Ecological Networks in Urban Landscapes

This research focuses on the topic of ecological networks in urban landscapes. Analysis and planning of ecological networks is a relatively new phenomenon and is a response to fragmentation and deterioration of quality of natural systems. In agricultural areas and with existing nature preserves this work has been advancing. In urban areas, however, the problems of land use intransigence, political and jurisdictional issues create a difficult environment for implementing ecological networks. Differences also exist between Europe and North America. In North America, and in particular the western United States, planning authority rests with individual municipalities, making planning at landscape or regional scale difficult.The specific questions addressed in this research program revolve around the viability of planning an ecological network in an urban landscape. Can such a concept withstand the tests it will be given in a political and economic context of an urban planning process? To address this question, two principal research objectives were established. First, the development and articulation of a planning method will demonstrate that ecological concepts. and in particular the concept of ecological networks, can be integrated into the urban planning process. Second, the establishment of an ecological network will improve the viability of ecological systems in an urban context. This research provides a theoretical framework and a model to test this proposition. A planning method is articulated and a series of assays of landscape structure are used to examine the viability of an ecological network in the Phoenix, Arizona urban area. It is intended that the establishment of a planning method and a structure for assay will make this concept applicable in various urban situations.The planning method is most appropriately characterised as a hierarchical systems approach. Analysis and planning occur at three scales:<ol><li>landscape (regional);</li><li>community (municipal); and</li><li>site (local).</li></ol>At landscape scale, the Phoenix. Arizona urban area (7,300 sq. km.) is studied. At the community level, the city of Scottsdale Arizona (480 sq. km.) is examined. And, at site scale, a number of patches and corridors ranging from 15 to 75,000 hectares are studied. The systems studied include hydrological, habitat and cultural. These are examined independently to ensure integrity from each specific perspective and then integrated to establish a multiple use perspective in the ecological network.The planning method includes 10 steps. First is the definition of the study area by integrating political and natural boundaries. Second is examination of the regional context. Third is documentation of landscape change within the study area by examining historical aerial photographs and other records. Fourth is assessment of natural and cultural resources at landscape scale and determination of existing and potential value as ecological network components. Fifth is formulation of independent landscape scale system plans for hydrology, habitat and cultural opportunities. Sixth is formulation of a multiple use ecological network plan at landscape scale, establishing priorities for ranking of integrated uses and identification of sites for restoration, preservation or management. Seventh is development of community level system plans for hydrology, habitat and cultural opportunities. These are prepared at the scale of individual municipalities. Eighth is development of a multiple use network plan at community scale that ties back to the landscape scale plan. Ninth is development of local or site plans for network elements to facilitate preservation, restoration or management. And tenth is continual monitoring and feedback.Based on the previously described method, an optimal plan was developed for the Phoenix urban area, the municipality of Scottsdale and six prototypical network sites. An assessment of the optimal plan was undertaken using landscape structure indicators. Three principal analyses were utilized:<ol><li>patch content analysis;</li><li>corridor content analysis; and</li><li>network structure analysis.</li></ol>Patch and corridor content analyses examined the internal characteristic and immediate context for each of the 89 ecological network elements. The network structure analysis incorporates a process for aggregating results of patch and corridor analyses and incorporates indicators that describe interrelationships between landscape elements. For each of these analyses the existing condition was compared to the optimal plan to demonstrate the level of change that can be expected. The most notable results of this assessment indicate the following.The patch content analysis reveals<ol><li>an increase in mean native vegetation coverage of 10%,</li><li>an increase in matrix utility value of 14%, and</li><li>an increase in naturalness of 15%.</li></ol>The corridor content analysis reveals<ol><li>an increase in mean corridor filter width of 19%,</li><li>an increase in mean vegetation coverage of 9%,</li><li>an increase in matrix utility values of 15%,</li><li>elimination of 59 gaps or barriers in existing corridors, and</li><li>an increase in naturalness of 17%.</li></ol>The network structure analysis reveals<ol><li>an increase in overall matrix utility index of 3%,</li><li>the degree of network circuitry increased by 20% and</li><li>the gamma index of connectivity increased by 12%.</li></ol>The conclusions of this research are that an ecological network plan provides modest but important improvement in ecological systems in the Phoenix urban area. It is apparent that implementation of an ecological network in an urban area utilising existing open space elements is feasible and the investment required is modest. Although this method, as outlined in this study, is geared to a specific planning context, it may have applications in other similarly expanding communities in North America or elsewhere. The principal benefit of this approach is that it can be developed incrementally and without initial commitment of extensive resources. Finally, the use of landscape structure indicators provides another useful tool for assessing viability of ecological networks. As these indicators are used more extensively thresholds can be recognized that will help understand the health of these systems