Brian Enquist1, Xiao Feng2, Brad Boyle3, Brian S. Maitner4, Erica Newman5, Peter M. Jørgensen6, Patrick Roehrdanz7, Barbara Thiers8, Robbie Burger9, Richard T. Corlett10, Thomas Couvreur11, Gilles Dauby12, John C. Donoghue II4, Wendy Foden13, Pablo A. Marquet14, Cory Merow15, Guy F. Midgley16, Naia Morueta-Holme17, Danilo Neves4, Ary T. Oliveira-Filho18, Nathan Kraft19, Daniel S. Park20, Robert K. Peet21, Michiel Pillet22, Josep M. Serra-Diaz23, Brody Sandel24, Mark Schildhauer25, Irena Śimová26, Cyrille Violle27, Jan J. Wieringa28, Susan K. Wiser29, Lee Hannah30, Jens-Christian Svenning31 and Brian McGill32, (1)The Santa Fe Institute, Santa Fe, NM, (2)Institute of the Environment, Florida State University/University of Arizona, AZ, (3)Ecology and Evolutionary Biology Department, University of Arizona, Tucson, AZ, (4)Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, (5)Ecology and Evolutionary Biology, University of Arizona, TUCSON, AZ, (6)Missouri Botanical Garden, St. Louis, MO, (7)Conservation International, Washington DC, DC, (8)William and Lynda Steere Herbarium, The New York Botanical Garden, Bronx, NY, NY, (9)Biology, University of Kentucky, Lexington, KY, (10)Department of Biological Sciences, National University of Singapore, Singapore, (11)DIADE, IRD, Université Montpellier, Montpellier, France, (12)AMAP, IRD, CIRAD, CNRS, INRA, Université Montpellier, Montpellier, France, (13)Cape Research Centre, Cape Town, South Africa, (14)Santa Fe Institute, Santa Fe, NM, (15)Department of Ecology and Evolutionary Biology, University of Connecticut, Storss, CT, (16)Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa, (17)University of Copenhagen, Center of Macroecology, Evolution and Climate, Copenhagen, Denmark, (18)Programa de Pós-graduação em Biologia Vegetal, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, (19)Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, (20)Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, (21)Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, (22)Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, (23)Department of Biosciences, Aarhus University, Aarhus, Denmark, (24)Department of Biology, Santa Clara University, Santa Clara, CA, (25)National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, CA, (26)Center for Theoretical Study, Charles University in Prague and Academy of Sciences of the Czech Republic, Praha, Czech Republic, (27)Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Montpellier, France, (28)National Herbarium of The Netherlands, Wageningen University Branch, Wageningen, Netherlands, (29)Landcare Research, Lincoln, New Zealand, (30)Donald Bren School of Environmental Science & Management, University of California, Santa Barbara, Santa Barbara, CA, (31)Department of Biology, Section for Ecoinformatics and Biodiversity, Aarhus University, Aarhus, Denmark, (32)School of Biology and Ecology / Mitchell Center for Sustainability Solutions/Mitchell Center for Sustainability Solutions, University of Maine, Orono, ME
Background/Question/Methods
A key feature of life’s diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Rare species are orders of magnitude more likely to go extinct, making it puzzling how so many rare species can be maintained. Understanding rarity and the maintenance of rare species is also central to conservation biology and to understanding current and future changes in biodiversity due to global change. Despite this importance, we know unexpectedly little about the causes of commonness and rarity and their maintenance at a global scale Here, we use a global botanical database of unprecedented coverage to (i) assess global patterns of plant rarity, (ii) test several proposed hypotheses underlying the generation and persistence of rare species, (iii) identify regions that harbor hotspots of rare species and explore the drivers of these spatial patterns, and (iv) assess how current patterns of human impact and future climate change scenarios may affect plant diversity via impacts on rare species. For all known land plants (Embryophyta), we have compiled a global database of standardized botanical observation records—the integrated Botanical Information and Ecology Network (BIEN); http://bien.nceas.ucsb.edu/bien/. Together, these data constitute more than 200 million observations of plant species occurrences.
Results/Conclusions
A large fraction, ~36.5% of Earth’s ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results have important implications for conservation in the face of climate change and other human impacts. If ~36% of species are rare and threatened, then ~158,000 plant species are at risk of extinction. In addition, our analyses show that rapid rates of current human impact and projected future climate change appear to disproportionately affect regions that harbor most of these rare species, whereas the rare species likely have been in relatively more stable climates through their evolutionary history. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth’s plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.
