The role of habitat fragmentation in Pleistocene megafauna extinction in Eurasia

Alessandro Mondanaro,Luigi Maiorano,Neil R Edwards,Pasquale Raia,Lorenzo Rook,Philip B Holden,Silvia Castiglione,Moreno Di Marco,Marina Melchionna,Mirko Di Febbraro

doi:10.1111/ecog.05939

Abstract

The idea that several small, rather than a single large, habitat areas should hold the highest total species richness (the so‐called SLOSS debate) brings into question the importance of habitat fragmentation to extinction risk. SLOSS studies are generally addressed over a short time scale, potentially ignoring the long‐term dimension of extinction risk. Here, we provide the first long‐term evaluation of the role of habitat fragmentation in species extinction, focusing on 22 large mammal species that lived in Eurasia during the last 200 000 years. By combining species distribution models and landscape pattern analysis, we compared temporal dynamics of habitat spatial structure between extinct and extant species, estimating the size, number and degree of the geographical isolation of their suitable habitat patches. Our results evidenced that extinct mammals went through considerable habitat fragmentation during the last glacial period and started to fare worse than extant species from about 50 ka. In particular, our modelling effort constrains the fragmentation of habitats into a narrow time window, from 46 to 36 ka ago, surprisingly coinciding with known extinction dates of several megafauna species. Landscape spatial structure was the second most important driver affecting megafauna extinction risk (ca 38% importance), after body mass (ca 39%) and followed by dietary preferences (ca 20%). Our results indicate a major role played by landscape fragmentation on extinction. Such evidence provides insights on what might likely happen in the future, with climate change, habitat loss and fragmentation acting as the main forces exerting their negative effects on biodiversity.

Highlights

The imprint of humans on wildlife has gone through a long history, tracing back to the Late Pleistocene, when Homo sapiens started to colonize the world biota outside its African homeland, contributing to a massive extinction crisis affecting large mammals worldwide (Rule et al 2012, Sandom et al 2014, Berti and Svenning 2020)
The effect of H. sapiens on its mammalian preys and competitors is more apparent where species were naïve to the new super-predator, that is in the Americas and Oceania, whilst the signature of human effects is milder in Africa and Eurasia and possibly superseded by the contemporary effects of intense global climate change there (Cooper et al 2015, Carotenuto et al 2016, Di Febbraro et al 2017)
Large-scale investigations on Pleistocene ecosystems and their evolution are common for North America (Tóth et al 2019, Seersholm et al 2020) and Oceania (Rule et al 2012, Hocknull et al 2020) but rare for Eurasia, despite the highquality fossil record

Summary

Introduction

The pervasive presence of humans is impacting the extension and diversity of natural habitats as well, leaving wildlife with little space to survive (Newbold et al 2015) In this context, it becomes necessary to understand how habitat availability and fragmentation will affect the chance of species survival in the long term. Fahrig (2013) proposed that species richness in a given place increases with the amount of habitat present in the surrounding area, whereas the size and isolation of individual habitat patches within the area are unimportant This ‘habitat amount hypothesis’ (HAH), implies that the degree of fragmentation, as well as any other habitat geographic configuration characteristics, does not affect the chance of species survival. The HAH debate is intriguing, both because it has no clear-cut explanation and because it contrasts with the several studies demonstrating large and well-connected habitat patches are beneficial to species’ survival (Fahrig 2003, Reed 2004, Blomqvist et al 2010, Haddad et al 2015, Lino et al 2019)

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Results

Conclusion