A pressure–state–response approach to cumulative impact assessment

Cumulative impact assessment (CIA) is particularly challenging when several projects from different proponents are presented simultaneously for a region. The impacts of such projects are typically assessed individually, but approaches and methods commonly applied to single-project impact assessment may not be adequate to such problems. The pressure–state–response (PSR) model was adapted to tackle cumulative impacts of ten projects concentrated in an iron ore mining region in Southeastern Brazil. Using information from individual assessments, a set of indicators was built to depict current and future pressures on valued environmental and social components, to describe the current and to derive trends for the future state of the environment, and to review mitigation responses. It was found that the future state will likely be critical for both air and water quality, possibly stable for natural vegetation, due to the likely combined result of rehabilitation and offsets, and for both cultural heritage and public roads, due to likely effect of mitigation. Relying on individual assessments proved to be unsatisfactory, because key information on both the characteristics of the projects and baseline are largely inconsistent across studies and presented in very different formats. An indicator-based PSR approach to CIA is information-intense and is recommended only when databases are reliable and built on the basis of standard protocols. The need to better understand cumulative impacts and to provide corresponding, landscape or watershed scale, mitigation and management responses could be a driver for a more widespread and consistent use of standardized indicators in individual impact assessments.