野生のミツバチ減少、北米の農作物に打撃　受粉で想定以上の役割

【パリＡＦＰ＝時事】北米の主要農作物の生産において、野生のミツバチが花粉媒介者として約15億ドル（約1580億円）相当の価値をもたらしており、野生のミツバチ減少が経済的に重要な農業の生産性を脅かすと警告する論文が、英学術専門誌「英国王立協会紀要」に発表された。（写真は資料写真）
　米農務省が出資したこの研究は、世界中で昆虫の個体数が急減することにより、作物の受粉や自然の食物連鎖に悲惨な結果をもたらす恐れがあることを証明している。
　米国とカナダの大学の研究者らは、野生のミツバチや飼育されているミツバチに受粉を依存する主要な７種の果物、野菜、木の実を調査。飼育されているミツバチも花粉交配用に、農場を転々と移動させられることが多い。
　以前から米国ではミツバチが最も経済価値の高い花粉媒介者とみなされてきたが、中でも野生のミツバチが「集約的農業地域においても」、これまでの認識よりもはるかに大きな役目を果たしていることが今回の研究で判明した。
　論文の著者らは「調査対象作物の多くで、花粉媒介者の減少が収穫量や生産高の減少に直結する恐れがあることが示された。また主要な農作物生産地域で、調査対象作物の大半の受粉に野生のミツバチが貢献していることも明らかになった」と説明した。
　論文はまた、農業企業が野生のミツバチの減少問題に取り組まずに殺虫剤や肥料に投資しても、利益はほとんど得られないと結論付けている。
　昨年発表された画期的な研究によると、世界の全昆虫種のうち半数近くが減少傾向にあり、３分の１は今世紀末までに絶滅する可能性がある。またハチ６種のうち１種は、すでに局地的に絶滅している。絶滅の主な原因は生息地の減少や殺虫剤の使用だとみられている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/07/29-13:22）

Wild bees are worth some $1.5 billion to key fruit and vegetable crops in North America, according to new research that warned declines in these pollinators threatens the productivity of economically important agriculture.
The study, which had funding from the United States Department of Agriculture, comes as evidence of steep drops in insect populations worldwide prompts fears of dire consequences for crop pollination and natural food chains.
Researchers from several US and Canadian universities looked at seven major fruit, vegetable and nut crops that are dependent on pollination -- by wild bees and managed honeybees, which are often transported around farms as hired crop pollinators.
While honeybees have traditionally been seen as the most economically valuable pollinators in the US, the study found wild bees play a much greater role than has been previously acknowledged, even in agriculturally intensive regions.
Our findings show that pollinator declines could translate directly into decreased yields or production for most of the crops studied, and that wild species contribute substantially to pollination of most study crops in major crop-producing regions, the authors said.
Researchers collected data from 131 farms in the US and parts of Canada on the prevalence of different types of bees, the amount of pollen distributed per flower visit and crop yield.
This allowed them to estimate that the nationwide annual production value of wild pollinators to the crops studied was over $1.5 billion, compared with $6.4 billion for honeybees -- a figure dominated by their $4.2 billion value to almond production.
Researchers found that in six crops -- pumpkin, apple, sweet cherry, tart cherry, blueberry and watermelon -- wild bee species deposited on average more pollen per flower visit than honeybees.
The exception was in California's vast almond fields, where there were often no sign of any wild bees at all.
- Conservation value -
The study, published in the journal Proceedings of the Royal Society B, found that five out of the seven crops showed evidence that a lack of pollinators was limiting production.
They concluded that agricultural firms would see little benefit in investing in pesticides and fertilisers without tackling wild pollinator declines.
Insects are the world's top pollinators -- 75 percent of 115 top global food crops depend on animal pollination, including cocoa, coffee, almonds and cherries, according to the UN.
In a landmark study last year scientists concluded that nearly half of all insect species worldwide are in decline and a third could disappear altogether by century's end.
One-in-six species of bees have gone regionally extinct somewhere in the world.
The main drivers of extinction are thought to be habitat loss and pesticide use.