Scientists have identified 42 “witness trees” to track unfolding climate change in Ireland in a unique research project to be pursued over the next 30 years.
The research being conducted by botanists in Trinity College Dublin will also pinpoint which species are best for cleaning outdoor air – by removing smog from the atmosphere in the course of their natural growth.
Trees make wonderful natural witnesses to environmental change because they are usually very long-lived (some flowering trees live beyond 1,000 years), so typically witness change in a way shorter-lived species do not, said Prof Jennifer McElwain, who is leading the project.
“They are [also] highly responsive to their environment, moulding the parts they grow every year such as new leaves and twigs – and even their physiological behaviour – to the prevailing conditions of the time,” she added. “They are, in effect, giant biological sensors with the potential to provide scientists with detailed, highly accurate, long-term datasets on the state on the environment.”
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With postgraduate researcher Midori Yajima, and outreach manager at Trinity Botanic Garden Michelle Murray, they have identified 21 trees in the garden to be witness trees ranging across alder, strawberry tree, hazel, ginkgo, common oak and wollemi pine. The participation of the National Botanic Gardens has brought the number of trees up to 42.
They will be studied to see how they respond to smog caused by atmospheric particulate pollution and to changes in levels of carbon dioxide.
“By recording data every year for the next 30, we will build up a valuable long-term data set and be able to make highly informed decisions as to which species can best clean our air, and which species are most likely to survive and thrive in our changing environment. In this way, we hope to shape ongoing and future green policy and make a major societal impact,” Prof McElwain said. This will indicate which species should be proactively protected and planted with the future in mind.
[ When the extreme heat hits Ireland, we’ll be grateful to the treesOpens in new window ]
Every summer they will observe critical functions in the trees, which will outline their health and ability to capture particulate matter pollution, known as PM. To assess their ability to capture smog, the scientists will assess quantities captured by each tree of inhalable PM10 particles, which are relatively large, and fine inhalable PM2.5 particles, which are tiny.
To assess the trees’ general health (and track how this changes with the environment), they will measure their “stomatal conductance”, which is the rate of exchange of water and CO2 between the plant and the atmosphere. As this is central to keeping the tree alive, it is a good indicator of general health.
Prof McElwain added: “We are delighted that the National Botanic Garden joined the project ... More trees means more data, which will help us to be more confident in any key messages we pass on from the witness trees to the researchers and policymakers who can make a difference in the future.”
The project has been funded by Dr Beate Schuler and the European Research Council.
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