Leptogium rivulare is a globally rare lichen with very restrictive habitat requirements (the periodically inundated substrate, bases of trees or rocks; Jørgensen 2007). Potential habitats are easily diminished oreven eliminated by natural processes (e.g. interference with the extent or duration of spring flooding) or the deterioration of habitats may be caused by human activities. This taxon has only a few rich subpopulations of stable condition worldwide (in Republics of Marii El and Komi, Russia, and in Ontario, Canada). In most documented locations it is represented by single or few thalli although suitable substrate is present and careful searching for the species has been performed. In six historical locations (Canada, Estonia, Finland and USA), this taxon is considered extinct.
Assessment Considering criterion A, information about population reduction is based on records of this species. Altogether 30 localities in Europe and North America are documented and of these six are considered extinct (single localities in Estonia and Finland, subpopulations in Illinois and Vermont in USA, and two subpopulations in Ontario, Canada). Population size reduction is estimated at 20% over the last three generations. This is less than 30% and thus, this species does not qualify for Vulnerable. However, future decline is projected in quality of habitat as the largest subpopulations in Canada (Ontario, Ottawa) are under threat of urban development and recreational activity. In Russia, for example in the Republics of Marii El and Komi, the pollution of rivers is another potential threat for this species as only unpolluted water streams are considered suitable for it. This species is assessed as Near Threatened.
Assessor/s: Randlane, T.; Reviewer/s: Scheidegger, C. & McMullin, T.; Contributor(s): Aptroot, A., Spribille, T., Perez-Ortega, S & Paukov, A.
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