Using a set of landscape metrics to assess the impact of urban development on ecosystem fragmentation
Ezer Fischler, Yohay Carmel
Urban development processes have both direct and indirect impacts upon the open space and upon ecology. Urban sprawl produces fragmentation of the landscape, which may degrade ecosystems. Over time, a number of measures have been developed to assess the degree of fragmentation. However, there has not yet been an attempt to identify and select a system of these measures for purposes of guiding metropolitan planning and evaluating the scope of damages from fragmentation produced by different development scenarios. The purpose of this research is to develop an applicative method for estimating the magnitude of fragmentation caused by urban development using a set of selected landscape metrics. The method is assessed empirically in the region of the Alonim Hills, following a plan to establish two new communities in the region, Issaschar and Haruv. The study was performed in the entire Alonim Hills region (92 square kilometers). Data were collected at a scale of 1:5000, using high-resolution aerial photography and GIS software. Land use was classified into built-up and open space. The research had two stages. In the first stage, the most sensitive indicators that reflected fragmentation resulting from the establishment of Issaschar and Haruv were identified. In the second stage, the impact of fragmentation on the land in the test area was assessed using the selected set of landscape metrics, and alternative development scenarios were evaluated. Eight alternatives were evaluated, varying the location and the shape of the two planned communities. This analysis revealed that expansion of existing communities results in much less fragmentation compared to constructing new communities. Fragmentation was found to be sensitive to changes in the structure of the existing community. Comparing among alternatives, it was found that the current plan for the two communities is the worst of all 8 scenarios inspected, meaning that it resulted in fragmentation that is at least twice as that of any other plan evaluated. The smallest degree of fragmentation resulted from moving the communities to other locations within the region and where their spatial shape was designed according to ecological considerations. An additional conclusion is that it is possible to derive a set of metrics that can be used to assess expected ecological impact of particular development plans in terms of the degree of fragmentation.