The main aim of the HABMAP modelling work was
to use physical datasets to predict the occurrence of benthic
habitats throughout the southern Irish Sea.
The HABMAP model is geographical information system (GIS) based
and uses the strength of the association between ecology (biotopes)
and the physical environment (water depth, salinity, sediment type,
bedforms, bed shear stress, temperature and light attenuation) to
predict habitat occurrence. The model uses observed (i.e. from
survey data) environmental tolerance ranges (e.g. depth 10-20m,
sediment type = sand or gravel) to build physical profiles for each
biotope. These profiles are then used to identify other areas of
seabed where we would also expect the biotopes to occur. Maps
can then be created for each biotope showing areas where it is
known to occur and where it is predicted to occur.
For each subtidal biotope recorded in the HABMAP area we
produced maps showing the actual and predicted distributions. We
also assessed the confidence of our predictions (full details of
this process are given in the HABMAP report). Our final GIS dataset
lists the recorded and predicted biotopes found in each area of the
southern Irish Sea in order of confidence. Maps of individual
biotope distributions as well as final combined map layers are
available from the downloads section.
Once combined into a final map, the individual biotope
predictions often overlap. This example shows a polygon where three
different biotopes have been predicted in the same area, and ranked
by probability of occurrence.
The figure on the left is a biotope map for the seabed off
the north west of Anglesey and shows the data underlying the map
for the polygon with dark blue hatch shading (BIOTOPE1= the biotope
code for the most likely biotope, PRESENCE1=whether the biotope has
been recorded in that polygon (present) or has been predicted to
occur (predicted), RESULT1= confidence score, BIOTOPE2= the biotope
code for the second most likely biotope etc).
A map was generated for each biotope in the HABMAP modelling
process, accompanied by an indication of the corresponding
‘presence and spatial confidence’ for each predicted polygon. The
figure on the left shows the recorded and predicted distribution of
a mixed sediment biotope (SS.SMx.OMx.PoVen) throughout the HABMAP