Do the bumblebees that escape from greenhouses affect indigenous pollinators?

More than two million commercial colonies of bumblebees are used each year worldwide to pollinate nearly 20 types of crops. These bumblebees can represent a risk for wild pollinators, especially those with whom they share both flower resources and pathogens. To date, however, there is little evidence on the impact of commercial bumblebees on pollinator communities in Europe. That's why a team of researchers from the Higher Council for Scientific Research (CSIC) has launched a study to investigate this issue.

The research has been carried out by the team of the Doñana Biological Station (EBD) of the CSIC, the Autonomous University of Barcelona, and the University of Almeria in 80 plots of natural habitat at increasing distances from greenhouses in the Almeria region of Cabo de Gata- Nijar (the most extensive greenhouse growing area in the world, according to the study), where part of the bumblebees that are used to pollinate vegetables go out to expand their diet and visit other wild plants in the closest areas.

The research allowed the scientist to observe that there is a sharp reduction in commercial bumblebee densities at increasing distances from greenhouses, and most bumblebees (95%) forage within a radius of less than 200 m from them.

"This data is positive and may indicate that the area of influence that this introduced species may have in the area is very small, at least to date. However, this does not guarantee that there are naturalized colonies of bumblebees in the environment, such as we have observed in other regions, for example, in Huelva," stated researcher Alejandro Trillo.

However, at least 41% of the analyzed bumblebees had a high prevalence of parasites, trypanosomatids, microsporidia, and neogregrins; and, even though there are no native bumblebees in this area, several of these parasites also affect other pollinator species, such as honey bees, which are frequent in the same area and whose resource niches overlap.

Despite these observations, the study, published in the Agriculture, Ecosystems and Environment journal, concluded that the quantity and diversity of the rest of pollinators were not affected a priori by commercial bumblebees, given the low number of bumblebees that have been detected in the environment and the fact that they remain close to the greenhouses; However, the team does not rule out that there are less perceptible effects related to the transmission of pathogens or direct competition with specific species.

"Producers should consider actions, such as preventing the escape of commercial species from greenhouses or monitoring their health before being used in crops, to minimize future risks," stated researcher Montserrat Vila.



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