2026-11-12 アリゾナ大学
アリゾナ大学と南フロリダ大学を中心とする国際研究チームは、地球温暖化に伴う極端な干ばつが、乾燥環境に適応したサボテン類にも深刻な絶滅リスクをもたらすことを明らかにした。Natureに掲載された研究では、アメリカ大陸に分布するサボテン科993種について、約65万件の分布記録と将来の干ばつ予測を組み合わせ、生息適地の変化を解析した。従来の気候モデルは長期的な平均気温や降水量を中心に評価していたが、極端な干ばつを考慮すると、91％の種で干ばつを含むモデルの予測精度が高かった。今世紀末までに、対象種の69～72％で生息適地の減少が予測され、25～35％の種では適地の80％以上を失う可能性が示された。特にチリ、ペルー、ブラジル北東部などのサボテン多様性の高い地域で影響が大きいと予測される。本研究は、気候変動による生物多様性への影響評価に極端気象を組み込む必要性を示しており、サボテンだけでなく他の植物群の絶滅リスク評価や保全計画にも重要な知見を提供する。
＜関連情報＞
- https://news.arizona.edu/news/new-research-finds-even-cacti-are-severely-threatened-warmer-drier-world
- https://doi.org/10.1038/s41586-026-11265-1
深刻な干ばつと温暖化がサボテンの絶滅リスクを高める（Severe drought and warming increase the extinction risk of cacti）
Michiel D. Pillet, Brian S. Maitner, Mónica Arakaki, Diogo S. A. Araujo, Marc A. Baker, Duniel Barrios, Bradley L. Boyle, David D. Breshears, Xiao Feng, Bárbara Goettsch, Pablo C. Guerrero, Tania Hernández-Hernández, Lucas C. Majure, Beatriz M. Meriño, Efthymios I. Nikolopoulos, Raúl Puente-Martínez, Patrick R. Roehrdanz, Josep M. Serra-Diaz, Mark C. Urban, Cory Merow, Brian J. Enquist
Nature (2026) Published: 11 November 2026
DOI：10.1038/s41586-026-11265-1
Tii-summary
気候変動に伴い極端な気象現象の頻度と強度が増加しているが、その生物種の分布や絶滅リスクへの影響は十分に評価されていない。本研究では、乾燥に強いことで知られるサボテン科993種を対象に、648,316件の分布記録と高温の複合影響を含む深刻な干ばつデータを統合し、将来の生息適地を予測した。その結果、極端な干ばつを組み込んだモデルは、91％の種で長期平均気候に基づくモデルより高い支持を得た。100 kmの移動能力を仮定した場合、生息適地の減少が予測される種の割合は58～61％から69～72％に増加した。また、適地の25％超を失う種は26～43％から55～58％に、80％超を失う種は1～15％から25～35％に増加した。さらに、移動能力がない場合には、84～85％の種で適地の減少が予測された。こうした変化は地域ごとの種多様性にも影響し、5つの生物地理区では種数が25％以上減少する可能性が示された。本研究は、長期平均の気候条件だけを用いた従来の生物分布予測では、極端な干ばつによる生物多様性の損失を過小評価する可能性を明らかにした。気候極端現象を生態学的予測に組み込むことが、将来の絶滅リスク評価と効果的な生物多様性保全に不可欠であることを示している。
Extreme climatic events are increasing in frequency and intensity under climate change, yet their effects on species distributions and extinction risk remain insufficiently understood. In this study, researchers assessed 993 cactus species using 648,316 occurrence records, integrating severe drought data that also account for the compounding effects of warmer temperatures into species distribution models. Models incorporating severe drought were better supported than conventional long-term mean-climate models in 91% of cases. Assuming a dispersal distance of 100 km, the proportion of species projected to lose suitable climatic area increased from 58–61% to 69–72% when severe drought was included. The proportion expected to lose more than 25% of suitable area increased from 26–43% to 55–58%, while the proportion projected to lose more than 80% increased from 1–15% to 25–35%. When dispersal was restricted from 100 km to zero, 84–85% of species were projected to lose suitable climatic area. These changes also reduced regional species richness, with five bioregions potentially losing more than 25% of their species. The findings demonstrate that conventional species distribution models based on long-term mean climate can substantially underestimate biodiversity vulnerability by overlooking extreme drought events. Incorporating climatic extremes into ecological forecasting will therefore be essential for improving extinction-risk assessments and developing effective conservation strategies across species and ecosystems.
Extreme climatic events are increasing in frequency and intensity under climate change, yet their effects on species distributions and extinction risk remain insufficiently understood. In this study, researchers assessed 993 cactus species using 648,316 occurrence records, integrating severe drought data that also account for the compounding effects of warmer temperatures into species distribution models. Models incorporating severe drought were better supported than conventional long-term mean-climate models in 91% of cases. Assuming a dispersal distance of 100 km, the proportion of species projected to lose suitable climatic area increased from 58–61% to 69–72% when severe drought was included. The proportion expected to lose more than 25% of suitable area increased from 26–43% to 55–58%, while the proportion projected to lose more than 80% increased from 1–15% to 25–35%. When dispersal was restricted from 100 km to zero, 84–85% of species were projected to lose suitable climatic area. These changes also reduced regional species richness, with five bioregions potentially losing more than 25% of their species. The findings demonstrate that conventional species distribution models based on long-term mean climate can substantially underestimate biodiversity vulnerability by overlooking extreme drought events. Incorporating climatic extremes into ecological forecasting will therefore be essential for improving extinction-risk assessments and developing effective conservation strategies across species and ecosystems.
出典：Nature, Published 2026-11-11
