Almost one in 10 of Europe's bee species is facing extinction, conservation experts have warned.
The first ever assessment of all 1,965 species of bees found across Europe found that 9.2% were threatened with extinction, while the situation was even worse for bumblebees, with a quarter at risk of dying out.
Seven species were at the highest level of risk, critically endangered, with three of the bees found only in Europe, while 46 were endangered and 24 were vulnerable to extinction, the assessment found.
Experts also warned that 5.2% of species were considered likely to be threatened in the near future, in the face of threats including more intensive agriculture, pesticides, increasing urban development, climate change and wild fires.
More than half the species (57%) could not be properly assessed for their conservation risk, because of a lack of experts, data and funding, the International Union for Conservation of Nature (IUCN) said.
The assessment was published as part of the IUCN European Red List of Bees and the Status and Trends of European Pollinators (Step) project, both funded by the European Commission.
Jean-Christophe Vie, deputy director of the IUCN global species programme, said: "This assessment is the best understanding we have had so far on wild bees in Europe.
"However, our knowledge about them is incomplete as we are faced with an alarming lack of expertise and resources.
"Bees play an essential role in the pollination of our crops. We must urgently invest in further research in order to provide the best possible recommendations on how to reverse their decline."
The experts said bees were being hit by changing agricultural practices including producing silage instead of hay from flower-rich grasslands, and widespread use of insecticides which harm bees and herbicides which reduce their food source of wild flowers.
Climate change was also raising the risk of extinction for most bee species, particularly bumblebees, as heavy rainfall, droughts, heatwaves and increased temperatures could alter and reduce their habitats.
The assessment also looked at western honeybees, the most well-known pollinator, but it is not clear whether the species now occurs as a truly wild rather than domesticated species, and so was classed as not having enough data to assess its status in the wild.
Step project co-ordinator Simon Potts said: "Public and scientific attention tends to focus on the western honeybee as the key pollinator, but we must not forget that most of our wild flowers and crops are pollinated by a whole range of different bee species.
"We need far-reaching actions to help boost both wild and domesticated pollinator populations. Achieving this will bring huge benefits to wildlife, the countryside and food production."
The experts called for a greater focus on bees in both managing protected areas and in agriculture polices, and better surveying.
More than four-fifths (84%) of Europe's food crops need insect pollination to boost product quality and yields, with pollinators contributing an estimated £16 billion a year across the continent.
Sandra Bell, nature campaigner for Friends of the Earth, said: "This latest stark warning about the decline of bees in Europe must be a wake-up call to governments. We rely on wild pollinators for most of our food crops, especially fruit and vegetables.
"Pesticides are clearly implicated as one of the threats to bees. The existing temporary EU ban on neonicotinoid insecticides must be made permanent and extended to all crops.
"But at the same time governments must do more to restore pollinator habitat and encourage less intensive forms of farming. In the UK we've lost 97% of our wildflower meadows. Now is the time to reverse that damage before it's too late for our bees."