Moving beyond presence and absence when examining changes in species distributions. (15th February 2017)

• Record Type: Journal Article
• Authors: Ashcroft, Michael B.; King, Diana H.; Raymond, Ben; Turnbull, Johanna D.; Wasley, Jane; Robinson, Sharon A.
• Is Part Of: Global change biology. Volume 23:Number 8(2017)
• Page Start: 2929
• Page End: 2940
• Publication Date: 2017-02-15
• Subjects: Antarctic mosses -- climate change -- geographic range -- negative binomial distribution -- population abundance -- presence‐absence data -- range shifts; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13628
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Species distributions are often simplified to binary representations of the ranges where they are present and absent. It is then common to look for changes in these ranges as indicators of the effects of climate change, the expansion or control of invasive species or the impact of human land‐use changes. We argue that there are inherent problems with this approach, and more emphasis should be placed on species relative abundance rather than just presence. The sampling effort required to be confident of absence is often impractical to achieve, and estimates of species range changes based on survey data are therefore inherently sensitive to sampling intensity. Species niches estimated using presence‐absence or presence‐only models are broader than those for abundance and may exaggerate the viability of small marginal sink populations. We demonstrate that it is possible to transform models of predicted probability of presence to expected abundance if the sampling intensity is known. Using case studies of Antarctic mosses and temperate rain forest trees, we demonstrate additional insights into biotic change that can be gained using this method. While species becoming locally extinct or colonising new areas are extreme and obviously important impacts of global environmental change, changes in abundance could still signal important changes in biological systems and be an early warning indicator of larger future changes. Abstract : Species distributions are often portrayed as binary representations of where they are present and absent. These are useful as rough guides but boundaries are virtually impossible to delineate accurately as the sampling effort to be certain of absence is prohibitive and populations near boundaries can be sparse and temporally variable. In this article, we highlight the advantages of focusing on relative abundance rather than presence‐absence and demonstrate methods that can be used to convert probabilities of presence to expected abundance. This has implications for climate change predictions and the management of invasive species and land‐use change.