Scientists Sound Alarm on Global Decline of Bee Species

Since the 1990s, up to 25% of reported bee species have disappeared from scientific records, suggesting a global decline in bee diversity.

This photo shows a giant Patagonian bumblebee (Bombus dahlbomii). Four decades ago, these bees were abundant in Chile and Argentina, but now they have become an uncommon sight. (Credit: Eduardo E. Zattara)

(CN) — Since the 1990s, up to 25% of reported bee species have disappeared from scientific records, suggesting a global decline in bee diversity, according to new research published on Friday.

A study published in the journal One Earth detailed the loss of bee species.

While their disappearance does not prove whether these species of pollinators are extinct, it indicates that at least some bee species have become too rare to be routinely observed in their natural habitats, say scientists at the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) in Argentina.

This decline comes at a time of increasing digital record keeping.

“With citizen science and the ability to share data, records are going up exponentially, but the number of species reported in these records is going down,” said study author Eduardo Zattara, a biologist at the Pollination Ecology Group from the Institute for Research on Biodiversity and the Environment, in a statement. “It’s not a bee cataclysm yet, but what we can say is that wild bees are not exactly thriving.”

Small in stature, bees play an outsized role in the health of the planet by pollinating hundreds of thousands of wild flowering plant species as well as 85% of all cultivated crops.

In short, if you ate food today, thank the farmers. If you grew food today, thank the bees, for without their incessant work, the crops would not yield food.

Like most natural species, bees are attuned to their environment, making them vulnerable to native habitat changes such as large-scale agriculture and expanding urban areas. Habitat loss and diseases introduced by invading bee species, such as the large garden bumblebee, can decimate wild bee populations.

For decades, scientists have warned of declining bee populations, but those findings generally focus on specific regions or types of bees. Zattara and fellow researcher Marcelo Aizen, who works with Zattara at CONICET, wanted a global perspective on potential threats to bees.

Together, the pair explored the Global Biodiversity Information Facility, an international network of databases containing over three centuries of records from museums, universities and private citizens that account for over 20,000 known bee species around the world.

Combing through publicly available data of bee specimens from 1946 to 2015, researchers found that the average number of specimens in the massive GBIF dataset have been declining since the 1990s.

“The 1990s mark the beginning of a globalization era that saw a large acceleration in land-use transformation worldwide, often resulting in a replacement of diverse habitats by monocultures, along with increased used of agrochemicals; this change, compounded with climate change and international bee trade and consequent pathogen introduction, represents a tough challenge to wild bee populations,” Zattara explained.

Most continents saw a decline in bee biodiversity, led by North America (including Central America and the Caribbean), Africa and Asia, while results in Europe, which showed two separate periods of decline — first in the 1960s and 1970s and more recently in the 1990s — seem to have stabilized.

Additionally, this decline is not evenly spread across bee species. For example, records of halictid bees — the second most common family — have declined by 17% since the 1990s, while those for melittidae, a much rarer family, have dropped by as much as 41%. Researchers say this indicates that uncommon bees are becoming rarer and rare bees may be nearing extinction.

Factoring in such data biases as shifts in museum collection strategies and increased observations in well-populated areas less known for fostering biodiversity, Zattara cautioned that his study does not prove that bee biodiversity is declining, but he hopes the “gloomy” results prompt swift action to bolster bee populations.

“Something 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,” Zattara said. “The next step is prodding policymakers into action while we still have time. The bees cannot wait.”

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