Lichens as an Indicator of Sea-Level Rise

Abstract

Coastal areas around the globe are threatened with sea-level rise (SLR). Many of these areas support coastal forests, and determining the threat is complicated by wind patterns and sea floor and shoreline variability, beyond simple elevational concerns. Lichens can be used as indicators of SLR at site specific locations. Developing vegetative indicators of SLR could assist land managers, municipalities, and homeowners in evaluating the risk of building homes, roads, and other structures in some locations. The absence of salt sensitive lichen species can be an indicator of SLR potential. We base this on lichen distribution patterns within two Florida state parks – one a barrier island, the other on the nearby mainland. Rapidly colonizing lichen taxa with asexual reproductive structures are poor indicators of SLR, because of their ability to quickly recolonize following storm events and other disturbances. Knowledge of lichen distribution patterns in combination with reproductive traits help facilitate the development of lichen indicator guidelines. We have learned that Coccocarpia palmicola, Dirinaria picta, and Heterodermia albicans do not appear to be salt-tolerant but have abundant asexual propagules and recolonize rapidly. Sites lacking salt sensitive lichens such as Bulbothrix laevigatula, Cryptothecia rubrocincta, Leptogium cyanescens and Parmotrema rampoddense could indicate areas that are at high risk to SLR at a fine scale. Such areas should be avoided for the construction of homes, roads, and other structures. Lichens make good indicator species and could help guide management of coastal areas in Florida and much of the U.S. southeast Coastal Plain.