Abstract 2012 EFLA Regional Congress - St. Petersburg

The urban development is continuing on reducing the amount of vegetation in the city, resulting in the fact that most cities are perceived as lacking green areas and presenting levels of pollution and bio climatic discomfort that are deteriorating the quality of life. Green structures have been recognized as an important contribution to improve these urban conditions, affecting surface temperature, hydrology, carbon storage and sequestration, and biodiversity. Despite the efforts of Local Governments to implement green structures in the cities, these conditions are mostly still inadequate.

In the city, parks and gardens are green areas of the city that – due to their identity – are part of the everyday life of the inhabitants. These spaces are classified and protected from urbanization by the City, as well as, and mainly, by the inhabitants. But the ecological matrix of the city is not limited to these spaces. On the other extreme of the scale of landscape values in the city, is the spontaneous vegetation covering slopes, vegetable gardens in empty plots or the vegetation in the inner-courtyards, which often have a negative image. These marginal spaces have their own dynamics, diversity, and many times they survive outside the municipal initiative.

Questioning the potential of the existing resources of the city as a structure capable to generate better environmental conditions, requires new dynamic tools to understand existing processes and relations at different scales. High resolution satellite imaging can provide accurate, economical and straightforward information to map, analyze and monitor the urban vegetation, since it offers a large and frequent temporal cover. The spatial dimension of urban ecology can be a useful planning tool, facilitating the comparison of existing urban areas helping to predict the ecological impact of new urban developments.

Through concepts such as structure, function, context, connectivity, dynamic, heterogeneity and hierarchy it's questioned what factors influence the marginal vegetation on the urban landscape at the different scales. 

marginal vegetation

The “Marginal Urban Vegetation” of the city of Lisbon, as a case-study, is identified, investigated and evaluated by means of satellite images. The evolution of this vegetation is monitored with images of the past 10 years, contextualized in the new urban plans for the city. Using landscape metric indexes, the structure of the vegetation is characterized, and its spatial patterning quantified. Through the analysis of data retrieved from Vegetation Indexes (such as the Normalized Differentiated Vegetation Index), information is gathered about how this vegetation works, in terms of productivity and water, in order to understand what can be its contribution for the ecological structure and its relation to the formal Urban Ecological Structure of the city. 

The urban vegetation induces several environmental, social  and aesthetic benefits to the city, and an incorrect urban planning, as well as an insufficient ecological structure can rise the environmental costs. It is fundamental to have the availability and knowledge of the environmental parameters of the existing vegetation; including the vegetation outside the planning instruments, but never the less affecting the ecological quality of the city. 

Sara Machado Doesburg
Department of Geosciences, Environment and Lanscape Planning
Faculty of Sciences, University of Porto