Witness Trees Project 2026 Fieldwork Campaign
Five years of monitoring trees for a more climate-resilient future
The Witness Tree Project is a long-term monitoring initiative that began in 2022 at the Trinity College Botanic Garden and expanded to the National Botanic Gardens in 2024. Each summer, researchers monitor 21 tree species to better understand how climate change is affecting tree health and resilience, while also investigating the important role these species play in retaining airborne pollutants in urban environments. The project has completed its 2026 summer fieldwork campaign this July.
This year’s fieldwork was led by Dr. Leticia Figueiredo Candido at the National Botanic Gardens, together with intern Julia and volunteers Blanka and Chiara. At the Trinity College Botanic Garden, the Research Assistant Msc. Richard Slevin led the field team, supported by interns Charles, and Antony and volunteers Liza, and Qudseya. Members of the Plant–Climate Interaction Lab, including Dr. Christos Chondrogiannis, Dr. Michelle Murray, and Dr. Miriam Słodownik, also contributed to data collection, continuing their involvement from previous years. A huge thanks to everyone who contributed to the data collection and continues helping the project.
During the campaign, researchers collected a range of physiological measurements to assess tree health and resilience. These included stomatal conductance, leaf temperature, and chlorophyll fluorescence. Leaf samples were also collected for carbon isotope (δ¹³C) analysis, with the goal of providing insights into long-term water-use efficiency and how trees respond to environmental stress.
In addition, leaf samples were collected to quantify the amount and chemical composition of particulate matter retained by different tree species, helping researchers evaluate the ecosystem service that urban trees provide by improving air quality. The team also collected herbarium specimens from all monitored species, creating a permanent historical record of the trees while providing valuable material for future studies, these specimens will be available at the Trinity College Dublin Herbarium.
The project’s genetic component also continued in 2026. This work, initiated in 2025 by Dr. Ailbhe Brazel, aims to identify molecular biomarkers associated with environmental responses in selected species, including alder, hazel, common oak, and maidenhair tree. This year’s sampling was carried out by Dr. Brazel together with research assistant James, continuing the development of this important aspect of the project.
The data collected during the 2026 campaign will contribute to the project’s long-term dataset, helping researchers better understand how urban trees respond to changing environmental conditions and informing evidence-based strategies for selecting resilient tree species for future cities.
How will pioneer salt marsh plants respond to rising CO2?
How will pioneer salt marsh plants respond to rising CO₂?
In the VAL Lab, a new experiment is underway using the PGC20 Growth Chambers. Over the next six months, Jenny Clarke – a second-year PhD researcher co-supervised by Iris Moller (Geography) and Jennifer McElwain (Botany) – will use the chambers to investigate the potential impacts of climate change on two species of pioneer salt marsh plants.
Jenny is growing Spartina anglica and Salicornia europaea under two scenarios: current climate conditions and a potential future, high-CO₂ climate. By comparing the two, she aims to determine how rising atmospheric CO₂ concentrations may affect the germination, establishment, and biophysical properties of each species.
To recreate a working salt marsh inside each chamber, Jenny uses a two-tank system. One tank represents the marsh itself, holding pots of tidal flat mud sown with seeds of one or both species collected from her field site on North Bull Island in Dublin Bay; the other supplies a reservoir of artificial seawater that floods the marsh semi-diurnally, reproducing the twice-daily tidal rhythm experienced by the pioneer zone at North Bull Island.
The ‘current’ climate conditions simulated by the chambers are informed directly by data collected at a monitoring station set up at her field site on North Bull Island. The raised-CO₂ conditions mirror these current settings in every respect except atmospheric CO₂, which is elevated to 820 ppm, in line with the IPCC’s SSP3-7.0 projection for the year 2100.
Salt marshes are among the most valuable habitats on our coastlines: they sequester large amounts of carbon, buffer the shore against storms and erosion, and support rich communities of plants, birds, and invertebrates. They are also highly sensitive to environmental change. By focusing on the pioneer species that first colonise the bare tidal flat, allowing marshes to establish and expand, Jenny’s work should help clarify how these critical ecosystems might respond as the climate continues to change over the coming century.
Cells to Ecosystems Summer School in Philadelphia, USA
Cells to Ecosystems Summer School in Philadelphia, USA
This summer, two members of our lab attended the Cells to Ecosystems Summer School at Haverford Campus in Philadelphia, Pennsylvania, USA. This programme offered participants in-depth training in trait-based palaeobotany and highlighted how plants can be used as tools to understand Earth systems and vegetation in Earth’s history. The course covered methods like field-based plant physiology measurements, fossil collection and analyses, as well as computational modelling.
Dr William J. Matthaeus participated as co-investigator and co-organiser of the programme, alongside Jonathan P. Wilson (who generously hosted the event at Haverford College), Joseph D. White (Baylor University), and Principal Investigator Daniel J. Peppe (Baylor University). Dr Miriam Slodownik participated as an attendee alongside six further selected students.
The diverse 10-day programme spanned lectures, practical sessions, and field trips. Highlights included fossil plant collecting in Centralia, a tour deep underground (and deep in time) in a historic coal mine (https://www.pioneertunnel.com/) which exposed Carboniferous coals, and a visit to Longwood Gardens (https://longwoodgardens.org/). The summer school was an excellent learning and networking experience and a great success for all organisers and attendees.
This course is supported by the National Science Foundation (NSF).
Jennifer McElwain Joins BBC Radio 4 Discussion on Tree Evolution
Jennifer McElwain Discusses the Evolution of Trees on BBC Radio 4
We are delighted to share that Jennifer McElwain, recently appeared on BBC Radio 4’s renowned programme In Our Time.
In the episode, The Evolution of Trees, Professor McElwain joined host Misha Glenny alongside Christopher Berry (Cardiff University) and Bill Baker (Royal Botanic Gardens, Kew) to explore one of the most important innovations in Earth’s history — the evolution of trees.
The discussion examined how the first trees emerged over 400 million years ago and went on to transform the planet by creating new ecosystems, altering the atmosphere, and shaping the landscapes we know today. The programme also explored how tree-like growth forms have evolved multiple times throughout plant history, highlighting the remarkable adaptability of plants.
In Our Time is one of the BBC’s longest-running and most respected radio programmes, bringing together leading experts from around the world to discuss major topics in science, history, culture, and philosophy. We are incredibly proud to see Professor McElwain sharing her expertise with such a broad international audience.
BBC Radio 4 – In Our Time: The Evolution of Trees (4 June 2026)
TY Students Explore Plant Ecophysiology at Trinity Botanic Gardens
Hands-on environmental monitoring and plant physiology activities as part of the Witness Tree Project outreach programme
Dr Ailbhe Brazel Awarded Prestigious Research Ireland Pathway Programme Grant
Building climate-resilient crops through research on low oxygen sensing and responses in plants
We are delighted to share that Dr Ailbhe Brazel has recently been awarded a prestigious Research Ireland Pathway Programme grant to investigate low oxygen sensing and responses in plants, with the aim of developing greater climate resilience in crops.
The Research Ireland Pathway Programme is a highly competitive national funding scheme designed to support outstanding early-career researchers in establishing themselves as independent research leaders. With an overall success rate of around 20%, the award represents a major achievement and supports researchers in building their own research programmes, including the supervision of postgraduate students.
Ailbhe has been working as a Teaching Fellow on the TERRAFORM Project since August 2024 and will now move on to develop her own independent research programme as a Research Assistant Professor in the Botany Discipline at Trinity College Dublin.
As part of the programme, Ailbhe is currently recruiting for a 3-month Research Assistant position and a funded 4- year PhD student to join the project.
Huge congratulations to Ailbhe on this fantastic achievement – we are excited to see this research programme grow and develop.
Plant Climate Lab at the Botany–Zoology Postgraduate Symposium 2026
On April 30th and May 1st, the annual Botany–Zoology Postgraduate Research Symposium 2026 took place at Trinity College Dublin, bringing together postgraduate researchers from across the School of Natural Sciences to share research spanning ecology, social science, zoology, and botany.
On the second day of the symposium, Dr Sate Ahmad delivered the keynote presentation on ecological restoration – the process of assisting the recovery of native ecosystems that have been degraded, damaged, or destroyed. The talk highlighted both the scientific and practical importance of restoration in responding to biodiversity loss and environmental change.
Plant Climate Lab postgraduate researcher Siddiq Muhammad also presented a 10-minute talk on the PlantChem Project: Investigating the Shift in Plant Chemistry Due to Climate Change – A Multidisciplinary Approach.
The presentation explored how rising atmospheric CO₂ and climate change may be altering the elemental composition of plants themselves — the fundamental “building blocks” of plant life. Using the same plant species collected from the same sites across 24 locations and seven major biomes, the study compared historic samples (1989–1991) with modern collections (2013–2015).
The findings revealed striking shifts in plant “elementomes”, with elemental composition changes ranging from 3% to as high as 61% over just a few decades. The greatest changes were observed in subtropical deserts, temperate rainforests, and dry tropical seasonal forests, highlighting how environmental change is physically restructuring plant chemistry on a global scale. These hidden shifts may have major implications for ecosystem functioning, herbivore nutrition, and global nutrient cycling.
The talk was followed by a lively Q&A session and received excellent feedback from the symposium organisers.
It was wonderful to see such a diverse and inspiring range of postgraduate presentations throughout the symposium, and a pleasure to reconnect with colleagues and friends across the School.
Nature as Medicine - Evaluating Forest Bathing for Student Wellbeing
Forest bathing at Trinity College Botanic Gardens as a growing green prescription for student mental health
The Witness Tree Walk & Talk
Exploring Witness Trees: Art Meets Science at the Botanic Garden
On 6 March 2026, the Plant Climate Lab hosted a Witness Tree Walk & Talk at the Trinity College Botanic Garden for artists from The Black Church Print Studio. The event brought together art and science through a shared exploration of trees as living witnesses to environmental change.
The afternoon began with an introduction to the Witness Tree project, outlining its scientific and cultural significance. Participants were then divided into four groups, each led by a member of our team – Prof. Jennifer McElwain, Michelle Murray, Leticia Candido, and Richard Slevin. As they moved through the garden, the artists were introduced to a range of witness tree species, learning about their ecological histories and the stories they hold within their growth.
Following the walk, the group gathered for coffee and conversation. This informal session provided an opportunity to examine plant specimens and leaf microphotography, as well as engage in a lively Q&A and discussion around themes of climate change, memory, and representation. These exchanges created a space for dialogue between scientific research and artistic practice.
The participating artists will now develop a series of print works inspired by their interpretations of the Witness Tree project, extending the conversation beyond the garden and into new creative forms.
This event highlighted the value of interdisciplinary collaboration, fostering fresh perspectives on environmental change and deepening public engagement with plant science.
Plant Climate Lab at PalAss 2025
Plant Climate Lab Contributions and Recognition at PalAss 2025
Members of the Plant Climate Lab attended and contributed to the 69th Annual Meeting of the Palaeontological Association, held in Portsmouth, UK, from 11–15 December 2025. The meeting brought together researchers from across the palaeontological community and featured a strong presence from our lab across the scientific programme.
Prof. Jennifer McElwain delivered the Annual Address, Exploring Earth’s dynamic atmospheres and ecosystems, highlighting how fossil plant proxies and palaeo-functional traits provide critical insights into long-term Earth system change. Dr Miriam Slodownik presented her research on the Austral Antarctic forest during the Early Eocene Climatic Optimum, contributing to discussions on polar ecosystems and climate sensitivity in deep time.
We are also delighted to congratulate Miriam on her election as Early Career Research Officer for the Palaeontological Association. With multiple members of the Plant Climate Lab participating in talks, sessions, and events across the meeting, PalAss 2025 was an excellent opportunity to showcase our research and engage with the wider palaeontological community.
