excerpts from: Global Bee Decline
Eduardo E. Zattara*, Marcelo A. Aizen

We analyzed publicly available worldwide occurrence records from the Global Biodiversity Information Facility spanning more than a century of specimen collection. We found a steep decreasing trend in the number of collected bee species occurring since the 1990’s, which today is half from that found in the 1950’s. Our results support the hypothesis of a massive global decline in bee diversity. 


zGlobal bee decline appears to be a relatively recent phenomenon which started in the nineties, at the beginning of the globalization era, and continues to the present. Bees thrive in heterogeneous habitats, even those driven by man, where they find a diversity of floral and nesting resources. However, land devoted to agriculture, particularly to monoculture, has expanded in several regions of the world since the 1990s.

This has led not only to higher habitat homogeneity, which can relate by itself to more impoverished and spatially homogeneous bee assemblages, but also to higher use of pesticides and other agriculture chemical inputs that have direct and indirect lethal and sub-lethal effects on bee health. Effects of climate change on shrinking bee geographical ranges have been also documented in Europe and North America. 

Lastly, a booming international bee trade has involved the co-introduction of bee pathogens, that may cause bee decline, like the emblematic case of the giant Patagonian bumble bee, Bombus dahlbomii. Increasing dominance by one or a few species can be observed at the regional scale, like the case of invasive Bombus terrestris in southern South America, or globally, as seen for the western honeybee,  Apis mellifera 

Although both domesticated and wild populations of the western honeybee seem to be declining in several countries, this species is still thriving globally.  Under the best scenario, this collapse can indicate that thousands of bee species have become too rare; under the worst scenario, they may have already gone extinct. 

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bioRxiv preprint first posted online Dec. 10, 2019; doi: http://dx.doi.org/10.1101/869784. The copyright holder for this preprint (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license.

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posted by PLB

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