Does the heathland flora in north-western Belgium show an extinction debt?

The large losses of heathland area since the end of the 18th century can be expected to have resulted in the decline or even extinction of many characteristic heathland species. Historical data on plant species distribution patterns can provide valuable information in this context. Therefore, the aims of this research are to study how the loss of heathland area has changed the presence of heathland and forest plant species in north-western Belgium using historical plant distribution data, and to test whether the heathland flora shows an extinction debt. Furthermore, plant traits determining extinction sensitivity are investigated.Our results revealed that, despite the dramatic reduction of heathland area (more than 99% of heathland was destroyed over a 230-year period), the loss of heathland species is relatively limited (11%) and is comparable with that of forest species (11%). Heathland species that have a long-term persistent seed bank or can propagate vegetatively are least sensitive to extinction. For forest species, on the other hand, growth form is the key determinant for extinction sensitivity. Long-lived woody species have a greater chance of persisting.The relatively low extinction numbers probably represent an extinction debt and the full effects of habitat loss may not have been fully manifested yet. Consequently, future extinctions are expected to occur unless environmental conditions are improved. Therefore, heathland restoration and prevention of further heathland area losses is required.