Assessing species richness trends: Declines of bees and bumblebees in the Netherlands since 1945

Abstract

Estimating and predicting temporal trends in species richness is of general importance, but notably difficult because detection probabilities of species are imperfect and many datasets were collected in an opportunistic manner. We need to improve our capabilities to assess richness trends using datasets collected in unstandardized procedures with potential collection bias. Two methods are proposed and applied to estimate richness change, which both incorporate models for sampling effects and detection probability: (a) nonlinear species accumulation curves with an error variance model and (b) Pradel capture–recapture models. The methods are used to assess nationwide temporal trends (1945–2018) in the species richness of wild bees in the Netherlands. Previously, a decelerating decline in wild bee species richness was inferred for part of this dataset. Among the species accumulation curves, those with nonconstant changes in species richness are preferred. However, when analyzing data subsets, constant changes became selected for non‐Bombus bees (for samples in collections) and bumblebees (for spatial grid cells sampled in three periods). Smaller richness declines are predicted for non‐Bombus bees than bumblebees. However, when relative losses are calculated from confidence intervals limits, they overlap and touch zero loss. Capture–recapture analysis applied to species encounter histories infers a constant colonization rate per year and constant local species survival for bumblebees and other bees. This approach predicts a 6% reduction in non‐Bombus species richness from 1945 to 2018 and a significant 19% reduction for bumblebees. Statistical modeling to detect species richness time trends should be systematically complemented with model checking and simulations to interpret the results. Data inspection, assessing model selection bias, and comparisons of trends in data subsets were essential model checking strategies in this analysis. Opportunistic data will not satisfy the assumptions of most models and this should be kept in mind throughout.

Citizen science involving farmers as a means to document temporal trends in farmland biodiversity and relate them to agricultural practices

“…These findings are in line with recent studies showing a decline in bees and butterflies, whether on a local (Hallmann et al, 2019), regional (Habel, Trusch, Schmitt, Ochse, & Ulrich, 2019), national (Dooren, 2019) or global scale (Sánchez-Bayo & Wyckhuys, 2019;van Klink et al, 2020). Soil taxa, including potentially flying species but with short-distance daily movements, such as beetles, show a more mixed picture, with a temporal decline in abundance in meadows and orchards but a more surprising increase in field crops and vineyards.…”

Butterfly communities track climatic variation over space but not time in the Iberian Peninsula

“…Opportunistic historical records from museum specimens and publications often represent the only evidence of species distributions and community composition before pronounced climate warming in the late twentieth century (Kharouba et al ., 2019; Montgomery et al ., 2020). In some cases, these historical data have been used to provide evidence of changes to insect distributions or diversity over the past century or more (Eskildsen et al ., 2015; Habel et al ., 2016, 2019; Lewthwaite et al ., 2017; Van Dooren, 2019; van Strien et al ., 2019). Historical data are subject to possible effects of sampling bias, including spatial or temporal variation in recorder activity, which complicates interpretation of changes to species distributions, abundance, or richness (Ries et al ., 2019; Didham et al ., 2020).…”

Endosymbionts that threaten commercially raised and wild bumble bees (Bombus spp.)

“…Bumble bees (Bombus species) are widespread globally, but most prevalent and diverse at high altitudes and high latitudes, where they can constitute a large proportion of the pollinator fauna. There is reason for concern about their status, as declines have been reported around the world (Arbetman et al 2017;Graves et al 2020;Soroye et al 2020;Van Dooren 2019), and a North American species has been listed as endangered and hasn't been seen since 2006 (https://biologicaldiversity.org/w/news/pressreleases/elusive-pacific-northwest-bumblebeelisted-as-endangered-2021-08-23/; accessed 18 January 2023). Bumble bees are important pollinators for both wild and cultivated plants, and there is now a thriving trade in commercial colonies, shipped to many parts of the world, for pollination of crops such as tomatoes, blueberries, and raspberries, both in greenhouses and open fields (Velthuis & van Doorn 2006).…”