News in Science

Agriculture yet to feel sting of bee decline

A decline in bees and other insect populations is yet to impact on global crop yields, according to an international study.

But in the latest edition of Current Biology, researchers warn an increasing reliance on crops that need pollination could lead to future problems.

Co-author Dr Saul Cunningham, of CSIRO Entomology, says the research was prompted by increasingly alarmist views about food availability in the face of declines in insect pollinator populations.

Research into the reliance on bee pollination for global crop production, estimates about one in three mouthfuls of food comes from insect-pollinated crops.

Cunningham says the loss of bees and other insect pollinators is due, among other things, to a combination of disease, reduction in native vegetation and use of insecticides.

In particular managed honeybees, which are used by farmers to pollinate large tracts of monocrops, have been decimated by disease in the form of the varroa mite and colony collapse disorder.

During the 2006-07 northern hemisphere winter, a quarter of US beekeepers lost more than half of their hives.

Cunningham says the research team, which included scientists in Australia, Argentina, Germany and the US, looked at global crop yields during the past 45 years to determine whether the loss of pollinators was affecting the global food supply.

Dependence rating

They rated crops on how much they depended on pollinators for maximum production.

This ranged from zero for crops such as wheat that are pollinated by the wind to 100% for crops such as almond trees that will not produce nuts without pollination.

He says they were surprised to find crop yields in the 45-year period had grown consistently by about 1.5% a year due to improvements in agriculture.

More importantly however there was "little evidence of difference in relative yield between pollinator dependent and non-dependent crops".

Cunningham says if global crop yields were being affected by the pollinator shortages they would have expected pollinator-dependent crops to show reduced yield during the past few years.

He says the study highlighted a surprising trend toward more reliance on pollination-dependent crops such as canola and soybean, particularly in developing countries.

In 1961 pollinator-dependent crops contributed 13.7% to total agriculture production in the developing world, he says. By 2006 the figure had risen to 22.6%.

"This trend might be further exacerbated in the future as some fast-expanding, insect-pollinated crops, such as oil palm and canola, are candidates for large-scale biofuel production," the paper says.

Cunningham says this suggests strategies need to be thought through to ensure a supply of pollinators to meet this demand.

"Let's not panic; we're not going to starve. Crop production is increasing and we are getting better and better at agriculture," he says.

"At the same time we don't want to assume there is no problem. There is no decrease in yields yet but the increase in demand for pollinators sets up the possibility of shortages in the future."