GIS and Remote Sensing for habitat mapping

In February the Welsh Section of the CIEEM convened a conference in Aberystwyth to consider the role of remotely sensed imagery in habitat mapping.

The need for detailed, up-to- date information on the land cover and habitats that comprise our environment is greater than ever. The UK has signed up to ambitious targets to halt decline in the natural diversity of our environment by 2020, but before we can protect or consider ‘future land use choices’ we need to know where different habitats are, their extent, and their status.

There is a long tradition of using remotely sensed data in the form of aerial photography to help field ecologists map habitats in our environment. In the past, maps derived from aerial photos were manually interpreted, with follow-up field visits used to check the species composition and to validate/modify the maps. The resultant maps were hand digitised for use in a GIS system. Recent advances in remote sensing, including the use of satellite imagery and colour infra-red photography, have revolutionised the usefulness of this technology for habitat mapping and modelling.

Seeing red

Satellite images contain spectral information outside of the visible spectrum into the near and short-wave infrared regions. Near infrared (NIR) light reflectance is strongly related to the internal structure of vegetation. This allows identification of different types of species, for example oak trees have a high NIR reflectance whilst for gorse needles NIR reflectance is low. Spectral reflectance values in the short-wave infrared region provide information regarding wetness and dryness.

A further advance in remote sensing is the use of ‘object-based analysis’ that enables ‘automatic digitisation’ of the imagery where the computer segments the image on the basis of similar colour and texture.

As objects have a geographic location for features such as slope and altitude, such information can be used in the modelling of the data. It is therefore possible to separate many different habitats; the “Making Earth Observation Work for UK biodiversity” project from the Joint Nature Conservation Committee2 describes those habitats that can be identified either solely or partially from Earth Observation (EO).

Down to earth

Field survey is important for checking habitats that can only be partially identified by EO; e.g., to establish whether a grassland is species-rich semi-improved, or simply a neglected improved grassland full of thistles. Field survey is also vital wherever detailed information is needed on species composition and abundance. EO comes into its own when information is needed for areas that are difficult or dangerous to survey on the ground, such as peat bogs, mudflats and mangroves. It also has the capability to acquire seamless habitat cover information for extremely large areas at a relatively low cost, and to track habitat changes over time.

As our ability to map and monitor changes in habitats improves, along with our ability to handle larger, more complex spatial datasets, we are able to harness the power of GIS in an ever-widening range of applications such as geostatistical modelling that can analyse the condition and suitability of habitats for target species, and how these may change under different scenarios, such as climate change.

Ecologists toolbox

Some current and wide-ranging ecological applications of GIS and remote sensing were presented at the conference. Topics addressed included the production of an updated Phase 1 habitat map of Wales; ecological applications of crowd-sourcing technology; modelling ecosystem services of the environment, and combining species and environmental data to form predictive models of reptile and amphibian distribution. It is clear that the ecologist’s toolbox is continuing to expand, providing ever more options for environmental and ecological assessment.

¹www.cieem.net/geographic-sections/8/02.-wales

²https://www.gov.uk/government/organisations/department-for-environment-food-rural-affairs

Abstracts and presentations from the CIEEM Welsh Section Conference 2014 can be found on the CIEEM website at www.cieem.net/2014-welsh-section-conference

Dr Katie Medcalf CEnv., MCIEEM, is Environment Director for Environment Systems based in Aberystwyth (www.envsys.co.uk)

Pictured above:

1. Dr Emyr Roberts, Chief Executive of Natural Resources Wales, addresses the CIEEM Welsh Section Conference

2. CIEEM Welsh Section Conference, 21 February 2014, Aberystwyth University

3. Katie Medcalf CEnv MCIEEM addresses the CIEEM Welsh Section Conference