Embracing 200 square miles of central England, The National Forest is transforming the landscape of parts of Derbyshire, Leicestershire and Staffordshire. Spearheading the initiative is the National Forest Company (NFC), sponsored by defra.
A signiﬁcant problem for biodiversity is the fragmentation of important habitats. Our woodlands once covered large areas of the country, but, are now reduced to islands in a sea of farmland and other open habitats. Species marooned in these islands are unable to expand or alter their natural ranges. At its inception in 1995, 11% of the area of The National Forest consisted of woodland and other wildlife habitats. By 2010, the planting of over 7.8 million trees had seen this ﬁgure rise to 23% and led to the creation of over 60 square kilometres of new habitats. While this has led to the creation of signiﬁcant areas of new habitats, they are often fragmented.
The NFC’s goal is to see a robust network of interconnected woodlands and other habitats covering 33% of the Forest area. To achieve this, it recognised the need to analyse habitat connectivity on a landscape-scale across the whole Forest. This would help identify existing habitat networks and areas of high fragmentation, and inform strategic decisions to target efforts to create a robust landscape of interconnected habitats, that are best placed to meet the challenges of the future.
NFC developed a geographical information system (GIS) for mapping ecological connectivity. The system is based on the principle that habitats are more or less permeable to the colonisation of different species. To use the example of woodland, which is the main habitat being created in The National Forest, a broadleaf woodland species is more likely to be able to spread across an area of scrub than an area of intensively managed pasture or, to put it another way, scrub is more permeable to woodland species than pasture.
Using Natural England research published in its Metadata for England Habitat Network (R Catchpole 2007), each Forest habitat was given a value based on its permeability to species from four key habitat types: woodland, grasslands, heathland and mire/fen/bogs. Every habitat in the 200 square miles of The National Forest had to be digitised onto MapInfo® using data held by partner organisations, analysis of aerial photos and the NFC’s maps of habitats created through its own work.
The resulting habitat maps can then be run through the NFC’s GIS application, which analyses the relationships between habitats to identify blocks of interconnected habitats and output maps showing ecological networks. These maps can be colour-coded using a simple ‘trafﬁc light’ scheme where large networks of interconnected habitats are mapped as green, while small isolated blocks of habitats are shown in red.
At the start of this process the NFC only licensed raster-based products from Ordnance Survey. This meant that each habitat block had to be hand drawn to match raster boundaries, which was very time consuming and open to human error. Accuracy is particularly signiﬁcant for the analysis of habitat networks. Features such as roads are some of the biggest barriers to the movement of species across a landscape, and errors in mapping their width can dramatically affect the mapping of interconnected habitats. An A-road digitised from the 1:25 000 Scale OS Explorer Map can be 12 m wide, while in reality it is just 7 m across. To the mapping software, this can create a false barrier to the movement of species and create a break in a habitat network.
NFC joined the Pan Government Agreement, the precursor to the new Public Sector Mapping Agreement which started on 1 April 2011. They now have access to an even wider range of digital products including OS MasterMap®.
NFC is now updating its habitat maps using OS MasterMap polygons as the foundation for habitat blocks. This increases the speed with which data can be digitised and also improves the accuracy of the mapping produced.
NFC can now assume that mapped habitat blocks accurately represent conditions ‘on the ground’, and that the analysis of connectivity is not being skewed by mapping errors. OS MasterMap has also provided a wealth of detail that was not previously available. Individual houses and gardens can now be mapped, where previously it was not possible to map anything more than the settlement blocks shown on the 1:25 000 Scale OS Explorer Map. This additional detail allows NFC’s software to more accurately calculate the potential for species movement.