Securing Biodiversity in Breckland - European Commission

Losses of Characteristic LichensOf the assemblage of rare crustose lichens growing on compacted exposed chalk, two were restrictedto Breckland in the UK and a third was only recorded inland in the Breckland. These species havebeen subject to surveillance and survey over the last three decades and this shows that: the Starry Breck Lichen Buellia asterella is now extinct in the UK (post 1997). by 2002 the Scaly Breck Lichen Squamarina lenitigera (restricted to Breckland within the UK)had been lost from three of the four sites at which it still occurred in the 1980s and nowsurvives as only c.10 thalli at a single site (B. Nichols pers. comm.). Scrambled-Egg Lichen Fulgensia fulgens within the UK known inland at only a single locality inthe Wangford area of Breckland (where it had been recorded since the late 1800s), wasextirpated in Breckland in 1993 or shortly after.Breckland colonies of these species occurred on areas of exposed chalk drift created between 1880-1945, by flint mining, soil trenching, track-ways, removal of material for road building and creation ofanti-glider trenches and mounds. There was a long delay before it was recognised that physicaldisturbance and creation of fresh bare chalk was essential for the rejuvenation and continued vigourof colonies. Other factors including encroaching trees, reduced wind and drought exposure andpossible effect of aerial nitrogen deposition may also have contributed to declines and losses 2 . Turfstripping was eventually carried out at Lakenheath Warren in 1997 and a positive response ofSquamarina lentigera and Buellia asterella was initially noted. Turf stripping was also carried out atother key sites in the late 1990s (including Weeting and Thetford Heaths). However, by this timeFulgensia fulgens had already been lost, despite attempts at translocation, Squamarina lentigera wasrestricted to just two colonies and Buellia asterella to a single locality, with surviving colonies of bothspecies already greatly reduced in extent. At Lakenheath Warren the last remnants of Buelliaasterella and Squamarina lentigera were lost following introduction of cattle grazing to the site in2000. Following loss of the original Squamarina lentigera colony at Weeting Heath in 1990/91(Gilbert 1991), a new colony of this species was discovered at this site by Bev Nichols in 1997, thatinitially appeared to be stable in numbers, but this too now appears to be extinct, despite attemptsto create suitable new exposed chalk substrate.Recommendation: Surveillance and monitoring of created chalk exposures should be repeated intermittently toexamine whether rare terricolous lichen species re-colonise by long-distance spore transport.2 For a long time air pollution was blamed as causing simultaneous region-wide declines in these rare lichens andcertainly may have been a synergistic and contributing factor. However, in 1991 vigorous and thriving colonies ofSquamarina lentigera occurred where bare compacted chalk was rejuvenated along a trackway, while abundant fruitingof larger thalli was noted at remaining colonies at declining sites in 1992 and 1997. Data held by Natural England showsthat, between 1973-1991, at Lakenheath Warren, most colonies were encroached by perennial grasses, Hieraciumpilosella, Cladonia rangiformis and creeping mosses (particularly Hypnum cupressiforme). Crucially, the surface pH ofsubstrates was reduced, Watt (1940) recorded pH 7.9-8.2 for the top 4cm of Grassland A sites (Gilbert 1991; Hitch &Lambley 1993) in contrast on the Fulgensia mounds in 1991, values were substantially lower (pH 7.0-7.6 for soil 0-2cm or0-4cm).108