by Yolanda van Heezik, Department of Zoology, The University of Otago

How well does your garden support native biodiversity? If native biodiversity in the town or city where you live is something you are passionate about, or even just want to contribute to, would you be interested in an accreditation that recognises the contribution your garden makes to city-wide native biodiversity, and also helps you identify how you could make your garden even better? Garden Star is an initiative that some of us are currently developing to try to promote native biodiversity in NZ’s urban areas.

A vegetated garden with multiple layers

As any gardener can tell you, gardens are places where we can create beauty, grow food, feel calm and relax, socialise, and also feel some spiritual connection to the natural world. For the very young and the elderly, and those with limited mobility, something we all experienced during lockdown earlier this year, our gardens become even more important places for supporting our wellbeing. Gardens can be home to many species of plants and animals, so the way we landscape and manage our gardens, and the plants we choose to nurture, all affect how well our gardens function as a space where other species can thrive. As an urban ecologist, I try to understand our cities from the perspectives of different types of creatures, all of which need appropriate spaces and suitable resources to grow and reproduce. City parks and reserves play an important role in providing appropriate living conditions for a range of native species, but on their own they are not enough. Fortunately, those public green spaces are all interconnected by the largest single green space type found in our cities – private gardens!

What role do gardens play in supporting biodiversity?

Gardens cumulatively make up the biggest green space across most cities and provide “stepping-stone habitat” that connects fragments of natural vegetation. All cities include inhospitable features that are very difficult for some creatures to live in or even to cross, such as busy roads, or areas of dense development with little vegetation. Street trees and gardens are potentially small oases functioning as stepping-stones, enabling animals to navigate through any unwelcoming areas. In Dunedin, 36% of the urban city area is covered by gardens, and even in very large cities in the UK private gardens are a significant proportion; e.g., between 22% and 28% in London, Glasgow and Sheffield. However, gardens vary hugely in their size and structure, meaning that some are much better at supporting native biodiversity than others. Given the large area covered by gardens, changes that individual householders make to their own gardens can significantly improve the liveability of our cities for other animals, even if each person’s changes are small. It would make a huge difference if a decent proportion of households were willing to play a part in managing their gardens to support native biodiversity, but how can householders be incentivised to do this?

A Dunedin back yard comprised mostly of lawn with few native species

Garden Star concept

Earlier this year, I attended a conference in Auckland called Urban Futures, which brought together city planners, urban designers, policy designers, civil engineers, architects and managers of urban infra-structure, with the goal of discussing how sustainable, liveable cities can be designed. While urban biodiversity was clearly not on the radar of just about every speaker there, my presentation on the importance of creating urban areas that support native biodiversity struck a chord with one conference attendee, who works for Kainga Ora, the organisation responsible for the construction of tens of thousands of houses across New Zealand. She was concerned at the absence of any requirements to protect or encourage biodiversity in the gardens and shared spaces of these future homes. My conversation with her, over a glass of white wine, lead to the Garden Star initiative.

She drew my attention to “Homestar”, which is an independent national accreditation, run by the not-for-profit Green Building Council, which evaluates the health, warmth and efficiency of New Zealand houses. A home is rated on a scale from 6 to 10. We thought, why not create a national accreditation scheme to recognise and encourage native biodiversity in private and community gardens? Could such a scheme acknowledge efforts made by developers and householders to protect or enhance biodiversity in gardens in new builds, and also provide guidance for those who wish to improve the native biodiversity in their own gardens? Although a biodiverse garden might not improve the value of a home in the same way that the “Home Star” accreditation does, neighbourhood initiatives might shift norms, and those who engage with the process could derive other benefits through partnerships between Garden Star and other entities. I had previously been considering some kind of local initiative, but after my wine-fuelled conversation I started to think nationally. All fired up I returned back home to Dunedin, where I enthused my colleague and husband, Prof Phil Seddon, with the concept, and together we are now working towards making Garden Star into a reality.

A suburb with gardens containing a lot of habitat for native species

Garden star – steps to becoming a thing

A first step was selling the concept to an NGO that, like the Green Building Council for Home Star, would be willing to adopt the scheme. Here’s where Phil’s networks paid off, with the result that the Endangered Species Foundation enthusiastically committed to supporting the development of the Garden Star accreditation. ESF CEO, Cheryl Reynolds has been super-enthusiastic about promoting the concept to various movers and shakers.

The next step for Phil and me was developing a tool that could be applied to gardens to evaluate their biodiversity value, on the basis of a single visit. At the scale we intended to apply Garden Star we would not have the time or resources to devote to collecting detailed ecological data from each garden. Tapping into our networks again, we assembled about 20 experts into what we call our TAG team (technical advisory group), which included animal and plant ecologists, entomologists, landscape gardeners, and people from councils, enviro-schools, universities, Manaaki Whenua Landcare Research, Plant & Food, polytechnics and private consultancies. We asked them to identify those features of gardens that they thought were important indicators of biodiversity – and they came up with a list of more than 160! We categorised these features and reduced them and then asked the TAG to indicate their relative importance. From this information we came up with an approach that involves evaluating vegetation extent and quality, but also surveys the householder to learn about garden management, and other factors that might affect native biodiversity, such as bird feeding or not enough pest control. We first tested our fledgling tool out on our own garden and found that it did a good job at identifying features we could improve on to raise our score (too much lawn and paved areas). This summer, we have two students, Emma and Jacqui, trying out the rating tool on a number of different garden types in two urban centres, and also in school grounds to see how well it performs.

When we have pored over the data provided by Emma and Jacqui we will evaluate how well the rating tool works: does it provide a range of scores that can be translated into star ratings? There are a number of issues we know we need to deal with. For example, the TAG came up with a number of features that were relevant to environmental sustainability (e.g. food production, water conservation) rather than native biodiversity: should these be acknowledged in the form of a sustainability tick, sitting beside the star rating? And how should we deal with small properties or very large ones? It is necessary to devise a rating method that doesn’t disadvantage householders with smaller property sizes. Our own research has also shown that the cost of implementing some of the measures to improve backyard biodiversity can be a major barrier for many people: should socio-economic status of householders be taken into consideration as well? And what if the garden is the only biodiverse garden in a neighbourhood of poorly vegetated yards? Should those householders gain extra points for being neighbourhood pioneers? As we move into a pilot phase across more cities, these are the some of the issues we will need to consider, as we refine the rating tool.

3 thoughts on “Garden Star: Supporting Urban Native Biodiversity

  1. Hi interesting concept though quite a challenge to meaningfully implement given increasingly smaller sections with more intensive housing. Encouraging more use of native plants that cope better in challenging conditions would be a great start. Here in Wellington we are lucky to have Otari- Wiltons bush with wonderful native gardens for inspiration. Working with existing garden groups and revegetation groups would be a way to start spreading interest beyond the councils and schools that you mention.


  2. Just heard Yolanda talking on National radio. What a wonderful initiative. Would love to see the Council in Tauranga involved.


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