Professor KUME Atsushi and his research group have revealed that street trees also become healthier as a result of air pollution control measures

2025.01.24 Environment & Sustainability

18-year monitoring study in Kyoto reveals improved photosynthesis

Point

  • An 18-year monitoring study in Kyoto revealed that significant improvements in air pollution led to enhanced photosynthesis in street trees. However, the reduction in traffic volume during the COVID-19 pandemic from 2020 to 2023 had little impact on air pollution improvement and did not affect the photosynthesis of street trees.
  • This is the first study to demonstrate that continuous air pollution control measures have increased the photosynthesis of street trees. Additionally, it is the first to confirm how the reduction in traffic volume due to the COVID-19 pandemic affected the photosynthesis of street trees.
  • This study is significant in demonstrating that continuous efforts in air pollution control enhance the photosynthesis of urban trees, increase their carbon dioxide absorption capacity, and contribute to the improvement of urban environments.

Abstract

Professor HANBA and colleagues from the Department of Applied Biology at Kyoto Institute of Technology revealed through a study conducted in Kyoto from 2005 to 2023 that significant improvements in air pollution have enhanced the photosynthesis of street trees. Comparing the periods 2020-2023 and 2005-2008, nitrogen dioxide concentrations, a major air pollutant, decreased by 60% over these 15 years, while the photosynthesis of street trees such as azaleas and cherry blossoms increased by 25%. The reduction in nitrogen dioxide concentrations in Kyoto over these 15 years is largely due to the effects of the enactment and revision of the Automobile NOx Law*1, which improved the environmental performance of trucks. This study demonstrates that continuous efforts in air pollution control not only benefit human health but also have positive effects on street trees

On the other hand, the COVID-19 pandemic from 2020 to 2023 led to a reduction in traffic volume due to the stagnation of economic activities. However, the decrease in nitrogen dioxide concentrations during this period was only about 5%, and it did not improve the photosynthesis of street trees. While it has been reported that air pollution improved in cities around the world due to the pandemic, it is believed that in Japan, where air pollution had already been improved, the impact was not significant enough to enhance the photosynthesis of street trees.


Glossary

*1 Automobile NOx Law
Specifically, the Automobile NOx and PM Law, which is the Special Measures Law for the Reduction of Total Emissions of Nitrogen Oxides and Particulate Matter from Automobiles in Designated Areas.


Paper Information

Journal: Scientific Reports
Title: The impact of air pollution control measures and the COVID-19 pandemic on photosynthesis in urban trees
Authors: Takumi Matsuura, Yousuke Okamoto, Mayu Matsumoto, Takashi Kiyomizu, Luisa Kumpitsch, Atsushi Kume, and Yuko T. Hanba
DOI:10.1038/s41598-024-85080-x


For Research-related inquiries

KUME Atsushi, Professor