More than a billion jobs and three quarters of the world's crops depend on bees and other pollinators, say experts.

Scientists are warning that urgent action is needed to halt a global decline in pollinators which threatens economies and food supplies.

The authors of a major United Nations report blame the decline of pollinators on habitat loss, climate change and farming methods.

Possible solutions include building "bee highways" to allow the insects to move freely between foraging locations, reducing "green deserts" - landscapes dominated by a single crop species - and helping farmers work with nature.

Lead scientist Professor Simon Potts, from the University of Reading, said: "We conducted the most thorough review of the science ever undertaken, sifting through all the available evidence, to provide governments with the best and latest evidence on pollinator decline.

"The UN report is a good start, but now we need action. We need governments, farmers, industry and the public around the world to act to stop further declines in bees and other pollinating animals.

"It's not all bad news for bees, and luckily we still have options to help. Doing nothing is a big risk that could endanger the global supply of nutritious foods and the livelihoods of millions of people."

The report published in the journal Nature estimates that 1.4 billion jobs worldwide depend on pollinating insects such as bees, beetles and butterflies.

Three quarters of the world's crops, worth 500 billion dollars (£403 billion), rely on nature's pollinators, say the experts.

In addition, the report highlights how safety procedures for new pesticides and genetically modified (GM) crops could be tightened to protect beneficial wild insects.

Currently, regulators only require manufacturers to assess risks to managed honeybees, not wild species.

Pollinator decline will be high on the agenda at UN conservation talks taking place in Cancun, Mexico, next month.

Bee expert Norman Carreck, from the Laboratory of Apiculture and Social Insects at the University of Sussex, called the report "wide-ranging and novel".

He added: "It has been widely reported in the media that the human population would starve without bees. This is not true, because many of the world's staple food crops are wind pollinated, but this review emphasises the complexity of the relationship.

"Animal pollinated crops supply many vital micronutrients and a lack of such crops due to pollinator decline could lead to deficiencies and other human disease."

Lena Wilfert, senior lecturer in molecular evolution at the University of Exeter, said: "This review ... shows that diverse pollinator populations are crucial for a wide range of factors influencing human well-being, beyond the immediate pollination of crops.

"Importantly, (the) work shows how ecological intensification of agriculture and ecological infrastructure can tackle the threats to pollinator diversity and abundance."

Friends of the Earth nature campaigner Sandra Bell said: "Governments across the world must act on this stark warning from scientists and take far tougher action to protect our bees and other pollinators, which are crucial for our food security and well-being.

"Intensive farming is a key threat which the UK Government must address as part of its Brexit strategy."