The analysis of spatio-temporal forest changes (1775–2000) in Flanders (northern Belgium) indicates habitat-specific levels of fragmentation and area loss

Spatio-temporal forest changes can
have a progressive negative impact on the habitat of
species that need forest continuity, i.e. the continuous
presence of forest. Long-term species data that
demonstrate such an impact are often not available.
Instead we applied a spatial analysis on maps of the
historical and present-day forests, by calculating
landscape indices that explain forest plant species
diversity.
We digitized for this purpose, forests in
Flanders (northern Belgium, 13,500 km2) at four
time slices (1775, 1850, 1904–1931, 2000) and created
a map of forest continuity in 2000. The ecological
relevance of the analysis was further enhanced by a
site classification, using a map of potential forest
habitat types based on soil–vegetation relationships.
Our results indicated that, between 1775 and
2000, forests occupied 9.7–12.2%of the total study area.
If continuity was not taken into consideration, forest
fragmentation slightly increased since 1775. However,
only 16 % of the forest area in 2000 remained
continuously present at least since 1775 and is therefore
called ancient forest (AF). Moreover, connectivity of
forest that originated after 1775, called recent forest, was
low and only 14%was in physical contact with AF. The
results were habitat-specific as forest on sites that are
potentially suitable for a high number of slow-colonizing
species, e.g. ancient forest plants, were affected most.
We discuss that a GIS analysis of this
kind is essential to provide statistics for forest
biodiversity conservation and restoration, in landscapes
with a dynamic and heterogeneous forest cover.