forest) is a pair of residential towers (110 and 76 meters high) in the Porta Nuova district of Milan, Italy. Photo: Jerome Leblois / Hans Lucas / Hans Lucas via AFP
“At a more modest scale, we can achieve a lot more with green roofs and green walls, and there’s lots of small spaces that we can plant things as well.”
One good tip for people is to have a cluster of shrubs and trees in their gardens, she says.
“You immediately increase the value of that tree a lot if it has some shrubs underneath it, and if you have these kind of clusters which are not too far apart, then those form kind of like stepping stones for species.
“It helps them navigate around areas which might be much less attractive just like a bare lawn.”
Lizards in Auckland are also suffering from tidy gardens, ongoing human development, and mammalian predators, she says.
“[Having] piles of rocks are actually quite important because they are a refuge that the lizards can get into but even then, mice eat lizards so the piles of rocks, if the gaps in them are big enough to let mice in them then the lizards won’t be safe there either.”
Although, prof van Heezik notes that the most spotted lizard in Auckland is the Australian invasive plague skink lizard, which has the potential to outcompete native lizards.
The researchers are now looking to get councils to adopt the scheme and believe an app would be best suited to help households navigate the star system and link them to information.
“Next year, we’re hoping to look at how we can further develop the tool to apply to a more built environment so that it would apply to say people living in apartments that might have balconies and the buildings themselves too, like it’s possible to create buildings that have more biodiversity associated with them.”