A new method for monitoring the decline in bee populations may prove a useful tool in much-needed conservation efforts. It requires only a few hundred pan traps: bright shallow bowls partly filled with soapy water or propylene glycol.

When United Nations experts noticed that crop production was flagging in seven countries around the world, from Brazil to Nepal, they contacted Gretchen LeBuhn, an associate professor at San Francisco State University who studies bees.

The world's food crisis, where 1 billion people are already going hungry and a further 2 billion people will be affected by 2050, is set to worsen as increasing heatwaves reverse the rising crop yields seen over the last 50 years, according to new research.