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Researchers at the University of Tsukuba estimated Japan's spring leaf flush dates in recent years using data from the Second-generation Global Imager (SGLI) sensor onboard the Japan Aerospace Exploration Agency's (JAXA) Global Change Observation Mission-Climate (GCOM-C) satellite. Their analysis revealed that in 2023 and 2024, years characterized by exceptionally high spring temperatures, leaf flush occurred significantly earlier than usual, indicating that elevated temperatures linked to climate change are affecting Japanese ecosystems.

Tsukuba, Japan—Previous research had predicted that global warming would lead to earlier spring flowering and leaf flush. This study used satellite-based observations to verify that this phenomenon occurred under the unusually high spring temperatures of 2023 and 2024.

Based on data from JAXA's GCOM-C satellite, researchers estimated the start of season (SOS), which is the onset of spring leaf flush, for the period 2018-2024. In 2023, SOS occurred 3 to 7 days earlier than the 2018-2024 average in the Kanto and Chubu regions. In 2024, similar shifts were observed in the Hokuriku, Tohoku, and Hokkaido regions. Notably, in the area surrounding the Shirakami Mountains, a UNESCO World Natural Heritage site, SOS in 2024 was approximately 9 days earlier than the multi-year average. These deviations were more pronounced in years with elevated spring temperatures, suggesting that global warming and other temperature-increasing factors are exerting broad ecological impacts across Japan.

The study also examined the relationship between SOS and spring air temperature (February to April), finding that a 1 K rise in temperature advances SOS by an average of 4.4 days. When applied to future climate scenarios, this corresponds to SOS occurring approximately 7 days earlier under RCP 2.6 (representing the lowest temperature increase scenario) and about 21 days earlier under RCP 8.5 (the highest temperature increase scenario). Understanding how ecosystems respond to such temperature increases is essential for assessing the ecological impacts of future climate change, as earlier SOS can impose various stresses on ecosystems. As extreme weather events are expected to become more frequent, continued satellite-based monitoring and expansion of field observation networks will be critical for tracking and mitigating these effects.

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This study was supported mainly by ER3GCF102 (led by Kenlo Nasahara) of the 3rd Research Announcement on Earth Observation (EORA3; 2022-2024) of the Japan Aerospace Exploration Agency (JAXA).

Original Paper

Title of original paper:

Impact of high temperature in 2023 and 2024 on spring leaf flush phenology in Japan derived by GCOM-C satellite.

Journal:

Scientific Reports

DOI:

10.1038/s41598-025-94623-9

Correspondence

Associate Professor NASAHARA(NISHIDA) Kenlo
Institute of Life and Environmental Sciences, University of Tsukuba

MIZUNO Yuki
Degree Programs in Life and Earth Sciences, Graduate School of Science and Technology, University of Tsukuba

Related Link

Institute of Life and Environmental Sciences

Degree Programs in Life and Earth Sciences, Graduate School of Science and Technology