Worldwide occurrence records suggest a global decline in bee species richness

Feb. 25, 2021    795

This photo shows a giant Patagonian bumblebee (Bombus dahlbomii). Credit: Eduardo E. Zattara

Worldwide occurrence records suggest a global decline in bee species richness

There are over 20,000 species of wild bee, and they are fundamental to the reproduction of wild plant species and to the pollination of 85% of food crops. Decline in the abundance and diversity of bees is well established at the local level, but few large-scale, global analyses exist to assess the current state of bee diversity worldwide.

A study led by Eduardo E. Zattara from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) in Argentina analyzed historical occurrence data from the Global Biodiversity Information Facility and found that since the 1990s, up to 25% of reported bee species are no longer being reported in global records. While this does not mean that these species are all extinct, it might indicate that these species have become rare enough that no one is observing them in nature. 

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Check out the Q&A from the author, Eduardo E. Zattara, a biologist at the Pollination Ecology Group from the Institute for Research on Biodiversity and the Environment (CONICET-Universidad Nacional del Comahue). He also holds an appointment at the Smithsonian Institution, where he researches phylogeny and regeneration of ribbon worms, and in the Department of Biology at University of Indiana. 

Why is assessing bee decline so important?

“We have to remember that ‘bee’ doesn't just mean honeybees, even though honeybees are the most cultivated species. Our society's footprint impacts wild bees as well, which provide ecosystem services we depend on. Something bad is happening to the bees, and something needs to be done. We cannot wait until we have absolute certainty because we rarely get there in natural sciences. The next step is prodding policymakers into action while we still have time. The bees cannot wait.”

What surprised you about your findings?

“With citizen science and the ability to share data, records are going up exponentially, but the number of species reported in these records has been going down steadily since the 1950s and then sharply since the 1990s. It’s not a bee cataclysm yet, but what we can say is that wild bees are not exactly thriving.”

What would your colleagues take away from this work?

“It's not really about how certain the numbers are here. It's more about the trend. It's about confirming what’s been shown to happen locally is going on globally. And about the fact that much better certainty will only be achieved as more data are shared with public databases.” 

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Highlights from the study

  • This is the first large-scale global analysis of bee diversity decline, contrasting with existing studies at the local level.
  • Analysis of public occurrence reports of over 20,000 bee species shows a steady decline in the number of reported species since the 1950s and a sharp decline since the 1990s.
  • Decline in number of reported species since the 1990s averaged at 25%. However, it was not evenly distributed among bee families, ranging from 17% for halictid bees to as high as 41% for family Melittidae.

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