Como la escala afecta a las eia

Environmental Impact Assessment Review 22 (2002) 289 – 310 www.elsevier.com/locate/eiar

How scale affects environmental impact assessment
˜ Elsa Joao*
Department of Geography, University of Strathclyde, Graham Hills Building, 50 Richmond Street, Glasgow G1 1XN, Scotland, UK Received 1 June 2001; received in revised form 1 April 2002; accepted 1 April 2002

Abstract This paper evaluatesthe influence of geographical scale on the outcomes of Environmental Impact Assessments (EIAs). The paper presents results obtained by using spatial data with different scales for an EIA for a proposed road bypass in Southeast England (the Hastings Bypass). Scale effects were measured separately for spatial extent and spatial detail, and were measured both quantitatively using a GeographicalInformation System (GIS) and qualitatively using the judgement of EIA experts. The study found that changes in scale could affect the results of EIAs. For example, the impact significance and the number of houses affected by air pollution from the road varied according to the scale used. These observed scale-dependent changes suggest that scale choice can have important repercussions for the accuracyof an EIA study. This situation is made more serious when it is recognized that many environmental impact statements (EIS) fail to mention in explicit terms the scale used. The paper concludes with recommendations for future practice on how best to control the quality of EIAs in relation to scale choice. D 2002 Elsevier Science Inc. All rights reserved.
Keywords: Scale effects; Spatial extent;Amount of detail; Environmental impact assessment; Quality control

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Tel.: +44-141-548-3601; fax: +44-141-552-7857. ˜ E-mail address: elsa.joao@strath.ac.uk (E. Joao).

0195-9255/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 1 9 5 - 9 2 5 5 ( 0 2 ) 0 0 0 1 6 - 1

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E. Joao / Environmental Impact Assessment Review 22 (2002) 289–310 ˜

1.Introduction This paper investigates to what extent the choice of scale can affect the outcomes of Environmental Impact Assessments (EIAs). In other words, is it possible that EIA results are more an artefact of the scale of the data used rather than the situation in the real world being studied? If that was the case, and the scale effects were ignored, then there could be serious repercussions for EIAaccuracy and quality. To date, EIA practitioners and researchers have largely ignored this topic. This study puts scale under the spotlight to stimulate a debate about this important issue. In this paper the word ‘scale’ is considered to have two key interrelated meanings relevant to EIAs: scale as spatial extent of the assessment; and scale as amount of geographical detail or granularity. Thetwo are, however, related, as the spatial extent of the assessment will usually affect how detailed the assessment will be, i.e., an EIA of a larger area cannot afford the same amount of detail as a local assessment. This suggests the existence of a ‘ratio’ between extent and detail that constrains the data volume that is reasonable to analyse for a particular project (Goodchild and Quattrochi,1997). The notion of scale can be applied both to temporal and spatial aspects, and both are important to EIAs. The research presented in this paper, however, concentrates on the spatial scale only. Scale is a key research topic in many disciplines, such as hydrology, archaeology and ecology, and much has been written describing the problem of scale and the methods for studying scaling (e.g., Levin,1992; Quattrochi and Goodchild, 1997; Tate and Atkinson, 2001; Turner and Gardner, 1991; Wiens, 1989). But at the same time scale remains a complex and misunderstood issue. ‘Scale is one of the most fundamental yet poorly understood and confusing concepts underlying research involving geographic information’ (Montello and Golledge, 1999, p. 3). The importance of scale issues has even led some...