By Sarah Yang, UC Berkeley

Pollinators such as bees, birds and bats affect 35 percent of the world's crop production, increasing the output of 87 of the leading food crops worldwide, finds a new study published today (Wednesday, Oct. 25), in the Proceedings of the Royal Society B: Biological Sciences and co-authored by a conservation biologist at the University of California, Berkeley.

The study is the first global estimate of crop production that is reliant upon animal pollination. It comes one week after a National Research Council (NRC) report detailed the troubling decline in populations of key North American pollinators, which help spread the pollen needed for fertilization of such crops as fruits, vegetables, nuts, spices and oilseed.

Of particular concern in the NRC report was the decline of the honey bee, a species introduced from Europe and a critical pollinator for California's almond industry. The report pointed out that it takes about 1.4 million colonies of honey bees to pollinate 550,000 acres of this state's almond trees.

In an effort to better understand how dependent crop production is upon pollinators worldwide, an international research team led by Alexandra-Maria Klein, an agroecologist from the University of Goettingen in Germany, conducted an extensive review of scientific studies from 200 countries and for 115 of the leading global crops.

Claire Kremen, an assistant professor at UC Berkeley's Department of Environmental Science, Policy, and Management, is co-author of this new study.

"There's a widely stated phrase in agriculture that you can thank a pollinator for one out of three bites of food you eat," said Kremen, who is also a member of the Committee on Status of Pollinators that produced the NRC report and leader of a group at the National Center for Ecological and Analysis and Synthesis that co-sponsored the work. "However, it wasn't clear where that calculation came from, so we set out to do a more thorough and reproducible estimate, and we wanted to look at the impact on a global scale."

What the researchers found fell in line with the dictum to which Kremen referred. Out of the 115 crops studied, 87 depend to some degree upon animal pollination, accounting for one-third of crop production globally. Of those crops, 13 are entirely reliant upon animal pollinators, 30 are greatly dependent and 27 are moderately dependent.

The crops that did not rely upon animal pollination were mainly staple crops such as wheat, corn and rice.

The NRC report notes that honey bees in North America have been decimated by infestations of parasitic mites that were inadvertently introduced to the United States. In addition, honey bees are battling antibiotic-resistant pathogens and competition from Africanized honey bees.

Kremen added that honey bees, particularly ones in the wild versus those in managed hives, are negatively impacted by habitat loss and a variety of non-sustainable farming practices. These impacts also affect native species of wild bees. There are 4,000 species of native bees in North America alone.

"We've replaced pollination services formerly provided by diverse groups of wild bees with domesticated honey bees," said Kremen, who recently co-authored another study showing that wild bees interacting with honey bees can lead to a five-fold increase in pollination efficiency. "The problem is, if we don't protect the wild pollinators, we don't have a backup plan."

Kremen suggested an approach to a more sustainable form of agriculture, one that de-emphasizes the use of synthetic fertilizers and builds in more of a reliance on natural ecosystems.

Some changes may involve mere tweaks to current practices, such as allowing weeds and native plants to grow and prosper along the border of the primary crop, she said. Such non-crop plants, which are currently killed off by herbicides, can sustain a variety of wild bee species when the primary crops are not in bloom.

Another change could be to switch from flood irrigation, which drowns bee species that nest in the ground, to spray irrigation when feasible, said Kremen.

The study in the Proceedings of the Royal Society B highlights what is at stake if steps to improve pollinator biodiversity are not taken.

"Passion fruits in Brazil are hand-pollinated through expensive day-laborers as the natural pollinators, carpenter bees, are hardly available because of high insecticide use in the agricultural fields and the destruction of the natural habitats," said lead author Klein.

Klein said that in the cities of Brazil, the high prices for fruits and vegetables are pushing people to turn to less healthy alternatives, including fatty meats and sugar products. As a result, she said, obesity rates seem to be rising.

"The stability of crop yields not only depends on pollination, but also on further ecosystem services," Klein added. "Therefore, we need landscapes carefully managed for a diversity of functionally important groups of organisms that sustain many important ecosystem services such as pollination, pest, pathogen and weed control, and decomposition."

This study was also supported by the Sixth European Union Framework program.

Source: INRA

L’impact des pollinisateurs sur la production des cultures

Une synthèse bibliographique, a laquelle a participé un chercheur de l'INRA d'Avignon, fait le point sur l’importance des pollinisateurs pour notre environnement et la biodiversité au niveau mondial. Ce travail est publié dans la revue Proceedings of the Royal Society B: Biological Sciences du 25 octobre 2006.

Il n’existait à ce jour que des estimations très approximatives du nombre de cultures qui dépendent des animaux pour assurer leur pollinisation et du degré de cette dépendance. Un groupe de chercheurs d’Allemagne, de France (INRA d'Avignon), d’Australie et des Etats-Unis a réalisé une large revue bibliographique des travaux scientifiques portant sur les 115 cultures les plus importantes pour plus de 200 pays afin d’évaluer la dépendance aux pollinisateurs de la production agricole mondiale utilisée directement par l’homme pour sa nourriture.

La production de plus de 3/4 des cultures : la majorité des cultures fruitières, légumières, oléagineuses et protéagineuses, de fruits à coques, d’épices et de stimulants (café, cacao) bénéficient de l’activité pollinisatrice des animaux, alors qu'un quart cultures n’en dépendent pas du tout. En terme pondéral, 35% de la production mondiale de nourriture résulte de la production de cultures dépendant des pollinisateurs, 60% provient de cultures qui ne dépendent pas des pollinisateurs (principalement les céréales comme le blé, le maïs et le riz) et 5% provient de cultures pour lesquelles l’impact des pollinisateurs est encore inconnu.

Quelques cultures sont totalement dépendantes des pollinisateurs pour leur production de fruits et de graines : le cacao, l’une des plus importante cultures vivrières dans les pays tropicaux, la vanille, les courges et potirons, les melons et pastèques, les fruits de la passion, les anonnes et les sapodilles, ainsi que les noix du Brésil et de macadamia. En l’absence de pollinisateurs, elles ne produisent qu’avec l’aide de l’homme qui doit alors les polliniser manuellement. La plupart des cultures montrent un accroissement de leur production entre 5 et 50% en présence de pollinisateurs, qui sont des abeilles pour la plupart.

L’équipe de chercheurs a pu montrer en s’appuyant sur des études réalisées sur 9 cultures sur 4 continents que l’intensification de l’agriculture et l’anthropisation de l’environnement mettaient en péril les abeilles sauvages et la stabilité du service de pollinisation qu’elles assurent.

Selon Bernard Vaissière (2ème auteur, INRA Avignon) "La sélection des cultures par l’homme au cours des millénaires a eu pour objectif de développer des variétés qui produisent de la nourriture de façon fiable dans un environnement variable. Mais cette sélection a toujours eu lieu en présence d’une abondance de pollinisateurs car les parcelles étaient de petites tailles et à proximité d’éléments d’habitat naturel. Aujourd’hui nous trouvons que plus de 75% des cultures qui nourrissent l’humanité et 35% de la production de nourriture dépendent encore des pollinisateurs, c’est-à-dire des abeilles pour la plupart. Mais les pratiques de production et les paysages agricoles qui en résultent ont évolué considérablement ces dernières années de sorte que maintenant les pollinisateurs sont souvent trop rares pour pouvoir polliniser les cultures de façon fiable et efficace. Nos résultats apportent un vibrant rappel sur le rôle essentiel que jouent les pollinisateurs dans notre vie quotidienne, en particulier au niveau de notre alimentation puisque leur activité pollinisatrice nous permet d’avoir de nombreuses denrées essentielles mais aussi agréables comme le café et le chocolat, les huiles végétales et les fruits à coques, et la plupart des fruits et légumes".

Source :
Klein, A. M., Vaissière, B. E., Steffan-Dewenter, I,. Cunningham, S. A., Claire, K., & Tscharntke, T. Importance of pollinators in changing landscapes for world crops. Proceedings of the Royal Society of London, Series B. online first: http://www.pubs.royalsoc.ac.uk/index.cfm?page=1087