NatureLinks

Rapid urbanisation in the Perth and Peel region of Western Australia is fragmenting the natural landscape causing significant habitat loss, endangering the area’s unique biodiversity. Urbanisation is increasingly reducing the size of remaining natural areas.

Urbanisation footprint mapping by Daniel Jan Martin, 2022

The smaller the natural area, the less diversity it can support, especially in the long-term.

Isolated protected natural areas (reserves) act like islands, each island is separate from each other and the biodiversity supported is only as much as the individual island can support.

To sustain biodiversity, native fauna need to be able to move between remaining sources of food and shelter to maintain healthy populations.

Urban infrastructure can be hostile, exposing species to hazards such as dehydration, traffic and predation. However urban design can enhance support of biodiversity through urban greening and especially, by creating linkages between habitats: NatureLinks.

Links between protected natural areas increase the total area available to support biodiversity. Each natural area connected by a NatureLink cumulatively adds to the total area. If all natural areas were supported by a network of NatureLinks then a high level of biodiversity could be supported.

The distance wildlife or plant seeds can travel through an urban matrix differs between species. So, connectivity is different for each species. The maximum distance an organism is likely to move across a landscape to reach its destination is known as its Ecological Distance Threshold (EDT). EDTs are different for all species.

For many species a distance of 50m or less between habitat can be enough for them to become isolated  [6] .

The map to the right shows the connectivity of protected natural areas for species that can travel up to 50m. Dark shading means well connected, shading through red, to light cream in areas of poor connectivity.  

Some species can travel up to 500m for food and shelter  [6] .

Fewer still can travel 1500m or more  [6] . This means, in a fragmented landscape, connectivity varies depending on a species Ecological Distance Threshold.

Connectivity is good where there is plenty of remnant native vegetation outside protected reserves; for example, around the fringes of Perth where remnant vegetation occurs in State Forest, or has not yet been cleared for urban development. In these areas, the priority for NatureLinks is to ensure clearing does not reduce connectivity.

In contrast, in the centre of Perth, natural areas are very isolated due to high urban density. To improve connectivity here we need to prioritise conserving and restoring remaining natural areas and retrofit the landscape with urban greening through NatureLink best practice (see below).

NatureLinks are nature-friendly pathways joining two (or more) protected natural areas, that provide the least risk to species moving across the urban landscape.

They were identified using data from the entire Perth and Peel regions.  A spatial analysis  of the connectivity of our urban bushland was assessed and NatureLinks were created using least cost path modelling in a geographical information system (GIS).

NatureLinks have been scientifically mapped to provide a route through the most nature-friendly or least hostile urban landscapes. This path may not be the shortest, but it will be the one that offers the best chance of a successful migration from one natural area to another.

The NatureLinks were mapped by first allocating a level of risk (or cost) to wildlife survival to different land use types. Lowest cost (most nature-friendly) land uses are undisturbed natural areas, with increasing cost from lawned parks or agricultural areas, to paved areas or buildings and finally freeways that provide hostile barriers to wildlife movement.

The degree of risk is shown in the map to the right from lowest risk (low cost - darkest shading) to highest risk (high cost - lightest shading). This is known as the cost layer in GIS.

Once the cost layer was created, the source and destination points for wildlife movement were identified. These are the natural areas protected in reserves that are home to our native flora and fauna.

Protected natural areas included:

• National Parks
• Nature Reserves
• Conservation Parks
• RAMSAR sites
• IUCN Category 1-4 lands
• CALM Act lands
• Conservation Category Wetlands
• Botanic Gardens and Parks Authority lands

As well as:

• Bush Forever Sites
• Regional Reserves
• Class A Nature Reserves (Cat 1 & 2)

Computer modelling then fitted ‘least cost paths’ across this landscape each joining a protected natural area to another: NatureLinks.

Each NatureLink provides the best path from one protected natural area to another.

Feel free to explore the map by double clicking using the zoom icons (+ and -) in the bottom of the map.

You can also click and drag the mouse to pan around the map.

Press the home icon to return to the starting position.

These suggested NatureLinks provide a scientific basis and focus for improving the biodiversity connectivity and greening in your area. Rather than starting out with a blank slate, you can view these NatureLinks, see what land uses - road verges, residential gardens, green spaces, public open spaces, drains – they intersect and consider how you might improve locations along these pathways.

Everyone can be involved in improving NatureLinks from individuals  (e.g. visiting    ReWild Perth   to create a biodiverse garden in your backyard) to organisations (e.g. creating an underpass where there are major roads). NatureLink Perth will be working towards providing guidance and resources to help everyone with best practice for different land uses intersecting or adjacent to NatureLinks.

Like wildlife or ecological corridors, NatureLinks facilitate movement of native species but there is a critical difference between them.

Traditionally, wildlife or ecological corridors are thought of as an area of habitat connecting natural areas. Such areas might be a particular width (e.g. 50 or 100m wide) of native vegetation and exclude other uses within the corridor.

In urban areas, the high level of competition for different land use and the need for our cities to be increasingly high density makes such a concept fraught with conflict and is unlikely to succeed.

In contrast, NatureLinks do not ascribe a land use to the path, instead they promote multi-functional, nature-friendly best practice along their length. So NatureLinks are wildlife or ecological linkages but not wildlife or ecological corridors.

This is an important distinction from wildlife or ecological corridors, as multiple land uses are compatible with NatureLinks.