Bee in flight

A project to make conservation science accessible and relevant to conservationists and policymakers launches its first major synopsis of evidence, on bee conservation.

In areas where good quality data are available, severe declines in many species have been documented

Dr Simon G. Potts

For the first time, scientific knowledge and experience about how to conserve wild bees around the world has been brought together by conservation scientists led by Professor William J. Sutherland and Dr Lynn Dicks at the University of Cambridge.

The synopsis of evidence on bee conservation is meant to inform people taking action or spending money to help wild bees - anyone from farmers to international NGOs - about what works and what doesn't. It is part of a project called Conservation Evidence, which aims to make conservation practice more science-based.

Bees are the most important pollinators globally, and their decline has received much publicity. "There are more than 25,000 species of bee worldwide," says Dr Simon G. Potts, an expert on pollinator conservation from the University of Reading who advised on the development of the bee synopsis. "In areas where good quality data are available, severe declines in many species have been documented." In response, governments and international organisations are now investing in pollinator conservation.

The bee synopsis, developed in partnership with an international group of bee experts, lists 59 different actions you could take to benefit wild bees. They range from providing nest boxes or planting flowers to training beekeepers to keep native species. For each intervention, evidence is summarised in plain English.

In some cases, the evidence tells a clear story. Leaving strips at the edge of crop fields untreated with herbicides and pesticides does not help bumblebees, for example - two replicated trials in the UK have found no more bees on these strips than in ordinary crop fields. But there is evidence from many parts of the world that providing nest boxes on agricultural land can benefit solitary bees. Twenty-nine studies show that solitary bees, including endangered species, will use nest boxes and three studies show numbers of nesting bees can double over three years with repeated nest box provision.

Bees can be problematic in places where they are not native, and there is some evidence about how to reduce the impacts of invasive bee species. A concerted effort to eradicate European buff-tailed bumblebees from small patches of Japanese countryside, for example, increased numbers of native bumblebees, but did not remove the invaders altogether.

"This synopsis is a great step forward in providing a clear evidence base for anyone setting out to conserve wild bees, from conservation agencies to individuals," says Professor Andrew Bourke, a bumblebee expert from the University of East Anglia, UK, and member of the Advisory Board for the bee synopsis. He was surprised by the often low success rate of artificial nest boxes for bumblebees. "This work highlights how much more there is to learn about bees," he says.

As well as helping to inform decisions about bee conservation, the synopsis shows where there are gaps in our knowledge. There is no direct evidence to show whether increasing the amount of natural habitat in farmed areas can help bees, for example, and very little evidence for the effects of restricting pesticide use on bees, although conservationists often advocate these actions. "Habitat preservation and the proper application and use of insecticides are the most important issues in bee conservation now," says Peter Kwapong, of the International Stingless Bee Centre in Ghana, a member of the Advisory Board. Clearly, these are areas where research should focus.

The Conservation Evidence project also has an open access journal where conservationists can document their experience and an online database of evidence published elsewhere, relating to conservation interventions. The series of synopses, of which Bee Conservation is the first, will cover other major species groups, habitat types and issues. Synopses are already being prepared for birds, butterflies, grassland and farmland.

"The bee synopsis brings together, for the first time, a systematic overview of conservation practices that can really help protect bees," says Potts. "The challenge now is for policymakers to take up these actions."

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