Using environmental niche models to identify Malagasy bat biodiversity hotpots and conversation priorities in the face of climate and human land use changes.

Abstract

Madagascar represents a global hotspot of endemism, but it faces numerous threats to its biodiversity, including impacts of climate and human land use changes. In this study, suitable habitat space of 25 Malagasy bat species was modelled under past, current and future climate projections, asking three questions: (i) Do Malagasy bat richness hotspots change over different climatic projections and human land use in the past to present to future?; (ii) Do current and future hotspots fall within Madagascar’s current protected areas (PAs)?; and (iii) Can areas be included in the current protected areas to better protect the Malagasy bat hotspots? A decline in suitable habitat space for bat species was anticipated, and, hence, decreased hotspots under warmer (Last Inter-glacial (LIG) and future) climate scenarios, particularly in combination with human land use. It was also expected that changes in climate would influence bats similarly within functional groups (FGs) and differently across functional groups. Specifically, it was predicted that bats adapted to forage in vegetation (clutter FG) should be more affected than bats adapted to hunt insects near vegetation (clutter-edge FG) and high above vegetation (open-air FG). It was further predicted bat richness hotspots would have poor coverage by Madagascar’s PA network for current and future scenarios, due to broad distribution ranges of bats and limited area coverage of PAs across the island. Suitable habitat space was modelled for bat species using environmental niche models (ENMs), taking an ensemble modelling approach to identify the most suitable ENM for each species. Species richness was quantified by stacking suitable habitat maps of individual bat species. The results showed that richness hotspots shifted in size and geographic position under different climate change scenarios. Generally, changes from warm to cold climates decreased the potential suitable habitat space of clutter bats yet increased those of clutter-edge and open-air bat species. In contrast, changes from cold to warmer climates decreased the suitable habitats of clutter bats more than those of clutter-edge and open-air bats. Null model analyses showed that under both cold and warm climatic conditions, the observed overlap in suitable habitat between clutter and clutter-edge functional groups was lower than expected, whereas overlap in suitable habitat between clutter-edge and open-air functional groups was higher than expected by chance. Further, suitable habitat space of bat species was only partially covered by the PA system for climate change and human land use scenarios (range 2 – 20%). Although most of the bat richness hotspots are in PAs, this coverage will decrease with predicted future climate change. It is suggested that an additional 58,077 km should be added to the current protected areas to ensure adequate protection under future climate and land use.