Heavy grazing by extremely high densities of reindeer (Rangifer tarandus) on St. Matthew Island resulted in degradation of lichen stands. Grasses, sedges, and other vascular plants initially increased in response to the removal of lichens under heavy grazing pressure by reindeer. 22-years following the crash die-off of the reindeer, mosses had invaded large portions of the ground area denuded of lichens, and lichens had recovered to only 10% of the standing crop of living lichen biomass occurring on adjacent Hall Island where there is no history of grazing. Vegetation composition on both islands consisted mainly of a lichen mat before the introduction of reindeer, then shortly after reindeer introduction, shrubs, grasses, and forbs increased on St. Matthews Island while Hall Island remained a climax lichen community. The lichen species that were present on St. Matthews Island after 20 years of recovery were not climax species, they were less preferred, non-climax lichen species. Most likely, recovery of the lichen mat to a pre-reindeer state is going to be a very slow process.
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