C2. Habitat connectivity

 

Type: State indicator

 

Indicator Description

Until 2013, this indicator was based on an analysis of the change in habitat connectivity for selected broad habitats in the wider countryside.  The start point of the data series was 1990, but it has not been possible to update the indicator since 2007.  A new indicator based on population synchrony has been suggested, but needs more work before an experimental statistic could be published.

Summary

 

No update since previous publication

Connectivity is a measure of the size and distribution of patches of habitat and the relative ease with which typical species can move through the landscape between the patches. Habitat loss and fragmentation can reduce the size of populations and hinder the movement of individuals between increasingly isolated populations, threatening their long-term viability.

Progress to date

Following the adoption of theStrategic Plan for Biodiversity 2011–2020, the UK biodiversity indicators were reviewed, and a programme of work put in place to develop and refine the indicator set for future reporting to the CBD.  A small number of refinements were identified where there are issues with current indicators.  Indicators for reporting on habitat connectivity were identified as one of the areas requiring refinement.A measure of connectivity has been published previously within the biodiversity indicators set, based on an analysis of changes in land cover recorded in the Countryside Survey – a detailed periodic audit of a statistically representative sample of land across Great Britain.  Expert opinion was used to assess the relative likelihood of movement by species characteristic of each habitat between habitat patches across different intervening land cover types found in the survey.  The measure required further analysis to better explain the causes of the changes in connectivity and, as a result, the information available was insufficient for an assessment of change to be made, despite the statistically significant increase seen in connectivity in neutral grassland habitat observed.  It has not been possible to undertake the analysis required and, given the latest data available for the indicator is from 2007, it has been decided by the UK Biodiversity Indicator Steering Group that this indicator is now too out-of-date to be retained within the indicator set, and the previous data and analysis has been moved to the background section of this fiche.

During 2015, CEH, JNCC and Defra, based on a review of the specialist literature, investigated the possibility of using the level of synchrony in the fluctuations of annual population counts of butterflies as a proxy of connectivity.  The exploration used data for four species of butterfly associated with woodland, collected through the UK Butterfly Monitoring Scheme (UKBMS).  Population synchrony, measured as the level of correlation in time-series of annual abundance between site comparisons, is known to be influenced by distance, habitat similarity and geographic location.  After accounting for these factors, evidence has shown synchrony is positively related to landscape suitability (Powney et al. 2010, 2011) and landscape features that promote dispersal ability (Powney et al. 2012).  Furthermore, population synchrony is positively related with the frequency of actual movements of individuals (Oliver et al. 2017).  Based on this evidence, population synchrony has been shown to be an effective measure of functional connectivity, with higher levels of synchrony associated with higher functional connectivity.  The test has so far only been focussed on connectivity derived from data on four species of woodland butterflies.  The next stage is to expand the work, looking to broaden taxonomic coverage to include birds, and more habitats, unfortunately further development was not possible in 2016-17.

 

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Last updated: August 2017

Latest data: 2007