1.4 Information-based Environmental decision-making – the role of GIS

With many problems affecting GIS in environmental decision-making (the limitations of data quality, the complexity of many management problems, etc. etc.), it is tempting to think that GIS has only a limited role to play. However, it is worth emphasising the positive impact that GIS can have to an environmental management problem as well as some of its weaknesses. This object therefore describes the specific contribution that GIS can make to environmental decision-making.

Some of the key strengths of GIS in information-based environmental management can be summarised as follows:

More objective indicators

Indicators are one tool for managing environmental resources. Pressure indicators describe factors that are likely to adversely affect a resource, such as the number of boreholes used to extract water from an aquifer. State indicators indicate the status of the resource, such as the depth to water table or the discharge from major rivers within a study area. Response indicators document attempts to improve the condition of a resource or counteract pressures on it. For example, a response indicator might be the number of licences granted to extract water from a given aquifer.

Very often, indicators need to be compared across different periods. For example, in introducing a new agri-environment scheme, we might collect data at the start of the scheme that indicate the total length of hedgerows within a given study area. To evaluate how well the agri-environment scheme has worked, we might collect the same data on hedgerows after the scheme has been running for a number of years. For this approach to be effective, it is important that the baseline inventory of hedgerows uses the same methodology as the subsequent follow-up inventory of hedgerows. GIS can be used to ensure this consistency of methodology – for example, by adopting the same approach to digitising hedgerows from aerial photographs in both cases. Some authors also distinguish between global and local environmental indicators. Global indicators are used for comparisons between different sites, whereas local indicators are specific to a given case study area.

Bringing data together

Many environmental management issues involve not only monitoring the status of the environment, but also the anthropogenic (man-made) pressures upon it. For example, understanding changing nitrate concentrations in rivers and streams involves not only monitoring the water quality in these bodies, but investigating the sources of these nitrates – generally fertiliser applied to arable fields. Through its overlay facility, GIS can link together map layers depicting human pressures (the locations where fertiliser has been applied) with their environmental consequences (water bodies with high nitrate concentrations).

GIS can also be used to bring several different map layers together into a single environmental index. For example, we might require a composite index of habitat suitability for water vole, which brings together riverbank vegetation, the type of riverbed (gravel or sand) and the gradient of the riverbed. To produce a composite index that combines these 3 elements of a suitable habitat, we can multiply each map layer by a weight indicating its relative importance. The 3 weighted map layers can then be added together within a GIS using map overlay. The resultant map layer is a single, composite map of habitat suitability for water vole.

Involving the public in decision-making – P-GIS

Another important role for GIS in environmental management is as a means of involving the public in decision-making. On the one hand, the highly technical nature of GIS makes it difficult to involve the public in GIS processing and data collection. However, its highly graphical nature means that maps, particularly those delivered over the Internet, can be an excellent way of engaging the public in decision-making.

Participatory GIS (P-GIS for short) aims to involve the public in the GIS planning process. The public may be consulted over the input data, asked about the kinds of question that they would like answered, and informed about the analyses undertaken using the GIS. Instead of decisions being taken by a skilled, technical GIS officer, they are taken by the broader community. For example, in a Nepalese forestry project (see list of NCGIA references below), the community might be asked to verify patterns of land ownership and GIS-based maps used as a way of ‘talking through’ land rights disputes within the local community.

---

---