H2: Distribution of invasive non-native species and plant pests and diseases
Short Description
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 2024 in a finalised form. An interim indicator is presented here that shows trends in the number of 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 to develop the indicator drawing on existing data (for example, data on the change in distribution of invasive non-native species in freshwater, marine (coastal), and terrestrial environments in GB is available in UK Biodiversity Indicator B6 - Pressure from invasive species). Exploratory work is ongoing to consider the future finalisation of this indicator in terms of both scope and methodological design.
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.
Indicator components
Figure H2: Number of additional tree pests and diseases becoming established in England, 2000-2009 to 2013-2022
Table H2: Number of additional tree pests and diseases becoming established in England, 2000-2009 to 2013-2022
| 10 year period | Value |
|---|---|
| 2000-2009 | 7 |
| 2001-2010 | 6 |
| 2002-2011 | 6 |
| 2003-2012 | 6 |
| 2004-2013 | 4 |
| 2005-2014 | 4 |
| 2006-2015 | 4 |
| 2007-2016 | 3 |
| 2008-2017 | 4 |
| 2009-2018 | 5 |
| 2010-2019 | 4 |
| 2011-2020 | 4 |
| 2012-2021 | 4 |
| 2013-2022 | 3 |
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, remaining at this level until dropping to 3 in 2013-2022. In total, 11 tree pests and diseases became established in England in the 21 years from 2000 to 2022 and of these, the 3 ‘established’ between 2013 and 2022 are:
- 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
There has been a decrease (improvement) in the number of additional tree pests and diseases becoming established over the short, medium and long-term time 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 5 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. Summaries by 25 Year Environment Plan goal and information on indicator links are presented in the Assessment results.
Table H2: Assessment of change
| Component | Subcomponent | Period | Date range | Percentage change | Smoothing function | Assessment of change |
|---|---|---|---|---|---|---|
| H2 | None | Short term | 2008-2017 to 2013-2022 | -25.00 | Unsmoothed | Improvement |
| H2 | None | Medium term | 2003-2012 to 2013-2022 | -50.00 | Unsmoothed | Improvement |
| H2 | None | Long term | 2000-2009 to 2013-2022 | -57.14 | 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.