Woodland biodiversity decline and fragmentation
Habitat fragmentation at a variety of scales has been widely linked with the decline of many species globally. Over recent decades there has been a recorded decline in the biodiversity of many semi-natural woodlands and open habitats despite protection through designation (SSSI and NNR). The long-term viability of woodland biodiversity, which evolved within a highly connected and extensive habitat, is threatened by fragmentation, as it leads to smaller and more isolated woodlands. Many ecologists advocate the maintenance and improvement of connectivity between fragmented woodland populations, with growing interest in the use of habitat networks to reverse the effects of fragmentation by expanding and linking isolated habitats.
Since the post glacial colonisation, Britain's woodland, which is thought to have once covered over 75% of the land area, has been fragmented to such a degree that less than 5% remained by the beginning of the 19th Century. Afforestation throughout the 20th Century has increased woodland cover to 16.8 % in Scotland, 15% in Wales and 8% in England. However, the ancient semi-natural remnant woodlands remain largely fragmented: new plantations provide unfavourable habitat, and are spatially unconstrained; while the surrounding matrix is often intensively managed, remaining unsuitable for woodland species dispersal.
International development of habitat networks
The concept of species conservation through habitat networks has developed rapidly since the signing of the Convention on Biological Diversity. This has prompted a new international acceptance and emerging agreement of the need to conserve biological diversity using an approach which includes the planning, establishment and adaptive management of protected-area networks.
At the international scale, following an agreement between 55 European countries in 1995, the Pan-European Ecological Network began a program to develop habitat networks based on data at a resolution of 1 km from the CORINE biotope database and the general soil type distribution in Europe. At the regional scale, habitat networks for wide-ranging species have been assessed in the design and planning of nature reserves and conservation.
Forest habitat networks (FHNs) in Britain
In Britain, the concept of woodland expansion via FHNs has gained considerable support throughout the last decade largely from the efforts of George Peterken and policy outlined in the forestry strategy documents.
JIGSAW challenge funding has provided the financial incentive to link fragmented native woodlands.
Forestry Commission Wales and the Countryside Council for Wales commissioned two projects to develop understanding of FHNs in Wales.
The adoption of FHNs was recommended by Scottish Natural Heritage (SNH), to reverse fragmentation and rebuild significant areas of native woodland, primarily to conserve and enhance woodland biodiversity.
It is assumed that the development of FHNs will help reverse woodland fragmentation, and in particular reverse the fragmentation of ancient woodland habitat. Indeed it has been argued that this will maintain genetic contact both within and between meta-populations and, in turn, provide greater species resilience in times of external stress, such as climate change.