Introduction to Unit 6: Environmental Monitoring with GIS
Environmental managers are often not only working with spatial data (which concern a particular location on the Earth’s surface) but with spatio-temporal data, which relate to a particular location and a particular time. Time is sometimes referred to as the ‘fourth dimension’, with the first two dimensions being location (represented by both an x- and y-coordinate) and altitude (represented by a height or z-coordinate).
Spatio-temporal data are useful in environmental management for several reasons. Environmental managers often make spatial decisions, which affect a particular portion of a study area. For example, farmers may be paid an agri-environmental subsidy not to use pesticides or fertilisers in water-meadows, but they may be free to apply agro-chemicals elsewhere on their land. Tourism activities and new construction may be restricted within a conservation area, such as a Site of Special Scientific Interest, but outside of such areas, construction and tourism may grow unchecked. To evaluate such site-specific management decisions, environmental monitoring needs to take place. Typically, this entails collating data for a baseline period and for one or more periods subsequently. To be truly adaptive in our management, we need to be monitoring the effect that our decisions have on the environment.
Similarly, an integral part of environmental planning entails forecasting into the future. For example, we may have information about the current distribution of vegetation types across a given country, but will vegetation patterns alter if climate change takes place? What would happen if we decide to reintroduce a locally extinct species back into a given area by releasing breeding pairs at a particular site?
Furthermore, many environmental processes are inherently dynamic. Whilst underlying geology and landforms remain more or less unchanged from one year to the next, climate, land cover, and species distributions may change rapidly. This rapidly changing environment needs to be adequately reflected in our spatial databases.
This unit explores how spatio-temporal data can be managed within a GIS and comprises the following sections:
- Introduction to time in environmental GIS
- Formats for spatio-temporal environmental data
- Analysing Spatio-Temporal Data – Measuring change over time
- Analysing spatio-temporal data – Understanding animal movement
- Analysing spatio-temporal data – Spatially distributed dynamic models
- Spatio-temporal data – Patterns using GIS
The first section ‘introduction to time in environmental GIS’ explains some key concepts in spatio-temporal analysis, whilst the second section ‘formats for spatio-temporal environmental data’ describes the different ways in which this type of information can be stored within a GIS. The third section (‘measuring change over time’) briefly looks at monitoring and how GIS can be used to quantify changes in our environment. It should be borne in mind that environmental monitoring with GIS is a broad topic and this section provides an introductory look at a very wide field of research.
The fourth and fifth sections are concerned with how dynamic environmental processes can be handled in a GIS. The fourth section (‘understanding animal movement’) describes how data on wildlife tracks can be processed and described within a GIS. In the fifth section, we will look at ‘spatially distributed dynamic models’. These models are simplified representations of environmental processes that explicitly describe variation in the environment from one place to the next and from one time period to the next. Many GIS packages now have tools for creating such models and we will explore these through a practical activity, which involves modelling soil water deficits across Amazonia. In the final part of this unit, we look at statistical methods for analysing data over time, taking the particular example of environmental point patterns such as points where wildlife have been located or geomorphological features like dune crests.