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Impact of climate change on bird populations

Indicator Assessment Created 17 Sep 2009 Published 21 May 2010 Last modified 04 Sep 2015, 06:59 PM
Indicator codes: SEBI 011

Key messages

Climate change is having a detectable effect on bird populations at a European scale, including both negative and positive effects.

The number of bird species whose populations are observed to be negatively impacted by climatic change is three times larger than those observed to be positively affected by climate warming in this set of widespread European land birds.

The Climatic Impact Indicator, which illustrates the impact of climate change on bird populations, has increased strongly in the past twenty years, coinciding with a period of rapid climatic warming in Europe. Potential links between changes in bird populations and ecosystem functioning and resilience are not well understood.

What are the negative (and positive) impacts of climate change on biodiversity?

Climate change impact indicator for European birds

Note: How to read the graph: The indicator demonstrates the impact of climate change on widespread bird populations has increased strongly in the past twenty years. The Climatic Impact Indicator (CII) measures the divergence between the population trends of bird species projected to expand their range and those predicted to shrink their range due to climate change.

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Weighted population trend of species predicted to lose range in response to climatic change (92 species)

Note: How to read the graph: The weighted population index of species expected to lose in range due to climatic change has decreased by 20% since 1989.

Data source:

Gregory, R. D.; Willis, S. G.; Jiguet, F.; VoYíaek, P.; KlvaHová, A.; van Strien, A.; Huntley, B.; Collingham, Y. C.; Couvet, D. and Green, R. E., 2009. 'An Indicator of the Impact of Climatic Change on European Bird Populations'. PLoS ONE 4(3): e4678. doi:10.1371/journal.pone.0004678.

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Weighted population index of species predicted to gain range in response to climatic change (30 species)

Note: How to read the graph: The weighted population index of species expected to gain in range due to climatic change has increased by over 30 % since 1989.

Data source:

Gregory, R. D.; Willis, S. G.; Jiguet, F.; VoYíaek, P.; KlvaHová, A.; van Strien, A.; Huntley, B.; Collingham, Y. C.; Couvet, D. and Green, R. E., 2009. 'An Indicator of the Impact of Climatic Change on European Bird Populations'. PLoS ONE 4(3): e4678. doi:10.1371/journal.pone.0004678.

Downloads and more info

The Climatic Impact Indicator (CII) measures the divergence between the population trends of bird species projected to expand their range and those predicted to shrink their range due to climatic change. The indicator is based on a combination of observed population trends monitored from 122 common bird species in 20 European countries over 26 years, and projected potential shrinkage or expansion of range size for each of these species at the last part of this century (2070 - 2099), derived from climatic envelope models. The ensemble in this case is the average climate envelope forecast based on six differing future scenarios.

As with any biological data, there is annual variation and statistical noise around the observed trend in the CII. However, the general trend of the CII is clearly upwards indicating that climatic change is having an increasing impact on bird populations. Where the trend is downwards, this means that the impact of climate warming on bird populations is being overridden by other pressures in the environment; these could be man-made pressures, or natural ones, such as cold winter weather. The CII demonstrates unequivocally and for the first time that climatic change has affected bird populations at a European scale. It shows conformity between observed population trends and modelled projections of how each species should respond to climatic warming.

The CII fell in the 1980s reflecting the influence of cold winter weather events during this time (especially around 1980 and 1985 when such events significantly increased mortality in small birds) combined with other known drivers, such as land use change and agricultural intensification, which acted to depress bird populations. The indicator shows no signal of climatic warming until approximately 1986. The stable temperatures in the early 1980s represent the end of a period of stable annual average temperature in Europe that began around 1950.

From the late 1980s, however, the CII shows the effects of climatic warming on bird population trends, similar to that predicted by the climatic envelope models; and the impacts have increased roughly linearly to date. The number of bird species whose populations are observed to be negatively impacted by climatic change is three times larger than those observed to be positively affected by climate warming in this set of widespread European land birds. The CII has increased rapidly in the past twenty years, coinciding with a period recognised by climatologists as a time of rapid observed climatic warming in Europe.

A closer analysis reveals that the sub-indicator figures, which lie behind the construction of the CII (Figures 2 and 3), show differing fortunes for those species whose ranges are predicted to be negatively impacted by climatic warming compared to those positively impacted. While many European land birds show signs of decline in response to warming (92 species predicted to shrink in range size, reflected in sub-indicator figure 2), some bird populations have responded positively to climatic change and have increased in number (the 30 species predicted to gain range size, reflected in sub-indicator figure 3). This is likely to have led, and will increasingly lead, to changes in species composition at a regional scale. We can only speculate as to the potential correlation between such changes in bird populations and ecosystem function and resilience. It is suggested that increasing climatic effects might alter ecosystem functioning and resilience.

The effects of climate change for some migratory bird species may be most severe outside their European range and a comprehensive response would need to be effective beyond European territory.

NOTES

The indicator is based on the combination of two data sets:
(i) Population trend data on 122 common and widespread bird species for any part of the period between 1980 and 2005 in 20 European countries (from the Pan-European Common Bird Monitoring Scheme: PECBMS). See Gregory et al. (2005, 2008);
(ii) Climatic envelope model projections for each of the 122 species for the simulated future between 2070 and 2099 showing an expanding potential geographical range or a decreasing potential geographical range. These are based on an ensemble forecast built on three General Circulation Models and two IPCC SRES emissions scenarios. See Gregory et al. (2009), Huntley et al. (2007, 2008).

METHODS IN BRIEF

The CII is calculated in two steps. First, the 122 bird species were divided into those for which the ensemble climatic envelope model projection indicated an increase in a potential geographical range (30 species: sub-indicator figure 3) and those with projected decreases in their geographical range (92 species: sub-indicator figure 2). For each of the two groups of species, a multi-species population index (proceeding from population indices for individual species) was then calculated, with the weight of the contribution of each species to the index being based on the modelled projected change in a potential range extent. Extreme projections of the range increase, or loss, for individual species, thus, have a greater influence on the line. In simple terms, population trends displayed by birds predicted, in the models, to be significantly affected by climatic changes (either negatively or positively) register a strong influence over the direction of the lines shown in the subindicator figures.
In the second step, the CII itself is calculated for a given year. It is done as a ratio between the index for species whose potential range is projected to increase (30 species, reflected in sub-indicator figure 3) and the index for the species whose geographical range is projected to decrease (92 species, reflected in sub-indicator figure 2). The two lines have equal weighting in the indicator. The methodology developed here is equally applicable to any other species group where equivalent information is available. For full methods and discussion, see Gregory et al. (2009).

FURTHER INFORMATION

Indicator specification and metadata

Indicator definition

The Climatic Impact Indicator (CII) measures the divergence between the population trends of bird species projected to expand their range, and those predicted to shrink their range due to climatic change. The indicator is based on a combination of observed population trends monitored from 122 common bird species in 20 European countries over 26 years, and projected potential shrinkage, or expansion, of range size for each of these species at the end of this century (~2070-2099), derived from climatic envelope models. The ensemble in this case is the average climate envelope forecast based on six differing future scenarios.

Units

weighted index (relative values)


Policy context and targets

Context description

Climate change is having a detectable effect on bird populations at a European scale, including evidence of negative as well as positive effects on their populations.

The number of bird species observed to be negatively impacted by climatic change is three times larger than those observed to be positively affected by climate warming in this set of widespread European land birds.

The Climatic Impact Indicator (CII), which illustrates the impact of climate change on bird populations, has increased strongly in the past twenty years, coinciding with a period of rapid climatic warming in Europe.

Potential links between changes in bird populations and ecosystem functioning and resilience are not well understood. It is suggested that increasing climatic effects might alter ecosystem functioning and resilience.

Relation of the indicator to focal area


The indicator demonstrates how climate change is impacting upon a component of biodiversity, i.e. populations of widespread and common birds, at a European scale over the past twenty years.

Relation of this indicator to other indicators


The information on European species' trends used here also contribute to the wild bird indicator under the heading: Trends in abundance and distribution of selected species.

Targets

No targets have been specified

Related policy documents

No related policy documents have been specified

Methodology

Methodology for indicator calculation

The CII is calculated in two steps. First, we divided the 122 bird species into those for which the ensemble climatic envelope model projection indicated an increase in potential geographical range (30 species) and those with projected decreases in geographical range (92 species).  For each of the two groups of species, we then calculated a multi-species population index from population indices for individual species, with the weight of the contribution of each species to the index being based on the modelled projected change in potential range extent. Extreme projections of range increase, or loss, for individual species thus have greater influence on the line. In simple terms, population trends of birds predicted to be strongly affected by climatic change in our models (either negatively or positively) strongly influence the direction of the lines shown in the sub-indicator figures.  For example, the Sardinian Warbler, Subalpine Warbler, Bee-eater and Cirl Bunting are increasing strongly and are projected to do so.  The snipe Meadow Pipit, Brambling and Willow Tit are declining strongly and are projected to do so.

In the second step, the CII itself is calculated in a given year as the ratio of the index for those species projected to increase in potential range (30 species) to the index of those species projected to decrease in geographical range (92 species).  The two lines have equal weighting in the indicator.

The CII shows conformity between observed population trends and projections of how each species' population should respond to climatic warmingThe CII increases when population trends go in the direction predicted by the modelsThe CII decreases when population trends go in the opposite direction predicted by the models.

In the analysis, we also looked at the influence of the habitat choice of the birds, their migratory behaviour and their body mass (as a proxy for life history characteristics) in predicting bird trends and in potentially influencing the CII.  Although population trends covary with these factors (e.g. farmland birds and long-distance migrants have declined strongly) these correlations do not confound the relationship between trends and the climate projections, nor do they confound the CII.
The methodology developed here is equally applicable to any other species group where equivalent information is available. For full methods and discussion, see Gregory et al. (2009) An indicator of the impact of climatic change on European bird populations (In press).

The indicator is based on the combination of two data sets:

  1.  Population trend data on 122 common and widespread bird species for any part of the period 1980 - 2005 in 20 European countries (from the Pan-European Common Bird Monitoring Scheme: PECBMS). See Gregory et al. 2005, 2008
  2. Climatic envelope model projections for each of the 122 species for the simulated future 2070-2099 showing an expanding potential geographical range or a decreasing potential geographical range. These are based on an ensemble forecast built on three General Circulation Models and two IPCC SRES emissions scenarios. See Gregory et al. In press, Huntley et al. 2007, 2008.
The bird trend data come from 20 European countries: Austria, Belgium (Wallonia), Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, United Kingdom. Climate envelope models were fitted to European species' ranges and the climatic projections cover the whole of Europe.

Methodology for gap filling

N/A

Methodology references

Uncertainties

Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty

MAIN DISADVANTAGES OF THE INDICATOR

Although the indicator provides a simple visual depiction of the impacts of climatic change on bird populations through time, the underlying modelling of bird trends and climatic envelopes for species are complex (although fully documented in a peer-reviewed paper). Climatic warming has led to a small number of bird species increasing in number in Europe, but a much larger number declining in number, so overall climatic change poses a threat to biodiversity, but individual species might still benefit from a warming environment.

    ANALYSIS OF OPTIONS

    Climate change is having a detectable effect on biodiversity at a European scale, including evidence of negative as well as positive effects on their populations.

    Data sources

    Generic metadata

    Indicator codes
    • SEBI 011
    Dynamic
    Temporal coverage:
    1980-2005
    Geographic coverage:
    Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland, United Kingdom

    Contacts and ownership

    EEA Contact Info

    Katarzyna Biala

    Ownership

    EEA Management Plan

    2010 1.2.2 (note: EEA internal system)

    Dates

    Frequency of updates

    Updates are scheduled every 5 years
    European Environment Agency (EEA)
    Kongens Nytorv 6
    1050 Copenhagen K
    Denmark
    Phone: +45 3336 7100