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C2 Habitat Connectivity

Experimental statistic: The UK biodiversity indicators project team would welcome feedback on the novel methods used in the development of this indicator.

Type: State indicator

Indicator Description

Connectivity is a measure of the relative ease with which typical species can move through the landscape between patches of habitat. 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.

This indicator illustrates changes in functional connectivity – the ability of species to move between resource patches – of 33 butterfly and 29 woodland bird species in the UK. The indicator is based on a measure of population synchrony, which is the level of correlation in time-series of population growth rates from different monitoring sites. Quantifying functional connectivity will allow more targeted landscape conservation management to help reduce the risk of species extinction.

Contents

  1. Summary
  2. Downloads

Summary

No new data point but this indicator has been updated to include woodland birds.

For UK butterflies, the average functional connectivity between 1985 and 1995 was relatively stable, the unsmoothed index fell to a low of 48% in 2004, and then rose. The level of functional connectivity in 2012 (110%) is 10% greater than in the start year of 1985, with 72% of species increasing in connectivity in the late short term (2000 to 2012), see Figure C2i. The long-term trend from 1985 to 2012 masks mixed, individual species trends, with 33% of species increasing in functional connectivity, 19% decreasing, and 48% showing no significant change.

For UK woodland birds, the average functional connectivity between 1985 and 1996 was relatively stable. However, between 1999 and 2012 the unsmoothed index declined to a low of 44% of its 1999 base-line value in 2005 and although it has since shown some signs of recovery, most species (57%) have declined in connectivity in the late short term (1999 to 2012)[1], see Figure C2ii.

Figure C2i. Functional connectivity of butterflies in the UK, 1985 to 2012, using a 10-year moving window.

A line graph showing changes in the average functional connectivity index of UK butterfly species from 1985 to 2012. The index remained relatively stable between 1985 and 1995 before falling to a low of 48% in 2004. It has since recovered and in 2012 had reached 110% of its 1985 base-year value. A 100% stacked bar chart showing the percentage of individual UK butterfly species that have either increased, decreased or shown no significant change in functional connectivity over 3 time periods. In the long-term period (1985 to 2012) almost half of all UK butterfly species (48%) showed no significant change whereas in the early short-term period (1985 to 1996), 62% decreased in functional connectivity and in the late short-term period (1999 to 2012) almost three-quarters (72%) increased in functional connectivity.

Notes:

  1. The connectivity index was calculated as the mean value of population synchrony using a 10-year moving window. The index values were extracted from a statistical (mixed effects) model which accounts for other factors known to influence population synchrony, therefore focusing the measure on functional connectivity.
  2. The line graph shows the unsmoothed average trend (dashed line), and the smoothed average trend (using a LOESS regression function; solid line) of functional connectivity over time across all 33 species. The shaded area represents the 95% confidence interval around the smoothed average trend.
  3. The figure in brackets shows the number of species in the index.
  4. The number of individual species included in each time period varies due to the availability of data: there were 21 species in the long-term period, 24 in the early short-term period and 31 in the late short-term period. In all, 33 species from three habitat types (woodland, grassland, and garden and hedgerows) are included in the indicator.
  5. The bar chart shows the percentage of species within the indicator that have shown a statistically significant increase, a statistically significant decrease, or no significant change in functional connectivity over three time periods (long term, 1985 to 2012; early short term, 1985 to 2000; and late short term, 2000 to 2012).

Source: UK Butterfly Monitoring Scheme, University of Reading.

Figure C2ii. Functional connectivity of woodland birds in the UK, 1985 to 2012, using a 10-year moving window.

A line graph showing changes in the average functional connectivity index of UK woodland bird species from 1985 to 2012. The index remained relatively stable between 1985 and 1995 before falling to a low of 44% of its 1999 value in 2005. It has since recovered a little and in 2012 had reached 66% of its 1999 base-year value. A 100% stacked bar chart showing the percentage of individual UK woodland bird species that have either increased, decreased or shown no significant change in functional connectivity over 2 time periods. In the early short-term period (1985 to 1996), most species (76%) showed no significant change in functional connectivity wheras in the late short-term period (1999 to 2012) more than half (57%) decreased in functional connectivity.

Notes:

  1. The connectivity index was calculated as the mean value of population synchrony using a 10-year moving window. The index values were extracted from a statistical (mixed effects) model which accounts for other factors known to influence population synchrony, therefore focusing the measure on functional connectivity.
  2. The line graph shows the unsmoothed average trend (dashed line), and the smoothed average trend (using a LOESS regression function, solid line) of functional connectivity over two time periods (1985 to 1996 and 1999 to 2012) across all 25 or 23 species. The shaded area represents the 95% confidence interval around the smoothed average trend.
  3. The gap in the time series is due to the non-availability of data for 1997 and 1998.
  4. The figures in brackets show the number of species in the index.
  5. The number of individual species included in each time period varies due to the availability of data: there were 25 species in the early short-term period and 23 in the late short-term period.
  6. The bar chart shows the percentage of species within the indicator that have shown a statistically significant increase, a statistically significant decrease, or no significant change in functional connectivity over two time periods (early short term, 1985 to 1996; and late short term, 1999 to 2012).

Source: British Trust for Ornithology, University of Reading.

As this is an experimental statistic it has not been assessed. The UK biodiversity indicators project team would welcome views on whether Figure C2i and/or Figure C2ii should be the headline measure, together with comments on the value of this new indicator (i.e. is this measuring something readers feel should be measured?) and the quality of the new indicator (i.e. how well does it measure connectivity?).

[1] There is no assessment of the long-term trend or the numbers of species that have increased, deceased or shown no change over the long term because of the break in the time series between 1996 and 1999.

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Downloads

Download the Fiche and Datasheet from the JNCC Resource Hub

Last updated: September 2019

Latest data:

Experimental statistic on Functional Connectivity: 2012 (mid-year of most recent 10-year moving window of data)

Archived measure of Habitat Connectivity: no update (2007)

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Categories:

UK Biodiversity Indicators 2019

Published: .

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