Global bee population decline not nearly as bad as it seems

Posted Oct 18, 2008 by Bart B. Van Bockstaele
The global decline of bee populations is said to have dramatic consequences for our food production. Research now shows that agriculture is largely unaffected by this phenomenon.
Bumblebee on bull thistle
A bumblebee (Bombus impatiens) is collecting nectar on a bull thistle (Crisium vulgaris).
Bart B. Van Bockstaele
The dramatic global decline of pollinator (mainly bee) populations, also known as Colony Collapse Disorder, was predicted to have dire consequences for agriculture and hence for our food supply. Surprisingly enough however, pollinator dependent agricultural crops are mostly unaffected.
Anna Petherick reports in Nature that this is the conclusion of a study by Alexandra Klein and her colleagues at the University of California, Berkeley. They have used data from the FAO (Food and Agriculture Organisation of the United Nations) spanning a period of 1961 to 2006 to compare the yields of crops that require pollination with crops that do not require pollination.
They discovered that the yields for both types of crops have risen consistently over the years with an average of about 1.5% per annum. Even when they divided the data into crops from developing countries and crops from developed countries, they found no differences.
Even when the team looked specifically at crops that are virtually exclusively grown in the tropics, no differences were found between crops that need pollinators, such Brazil nut, cocoa and oil palm, and crops that only need the wind for their pollination.
These results are surprising because they seem to contradict older studies that found a very large impact on a local scale.
In 2004, Taylor Ricketts, head of the conservation science programme of WWF, found that pollinating insects increased the yield of coffee by 20% for plants that were located less than one kilometre from the forests in Costa Rica.
In 2005, Jacobus Biesmeijer of the University of Leeds led a team that found evidence of a decline of the bee diversity in the United Kingdom and the Netherlands which coincided with a decline of outcrossing plant species in comparison to other types of plants.
The worries about a veritable pollination crisis are so strong that they are being discussed on the level of international politics. One notable example of this, is the start of the International Initiative for the Conservation and Sustainable Use of Pollinators (IPI) at a meeting of the United Nations in 2000.
Some scientists think that the pollination crisis is being exaggerated. Jaboury Ghazoul, a plant ecologist at ETH Zurich, Switzerland, thinks that this crisis is mainly driven by a fall in crop-pollinating honeybees in North America and of bumblebees and butterflies in Europe.
There is also other data that shows that native pollinators in other locations respond in more mixed ways to changes in the environment and, according to Ghazoul, there are not very many staple food crops that depend on insect pollinators.
Linda Collette, the overseer of the IPI programme and a senior officer on crop associated biodiversity at the FAO, says that there was some disagreement about how much pollinators are declining when the IPI was established.
Alexandra cautions that her findings do not necessarily show that there is no global pollination crisis. She thinks that the data may not show, for example, how farmers have adapted to the problem.
To pollinate almond trees, for example, many growers move honeybees into their orchards. They use pheromones to stimulate their foraging activities. Some go even so far as to placing compatible pollen in the bee's hives in order to transport them to the desired almond variety. Many passion-fruit growers in Brazil even pollinate by hand.
The use of farm workers instead of insects does not necessarily represent a crisis for the FAO. "At the end of the day, what's important to the FAO is crop production," says Collette. "There may be labour costs involved in pollinating crops but there could also be market benefits — if the fruits are better from that, for instance."
Klein, on the other hand, warns that a sudden drop in crop yields may be around the corner.
"There could be a more widespread threshold effect coming," she says, "especially if the honeybee problems get worse in places like California."
This scenario may be more likely because farmers worldwide are increasingly turning to crops that are depending on pollinating insect. While these crops only presented 8.4% of the agricultural production in the developed world in 1961, this rose to 14.7% in 2006. "We assume that the trend will continue as many biofuels crops, such as canola, oil palm and jatropha, are pollinator-dependent plants," says Klein.