Wisdom from Amazon Trees: Natural Tips for Surviving Extreme Heat

Prologue—The Jungle at Dawn
A drone glides over the Amazon at dawn, shrouded in mist. As the orange light caresses the tops of the giant trees, countless leaves hidden in the canopy begin to shine simultaneously, as if a massive solar panel is coming to life. There was an unknown "negotiation with light" happening there—.

1. Background of the Research

The Amazon rainforest, known as the largest carbon sink on Earth, has been exposed to extreme droughts and high temperatures due to recent climate change. Satellites have been estimating photosynthesis using chlorophyll fluorescence (SIF), but an "inconvenient truth" has been reported where SIF actually increases during the dry season, making on-site verification urgent. phys.org

2. Researchers Challenging the Canopy

Leonardo Ziccardi and his team, during his doctoral program from 2019 to 2024, climbed over 200 giant trees exceeding 60 meters. Using a portable photosynthesis meter "MultispeQ," they simultaneously measured ① absorbed light amount (APAR) ② fluorescence ③ thermal dissipation ④ pure photosynthesis rate. The total sample size covered over 10,000 leaves, creating the first "full 3D resolution dataset" of the canopy. phys.org

3. The Revealed "Three-stage Utilization" Model

1. Balance Phase (Low to Medium Light)

   • Photosynthesis and fluorescence increase and decrease in tandem.

2. Buffer Phase (Strong Light + Mild Drought)

   • Rapid increase in thermal dissipation to suppress leaf temperature rise. Photosynthesis remains flat.

3. Crisis Phase (Strong Light + Severe Drought)

   • Thermal dissipation mechanisms reach their limit, and photosynthesis plummets. Fluorescence spikes, indicating leaf damage.

Conventional satellite algorithms that considered "fluorescence↑ = photosynthesis↑" missed the reversal phenomenon in the third phase. phys.org

Sunlight→Leaf→Fluorescence, Heat, Photosynthesis

4. Reactions on Social Media—"Admiration and Disquiet"

• @thepostdoctoral
  "This might fundamentally change how we interpret satellite data. Reaffirming the importance of ground observations!」 twitter.com

• @kgusler
  "Admiration for the persistence in climbing the giant tree. However, the SIF industry will require significant correction." twitter.com

• @MSUDOEPlantLab
  "Our MultispeQ is lighting up the future of tropical forests! Next, we plan to expand in Africa." x.com

Japanese researchers also say, "This is a result directly linked to the calibration of the satellite 'Shikisai' data" (Chiba University Satellite Observation Center).

5. Implications for Japan

• Remote Sensing Industry: Domestic startups engaged in SIF analysis for agriculture will require similar error correction when applying to arid crops.

• Forest Policy: By incorporating the three-step utilization model from this study when adopting photosynthetic efficiency as a sustainability indicator for tropical timber, the risk assessment of illegal logging can be refined.

• Education & Tourism: The illustrated "leaf light energy distribution" can be repurposed for environmental education in elementary and middle schools, as well as for eco-tourism guideboards.

6. Future Prospects

The research team plans to establish a multi-scale observation network integrating satellites, drones, and canopy sensors targeting the Rio Negro basin from 2025 to 2027. The development of a "physics-based AI model" that decomposes satellite SIF into heat dissipation, fluorescence, and photosynthesis in real-time will be key. Whether an early warning can be implemented before tropical forests reach a tipping point, Japan's technical cooperation is also being watched. phys.org