Research press release


Nature Climate Change

Butterfly populations on the verge of collapse



今回、Tom Oliverたちは、英国チョウ類モニタリング事業の129地点で収集されたチョウ個体群の長期データを調べて、1995年の大干ばつに対する28種のチョウの応答履歴を評価した。その結果、1995年の干ばつの後に大規模な個体群崩壊が起こった6種の乾燥感受性のチョウ(モンシロチョウ、キマダラジャノメ、シルワヌスコキマダラセセリなど)が同定され、生息地の分断化が進んでいない場合に個体群が急速に回復したことが判明した。Oliverたちは、さまざまな温室効果ガス排出シナリオと土地利用シナリオの予測を用いて、どのような景観管理を行うにせよ、単独で行うのであれば、2100年までに起こる地域的な個体群消滅の蔓延を阻止できないことを明らかにした。また、Oliverたちは、「対策を講じない」高排出シナリオにおいて、生息地の分断化が進んだ景観でのチョウ種の絶滅が早ければ2050年に始まることを見いだした。これに対して、強力な緩和策を必要とする低排出シナリオでは、生息地の分断化を抑えることで個体群の存続確率が50%を超える可能性が判明した。


Widespread extinctions of drought-sensitive butterfly populations in the UK could occur as early as 2050, with extreme droughts expected to become more frequent under various climate change scenarios, reports a paper published online this week in Nature Climate Change. The research shows that the chances of avoiding population collapses can be improved substantially through regional landscape management in combination with reductions in greenhouse gas emissions.

Restoring habitat connections fragmented by human activity, such as agriculture, may reduce population collapse of climate-sensitive butterfly species in response to extreme droughts and may also aid recovery. The effectiveness of land-use changes under future climate change, however, is unclear.

Tom Oliver and colleagues studied long-term butterfly population data from 129 sites of the UK Butterfly Monitoring Scheme to assess the historical responses of 28 species to an extreme drought event in 1995. They identify six drought-sensitive species, including the Cabbage White, Speckled Wood and Large Skipper butterflies, that experienced major population collapses following the 1995 drought and find that reduced habitat fragmentation was associated with faster population recovery. Using projections of different emissions and land-use scenarios the authors find that no level of landscape management alone would prevent widespread local population extinctions by 2100. In addition, for highly fragmented landscapes, under a high-emissions ‘business as usual’ scenario, the authors found that extinctions could begin as early as 2050. Under a low emissions scenario, which would require higher levels of mitigation, reducing habitat fragmentation could improve the probability of population persistence by 50%.

The authors conclude that restoring contiguous habitats, rather than solely maximizing habitat area, in combination with major emissions reductions is required to ensure the survival of drought-sensitive butterflies.

doi: 10.1038/nclimate2746


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