Fragmentation and internal disturbance of native vegetation reserves in the Perth metropolitan area, Western Australia

Remnant vegetation in metropolitan areas tends to be highly fragmented and affected by disturbances from the urban environment. A rapid survey in 71 nature reserves in the metropolitan of Perth noted surrounding land uses, types of disturbances, rated the level of weeds, rubbish, formal and informal walking paths and fire influence, and estimated vegetation condition. These data were analysed against information on reserve area and shape, connectivity to other native vegetation, period of patch encapsulation, distance from the city centre and local population density to reveal patterns of fragmentation and disturbance in the metropolitan area. Smaller reserves occurred in the highly populated inner metropolitan area, and these reserves displayed high levels of fragmentation, higher levels of weed infestation and path density and low vegetation condition. Reserves were larger, with high levels of connectivity and with less weed cover and higher vegetation condition in the outer metropolitan area. The research highlighted that whilst reserve attributes are largely set in inner urban areas, planning is required in outer metropolitan areas to ensure patches remain well connected and of optimal size and shape. Inner metropolitan reserves should also be preserved and managed, as they are highly valuable for representing the vegetation types that once occurred there, and for providing natural areas for inner city residents.