Conservation
Collema dichotomum - fruiting body close up.
The populations of the river jelly lichen have declined in many parts of its European distribution range. The UK Action Plan for the river jelly lichen lists the following threats for this species:
- eutrophication of streams
- increased silt loads in rivers and streams
- water acidification
- reduced water levels caused by water abstraction, e.g. from small-scale hydroelectric schemes
In the UK a new threat may result from the re-introduction of beavers, as these animals cause clearing of deciduous trees from the riverbanks and change the character of water course from rapid streams to a series of ponds with slow current. Both of these factors are important for the survival of Collema dichotomum.
If global warming has the predicted effects of raised temperatures and an increasing tendency towards “extreme” weather conditions (elongated dry periods and higher frequency of short heavy local rainfall events) a further threat to this species will be the loss of constantly cool waterbodies.
The species may be suitable as an early warning system for changes in freshwater habitats, but in the UK there are still large gaps in the recording of its distribution. Due to its rarity this species should not be collected. Nevertheless, good photographs with precise information on its location can contribute to a better understanding of its recent distribution and will help improve the baseline data for further research on this important freshwater lichen.