Cohabitation in Suburbia; Improving New Zealand's Biodiversity through Suburban Environments
THE PROBLEMOne of the major crises facing the world today is ever increasing biodiversity loss; the primary cause of which stems from land-use change (Sih et al., 2011). Land-use changes have a wider impact on biotic and abiotic life than what becomes evident in the immediate landscape surroundings. The five main impacts on landscape are habitat loss/fragmentation and isolation, the spread of exotic species, harvesting, pollution, and climate change (Sih et al., 2011).
In Aotearoa New Zealand, land cover has changed significantly from 80% native forest to only 20% in the 800 years of human settlement (Ministry for the Environment, 2019), leading to a huge loss of habitat for native bird species. With a growing population the demand for land dedicated to new housing continues to transform the New Zealand landscape.
This investigation considers how green-field housing expansion is changing land-use and land-cover, by examining the relationship between bird life and suburban landscapes. It seeks to identify and demonstrate ways landscape architecture can positively intervene in biodiversity loss and its associated environmental degradation, at the local scale. It speculates on how biodiverse communities are achieved or maintained in areas of human inhabitation.
IS IT A QUESTION OF PRESERVATION?
Habitat loss is a major reason for the loss of native bird species in New Zealand. As an attempt to mitigate this, New Zealand’s environmental legislation focuses primarily on preserving remnant patches of native vegetation. Around 32% of New Zealand’s land area is currently zoned as a protected area1. These areas are managed to protect biodiversity and typically allow low level of human activity (eg. walking, biking) but no permanent occupation.
There are also several laws in place to protect native bush and prevent deforestation and between 80-90% of surviving native bush is under management of the Department of Conservation. The Resource Management Act is key to the governance of this protection along with the New Zealand Forest Accord (Ministry of the Environment, 1997). Additionally, individual trees may be identified as significant or heritage trees by individual councils that require consent to remove.
It is evident in New Zealand that conservation methods are deployed to protect rare and vulnerable elements of biodiversity as a priority (Anderson, 1998, as cited in Midler, 2007). This approach creates pockets of native vegetation that can provide habitat for bird species, but such a focus does not address or guide a holistic approach to habitat protection within New Zealand. Whilst protected areas are vital habitat for many human sensitive native species, such as Kiwi, in most cases preservation is not enough to prevent overall species decline. As such, despite preservation efforts an estimated “eighty percent of our bird species are now threatened with extinction” (Forest & Bird, 2018).
WHAT ABOUT COHABITATION?
As preservation areas alone do not allow native bird species to thrive, opportunities to create habitats for wildlife within human-dominated landscapes become necessary (Rosenweig, 2003a).
When considering human-dominated areas, low levels of biodiversity are seen in dense urban areas1 and rural areas2, but there is a peak in low residential/ suburban areas. This peak is often attributed the wide variety of plant species occurring within residential homes. Though the use of exotic plant species is generally high, these species are often flowering or fruiting species which can provide year-round food sources for wildlife. The low density and restrictions on site coverage make the areas more easily traversed, with many trees and bushes providing resting points. (Beninde et al, 2015; Donnelly & Marzuff, 2004).
Settlements currently make up less than 10% of New Zealand’s land-use, but growing populations are leading to a rapid expansion of urban areas (Falconer, 2015). This expansion is in part vertical, with many city councils supporting increased densification in their central areas; but horizontal sprawl remains prevalent, with continued pursuit of low density residential development on land at urban margins.
The legal protection of state-owned reserve land and native bush remnants means that most land converted to housing in New Zealand is privately owned farmland. Given that suburban density affords higher levels of biodiversity than farmland, this would indicate that within a New Zealand context, suburban expansion actually has the potential to improve national biodiversity. Current New Zealand suburban environments support only a limited number of native bird species and the prevailing suburban design would have to change to support a wider range of native birds.
Additionally, surrounding land-use is shown to have an impact on the biodiversity value of reserve lands (Beninde et al, 2015). This research suggests a new suburban landscape could not only provide an expansion of habitable areas for native avian species, but also increase the success of existing local reserve lands, through improving the suburban environment, thus decreasing the negative impacts of habitat fragmentation.
The practice of landscape architecture offers the capacity and responsibility to consider how human occupied areas can begin to accommodate non-human species and direct our urban landscapes towards becoming co-habitable spaces. This research will therefore aim to capitalise on the potential of suburbia as a habitat for native bird species through the method of a design-led research. Using the potential of cohabitation as a driver, it will explore an alternative approach to green-field housing development. Here ecological principles are placed at the forefront of design, using a ‘green-field’ case-study site in Plimmerton’s designated Northern Growth Area of Porirua.