1 Trends in global insect abundance and biodiversity: A community-driven 2 systematic map protocol 3 Eliza M. Grames1*, Graham A. Montgomery2*, Neal R. Haddaway3,4 Lynn V. Dicks5, Chris S. 4 Elphick1,6, Tanner A. Matson1, Shinichi Nakagawa7, Manu E. Saunders8,9, Morgan W. Tingley1, 5 Thomas E. White10, Paul Woodcock11 and David L. Wagner1 6 1Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA 7 2Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA 8 3Stockholm Environment Institute, Stockholm, Sweden 9 4Africa Centre for Evidence, University of Johannesburg, Johannesburg, South Africa 10 5Conservation Science Group, Department of Zoology, University of Cambridge, UK; School of Biological Science, 11 University of East Anglia, Norwich UK 12 6Center of Biological Risk, University of Connecticut, Storrs, CT, USA 13 7Evolution & Ecology Research Centre, School of Biological and Environmental Sciences, University of New South 14 Wales, Sydney, NSW, Australia 15 8UNE Business School, University of New England, Armidale, NSW, Australia 16 9School of Environmental and Rural Sciences, University of New England, Armidale, NSW, Australia 17 10School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia 18 11Joint Nature Conservation Committee, Peterborough, UK 19 20 * These authors contributed equally to this work. 21 Abstract 22 Background: In recent decades, there has been growing concern about reported declines in insect 23 diversity and abundance, including sharp declines in some regions. These concerns have peaked 24 in the past two years with extensive media coverage and public attention focused on the potential Trends in global insect abundance and biodiversity 25 economic, social, and biological ramifications of reduced insect populations. The geographic 26 scope, rates, and magnitude of declines, however, are still largely unknown because insect 27 diversity and populations are subject to large inter-annual fluctuations, reports are scattered 28 throughout the literature in many languages, and much insect demographic data is unpublished. 29 These challenges make it difficult to understand the nature of declines, identify principal drivers, 30 and recommend conservation actions that will reap the largest benefits. 31 Methods: Using a community approach to evidence synthesis, we will assemble a dynamic 32 database of studies and datasets, both published and unpublished, that contain evidence regarding 33 long-term trends in insect populations and biodiversity. This database will be used to build a 34 living systematic map that identifies clusters of knowledge and gaps in the evidence base, which 35 will facilitate synthesis of existing knowledge clusters and will enable researchers in entomology 36 and conservation biology to prioritize future research efforts. This collaborative effort will 37 provide a comprehensive knowledge base with which researchers can begin to provide answers 38 to the important unanswered questions about global insect population and biodiversity trends. 39 1. Background 40 Recent studies documenting declines in insect abundance and biodiversity, especially from 41 Western Europe (e.g., Conrad et al. 2006, Shortall et al. 2009, Schuch et al. 2012, Hallman et al. 42 2017, Powney et al. 2019) and North America (Forister et al. 2010a, 2010b, 2016, 2018, Karban 43 & Huntzinger 2019, Mathiasson & Rehan 2019, Wepprich et al. 2019), have raised concerns of a 44 global insect conservation crisis with potentially dire consequences. The estimated 5.5 million 45 insect species globally (Stork 2018) play diverse, critical roles in their communities; insects are 46 essential pollinators, play key roles in nutrient cycling, are integral to food webs of terrestrial and 47 freshwater ecosystems, and regulate the populations of many plant and animal pests. From 2 Trends in global insect abundance and biodiversity 48 greater than 75% declines in insect biomass over three decades at sites in Germany (Hallman et 49 al. 2017), to range contractions in butterflies in the United Kingdom (Thomas et al. 2004), to 50 diversity and abundance declines in North America (Young et al. 2017, Loboda et al. 2018, and 51 references above) as well as reports from the Neotropics (Janzen and Hallwachs 2019, Lister and 52 Garcia 2018), insect abundance and biodiversity may be in decline at rates commensurate or 53 exceeding those of vertebrates (Dirzo et al. 2014). 54 Recent calls for more primary study data (Thomas et al. 2019, Wagner 2017, Montgomery et 55 al. in review), however, have brought attention to the relatively limited conclusions we can draw 56 from available primary studies because they are usually conducted at local or regional scales, 57 often proximate to areas of high human activity, across only a few years. Only a small fraction of 58 described insect species have any population monitoring programs, and the widespread lack of 59 baseline data for insect populations, high inter-annual variation in insect population levels, 60 potential publication biases, and the limited geographic scope of current findings are all obstacles 61 to interpretation of reported insect declines (Wagner 2020). Moreover, the relative contributions 62 of the diverse drivers of declines in abundance and biodiversity remain unclear. To better 63 understand the insect decline phenomenon, there is an urgent need to conduct rigorous synthesis 64 of existing data while working to identify and fill data and knowledge gaps. 65 Evidence synthesis incorporates information from multiple sources to inform decisions on a 66 specific issue. Systematic reviews and meta-analytical statistical tools are commonly employed 67 in evidence synthesis, and are valuable for the study of insect declines because of their ability to 68 identify and comprehensively synthesize large bodies of primary literature. Systematic mapping 69 is a relatively recently developed form of evidence synthesis (Peersman 1996, Clapton et al. 70 2009, James et al. 2016). Unlike systematic reviews, which typically aim to provide answers to 3 Trends in global insect abundance and biodiversity 71 specific questions related to impacts and effectiveness, systematic maps aim to describe the 72 nature of evidence bases, producing searchable databases of studies on a broad subject, 73 commonly acting as the first step in the evidence synthesis pathway (e.g. Haddaway et al. 2015). 74 Systematic maps are especially useful in their ability to highlight knowledge gaps and 75 knowledge clusters, helping to direct funding and guide needed primary research, whilst also 76 facilitating rapid synthesis of areas of similar studies, for example using meta-analysis. Here, we 77 aim to provide the first community-driven systematic map which will engage large numbers of 78 participants and stakeholders to synthesize literature on a topic requiring urgent attention: global 79 insect population and biodiversity trends. 80 1.1. Stakeholder engagement 81 This topic was suggested by a group of subject and evidence synthesis experts in response to 82 growing concern within the community about insect conservation, recently published papers, and 83 public discussion of insect declines. In order to develop a well-designed protocol, screen and 84 extract data from an expansive volume of evidence, and include a global body of literature 85 published in a multitude of languages, we will recruit a large group of worldwide community 86 members to drive the effort. We will develop a database of potentially interested community 87 members and organizations and request suggestions from community members for additional 88 stakeholders, and actively seek participants from underrepresented areas and disciplines. The full 89 stakeholder engagement and identification plan for this project is outlined in a supporting 90 document (Grames and Montgomery 2019). 4 Trends in global insect abundance and biodiversity 91 2. Objective of the review 92 We aim to assemble a thorough set of evidence, including both published and unpublished 93 studies and datasets, relating to global insect population trends, which will be used to populate a 94 detailed, interrogable systematic map database. We will visualize this database using interactive 95 evidence atlases, heat maps and other diagnostic plots along with a narrative synthesis. Our 96 systematic map will address the following review questions: 97 Where are knowledge clusters and gaps in temporal trends of insect abundance, 98 biomass, diversity, and geographic range? 99 What knowledge clusters exist that are amenable to quantitative analysis? 100 What knowledge gaps warrant further funding and attention in the form of primary 101 research studies? 102 2.3. Question components: POCS statement 103 Population: We will include studies of native, naturalized, and invasive insects in all 104 terrestrial and freshwater habitats globally. 105 Outcomes: We are interested in studies that test for changes in four outcome measurements 106 for insects: 1) geographic range 2) species occurrence or abundance 3) species richness and other 107 diversity indices, and 4) biomass. 108 Comparator: The comparator will be the previous year(s) in the study. We will not place any 109 restrictions on the time the study was conducted or on the timeframe over which observations 110 were made other than that data collection must span multiple years; the minimum time series 111 length for a study to be included