地球規模の山火事パラドックスの解明(UC Irvine-led research team uncovers global wildfire paradox)

2025-08-21 カリフォルニア大学アーバイン校(UCI)

カリフォルニア大学アーバイン校(UC Irvine)を含む研究チームは、2002年から2021年にかけて、世界の焼失面積が26%減少している一方で、人間が火災にさらされるリスクがほぼ40%増加したという「野火のパラドックス」を明らかにしました。これは、人口密集地と火災多発地域との空間的重なりが拡大したことに起因します。分析対象は、世界中で発生した1,860万件以上の火災データと人口分布。推計では、この期間だけで約4億4,000万人が野火による危険にさらされたとされ、これはEU全体の人口とほぼ同等です。特にアフリカが影響が大きく、全世界の人間の火災曝露のうち85%が同大陸で発生しており、コンゴ、南スーダン、モザンビーク、ザンビア、アンゴラの5か国だけで半数近くを占めています。アメリカ、ヨーロッパ、オーストラリアの3地域は合わせても2.5%未満にとどまります。西部アメリカやカリフォルニア州は燃焼面積に比して非常に高い人的被害に直面しており、全米の人間への曝露のうち72%がここで起きています。研究は科学誌『Science』に掲載され、アメリカ国立科学財団(NSF)の支援を受けています。

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焼失面積の減少にもかかわらず、世界的な山火事への人間曝露が増加している Increasing global human exposure to wildland fires despite declining burned area

Seyd Teymoor Seydi, John T. Abatzoglou, Matthew W. Jones, Crystal A. Kolden, […] , and Mojtaba Sadegh
Science  Published:21 Aug 2025
DOI:https://doi.org/10.1126/science.adu6408

地球規模の山火事パラドックスの解明(UC Irvine-led research team uncovers global wildfire paradox)

Editor’s summary

Wildfires are increasingly destructive to people and property globally as a result of both increased fire activity and human development at the urban-wildland interface. Seydi et al. quantified the number of people exposed to fires (i.e., those living within areas that have burned) at the global scale between 2002 and 2021. Over that period, fire exposure increased by 40% even as burned area declined globally. Almost all of the increase in exposure was in Africa, which accounted for more than 85% of all people directly exposed to wildland fires over the study period. —Bianca Lopez

Abstract

Although half of Earth’s population resides in the wildland-urban interface, human exposure to wildland fires remains unquantified. We show that the population directly exposed to wildland fires increased 40% globally from 2002 to 2021 despite a 26% decline in burned area. Increased exposure was mainly driven by enhanced colocation of wildland fires and human settlements, doubling the exposure per unit burned area. We show that population dynamics accounted for 25% of the 440 million human exposures to wildland fires. Although wildfire disasters in North America, Europe, and Oceania have garnered the most attention, 85% of global exposures occurred in Africa. The top 0.01% of fires by intensity accounted for 0.6 and 5% of global exposures and burned area, respectively, warranting enhanced efforts to increase fire resilience in disaster-prone regions.

 

米国における大規模山火事の人間とインフラへの曝露 Human and infrastructure exposure to large wildfires in the United States

Arash Modaresi Rad,John T. Abatzoglou,Jason Kreitler,Mohammad Reza Alizadeh,Amir AghaKouchak,Nicholas Hudyma,Nicholas J. Nauslar & Mojtaba Sadegh
Nature Sustainability  Published:03 July 2023
DOI:https://doi.org/10.1038/s41893-023-01163-z

Abstract

An increasing number of wildfire disasters have occurred in recent years in the United States. Here we demonstrate that cumulative primary human exposure—the population residing within the perimeters of large wildfires—was 594,850 people from 2000 to 2019 across the contiguous United States (CONUS), 82% of which occurred in the western United States. Primary population exposure increased by 125% in the CONUS in the past two decades; it was noted that there were large statistical uncertainties in the trend analysis due to the short study timeline. Population dynamics from 2000 to 2019 alone accounted for 24% of the observed increase rate in human exposure, and an increased wildfire extent drove the majority of the observed trends. In addition, we document the widespread exposure of roads (412,155 km) and transmission powerlines (14,835 km) to large wildfires in the CONUS, with a relative increase of 58% and 70% in the past two decades, respectively. Our results highlight that deliberate mitigation and adaptation efforts to help societies cope with wildfires are ever more needed.

 

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