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Mapping to inform conservation: a case study of changes in semi-natural habitats and their connectivity over 70 years

During the second half of the 20th century, the Western European landscape became more intensively used, affecting especially semi-natural habitats which are the principal hotspots for biodiversity. In particular, rural areas were altered dramatically in the pursuit of increased production ("intensification''): many previously low productivity areas were converted to arable land. Further severe losses of habitat were caused by urbanisation and building as well as afforestation for timber production. In addition to severe declines in the area of such habitats, these processes decreased the connectivity of remaining fragments, which became more isolated. Decreased connectivity reduces dispersal among plant and animal populations, leading to an elevated extinction risk at population and regional scales.

Successful future restoration of semi-natural habitat not only requires selection of sites which are amenable for restoration to the target habitat, but should ideally also aim to enhance habitat connectivity. Despite increasing interest in the restoration of such ecological networks, the process is not straightforward. The necessary first step is to map the long-term changes in habitat cover in a region, on an as fine scale as possible. Such maps will give baseline information on earlier habitat configurations and will allow planning of ecological networks and stepping stones based on ease of restoration through increasing connectivity of a variety of habitat types.

This first step was tested in Dorset, a county in the UK of over 2500 km2. We combined soil data with historical maps from the 1930s representing a time before the onset of intensive agriculture, developing habitat classifications comparable to contemporary land-use classifications. We digitised historical land use maps from the 1930s on a 25 x 25 meter resolution and compared this to the UK Land Cover Map of 2000.

For our example area, land use shifted dramatically to more intensive agriculture (Figure 1.): 97% of all semi-natural grasslands were converted into agriculturally-improved grassland or arable land as were large proportions of the heathlands and rough grasslands (-57%). The other important driver of change was afforestation (+25%). The larger habitat areas became fragmented, with average fragment size of different habitats falling by 31-94%. Furthermore, the connectivity between fragments dropped drastically, by up to 98%. Here connectivity is seen as the ability of seeds from one habitat patch to disperse and end up at another habitat patch of the same type (Figure 2).

Our case study demonstrates the power of such mapping methods. Based on this method we propose a quantitative framework for conservation planning on as fine as appropriate scales with a high resolution. Such method will help in identifying habitats for preservation and sets target levels of connectivity:

  1. translate high resolution maps of a more ideal historical situation and of the current situation into comparable GIS-layers;
  2. calculate the magnitude of loss of area and connectivity between the two time periods;
  3. identify the locations of semi-natural habitat to be preserved, for example based on the Natura 2000;
  4. decide the target connectivity level to be reached relative to the more ideal situation provided by the historical maps, and potentially based on knowledge of the requirements of key species;
  5. iteratively use probability or land use mapping to assign new areas, recalculating connectivity after every iteration. Hence, connectivity can be optimised based on available financial options and land availability.

Figure 1: Habitat maps of Dorset indicating 15 Broad Habitats (BHT) for: (a) 1930s, based on Dudley Stamp maps combined with the UK National Soil map; and (b) in 2000 from the Land Cover Map (LCM2000). The total area is 251,422 ha. Reproduced with minor changes from Hooftman & Bullock (2012).

Figure 2: Connectivity among habitat cells of semi-natural habitat types in the 1930s and 2000. Shown is Oi(r), the probability that seeds that disperse over distance r from a habitat patch end up at another patch of the same Broad Habitat (BHT) class. Reproduced (partly) from Hooftman & Bullock (2012).</p>


Hooftman, D. A. P., & Bullock, J. M. (2012). Mapping to inform conservation: A case study of changes in semi-natural habitats and their connectivity over 70-years. Biological Conservation, 145, 30-38.

European Commission DG Environment News Alert Service (2012). Habitat mapping method could help restore biodiversity. Science for Environment Policy, 290.

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