Wednesday, April 7, 2010
Les abeilles et notre diète
Je reproduis ici une lettre d'opinion de deux chercheurs, l'un de l'Argentine, l'autre de Calgary, qui expliquent le problème complexe de la perte de nos populations d'abeilles et l'avenir de la production de nourriture destinée aux humains. J'insère ce sujet dans un blog dédié à la rivière Richelieu et aux autres, parce que je crois que les rivières font parti intégrante de notre environnement, et qu'elles aussi souffrent du manque de biodiversité dans nos vallées. Je suis convaincue que les monocultures GM qui occupent la quasi totalité de nos terres agricoles sont la cause d'un grave déséquilibre qui se voit dans la chute de nos populations d'abeilles sauvages et domestiques, de nos bourdons, de nos papillons, et de nos oiseaux mangeurs d'insectes comme les hirondelles et les fauvettes. J'ai bien peur que les avertissements de Rachel Carson ne sont toujours pas entendus!
On explique dans cette lettre d'opinion du New York Times que plusieurs récoltes de fruits et noix prisés par les humains ne dépendent pas seulement des abeilles domestiques, mais aussi des populations d'abeilles et insectes sauvages. Qu'une demande accrue de ces fruits et noix exige des monocultures de plus en plus vastes qui privent les écosystèmes de la variété de plantes nécessaires à un équilibre naturel. Que les ruches pleines d'abeilles domestiques charriées ici et là où la demande de nourriture humaine se fait sentir ne suffit pas à remplacer la population locale saine d'une faune indigène.
Finalement, c'est un cercle vicieux: le nombre sans cesse plus petit d'insectes pollinisateurs pousse les surfaces agricoles à s'étendre, mettant en péril les milieux mixtes naturels que les insectes ont besoin pour survivre et se reproduire. Si on ne protège pas mieux les écosystèmes dont dépendent les insectes qui pollinisent nos récoltes, nous nous verrons obligés de limiter ce qu'un fermier peut produire. Ou nous résigner à ne plus manger certains fruits...
IN the past five years, as the phenomenon known as colony-collapse disorder has spread across the United States and Europe, causing the disappearance of whole colonies of domesticated honeybees, many people have come to fear that our food supply is in peril. The news on Wednesday that a Department of Agriculture survey found that American honeybees had died in great numbers this winter can only add to such fears.
The truth, fortunately, is not nearly so dire. But it is more complicated.
There is good news: While some areas are seeing a shortage of bees, globally the number of domesticated honeybee colonies is increasing. The bad news is that this increase can’t keep up with our growing appetite for luxury foods that depend heavily on bee pollination. The domesticated honeybee isn’t the only pollinator that agriculture relies on — wild bees also play a significant role, and we seem intent on destroying their habitats.
To understand the problem, we need to understand the extent of the honeybee’s role in agriculture. Humans certainly benefit from the way bees — and to a lesser extent, other pollinators like flies, beetles and butterflies — help plants produce fruits and seeds. Agriculture, however, is not as dependent on pollinators as one might think. It’s true that some crops like raspberries, cashews, cranberries and mangoes cannot reproduce without pollinators. But crops like sugar cane and potatoes, grown for their stems or tubers, can be propagated without pollination. And the crops that provide our staple carbohydrates — wheat, rice and corn — are either wind-pollinated or self-pollinated. These don’t need bees at all.
Overall, about one-third of our worldwide agricultural production depends to some extent on bee pollination, but less than 10 percent of the 100 most productive crop species depend entirely on it. If pollinators were to vanish, it would reduce total food production by only about 6 percent. This wouldn’t mean the end of human existence, but if we want to continue eating foods like apples and avocados, we need to understand that bees and other pollinators can’t keep up with the current growth in production of these foods. The reason is that fruit and seed crops that are most dependent on pollinators yield relatively little food per acre, and therefore take up an inordinate, and increasing, amount of land. The fraction of agriculture dependent on pollination has increased by 300 percent in half a century.
The paradox is that our demand for these foods endangers the wild bees that help make their cultivation possible. The expansion of farmland destroys wild bees’ nesting sites and also wipes out the wildflowers that the bees depend on when food crops aren’t in blossom. Researchers in Britain and the Netherlands have found that the diversity of wild bee species in most regions in those countries has declined since 1980. This decrease was mostly due to the loss of bees that require very particular habitats — bees that couldn’t adapt after losing their homes and food sources to cultivation. Similarly, between 1940 and 1960, as land increasingly came under cultivation in the American Midwest, several bumblebee species disappeared from the area. It is difficult to count and keep track of wild bee populations globally, but their numbers are probably declining overall as a result of such human activity.
Even if the number of wild pollinators remained stable, it would not be sufficient to meet the increasing demand for agricultural pollination. Could domesticated bees take up the slack? By looking at data from the Food and Agriculture Organization of the United Nations, we found that the number of managed honeybee hives increased by 45 percent during the past five decades. Unfortunately, this increase cannot counteract the growing demand for pollination or the shortage of wild pollinators. Domesticated bees mainly produce honey; any contribution they make to crop pollination is usually a secondary benefit. In most parts of the world, they provide pollination only locally and not necessarily where it is needed most.
Thus a vicious cycle: Fewer pollinating bees reduce yield per acre — and lower yield requires cultivation of more land to produce the same amount of food. Eventually, a growing shortage of pollinators will limit what foods farmers can produce. If we want to continue to enjoy almonds, apples and avocados, we have to cultivate fewer of them, more sustainably, and protect the wild bees that help make their production possible.
Marcelo Aizen is a researcher at the National Scientific and Technical Research Council of Argentina. Lawrence Harder is a professor of pollination ecology at the University of Calgary."
Excerpts from an opinion piece published in The New York Times here: http://www.nytimes.com/2010/03/25/opinion/25harder.html
I insist on the importance of maintaining healthy ecosystems, including wild and domesticated bees, here in a blog dedicated to the Richelieu river and its sisters because I'm convinced that was is bad for our land-based ecosystems can't be very good for our waterways. The vast GM monocultures grown in the Richelieu valley is not only detrimental to the bee, insect, bird and wildlife populations, but also to the aquatic food chain: witness the blue-green algae blooms, the endangered species like the Copper Redhorse and the Spiny Softshell Turtle.