Improving estimates of biodiversity loss Chase D. Mendenhall a,⇑ , Gretchen C. Daily a , Paul R. Ehrlich a a Center for Conservation Biology, Department of Biology, Stanford University, Stanford, CA 94305-5020, USA article info Article history: Received 26 August 2011 Received in revised form 29 January 2012 Accepted 31 January 2012 Available online xxxx Keywords: Agriculture Countryside biogeography Endemics-area relationship Extinction rates Species-area relationship Population diversity abstract Quantifying the magnitude of human-induced biodiversity loss is a critical yet daunting challenge. Recently, species extinction rate estimates using island biogeography theory have once again been called into question. Here we highlight two of the many factors making the traditional application of this approach problematic for measuring biodiversity loss: first, the extreme assumption that native habitats are surrounded by a sea of human enterprise largely incapable of sustaining native biodiversity and, sec- ond, the sole use of species-level extinction estimates, which always underestimates the loss of biodiver- sity. Here we show that a wide array of taxa make human-dominated, farming countryside their home beyond the borders of native habitats. With data on native tropical birds, we show how simple species numeration masks dramatic differences between habitat types in community composition (e.g. species diversity or functional diversity). Overlooking the countryside biota, coupled with a scientific paradigm that underestimates biodiversity loss by equating it with species extinction, will only exacerbate the ongoing crisis. This is especially true given the rapid expansion and intensification of agriculture threat- ening countryside biotas, and a persistent limited understanding of how population extinctions and changes in community composition alter ecosystem functioning and services that support human life and wellbeing. Ó 2012 Elsevier Ltd. All rights reserved. Navjot S. Sodhi dedicated his life to understanding and reversing the biodiversity loss now sweeping the planet. Ecologists recognize Earth’s biota is now already experiencing the sixth great extinction wave, but nonetheless quantifying its pace mid-stride remains difficult. Problems of estimating biodiversity loss persist, partly be- cause of the limitations and continued interpretation of species- area relationships (SAR) for estimating species extinction. The use of the SAR as the sole method for estimating biodiversity loss per- petuates the idea that only pristine habitats matter for conservation and dramatically underestimates biodiversity loss by ignoring pop- ulation and community changes. We examine the conventional assumptions that human-dominated habitats and landscapes are largely incapable of sustaining native biodiversity and that the bio- diversity crisis is best viewed by evaluating species extinction. Thirty years ago, extinction rates were estimated using the clas- sical framework of island biogeography (MacArthur and Wilson, 1967). The prevailing view was that the clues to the future of bio- diversity were to be found in remnants of native habitat – Noah’s Arks floating in a hostile flood of human enterprise. The logic was that most organisms are highly adapted to their native habi- tats and that few would be able to exploit areas heavily modified by human activities. In general, those few species would not require or merit protection and efforts should concentrate on preserving ecosystems in their pristine forms removed from areas of high human activity. A great deal of work has now reported that, to the contrary, hu- man-dominated ecosystems (currently constituting 75% of the glo- bal land surface; Ellis et al., 2010) collectively host substantial biodiversity, and that this reservoir of biodiversity is under threat from rapid intensification of agricultural production systems and other factors associated with human population growth and con- sumption (Bignal and McCracken, 1996; Fischer et al., 2008; Haslem and Bennett, 2008; Hughes et al., 2002; Perfecto et al., 2009). New theory (Koh et al., 2010; Nelson et al. 2011; Pereira et al. 2004; Pereira and Daily 2006;) and empirical study (Menden- hall et al., 2011) show how, for instance, many ‘‘tropical forest ani- mals’’ can make their homes outside of native habitats, and their ability to do so varies with a range of species traits (Daily, 2001; Daily et al., 2001, 2003; Horner-Devine et al., 2003; Ricketts, 2001; Sekercioglu et al., 2007). Moreover, different individuals within a population may use combinations of habitat that do not fit within the confines of the island paradigm (Fig. 1). Only a small fraction of the planet can be considered either pristine or com- pletely inhospitable, with the vast majority of biodiversity existing in habitats located somewhere in between (Ellis et al., 2010). Understanding how to sustain biodiversity and ecosystem pro- cesses and services in these habitats requires much more attention. There is tremendous opportunity to harmonize the conserva- tion of biodiversity with human activities in biomes worldwide. 0006-3207/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2012.01.069 ⇑ Corresponding author. Tel.: +1 650 723 3171; fax: +1 650 723 5920. E-mail address: cdm@stanford.edu (C.D. Mendenhall). Biological Conservation xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Please cite this article in press as: Mendenhall, C.D., et al. Improving estimates of biodiversity loss. Biol. Conserv. (2012), doi:10.1016/j.biocon.2012.01.069