title: Estimating local biodiversity change: a critique of papers claiming no net loss of local diversity.
abstract: Global species extinction rates are orders of magnitude above the background rate documented in the fossil record. However, recent data syntheses have found mixed evidence for patterns of net species loss at local spatial scales. For example, two recent data meta-analyses have found that species richness is decreasing in some locations and is increasing in others. When these trends are combined, these papers argued there has been no net change in species richness, and suggested this pattern is globally representative of biodiversity change at local scales. Here we reanalyze results of these data syntheses and outline why this conclusion is unfounded. First, we show the datasets collated for these syntheses are spatially biased and not representative of the spatial distribution of species richness or the distribution of many primary drivers of biodiversity change. This casts doubt that their results are representative of global patterns. Second, we argue that detecting the trend in local species richness is very difficult with short time series and can lead to biased estimates of change. Reanalyses of the data detected a signal of study duration on biodiversity change, indicating net biodiversity loss is most apparent in studies of longer duration. Third, estimates of species richness change can be biased if species gains during post-disturbance recovery are included without also including species losses that occurred during the disturbance. Net species gains or losses should be assessed with respect to common baselines or reference communities. Ultimately, we need a globally coordinated effort to monitor biodiversity so that we can estimate and attribute human impacts as causes of biodiversity change. A combination of technologies will be needed to produce regularly updated global datasets of local biodiversity change to guide future policy. At this time the conclusion that there is no net change in local species richness is not the consensus state of knowledge.
authors.affiliation: Department of Biology, McGill University, Montreal, Quebec, H3A 1B1, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Gonzalez
authors.affiliation: School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Cardinale
authors.affiliation: School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Ginger R H
authors.initials: GR
authors.lastname: Allington
authors.affiliation: Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, 02125, USA.
authors.forename: Jarrett
authors.initials: J
authors.lastname: Byrnes
authors.affiliation: School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: K
authors.initials: K
authors.lastname: Arthur Endsley
authors.affiliation: School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Brown
authors.affiliation: Department of Biology, Western Washington University, Bellingham, Washington, 98225, USA.
authors.forename: David U
authors.initials: DU
authors.lastname: Hooper
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota, 55108, USA.
authors.forename: Forest
authors.initials: F
authors.lastname: Isbell
authors.affiliation: Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1A4, Canada.
authors.forename: Mary I
authors.initials: MI
authors.lastname: O'Connor
authors.affiliation: Centre for Biodiversity Theory and Modelling, Theoretical and Experimental Ecology Station, CNRS and Paul Sabatier University, 09200, Moulis, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Loreau
mesh_terms: D044822:Biodiversity; D003247:Conservation of Natural Resources; D004463:Ecology; D053476:Extinction, Biological; D006801:Humans
keywords: Anthropocene; baselines; biodiversity monitoring; extinction; invasion; meta-analysis; species richness; time series