Whilst flawed, the Defra metric is currently the best habitat metric available in the UK and is under continued refinement and development. Alone, the metric doesn’t stand up as a pure measure of biodiversity uplift, however, as part of a basket of metrics as above it can be powerful helping to evaluate and improve habitats. It will help us measure and evaluate the priority habitats for the region.

Birds are fantastic indicator species because they are well- studied, generally have broad geographical ranges, and are sensitive to environmental change. They are included as a metric here because if restoration is successful, it will increase the availability of appropriate breeding grounds and this improvement in habitat quality will be reflected in a greater species richness and abundance in the avian population.

Taransay is an important site for ground nesting birds, including formanyredlistedmigratoryspecies,andtheoverallregeneration ofhabitatsonTaransayisanticipatedtoprovideadditionalhabitat for woodland and scrub nesting species.

As the primary producers and ecosystem architects of the terrestrial island ecosystem, plant diversity is the best proxy for the general health of the landscape. The plant community is an important source of food and its three-dimensional structure creates a complex habitat that provides shelter to most organisms living within the project area. A diverse plant community creates more niches which can support a greater diversity and abundance of other taxa. Additionally, the sensitivity of plants to variations in soil structure and composition means that shifts in their community structure can give an early indication of changes in the abiotic environment. Plant diversity is an important metric to include here because if habitat restoration is successful it will simulate increases in plant abundance and diversity.

Heathlands with a high level of management or grazing often host spider and beetle communities with low diversity, dominated by a few r-selected species affiliated with bare ground. Lower intensity management yields greater habitat heterogeneity and niche diversity which hosts more complex communities of both families. Heathland comprises the majority of the habitat on Taransay, however increased leaf-litter and habitat structure in planted woodlands and less intensive grazing of grassland habitats is also anticipated to enhance the diversity and abundane of beetle and spider species on Taransay. As invertebrates with low dispersal capabilities, increases in Araneid species will indicate an improvement in habitat resources and connectivity. While the same will be true for some Families of Coleoptera (i.e. Carabidae: Ground beetles), improved habitat may also favour greater colonization from healthy source populations of mobile species on Harris.

These arthropods are an important proxy for habitat availability and quality, niche variation and indication of ecosystem function.

Pollinator species richness and abundance is directly linked to floristic diversity, thus it is anticipated that the regeneration of Taransay’s beleaguered flora will support significantly greater populations of pollinators, potentially providing pollen resources that will facilitate permanent colonization/recolonization of some species that may currently be scarce vagrants on Taransay via dispersal from nearby Harris.

Again, these arthropods are an important proxy for habitat availabilityandquality,nichevariationandindicationofecosystem function.

Type: Abundance and Species Richness

Justification: Herpetofauna, as mesopredators, are integral to a balanced food web. Their diversity and abundance in HNV grasslands are key indicators of a healthy plant community and the provision of essential ecosystem functions like shelter.