Species-area relationships and biodiversity loss in fragmented landscapes.

Ryan A Chisholm,Wei Wei Seah,Yi Shuen Yeoh,Felix Lim,James Rosindell,Richard Condit,Fangliang He

doi:10.1111/ele.12943

Abstract

To estimate species loss from habitat destruction, ecologists typically use species–area relationships, but this approach neglects the spatial pattern of habitat fragmentation. Here, we provide new, easily applied, analytical methods that place upper and lower bounds on immediate species loss at any spatial scale and for any spatial pattern of habitat loss. Our formulas are expressed in terms of what we name the ‘Preston function’, which describes triphasic species–area relationships for contiguous regions. We apply our method to case studies of deforestation and tropical tree species loss at three different scales: a 50 ha forest plot in Panama, the tropical city‐state of Singapore and the Brazilian Amazon. Our results show that immediate species loss is somewhat insensitive to fragmentation pattern at small scales but highly sensitive at larger scales: predicted species loss in the Amazon varies by a factor of 16 across different spatial structures of habitat loss.

Highlights

To estimate the number of species lost as a result of habitat destruction, ecologists typically turn to species–area relationships (SARs), which take habitat area as an input and give species richness as an output
How many species are lost when an area of grassland goes under the plough or a forest falls by the axe? Ecologists have pondered the species–area question for almost a century (Arrhenius 1921), but have only recently come to grapple with the spatial nature of the problem, with the help of advanced computer simulations and mathematics (Durrett & Levin 1996; Rosindell & Cornell 2007; O’Dwyer & Green 2010; Grilli et al 2012)
We have compartmentalised the problem by first designating the ‘Preston function’ to be the wellstudied triphasic contiguous SAR that emerges from a spatial neutral model, and deriving new formulas that relate this existing work to a range of new fragmented SAR scenarios (Fig. S3)

Summary

Introduction

To estimate the number of species lost as a result of habitat destruction, ecologists typically turn to species–area relationships (SARs), which take habitat area as an input and give species richness as an output. This approach has several limitations (Lewis 2006). While traditional SARs assume that species persist only in remnant habitat areas, in practice some species may persist in non-habitat areas too. We retain the assumption that species live only inside habitat areas in order to focus on the third major limitation of the traditional species–area approach: the assumption that total habitat area is the only spatial parameter of importance. Fragmentation and spatial structure – of both habitat loss and species distributions – are critical

Methods

Results

Conclusion