Impact Type: Direct exposure to pollutant
Key Concerns:
Most Ramalina spp. are very sensitive to SO2 which has resulted in their disappearance from much of their former range.
R. farinacea which can stand up to 60 µg m-3, but it has disappeared from some parts of its former range in north-central England, London and Central Scotland due to air pollution (Seaward & Hitch 1982).
R. fastigiata which can stand mean winter levels of SO2 up to 35 µg m-3, has disappeared from centeral and northern England (Seaward & Hitch 1982).
R. fraxinea which can also stand mean winter levels of SO2 up to 35 µg m-3, is now very rare or extinct in most of central and SE England where it was once common (Seaward & Hitch 1982).
Additional Comments:
The critical level for Ramalina spp. may need to revised downwards (Bates 2001).
| Habitat/ Ecosystem Type | Critical Load/ Level | Status | Reliability | Indication of exceedance | Reference |
|---|---|---|---|---|---|
| Forests and semi-natural vegetation |
20 µg SO2 m-3 annual mean and half-year(Oct-March) mean |
UNECE, 2004 | quite reliable i.e. the results of some studies are comparable |
Low temperature appears to enhance the negative effects of SO2, and the lower critical level of 15 µg SO2 m-3 is used where the effective temperature sum (ETS) (i.e. the sum of temperatures) above 5oC is below 1000 degree days (d.d) (Ashmore et al., 1994). |
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