Bee species decrease and increase between the 1990s and 2018 in large urban protected sites

Michaela M Hofmann,Susanne S Renner

doi:10.1007/s10841-020-00238-y

Michaela M Hofmann, Susanne S Renner

Open Access

https://doi.org/10.1007/s10841-020-00238-y

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Abstract

Previous work has shown that among 428 species of bees occurring in Germany, decline or extinction over the past 40 years have been correlated with late-season emergence and restricted habitats, while other factors, such as pollen specialization, body size, nesting sites, and sociality, played no role in models that included a phylogeny of these bees. Doing best are spring-flying, city-dwelling species. Building on these results, we here investigate changes in bee diversity from the 1990s to 2018 at three protected sites within the city perimeter of Munich, focusing on the correlates of flight season (spring or summer), flight duration (in months), and number of habitats (one or two vs. three to six). Local species pools were assessed against the total species pool from 1795 onwards. Twenty years ago, 150 species were present at one or more of the sites, while in 2017/2018, this was true of 188 species, with the increase at two sites being of similar proportion. In two of the three areas, broad habitat use was positively correlated with persistence. Flight season or duration had no statistical effect. These results underscore the function of urban protected sites in bee conservation and imply that summer food shortages, which negatively affect bees in agricultural areas, play no role in urbanized regions so that late-season flight is not an extinction handicap.

Highlights

If the current rate of urbanization stays unchanged, models predict an increase in urban land cover by 1.7 million km2 by 2050, which would be approximately 1.4 times the area of 2012 (Zhou et al 2019)
We focus on bees, whose decline in European agricultural areas has been linked to parasites, pesticides, and lack of flowers (Goulson et al 2015; Seibold et al 2019)
From 1945 until 1957, the depot was owned by the US army, which used it as the Virginia Area Storage Facility

Summary

Introduction

If the current rate of urbanization stays unchanged, models predict an increase in urban land cover by 1.7 million km by 2050, which would be approximately 1.4 times the area of 2012 (Zhou et al 2019). Urbanization commonly is accompanied by surface sealing, reduced foraging and nesting sites for animals, light pollution, dense traffic, and other anthropogenic stressors. It reduces species richness and evenness for most biotic communities (Grimm et al 2008; Hernandez et al 2009). The degree of urbanization within cities varies, and studies have found high small-scale heterogeneity, providing conservation opportunities (Baldock et al 2019). This may be especially true for animals. We focus on bees, whose decline in European agricultural areas has been linked to parasites, pesticides, and lack of flowers (Goulson et al 2015; Seibold et al 2019)

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