A quarter of all known bee species haven’t been seen since the 1990s

By Karina Shah

Eduardo E. Zattara

The number of bee species recorded worldwide has been sharply decreasing since the 1990s.

Eduardo Zattara and Marcelo Aizen at the National University of Comahue in Argentina analysed how many wild bee species are observed each year as recorded in the Global Biodiversity Information Facility – a publicly available platform where researchers and citizens can record sightings of bee species.

They found that there were a quarter fewer species reported between 2006 and 2015, as compared with the records we have from before 1990.

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The decline is especially alarming considering the number of bee records in this database has increased by around 55 per cent since 2000, so it isn’t down to a lack of observations.

“Our work is the first long-term assessment of global bee decline,” says Zattara. Previous bee research has been confined to a specific species or a particular location.

The researchers found that the decline isn’t consistent across all bee families. Records of the rare Melittidae family of around 200 bee species have fallen by as much as 41 per cent since the 1990s, versus 17 per cent for the more common Halictidae family.

It may not necessarily mean unrecorded bee species are extinct, but they are now rare enough that people who tend to report bee sightings aren’t encountering them.

The destruction of natural habitats, heavy use of pesticides and climate change could explain this decline in species richness, says Zattara.

“We are producing more food to feed our growing population,” says Zattara. “[We are] using highly economically convenient ways to grow single-culture crops, which is removing a lot of the bees’ natural habitat.”

The global decline in species mirrors what has previously been reported in Britain. But the researchers note that studies in more remote areas are needed to gain a full picture, as most existing data comes from North America and Europe, where it may be easier to record bee species.

For example, it is easier to record and identify wildlife in places where people have increased access to smartphones with high quality cameras, says Gary Powney at the UK Centre for Ecology and Hydrology, who is worried about the findings. “These declines are alarming for both food security and the health of the natural world.”

Journal reference: One Earth, DOI: 10.1016/j.oneear.2020.12.005