Recently, increasing environmental threats to the functioning of landscape and biodiversity have heightened the need for developing new approaches to nature conservation. Green and ecological networks have been developed as an attempt to maintain the functioning of landscapes, promote the sustainable use and conservation of nature, support the movement of species and increase people's use and enjoyment of the nature (Bennett and Wit, 2001; Bennett and Mulongoy, 2006; Lawton et al., 2010). These can be achieved by the identification and selection of the main features of ecological and green networks based on ecological and / or social functions we intend them to fulfil as well as the determination of objective conservation measures.
The main purpose of this research is to focus on critically examining different ways of defining green and ecological networks and their functionality for biodiversity and people in the case of Sheffield, which were derived from different theoretical and professional perspectives (planning and ecology), and to explore the potential for different approaches to define ecological / green networks. Due to its multidisciplinary nature, this thesis uses a mixed research methodology, based on different methods of data collection and analysis.
This research commences with the analysis of existing green and ecological network approaches, namely the Green Network (Sheffield City Council) and the Living Don (Sheffield and Rotherham Wildlife Trust). In order to analyse these approaches, policy document analysis, semi-structured interviews and ArcGIS spatial analyses were conducted to understand the rationale, aims and the spatial structure of current networks in the case of Sheffield.
For the identification of criteria to develop alternative routes of connectivity, ArcGIS and FRAGSTATS were used. After generating land cover and land use maps at a very fine scale (2m raster resolution) and with different levels of detail, the alternative connectivity routes, for both biodiversity and people, were identified on the basis of two connectivity measures. The first set of spatial analyses took into account structural connectivity of landscape components as the main criteria, to develop potential routes using ArcGIS and FRAGSTATS in combination. On the other hand, based on functional connectivity, the second set of alternative connectivity routes were developed using a least-cost corridor approach in ArcGIS. For the delineation of alternative connectivity routes for biodiversity, 10 species were selected from 3 different taxon groups (birds, mammals and reptiles); and for people, the alternative routes from residential buildings to (a) green and open spaces, (b) public buildings and (c) industrial / commercial units were used considering the effects of physical / legal accessibility and slope. Then, existing approaches and derived alternative routes of connectivity were compared and contrasted to each other in ArcGIS, to analyse the relationship between their structural properties and the urban morphologies in which they occur, with a view to predicting the implications for ecological connectivity and use by members of the public.
The Sheffield City Council and the Sheffield and Rotherham Wildlife Trust aim at maintaining and enhancing ecological connectivity for the benefit of wildlife as well as supporting public enjoyment and movement, and both of their network approaches benefit from the linear connectivity formed around the main rivers, streams and valleys. However, it was found that there are significant differences in the representation, spatial coverage and arrangement of the Green Network and the Living Don based on the methods and the site selection criteria used for developing green and ecological networks.
Regarding the structural connectivity routes for biodiversity and people, significant differences were found in the spatial extent and arrangement of alternative routes. On the other hand, functional connectivity routes for biodiversity showed both similarities and differences in their spatial extents and arrangements according to selected species' habitat requirements and movement behaviours across the landscape. Similarly, functional connectivity routes for people changed as I used different destinations and parameters. The overall results of this research provide further support for the conceptual premise that the definition of green and ecological networks is highly dependent on the methodology, ecological and / or social functions that are considered, and also criteria for the inclusion of different habitats or land uses within the network.
