This indicator will show changes in the distribution of non-native invasive species and plant pests that have already established in England. Preventing the spread of invasive non-native species limits their ability to disrupt ecosystems and cause economic damage. Plant pests and diseases cause significant negative impacts and it is often more difficult to prevent their entry and establishment, therefore limiting spread is critical in preventing negative impact on native species and ecosystems. This indicator will utilise distribution data for a reference subset of priority invasive species and plant pests and diseases as an indication of the success of biosecurity measures in controlling their spread.
Readiness and links to data
This indicator is not available for reporting in 2023 in a finalised form. An interim indicator is presented here that shows trends in the number of additional tree pests and diseases becoming established in England since the year 2000. These data are published in the Forestry Commission’s Key Performance Indicators Reports.
Further work is required to identify species for inclusion and to develop the indicator drawing on existing data. The forthcoming review of the Outcome Indicator Framework in 2024 will consider future finalisation of this indicator in terms of both scope and methodological design, and new exploratory work is already ongoing.
Notes on indicator
This indicator enumerates those additional tree pests and diseases formally considered as becoming ‘established’ by the UK Plant Health Risk Group within a rolling 10-year period. Establishment is defined as ‘perpetuation, for the foreseeable future, of a pest within an area after entry’. This is the definition produced by the Secretariat of the International Plant Protection Convention.
It is not possible to sum the number of additional tree pests and diseases becoming established within each 10-year period to calculate the total number becoming established since 2000. This is because each tree pest or disease is included in up to 10 rolling 10-year time periods; adding them together would result in a greatly inflated total for the time period covered by this indicator.
Figure H2: Number of additional tree pests and diseases becoming established in England, 2000-2009 to 2012-2021
Table H2: Number of additional tree pests and diseases becoming established in England, 2000-2009 to 2012-2021
|10 year period||Value|
Trend description for H2
The number of additional tree pests and diseases becoming established in England within a rolling 10-year period fell from a peak of 7 in 2000 to 2009 to a low of 3 in 2007 to 2016. It subsequently increased again to 5 in 2009 to 2018 before falling to 4 in 2010 to 2019 where it has remained for 2011 to 2020 and 2012 to 2021. In total, 11 tree pests and diseases became established in England in the 21 years from 2000 to 2021 and of these, the 4 ‘established’ between 2012 and 2021 are:
- Chalara dieback of Ash (Hymenoscyphus fraxineus), considered established in 2012.
- Oriental chestnut gall wasp (Dryocosmus kuriphilus), considered established in 2016.
- Sweet chestnut blight caused by the fungus Cryphonectria parasitica, considered established in 2017.
- The Elm zigzag sawfly (Aproceros leucopoda), considered established in 2018, following a rapid expansion across Europe from eastern Asia
Assessment of change
An increase (deterioration) was observed for the number of additional tree pests and diseases becoming established in England over the short-term assessment period. However, there has been a decrease (improvement) over the medium and long term. However, this deterioration is due to a reduction in the number of additional tree pests and diseases becoming established in the baseline time period for this year’s short-term assessment (2007 to 2016) compared with the baseline time period for last year’s assessment (2006 to 2015); the actual number of additional tree pests and diseases becoming established in the most recent time period (2012 to 2021) has remained the same for the last 3 reporting periods. There has been a decrease (improvement) over the medium and long-term assessment periods
Change since 2018 has also been assessed. There has been a decrease (improvement) in number of additional tree pests and diseases becoming established since 2018. However, this is based on only 4 data points so should be considered as indicative and not evidence of a clear trend.
Further information on this assessment, along with details on the methodology, is provided in the Assessment background page. Summaries by 25 Year Environment Plan goal and information on indicator links are presented in the Assessment results pages.
Table H2: Assessment of change
|Component||Subcomponent||Period||Date range||Percentage change||Smoothing function||Assessment of change|
|H2||None||Short term||2007-2016 to 2012-2021||33.33||Unsmoothed||Deterioration|
|H2||None||Medium term||2002-2011 to 2012-2021||-33.33||Unsmoothed||Improvement|
|H2||None||Long term||2000-2009 to 2012-2021||-42.86||Unsmoothed||Improvement|
Note that percentage change refers to the difference seen from the first to last 10-year rolling time period in the specified date range.