trees

The Witness Tree Project continues to play a crucial role in advancing research on climate change through its focus on long-lived trees, which act as natural sensors of environmental change. In 2025, the project has made significant strides with new research initiatives, collaborations, and the involvement of a growing team of dedicated experts, students, and volunteers.

This year, Dr Miriam Slodownik, the lead of the Witness Tree Project, was responsible for leading the team at the National Botanic Gardens, where she focused on key questions regarding urban trees and their capacity to improve air quality. The research investigates which tree species are most effective at capturing particulate matter (PM) and explores the leaf traits that support PM uptake, including leaf area and surface texture.

Dr Ailbhe Brazel led a new initiative this year, collecting leaf samples from four tree species — alder, hazel, common Oak, and maidenhair tree — to identify molecular biomarkers of environmental responses. This research aims to deepen our understanding of how trees respond to environmental stressors and contribute to enhancing urban air quality.

A central theme of this research includes:

• Which tree species captures the most particulate matter (PM)?

• How do Leaf Area Index (LAI), leaf angles, and leaf size affect PM uptake?

• What specific leaf traits help increase PM absorption per tree?

By linking leaf traits with air quality data, the project is providing valuable insights to inform urban planning decisions aimed at improving air quality in cities.

Charlotte Salter-Townsend, a Master’s student, was also involved, examining which species within the Witness Tree Project have the highest PM capturing capacity. Charlotte’s work focuses on understanding how traits like leaf area, trichome density, and leaf size influence PM capture, and how these traits may work together to enhance the tree’s ability to absorb particulate matter.

At the Trinity College Botanic Gardens, Dr Michelle Murray led a separate team focused on monitoring the health of trees in response to environmental stressors such as temperature fluctuations and urban heat islands. Dr Christos Chondrogiannis supported the team, contributing to field collection and data analysis.

This year, a group of dedicated volunteers contributed significantly to the success of the project. A huge thank you goes out to Sophie, Lucy, Phoebe, Yidan, Ríona and Ciaran for their invaluable help. Their hard work, enthusiasm, and commitment to the project have been essential to the progress made this year.

The project remains highly active on social media, particularly through its Instagram platform, where updates and findings from the ongoing research are shared. Recent posts highlight the involvement of students, volunteers, and researchers in this year’s activities, showing the critical role that community engagement plays in the success of the project.