How can the fragmented landscape of a city be healed using bio-corridors that connect people and habitats through enhanced and restored ecosystem services? Increasingly biodiversity corridors – including pollinator paths – are used to provide places for wildlife to thrive, improve water quality and create open green spaces.

The continued loss of biodiversity worldwide made headlines recently with the release of two reports highlighting biodiversity is at crisis point. The WWF’s Living Planet Report 2018 reveals there has been a 60% decline in the population size of mammals, birds, fish, reptiles, and amphibians in just over 40 years. Meanwhile, a study published in the journal Science in August showed that since 1970, bird populations in the United States and Canada alone have declined by 29%, or almost three billion birds.

Closer to home, the government has released Te Koiroa o te Koiora, a discussion document on proposals for a biodiversity strategy for Aotearoa New Zealand. Almost two thirds of New Zealand’s 71 identified rare and naturally uncommon ecosystems are threatened, and 75% of terrestrial birds, 85% of reptiles and 70% of butterflies and moths are threatened or at risk of extinction.

With development and land use for humans being one of the leading causes of biodiversity loss, the concept of biodiversity corridors has taken on a greater significance. At WSP, it is important we lead the way in ensuring developments consider local and regional connectivity to support the natural migration of biodiversity.

“In simple terms a biodiversity corridor is an interconnected and linear habitat that wildlife, flora, fauna and microorganisms can travel and disperse easily because of that connection”, says WSP Technical Principal of Ecology, John Turner.

“They don’t always have to be entirely connected (contiguous corridors) – corridors can act as ‘stepping stones’ and those with small gaps can still prove functional. But it’s the linear nature of the habitat which is important and allows the movement of wildlife and dispersion of certain species of plants.”

John says his introduction to the concept of inter-connected corridors came in the mid-1980s when the concept was starting to be applied widely in the UK, but the idea’s origin started well before then. In New Zealand, the concept of biodiversity corridors has been used in urban planning and research management planning for several decades.

“Here in New Zealand, biodiversity corridors are often associated with waterways, such as streams. While the streams do get culverted and fragmented during the urbanisation process, sufficient streams remain in cities such as Hamilton for them to continue to act as biodiversity corridors. In urban settings, major streams often lend themselves to creating biodiversity and amenity corridors.”

Other forms of biodiversity corridors include terrestrial corridors, or green space corridors. “One example is the Eastern Green Belt in Hamilton – a linear corridor of exotic and native planting, inter-dispersed with public open spaces, playgrounds and playing fields. While these may seem like they are for human use only, they also provide corridors and access routes for wildlife too,” says John.

With an estimated $US650b worth of global crops put at risk every year from pollinator loss, another form of biodiversity corridor is gaining prominence. Pollinator paths are interconnected habitats that allow pollinators to travel more easily throughout a city, and WSP was involved in developing Auckland’s first pollinator highway.

“For the last 50 years we’ve been designing cities around cars,” says WSP’s Andrea Reid. “But we’re seeing a shift in thinking that could see streets become public realm, where cars will be permitted but not have priority. We’re already seeing this approach with an increase in design that is greener, promotes walking and cycling, and increases connectivity between existing parks and green spaces.”

“Add to this the increased trend towards urban gardening – whether at home or through community gardens – which is being driven by the desire to grow food locally to reduce food miles. The problem is, it’s really hard to grow food if you don’t have pollinators, which is why projects that create hubs are so vital.”

Andrea says pollinator paths link existing habitat to create pollinator highways to allow pollinators to travel more easily throughout the city. Hubs allow pollinators to shelter over winter and provide different food sources, helping them to travel around an area easily.

“In New Zealand we have over 30 species of native bees. Unlike the honey bee most of these bees are solitary and nest in the ground. We also have a variety of native birds, bats, lizards, skinks, butterflies, moths, flies, beetles and other insects that all contribute to the pollination of plants we need to survive.”

Andrea worked with Auckland Council, Auckland Transport and the Waitemata Local Board on Auckland’s first pollinator path in Grey Lynn, funded by the Waitemata Local Board. The path connects habitats in Cox’s Bay Reserve and Grey Lynn Park via Hakanoa Reserve and Kelmarna Gardens, and has been a huge hit with the local human (and pollinator) communities.

“We have a massive opportunity in New Zealand towns and cities to include more green infrastructure – that’s not as easy to do in other places in the world. With more thoughtful management of amenity green space and the installation of more urban greening features such as green roofs or living walls, we can create ecological networks at a finer grain throughout the city.”

Further south in Hamilton, John Turner and the WSP team have been working on a different type of corridor to support the local bat population to get around the urban environment. Bats frequently use the natural gullies around the region to travel and avoid built-up spaces and structures.

“We’ve been working extensively on the Hamilton Section of the Waikato Expressway, which intersects through gullies to the south of Hamilton. These gullies are important corridors for the local long-tailed bat population, a species with a threat classification of Nationally Critical,” says John.

“Since 2014 we’ve been completing annual bat surveys for Waka Kotahi – NZ Transport Agency (NZTA) to assess any impacts of the expressway on bat populations. We haven’t found any conclusive results as to what the effects might be, but we continue to work with NZTA to assess, plan and mitigate any impacts, using thermal imaging cameras and bat monitors to try to study bat activity and movements in association with the road structures through the gully.”

WSP has also been working on a section of the Te Awa walk and cycleway, which in its entirety stretches along the Waikato River, from Ngaruawahia in the north to Karapiro in the south. The Mangaonua Gully in Hamilton touches the city edge and is a corridor frequently used by bats to commute between roosting and foraging areas. WSP completed an ecological impact assessment of the walk and cycleway, to assess the effects on wildlife, ensuring they are minimised.

Wildlife isn’t the only benefactor of bio-corridors – they also deliver a range of other ecosystem services that improve spaces for the public and local communities – from delivering carbon sequestration, flood risk management and water quality improvement, to space for people to recreate in, encouraging physical and mental wellbeing.

John Turner, WSP Technical Principal of Ecology, has almost 30 years’ experience as an ecology consultant. He has substantial experience in the integration of existing ecosystems into plans for new developments and a special interest in retaining, enhancing and creating ecosystems within urban and sub-urban environments. His technical knowledge of ecosystems is wide ranging and includes forests, rivers, streams and lakes, and various types of wetlands.

Andrea Reid is a driven, multi-award-winning landscape architect working at WSP. She is passionate about the environmental enrichment of urban areas and has a particular interest in providing connected habitats for pollinators. Andrea has been involved with the design of a range of project types including public realm, parks, town centres, sport parks, wetlands, wayfinding design, cemeteries and ecological restoration.