C6. Insects of the wider countryside (butterflies)
UK Biodiversity Indicators 2017
This documents supports
C6. Insects of the wider countryside (butterflies)
Technical annex – Assessing change in England, Scotland and UK Butterfly Indicators
Tom Brereton, Butterfly Conservation
David Roy, Centre for Ecology and Hydrology
For further information on C6. Insects of the wider countryside (butterflies)
visit http://www.jncc.gov.uk/page-4236
For further information on the UK Biodiversity Indicators visit http://www.jncc.gov.uk/page-1824
Technical annex – Assessing change in England, Scotland and UK Butterfly Indicators
Tom Brereton, Butterfly Conservation
David Roy, Centre for Ecology and Hydrology
June 2017 update
Introduction
Long time series of species abundance data such as those collected through the UKButterfly Monitoring Scheme (UKBMS) and used to compile UK and England Biodiversity Strategy (EBS) Butterfly Indicators can not always be summarised adequately by linear trend lines. Theselong time series may show alternating periods of increase and decrease, andit can be difficult to separate patterns of genuine change from annual fluctuations. Consequently, methods that model smoothed trend lines through abundance data are becoming increasingly popular. An extension of the linear trend approach is the application of a smoothing technique that describes the pattern by assigning a trend level (= modelled abundance) to each year in the time series (similar to a moving average). There are several smoothing methods available such as polynomial regression, splines and Loess estimators. These models may be summarised as ‘flexible trend models’. The most popular flexible trend models for the analysis of wildlife populations are General Additive Models (GAMs) and these, for example, are used to produce the EBS Bird Indicators. However, GAMs do not present the complete time series and donot account for serial correlation which limits their applicability to butterfly data.
Another flexible trend method from the class of structural time series analysis has recently been developed (Visser, 2005) and applied to European birds(Gregory et al. 2007) and European butterflies (Brereton et al.2011) using TrendSpotter software (Visser, 2004). This is the approach used to describe and assess changes in the UK and EBS Butterfly Indicator updates published and updated annually from 2008 onwards. Unlike the GAM approach, the confidence interval of the trend line is not calculated by a bootstrapping method but by application of a time series analysis and the Kalman filter (Visser 2004). This approach uses one observation per time point (e.g. year or month) and therefore the uncertainty in the estimate of yearly index values (e.g. confidence intervals around each year index) is modelled indirectly in the annual fluctuations. The main advantage of the TrendSpotter analysis however is the calculation of confidence intervals for the differences between the trend level of the last year and each of the preceding years, taking into account serial correlation which is unique for flexible trend methods. This allows short-term trends to be usefully assessed.
TrendSpotter estimates smoothed population numbers µ1, µ2, . . . , µt, . . . , µN, for a time series with N equidistant measurements over time (y1, y2, . . . , yt, . . . , yN). The expectations of these smoothed population numbers are denoted as m1, m2, . . . , mt, . . . , mN. TrendSpotter also estimates the standard deviations of the smoothed population numbers: SD1, SD2, . . . , SDt, . . . , SDN. Finally, it estimates the standard deviations of the differences µN–µt, denoted here as SDN–t. The estimation of confidence intervals is based on the deviations of time point values from the smoothed line. This emphasises temporal variation as the main source of error, although measurement errors and errors due to imputation are implicitly incorporated in the yearly measurements.
In TrendSpotter, the flexibility of a trend is set by the value of a standard deviation of a noise process. This standard deviation (parameter) can be chosen by hand, or can be optimised by maximum likelihood optimisation (the default choice). If the parameter is set to zero, the estimated trend equals the well-known regression trend line (straight line). If the parameter is set to a very large number, the trend will go through all measurements y1, y2, . . . , yt, . . . , yN. All values for mI, SDI, and SDN–t are estimated by use of the Kalman filter. This filter is attractive, because it gives estimates with optimal statistical properties. Although normally distributed residuals are not a necessary condition for the proper use of the Kalman filter, it still is a desirable property. For example, all confidence limits assessed by ±1.96 X standard error can be interpreted as 95% confidence limits. Normality of residuals can be tested by a so-called normality plot.
In TrendSpotter, a statistical test is performed to compare the difference in the Index in the latest year versus other years in the series.
Yearly Change Rates and confidence intervals produced in the TrendSpotter output are used to classify the trends per year. The trend classification applied (see Soldaat et al. 2007) is given in Table 1.
Table 1: Classification of trends on the basis of the 95% confidence intervals of the yearly change rate in TrendSpotter smoothed indices. CL = confidence limit; CI = confidence interval (see Soldaat et al. for explanation).
Trend class / Criteria / DescriptionStrong Increase / Lower CL > 1.05 / > 5% increase / year ( doubling in 15 years)
Moderate Increase / 1.00 < lower CL ≤ 1.05 / Increase, but unsure whether > 5% / year
Stable / Confidence interval contains 1.00
AND lower CL ≥ 0.95
AND upper CL ≤ 1.05 / Population changes less than 5% / year
Moderate Decrease / 0.95 ≤ upper CL < 1.00 / Decrease, but unsure whether > 5% / year
Steep Decrease / Upper CL < 0.95 / > 5% decrease / year ( halving in 15 years)
Uncertain / Confidence Interval contains 1.00 AND (lower CL < 0.95 OR upper CL > 1.05) / CI too large for reliable classification
In summary structural time series models are essentially regression models in which the explanatory variables are functions of time and the parameters are time-varying. The Kalman filter is an efficient recursive filter that estimates the state of a dynamic system from a series of incomplete and noisy measurements. For mathematical details about structural time-series analysis and the Kalman filter please refer to Harvey (1989).
TrendSpotter is currently considered the best-available technique in the assessment of Butterfly Indicators. Regular reviews of methods to assess changes in butterfly indicators are needed however; techniques to model trends are an active area of statistical development.
Example of TrendSpotter outputs
The UK butterfly indicators and the corresponding smoothed trends for the period 1976-2014 are given in Figure 1. Tests for changes in smoothed indices between 2012and previous years are given in Table 2. Plots of the test results comparing years are given in Figure 2.
Table 2: Indices and trend classification for specialist and generalist species of the UK Populations of Butterflies Indicator
Habitat Specialist species / Wide Countryside speciesYear / Index / Smoothed Index / Trend class / Index / Smoothed Index / Trend class
1976 / 100 / 65 / Moderate decline / 100 / 70 / Moderate decline
1977 / 44 / 60 / Moderate decline / 44 / 71 / Moderate decline
1978 / 47 / 55 / Moderate decline / 61 / 71 / Moderate decline
1979 / 46 / 51 / Moderate decline / 69 / 72 / Moderate decline
1980 / 45 / 47 / Moderate decline / 59 / 72 / Moderate decline
1981 / 22 / 45 / Moderate decline / 53 / 72 / Moderate decline
1982 / 45 / 43 / Moderate decline / 88 / 73 / Moderate decline
1983 / 38 / 42 / Moderate decline / 82 / 73 / Moderate decline
1984 / 54 / 42 / Moderate decline / 102 / 74 / Moderate decline
1985 / 45 / 41 / Moderate decline / 68 / 74 / Moderate decline
1986 / 39 / 42 / Moderate decline / 64 / 74 / Moderate decline
1987 / 46 / 42 / Moderate decline / 58 / 74 / Moderate decline
1988 / 36 / 42 / Moderate decline / 55 / 74 / Moderate decline
1989 / 42 / 43 / Moderate decline / 82 / 75 / Moderate decline
1990 / 49 / 44 / Moderate decline / 85 / 75 / Moderate decline
1991 / 38 / 44 / Moderate decline / 92 / 75 / Moderate decline
1992 / 56 / 45 / Moderate decline / 104 / 74 / Moderate decline
1993 / 43 / 45 / Moderate decline / 56 / 74 / Moderate decline
1994 / 45 / 45 / Moderate decline / 62 / 74 / Moderate decline
1995 / 53 / 45 / Moderate decline / 79 / 73 / Moderate decline
1996 / 49 / 45 / Moderate decline / 86 / 73 / Moderate decline
1997 / 51 / 44 / Moderate decline / 92 / 72 / Moderate decline
1998 / 34 / 44 / Moderate decline / 66 / 71 / Moderate decline
1999 / 39 / 43 / Moderate decline / 62 / 70 / Moderate decline
2000 / 40 / 42 / Moderate decline / 65 / 69 / Moderate decline
2001 / 38 / 42 / Moderate decline / 59 / 68 / Moderate decline
2002 / 34 / 42 / Moderate decline / 61 / 67 / Moderate decline
2003 / 43 / 41 / Stable / 74 / 66 / Moderate decline
2004 / 47 / 41 / Uncertain / 75 / 65 / Moderate decline
2005 / 47 / 41 / Uncertain / 64 / 64 / Moderate decline
2006 / 50 / 41 / Uncertain / 64 / 63 / Stable
2007 / 33 / 40 / Uncertain / 46 / 62 / Stable
2008 / 28 / 39 / Uncertain / 45 / 60 / Stable
2009 / 35 / 39 / Uncertain / 63 / 59 / Stable
2010 / 49 / 38 / Uncertain / 65 / 58 / Stable
2011 / 48 / 37 / Uncertain / 59 / 57 / Stable
2012 / 24 / 36 / Uncertain / 36 / 56 / Uncertain
2013 / 36 / 35 / Uncertain / 67 / 55 / Uncertain
2014 / 40 / 34 / Uncertain / 62 / 54 / Uncertain
2015 / 35 / 33 / Uncertain / 58 / 53 / Uncertain
2016 / 26 / 32 / 43 / 52
Habitat Specialist / Wider Countryside Species
Figure 1:Time series analysis of the UK Populations of Butterflies Indicator. The solid lineshowsthe observed index; the dottedline is the smoothed trend line estimated by TrendSpotter. The dashed lines indicate the upper and lower boundary of the 95% confidence limits of the smoothed trend line.
Figure 2:Test result for the habitat specialist indicator comparing the difference index in the latest year with previous years in the series. The solid dots represent the difference in previous year index values compared withthe latest year, whilst dashed black lines indicate the upper and lower boundary of the 95% confidence limits of the test results. Previous year indices are different to the latest year, if both 95% confidence interval lines do not cross 0. In this example, 1976-2002are differentto (significantly lower than)2016.
Figure 3: Test result for the wider countryside indicator comparing the difference index in the latest year with previous years in the series. The solid dots represent the difference in previous year index values compared with the latest year, whilst dashed black lines indicate the upper and lower boundary of the 95% confidence limits of the test results. Previous year indices are different to the latest year, if both 95% confidence interval lines do not cross 0. In this example, 1976-2005 are different to (significantly lower than) 2016.
Trend assessment based on the TrendSpotter approach suggest that the 2016Habitat Specialist index was significantly lower than over the period 1976-2002, though the trend difference subsequently has largely been uncertain. The 2016Wider Countryside Index is significantly lower than over the period 1976-2005. Since 2006, the trend is classed as stable or uncertain.
References
Brereton T.M., Roy D.B., Middlebrook, I., Botham, M. & Warren, M. 2011. The development of butterfly indicators in the United Kingdom and assessments on 2010. Journal of Insect Conservation, 15, 139-151.
Gregory, RD, Vorisek, P, van Strien AJ, Gmelig Meyling AW, Jiguet F, Fornasari, L, Jiri R,Chylarecki P, Burfield, IJ (2007) Population trends of widespread woodland birds in Europe. Ibis: 149 (Suppl. 2), 78–97.
Harvey AC (1989) Forecasting structural time series models and the Kalman filter. Cambridge University Press, London.
Soldaat, LL, Visser, P, van Roomen, M, van Strien, A (2007) Smoothing and trend detection in waterbird monitoring data using structural time-series analysis and the Kalman filter. Journal of Ornithology. Vol. 148 suppl. 2. Dec. 2007.
Visser H (2004) Estimation and detection of flexible trends. Atm Environment 38:4135-4145.
Visser H (2005) The significance of climate change in the Netherlands. An analysis of historical and future trends (1901-2020). MNP report 550002007.
Appendix.Trend results for England and UK Butterfly Indicators 1976-2016 and Scotland 1976-2014
Indicator / Year / Index / Smoothed Index (SI) / SI Lower CL. / SI Upper CL. / Trend Difference (TD) / TD Lower CL. / TD Upper CL. / TREND CLASSIFICATIONUK hab. specialist / 1976 / 100 / 65 / 56.5 / 72.8 / -32.8 / -44.4 / -21.3 / Moderate decline
UK hab. specialist / 1977 / 44 / 60 / 53.0 / 66.1 / -27.7 / -38.2 / -17.2 / Moderate decline
UK hab. specialist / 1978 / 47 / 55 / 49.3 / 60.4 / -23.0 / -32.9 / -13.1 / Moderate decline
UK hab. specialist / 1979 / 46 / 51 / 45.7 / 55.7 / -18.8 / -28.4 / -9.2 / Moderate decline
UK hab. specialist / 1980 / 45 / 47 / 42.5 / 52.1 / -15.4 / -24.9 / -6.0 / Moderate decline
UK hab. specialist / 1981 / 22 / 45 / 40.0 / 49.4 / -12.9 / -22.3 / -3.4 / Moderate decline
UK hab. specialist / 1982 / 45 / 43 / 38.4 / 47.7 / -11.2 / -20.6 / -1.8 / Moderate decline
UK hab. specialist / 1983 / 38 / 42 / 37.4 / 46.7 / -10.2 / -19.6 / -0.8 / Moderate decline
UK hab. specialist / 1984 / 54 / 42 / 36.9 / 46.3 / -9.8 / -19.2 / -0.3 / Moderate decline
UK hab. specialist / 1985 / 45 / 41 / 36.8 / 46.1 / -9.6 / -19.1 / -0.2 / Moderate decline
UK hab. specialist / 1986 / 39 / 42 / 37.0 / 46.3 / -9.8 / -19.2 / -0.4 / Moderate decline
UK hab. specialist / 1987 / 46 / 42 / 37.3 / 46.6 / -10.1 / -19.5 / -0.7 / Moderate decline
UK hab. specialist / 1988 / 36 / 42 / 37.9 / 47.1 / -10.6 / -20.0 / -1.2 / Moderate decline
UK hab. specialist / 1989 / 42 / 43 / 38.5 / 47.7 / -11.3 / -20.7 / -1.9 / Moderate decline
UK hab. specialist / 1990 / 49 / 44 / 39.2 / 48.4 / -12.0 / -21.4 / -2.6 / Moderate decline
UK hab. specialist / 1991 / 38 / 44 / 39.9 / 49.1 / -12.6 / -22.0 / -3.2 / Moderate decline
UK hab. specialist / 1992 / 56 / 45 / 40.4 / 49.6 / -13.2 / -22.5 / -3.8 / Moderate decline
UK hab. specialist / 1993 / 43 / 45 / 40.7 / 49.9 / -13.5 / -22.9 / -4.1 / Moderate decline
UK hab. specialist / 1994 / 45 / 45 / 40.8 / 50.0 / -13.6 / -23.0 / -4.2 / Moderate decline
UK hab. specialist / 1995 / 53 / 45 / 40.7 / 49.9 / -13.5 / -22.8 / -4.1 / Moderate decline
UK hab. specialist / 1996 / 49 / 45 / 40.3 / 49.5 / -13.0 / -22.5 / -3.6 / Moderate decline
UK hab. specialist / 1997 / 51 / 44 / 39.7 / 48.9 / -12.4 / -21.9 / -3.0 / Moderate decline
UK hab. specialist / 1998 / 34 / 44 / 39.0 / 48.1 / -11.7 / -21.2 / -2.2 / Moderate decline
UK hab. specialist / 1999 / 39 / 43 / 38.3 / 47.5 / -11.0 / -20.5 / -1.5 / Moderate decline
UK hab. specialist / 2000 / 40 / 42 / 37.7 / 46.9 / -10.5 / -20.0 / -0.9 / Moderate decline
UK hab. specialist / 2001 / 38 / 42 / 37.3 / 46.5 / -10.0 / -19.7 / -0.4 / Moderate decline
UK hab. specialist / 2002 / 34 / 42 / 37.0 / 46.2 / -9.8 / -19.5 / -0.1 / Moderate decline
UK hab. specialist / 2003 / 43 / 41 / 36.9 / 46.1 / -9.6 / -19.4 / 0.1 / Stable
UK hab. specialist / 2004 / 47 / 41 / 36.7 / 45.9 / -9.5 / -19.3 / 0.3 / Uncertain
UK hab. specialist / 2005 / 47 / 41 / 36.4 / 45.7 / -9.2 / -19.0 / 0.7 / Uncertain
UK hab. specialist / 2006 / 50 / 41 / 35.9 / 45.2 / -8.8 / -18.6 / 1.1 / Uncertain
UK hab. specialist / 2007 / 33 / 40 / 35.4 / 44.7 / -8.2 / -18.0 / 1.7 / Uncertain
UK hab. specialist / 2008 / 28 / 39 / 34.7 / 44.1 / -7.6 / -17.3 / 2.1 / Uncertain
UK hab. specialist / 2009 / 35 / 39 / 34.2 / 43.5 / -7.0 / -16.5 / 2.4 / Uncertain
UK hab. specialist / 2010 / 49 / 38 / 33.5 / 42.9 / -6.4 / -15.4 / 2.7 / Uncertain
UK hab. specialist / 2011 / 48 / 37 / 32.7 / 42.1 / -5.6 / -14.0 / 2.8 / Uncertain
UK hab. specialist / 2012 / 24 / 36 / 31.7 / 41.3 / -4.6 / -12.2 / 2.9 / Uncertain
UK hab. specialist / 2013 / 36 / 35 / 30.4 / 40.5 / -3.6 / -9.9 / 2.7 / Uncertain
UK hab. specialist / 2014 / 40 / 34 / 28.8 / 39.9 / -2.5 / -7.2 / 2.2 / Uncertain
UK hab. specialist / 2015 / 35 / 33 / 26.5 / 39.7 / -1.3 / -3.9 / 1.3 / Uncertain
UK hab. specialist / 2016 / 26 / 32 / 23.7 / 40.0 / 0.0 / 0.0 / 0.0 / #Div/0!
UK wider countryside / 1976 / 100 / 70 / 59.1 / 81.6 / -18.8 / -34.7 / -3.0 / Moderate decline
UK wider countryside / 1977 / 44 / 71 / 60.6 / 80.8 / -19.2 / -34.3 / -4.1 / Moderate decline
UK wider countryside / 1978 / 61 / 71 / 62.0 / 80.2 / -19.6 / -34.0 / -5.1 / Moderate decline
UK wider countryside / 1979 / 69 / 72 / 63.2 / 79.8 / -20.0 / -34.0 / -6.0 / Moderate decline
UK wider countryside / 1980 / 59 / 72 / 64.3 / 79.5 / -20.4 / -34.0 / -6.7 / Moderate decline
UK wider countryside / 1981 / 53 / 72 / 65.3 / 79.4 / -20.8 / -34.2 / -7.4 / Moderate decline
UK wider countryside / 1982 / 88 / 73 / 66.1 / 79.5 / -21.3 / -34.5 / -8.0 / Moderate decline
UK wider countryside / 1983 / 82 / 73 / 66.7 / 79.6 / -21.7 / -34.9 / -8.5 / Moderate decline
UK wider countryside / 1984 / 102 / 74 / 67.3 / 79.8 / -22.0 / -35.2 / -8.8 / Moderate decline
UK wider countryside / 1985 / 68 / 74 / 67.7 / 80.0 / -22.3 / -35.5 / -9.1 / Moderate decline
UK wider countryside / 1986 / 64 / 74 / 68.0 / 80.2 / -22.6 / -35.8 / -9.4 / Moderate decline
UK wider countryside / 1987 / 58 / 74 / 68.2 / 80.4 / -22.8 / -36.0 / -9.6 / Moderate decline
UK wider countryside / 1988 / 55 / 74 / 68.4 / 80.6 / -23.0 / -36.3 / -9.7 / Moderate decline
UK wider countryside / 1989 / 82 / 75 / 68.5 / 80.7 / -23.1 / -36.4 / -9.7 / Moderate decline
UK wider countryside / 1990 / 85 / 75 / 68.5 / 80.8 / -23.1 / -36.5 / -9.7 / Moderate decline
UK wider countryside / 1991 / 92 / 75 / 68.4 / 80.7 / -23.0 / -36.5 / -9.6 / Moderate decline
UK wider countryside / 1992 / 104 / 74 / 68.3 / 80.5 / -22.9 / -36.3 / -9.4 / Moderate decline
UK wider countryside / 1993 / 56 / 74 / 67.9 / 80.2 / -22.5 / -36.0 / -9.1 / Moderate decline
UK wider countryside / 1994 / 62 / 74 / 67.5 / 79.8 / -22.1 / -35.6 / -8.6 / Moderate decline
UK wider countryside / 1995 / 79 / 73 / 67.0 / 79.3 / -21.6 / -35.1 / -8.1 / Moderate decline
UK wider countryside / 1996 / 86 / 73 / 66.4 / 78.7 / -21.0 / -34.5 / -7.5 / Moderate decline
UK wider countryside / 1997 / 92 / 72 / 65.7 / 77.9 / -20.3 / -33.7 / -6.8 / Moderate decline
UK wider countryside / 1998 / 66 / 71 / 64.8 / 77.1 / -19.5 / -32.9 / -6.1 / Moderate decline
UK wider countryside / 1999 / 62 / 70 / 64.0 / 76.2 / -18.6 / -31.9 / -5.3 / Moderate decline
UK wider countryside / 2000 / 65 / 69 / 63.0 / 75.3 / -17.6 / -30.8 / -4.4 / Moderate decline
UK wider countryside / 2001 / 59 / 68 / 62.0 / 74.3 / -16.6 / -29.6 / -3.6 / Moderate decline
UK wider countryside / 2002 / 61 / 67 / 61.0 / 73.2 / -15.6 / -28.4 / -2.8 / Moderate decline
UK wider countryside / 2003 / 74 / 66 / 59.9 / 72.1 / -14.5 / -27.0 / -2.0 / Moderate decline
UK wider countryside / 2004 / 75 / 65 / 58.8 / 71.0 / -13.4 / -25.6 / -1.2 / Moderate decline
UK wider countryside / 2005 / 64 / 64 / 57.7 / 69.9 / -12.3 / -24.0 / -0.5 / Moderate decline
UK wider countryside / 2006 / 64 / 63 / 56.5 / 68.8 / -11.1 / -22.4 / 0.2 / Stable
UK wider countryside / 2007 / 46 / 62 / 55.3 / 67.7 / -10.0 / -20.7 / 0.7 / Stable
UK wider countryside / 2008 / 45 / 60 / 54.1 / 66.7 / -8.9 / -18.9 / 1.2 / Stable
UK wider countryside / 2009 / 63 / 59 / 52.8 / 65.7 / -7.7 / -17.0 / 1.5 / Stable
UK wider countryside / 2010 / 65 / 58 / 51.4 / 64.9 / -6.6 / -14.9 / 1.7 / Stable
UK wider countryside / 2011 / 59 / 57 / 49.9 / 64.1 / -5.5 / -12.8 / 1.8 / Stable
UK wider countryside / 2012 / 36 / 56 / 48.3 / 63.6 / -4.4 / -10.5 / 1.7 / Uncertain
UK wider countryside / 2013 / 67 / 55 / 46.6 / 63.1 / -3.3 / -8.1 / 1.5 / Uncertain
UK wider countryside / 2014 / 62 / 54 / 44.6 / 62.9 / -2.2 / -5.6 / 1.1 / Uncertain
UK wider countryside / 2015 / 58 / 53 / 42.5 / 62.8 / -1.1 / -2.9 / 0.6 / Uncertain
UK wider countryside / 2016 / 43 / 52 / 40.2 / 62.8 / 0.0 / 0.0 / 0.0 / #Div/0!
UK all / 1976 / 100 / 64 / 56.4 / 71.5 / -17.7 / -28.5 / -6.8 / Moderate decline
UK all / 1977 / 44 / 64 / 56.8 / 70.7 / -17.4 / -27.8 / -7.0 / Moderate decline
UK all / 1978 / 56 / 64 / 57.2 / 69.9 / -17.2 / -27.3 / -7.2 / Moderate decline
UK all / 1979 / 61 / 63 / 57.5 / 69.1 / -17.0 / -26.8 / -7.3 / Moderate decline
UK all / 1980 / 56 / 63 / 57.7 / 68.5 / -16.8 / -26.4 / -7.3 / Moderate decline
UK all / 1981 / 37 / 63 / 57.9 / 68.0 / -16.7 / -26.0 / -7.3 / Moderate decline
UK all / 1982 / 69 / 63 / 58.1 / 67.6 / -16.5 / -25.8 / -7.3 / Moderate decline
UK all / 1983 / 61 / 63 / 58.2 / 67.2 / -16.4 / -25.6 / -7.2 / Moderate decline
UK all / 1984 / 81 / 63 / 58.2 / 67.0 / -16.3 / -25.4 / -7.2 / Moderate decline
UK all / 1985 / 60 / 62 / 58.2 / 66.7 / -16.2 / -25.2 / -7.1 / Moderate decline
UK all / 1986 / 54 / 62 / 58.1 / 66.5 / -16.0 / -25.1 / -7.0 / Moderate decline
UK all / 1987 / 56 / 62 / 58.1 / 66.4 / -15.9 / -25.0 / -6.8 / Moderate decline
UK all / 1988 / 48 / 62 / 58.0 / 66.2 / -15.8 / -24.9 / -6.7 / Moderate decline
UK all / 1989 / 64 / 62 / 57.8 / 66.1 / -15.7 / -24.7 / -6.6 / Moderate decline
UK all / 1990 / 70 / 62 / 57.7 / 65.9 / -15.5 / -24.6 / -6.4 / Moderate decline
UK all / 1991 / 64 / 62 / 57.5 / 65.7 / -15.3 / -24.4 / -6.2 / Moderate decline
UK all / 1992 / 83 / 61 / 57.3 / 65.5 / -15.1 / -24.2 / -6.0 / Moderate decline
UK all / 1993 / 54 / 61 / 57.0 / 65.3 / -14.8 / -23.9 / -5.7 / Moderate decline
UK all / 1994 / 58 / 61 / 56.7 / 65.0 / -14.5 / -23.6 / -5.5 / Moderate decline
UK all / 1995 / 71 / 60 / 56.3 / 64.6 / -14.2 / -23.2 / -5.1 / Moderate decline
UK all / 1996 / 70 / 60 / 55.9 / 64.2 / -13.7 / -22.7 / -4.8 / Moderate decline
UK all / 1997 / 74 / 60 / 55.5 / 63.7 / -13.3 / -22.2 / -4.4 / Moderate decline
UK all / 1998 / 52 / 59 / 55.0 / 63.2 / -12.8 / -21.6 / -4.0 / Moderate decline
UK all / 1999 / 53 / 59 / 54.4 / 62.7 / -12.3 / -20.9 / -3.6 / Moderate decline
UK all / 2000 / 56 / 58 / 53.9 / 62.1 / -11.7 / -20.2 / -3.2 / Moderate decline
UK all / 2001 / 51 / 57 / 53.3 / 61.5 / -11.1 / -19.4 / -2.8 / Moderate decline
UK all / 2002 / 49 / 57 / 52.7 / 60.9 / -10.5 / -18.6 / -2.4 / Moderate decline
UK all / 2003 / 61 / 56 / 52.0 / 60.3 / -9.8 / -17.7 / -2.0 / Moderate decline
UK all / 2004 / 65 / 55 / 51.4 / 59.6 / -9.2 / -16.8 / -1.6 / Moderate decline
UK all / 2005 / 60 / 55 / 50.6 / 58.9 / -8.5 / -15.7 / -1.2 / Moderate decline
UK all / 2006 / 61 / 54 / 49.9 / 58.3 / -7.8 / -14.7 / -0.9 / Moderate decline
UK all / 2007 / 42 / 53 / 49.1 / 57.6 / -7.0 / -13.5 / -0.5 / Moderate decline
UK all / 2008 / 38 / 53 / 48.2 / 57.0 / -6.3 / -12.3 / -0.3 / Moderate decline
UK all / 2009 / 51 / 52 / 47.3 / 56.4 / -5.5 / -11.0 / 0.0 / Moderate decline
UK all / 2010 / 62 / 51 / 46.3 / 55.8 / -4.7 / -9.6 / 0.1 / Stable
UK all / 2011 / 58 / 50 / 45.2 / 55.3 / -4.0 / -8.2 / 0.3 / Stable
UK all / 2012 / 32 / 49 / 44.1 / 54.9 / -3.2 / -6.7 / 0.3 / Stable
UK all / 2013 / 53 / 49 / 42.9 / 54.5 / -2.4 / -5.1 / 0.4 / Stable
UK all / 2014 / 54 / 48 / 41.6 / 54.3 / -1.6 / -3.5 / 0.3 / Stable
UK all / 2015 / 49 / 47 / 40.2 / 54.0 / -0.8 / -1.8 / 0.2 / Stable
UK all / 2016 / 37 / 46 / 38.7 / 53.9 / 0.0 / 0.0 / 0.0 / #Div/0!
England farmland hab. spec. / 1990 / 100 / 91 / 75.8 / 107.1 / -63.4 / -85.6 / -41.2 / Moderate decline
England farmland hab. spec. / 1991 / 60 / 91 / 77.1 / 104.1 / -62.5 / -83.4 / -41.7 / Moderate decline
England farmland hab. spec. / 1992 / 94 / 90 / 77.9 / 101.6 / -61.7 / -81.6 / -41.8 / Moderate decline
England farmland hab. spec. / 1993 / 79 / 89 / 78.3 / 99.5 / -60.8 / -80.1 / -41.6 / Moderate decline
England farmland hab. spec. / 1994 / 86 / 88 / 78.3 / 97.7 / -59.9 / -78.8 / -41.0 / Moderate decline
England farmland hab. spec. / 1995 / 104 / 87 / 77.8 / 96.1 / -58.9 / -77.6 / -40.1 / Moderate decline
England farmland hab. spec. / 1996 / 92 / 86 / 76.9 / 94.6 / -57.7 / -76.4 / -39.0 / Moderate decline
England farmland hab. spec. / 1997 / 101 / 84 / 75.6 / 93.1 / -56.3 / -75.0 / -37.5 / Moderate decline
England farmland hab. spec. / 1998 / 74 / 83 / 74.0 / 91.4 / -54.6 / -73.4 / -35.8 / Moderate decline
England farmland hab. spec. / 1999 / 81 / 81 / 72.2 / 89.6 / -52.8 / -71.7 / -34.0 / Moderate decline
England farmland hab. spec. / 2000 / 79 / 79 / 70.2 / 87.6 / -50.8 / -69.7 / -31.9 / Moderate decline
England farmland hab. spec. / 2001 / 74 / 77 / 67.9 / 85.5 / -48.6 / -67.5 / -29.7 / Moderate decline
England farmland hab. spec. / 2002 / 65 / 74 / 65.6 / 83.1 / -46.3 / -65.1 / -27.4 / Moderate decline
England farmland hab. spec. / 2003 / 81 / 72 / 63.0 / 80.6 / -43.7 / -62.4 / -25.0 / Moderate decline
England farmland hab. spec. / 2004 / 68 / 69 / 60.2 / 77.8 / -40.9 / -59.4 / -22.4 / Moderate decline
England farmland hab. spec. / 2005 / 87 / 66 / 57.3 / 74.8 / -38.0 / -56.2 / -19.8 / Moderate decline
England farmland hab. spec. / 2006 / 79 / 63 / 54.1 / 71.6 / -34.8 / -52.5 / -17.1 / Moderate decline
England farmland hab. spec. / 2007 / 46 / 60 / 50.8 / 68.2 / -31.4 / -48.6 / -14.3 / Moderate decline
England farmland hab. spec. / 2008 / 41 / 56 / 47.4 / 64.8 / -28.0 / -44.4 / -11.6 / Moderate decline
England farmland hab. spec. / 2009 / 50 / 53 / 43.8 / 61.3 / -24.5 / -39.9 / -9.1 / Moderate decline
England farmland hab. spec. / 2010 / 66 / 49 / 40.1 / 57.9 / -20.9 / -35.1 / -6.8 / Moderate decline
England farmland hab. spec. / 2011 / 61 / 45 / 36.2 / 54.6 / -17.3 / -30.0 / -4.7 / Moderate decline
England farmland hab. spec. / 2012 / 8 / 42 / 32.1 / 51.5 / -13.7 / -24.6 / -2.9 / Moderate decline
England farmland hab. spec. / 2013 / 12 / 38 / 27.7 / 48.9 / -10.2 / -18.9 / -1.5 / Moderate decline
England farmland hab. spec. / 2014 / 46 / 35 / 23.0 / 46.7 / -6.8 / -13.0 / -0.6 / Moderate decline
England farmland hab. spec. / 2015 / 39 / 31 / 17.9 / 45.0 / -3.4 / -6.7 / -0.1 / Moderate decline
England farmland hab. spec. / 2016 / 33 / 28 / 12.4 / 43.8 / 0.0 / 0.0 / 0.0 / #Div/0!
England farmland wider country / 1990 / 100 / 111 / 99.5 / 122.2 / -34.9 / -54.4 / -15.4 / Moderate decline
England farmland wider country / 1991 / 121 / 110 / 98.8 / 120.3 / -33.6 / -52.3 / -14.8 / Moderate decline
England farmland wider country / 1992 / 127 / 108 / 98.1 / 118.3 / -32.2 / -50.2 / -14.2 / Moderate decline
England farmland wider country / 1993 / 76 / 107 / 97.4 / 116.4 / -30.9 / -48.1 / -13.6 / Moderate decline
England farmland wider country / 1994 / 89 / 106 / 96.6 / 114.4 / -29.5 / -46.0 / -13.0 / Moderate decline
England farmland wider country / 1995 / 108 / 104 / 95.8 / 112.5 / -28.2 / -43.9 / -12.4 / Moderate decline
England farmland wider country / 1996 / 120 / 103 / 95.0 / 110.7 / -26.8 / -41.8 / -11.8 / Moderate decline
England farmland wider country / 1997 / 135 / 101 / 94.1 / 108.9 / -25.5 / -39.7 / -11.2 / Moderate decline
England farmland wider country / 1998 / 102 / 100 / 93.2 / 107.1 / -24.2 / -37.7 / -10.7 / Moderate decline
England farmland wider country / 1999 / 91 / 99 / 92.2 / 105.4 / -22.8 / -35.6 / -10.1 / Moderate decline
England farmland wider country / 2000 / 97 / 97 / 91.2 / 103.7 / -21.5 / -33.5 / -9.5 / Moderate decline
England farmland wider country / 2001 / 85 / 96 / 90.1 / 102.2 / -20.1 / -31.4 / -8.9 / Moderate decline
England farmland wider country / 2002 / 87 / 95 / 88.9 / 100.7 / -18.8 / -29.3 / -8.3 / Moderate decline
England farmland wider country / 2003 / 109 / 93 / 87.6 / 99.3 / -17.4 / -27.2 / -7.7 / Moderate decline
England farmland wider country / 2004 / 97 / 92 / 86.2 / 98.0 / -16.1 / -25.1 / -7.1 / Moderate decline
England farmland wider country / 2005 / 92 / 91 / 84.7 / 96.8 / -14.8 / -23.0 / -6.5 / Moderate decline
England farmland wider country / 2006 / 91 / 89 / 83.1 / 95.7 / -13.4 / -20.9 / -5.9 / Moderate decline
England farmland wider country / 2007 / 63 / 88 / 81.5 / 94.6 / -12.1 / -18.8 / -5.3 / Moderate decline
England farmland wider country / 2008 / 61 / 87 / 79.8 / 93.7 / -10.7 / -16.7 / -4.7 / Moderate decline
England farmland wider country / 2009 / 91 / 85 / 78.0 / 92.8 / -9.4 / -14.6 / -4.1 / Moderate decline
England farmland wider country / 2010 / 92 / 84 / 76.2 / 91.9 / -8.1 / -12.6 / -3.6 / Moderate decline
England farmland wider country / 2011 / 82 / 83 / 74.3 / 91.1 / -6.7 / -10.5 / -3.0 / Moderate decline
England farmland wider country / 2012 / 52 / 81 / 72.4 / 90.3 / -5.4 / -8.4 / -2.4 / Moderate decline
England farmland wider country / 2013 / 103 / 80 / 70.5 / 89.5 / -4.0 / -6.3 / -1.8 / Moderate decline
England farmland wider country / 2014 / 99 / 79 / 68.6 / 88.8 / -2.7 / -4.2 / -1.2 / Moderate decline
England farmland wider country / 2015 / 89 / 77 / 66.6 / 88.1 / -1.3 / -2.1 / -0.6 / Moderate decline
England farmland wider country / 2016 / 64 / 76 / 64.6 / 87.4 / 0.0 / 0.0 / 0.0 / #Div/0!
England farmland all / 1990 / 100 / 102 / 88.5 / 116.3 / -56.0 / -76.5 / -35.4 / Moderate decline
England farmland all / 1991 / 85 / 101 / 88.7 / 113.4 / -54.6 / -74.1 / -35.1 / Moderate decline
England farmland all / 1992 / 109 / 100 / 88.6 / 110.8 / -53.2 / -71.9 / -34.5 / Moderate decline
England farmland all / 1993 / 78 / 98 / 88.2 / 108.3 / -51.8 / -70.0 / -33.7 / Moderate decline
England farmland all / 1994 / 88 / 97 / 87.6 / 106.1 / -50.4 / -68.1 / -32.7 / Moderate decline
England farmland all / 1995 / 107 / 95 / 86.8 / 104.0 / -48.9 / -66.3 / -31.6 / Moderate decline
England farmland all / 1996 / 105 / 94 / 85.6 / 102.1 / -47.4 / -64.6 / -30.3 / Moderate decline
England farmland all / 1997 / 117 / 92 / 84.2 / 100.2 / -45.8 / -62.7 / -28.8 / Moderate decline
England farmland all / 1998 / 87 / 90 / 82.6 / 98.3 / -44.0 / -60.9 / -27.2 / Moderate decline
England farmland all / 1999 / 86 / 89 / 80.8 / 96.4 / -42.1 / -58.9 / -25.4 / Moderate decline
England farmland all / 2000 / 88 / 87 / 78.9 / 94.4 / -40.2 / -56.8 / -23.6 / Moderate decline
England farmland all / 2001 / 80 / 85 / 76.9 / 92.3 / -38.1 / -54.5 / -21.7 / Moderate decline
England farmland all / 2002 / 76 / 82 / 74.7 / 90.1 / -36.0 / -52.1 / -19.8 / Moderate decline
England farmland all / 2003 / 94 / 80 / 72.5 / 87.9 / -33.7 / -49.6 / -17.8 / Moderate decline
England farmland all / 2004 / 81 / 78 / 70.1 / 85.5 / -31.4 / -46.9 / -15.9 / Moderate decline
England farmland all / 2005 / 90 / 75 / 67.7 / 83.1 / -28.9 / -44.0 / -13.9 / Moderate decline