Bumblebees are frequent flyers – what are the impacts?

Addressing pollinator introduction policy and the effects introduced species can have on local ecosystems, Romina Rader, Manu Saunders and Tobias Smith discuss the recent Policy Direction, Coordinated species importation policies are needed to reduce serious invasions globally: The case of alien bumblebees in South America by Aizen et al.

Photo by A. Saez

Bumblebees (Bombus spp.) are large, iconic pollinators of many wild flowers and crops.  Their ability to buzz-pollinate flowers with poricidal anthers and their ease of husbandry has led to the domestication of several species as managed pollinators, particularly Bombus terrestris, a native to Europe.  In many countries, bumblebee colonies are now mass-produced to pollinate a range of different crops in greenhouses, polytunnels and open fields, with an estimated annual value of €55 million. The recent Policy Direction by Aizen et al.  investigates the consequences of this rapid expansion by reviewing the current literature concerning bumblebee introductions and discusses how the experiences of Argentina and Chile might inform future policy directives.

There are some important points to note that are raised by this article. First, it is clear that we have moved bumblebees around the world a lot! Bombus has now been introduced into 57 countries, 16 of which are outside the native range of the genus.   Outside of its natural range, B. terrestris has been a long-term resident of New Zealand since 1885, arrived on the island of Tasmania, Australia around 1992, then Chile, Japan, and Argentina.

Second, like most introduced species, many of these introductions are affecting other species. In countries where bumblebees are already present, introduced bumblebees have displaced native bumblebee species, reproduced with closely related bumblebee taxa and facilitated the spread of pathogens among bumblebee communities. Pathogens can also jump from one bee species to another.  For example, honeybee pathogens have been found on wild bumblebees and hoverflies. Bumblebee pathogens can also be transferred to honeybees.

Bombus en flor rota
Photo by A. Saez

Third, the densities in which they occur is an important issue to consider for future glasshouse enterprises.  Bombus terrestris in particular has been introduced to pollinate crops because they are considered effective pollinators (but not always …).  However, high densities are not great as excessive visits are thought to be detrimental to the yields of some crops.  For example, in raspberry fields high flower visitation is associated with decreased fruit size due to style damage of flowers. High densities are also associated with nectar-robbing which can affect the resources available to other pollinators.

Aizen et al.’s paper focuses on South America, but many of the issues discussed are globally relevant.  Given the reported impacts of managed pollinator introductions upon wild taxa of the same or different species, the B. terrestris one-size-fits-all approach may not be the most suitable mass-produced pollinator for every pollination purpose and location.  Where alternative, efficient native pollinators are available a cost-benefit approach is imperative to balance all social, economic and environmental risks with the gains.  This may well spark the development of new local pollinator industries – for example the rejection of non-native bumble bee introductions in Argentina led to the industrial rearing and commercialization of B. atratus, a bumble bee native to South America north of Patagonia for crop pollination.

Finally, it is highly likely that bumblebees will continue to expand into new regions as a result of the pollinator trade.  Coordinated actions that handle wild and managed pollinators together are essential if we are to balance the demands of food production with other social, economic and environmental concerns.  This means there needs to be some important conversations between researchers, industry, businesses and policy makers across borders to make evidence-based decisions. We need to address the pollination challenges facing greenhouse crops and the burgeoning market for pollinator mass-production is a fantastic opportunity to do this.  Coordinated actions will avoid conflicts with other industries, peoples’ livelihoods or other species living in the same environment.

Read the full Policy Direction, Coordinated species importation policies are needed to reduce serious invasions globally: The case of alien bumblebees in South America for free in Journal of Applied Ecology.

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