Population change in hyper-oceanic liverworts before and after hydroelectric power development: a preliminary study

Introduction. The best sites for oceanic bryophytes are typically in ravines that offer good potential for hydroelectric power (HEP) development. This preliminary study is the first to investigate population change in oceanic bryophytes of conservation concern at a site subject to HEP development.

Methods. Populations of five hyperoceanic liverworts were measured, Aphanolejeunea microscopica, Drepanolejeunea hamatifolia, Harpalejeunea molleri, Jubula hutchinsiae and Radula voluta, at two time periods, before and after HEP installation.

Results. Spanning almost four years, results reveal a dynamic system, with significant change in fine-scale distribution patterns, including many colony extinctions and colonisations. About 23% of colony losses of A. microscopica, D. hamatifolia and H. molleri appeared to result from exclusion by larger bryophytes, involving at least 17 species, in particular Ctenidium molluscum.

Conclusions. Inference with regards to effects of the HEP is not advised from this type of preliminary before and after study, based at a single site without controls. Given rapid recent growth of small HEP development and the enormous future potential, both in Britain and around the world, it is important to build upon this work and undertake comprehensive studies to detect possible impacts on bryophytes of conservation concern.