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This project assessed the potential ecological impact of the disease ash dieback on UK woodlands and species and investigated possible solutions which might be achieved through woodland management.

Research objectives

  • Identify ecological function of ash (decomposition, litter quality, nutrient cycling)
  • Identify ash-associated species
  • Assess suitability of alternative tree species
  • Develop management options and assess changes in woodland following infection of ash dieback in the 9 ash-relevant regions of the UK
  • Evaluate the short and long term impacts on ash related biodiversity of ash dieback
  • Develop resources (tools and case studies) for woodland managers


The research shows:

  • Ash is extreme in its ecological function
  • There are 953 species that use ash (ash-associated species) in the UK
  • Of the 48 alternative tree species assessed oak beech and sycamore are used by the most ash-associated species but other tree species were more similar to ash in ecological function and traits (e.g. bark pH, tree height, leaf shape and size)
  • Impact of ash dieback on obligate and highly ash-associated species in the short-term (1-10 years) was least with management scenarios (1) non-intervention and (2) no felling with natural regeneration promoted, was intermediated with (5) thinning and (6) felling with natural regeneration, and worst with scenarios (3) felling and (4) felling and replanting. In the long-term (50-100 years) there was little difference in impact between the scenarios with most species predicted to decline or risk extinction (scenarios predict >95% loss of ash trees)
  • Partially associated species are predicted to decline initially under all management scenarios following the arrival of ash dieback but after 50-100 years the majority are predicted to recover to (and some even exceed) current population levels

About the project

Carried out in two phases, the multi-funded project was delivered by a consortium of research organisations.


  • JNCC- (led Phase 1),
  • Natural England (led Phase 2)
  • Department of the Environment Northern Ireland
  • Forestry Commission
  • Scottish Natural Heritage
  • Natural Resources Wales


  • The James Hutton Institute (led Phase 1 & 2)
  • Forest Research
  • Royal Botanic Garden Edinburgh
  • University of Aberdeen
  • RSPB
  • Independent Bryologist

Project outputs:

• 15 case studies illustrate the procedure that managers can follow for individual sites to assess impact of ash-die back on ash-associated species in broadleaved woodland, and develop appropriate management responses.

• a database of information about ash-associated species, and the use that these species make of tree species other then ash (native and non-native)


  • Ash dieback (or ‘Chalara’), is the fungal tree disease which is increasingly affecting ash (Fraxinus excelsior) trees in the UK
  • Ash trees are important for biodiversity
  • Ash dieback could affect biodiversity with consequences for species conservation through to impacts on woodland ecosystem health
  • Deciding how to manage woodlands infected by ash dieback that also conserves biodiversity is an important issue


Started February 2013 and was completed in March 2014.


Alice Broome

Alice Broome

Senior Scientist - Priority species/ habitats