Modelling the Distribution of Santalum freycinetianum on Oʻahu, Hawaiʻi Using Bioclimatic Variables, Several Climate Scenarios and MaxEnt

Abstract

Experts in Hawaiian ecosystems have determined that one species of endemic Hawaiian Sandalwood, Santalum freycinetianum Gaudich. var. freycinetianum, referred to by native Hawaiians as iliahi, was once a widespread species within native ecosystems. It is estimated that over 90% of its population has been extirpated. Using MaxEnt, a series of distributions were calculated to identify suitable habitat variables and to predict the potential spatial distribution for the species S. freycinetianum on the island of Oʻahu in several climatic situations. Using a set of geographic points of species occurrence and a suite of environmental variables, areas with potential for successful restoration were identified. Occurrence data includes (a) historical georeferenced (1927-2006) and (b) current field-verified populations within the study area of O'ahu (2010-2012). The Bishop Museum Herbarium collection provided occurrence data from 40 previously documented sites, and 49 total locations with S. freycinetianum were investigated. Ten unique SDMs were produced to predict and rank suitable habitat for S. freycinetianum across four different climate scenarios (one current, one past, two future). Habitat suitability results from all models using coarse resolution climate data (1km) were very similar across different climate scenarios, suggesting that the distribution of Santalum freycinetianum may not be highly sensitive to climate change, or that these datasets are unsuitable for modeling a species distribution the island of O'ahu.