The Feanedock Oak stands out so clearly in the section of the Derbyshire National Forest that you would think it was calling to us. Surrounded by open fields, thorn hedges and young beech trees, a majestic old oak like this dominates the English countryside.
As the crowning glory of our woodlands, oaks support more life in the UK than any other native tree. At the foot of the Feanedock Oak, wrens, blackbirds, spiders, squirrels, song thrushes, hoverflies, butterflies, blackcaps, woodlice, ants and chiffchaffs can be heard and seen at a glance. For more than two centuries, it has provided a stable habitat, even for humans: a ruined dwelling lies in its shadow.
The development of a common oak (Quercus robur) affects everything that lives on and around it, from the crown to the ground. In recent years of heat and drought, the Feanedock oak lost two large branches.
In the summer of 2023, dendrochronologists—who research and date trees through their growth rings—sampled the trunk to study their “healthy” and “poor” growth years. They counted 195 rings, but they did not reach the center of the tree, so it was probably planted in the early 19th century, if not earlier. As a sapling, it would have welcomed Derbyshire miners crossing the fields from nearby villages to work in the newly dug coal pits or in the area’s many industrial potteries.
More than 200 years later, in July 2023, the Feanedock Oak (now about 36 meters tall) played a central role in the Ring of Truth. This creative collaboration between tree scientists and artists from the Walking Forest collective imagined a legal case set in the year 2030 between a plaintiff, the oak tree (in whose shadow the case was heard) and the UK government.
The plaintiff’s lawyer, Paul Powlesland, a nature rights lawyer, made his case to the judge and jury, alleging that the government had breached its legal obligations under the Climate Change Act 2008. Scientists from the University of Birmingham, including one of us (Bruno), acted as expert witnesses, providing evidence of the threats the tree faced due to increased heat, atmospheric CO₂, damage to the soil and diseases.
After hearing all the evidence, the assembled public, acting as a jury, issued their verdict. Many were fully aware that the plaintiff had remained there much longer than anyone else present, a silent witness to the damage caused by humans to the environment and landscape. They ordered the Secretary of State for Climate and Ecological Breakdown (as the position is known in 2030) to stop failing to meet legal obligations to protect this and all “anchor oaks”, and the communities that thrive or suffer under them.
That shocking moment under the Feanedock oak tree opened the door to a deeper question: how and what do trees remember?
Until recently, little was known about how memory works in long-lived organisms like trees, which experience decades, even centuries, of changing environmental pressures. So this is what our multidisciplinary research collaboration—including artwork, performance, and even a musical composition, as well as innovative science—set out to discover.
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How the memory of trees works
For trees, memory is not a metaphor, but a biological reality, recorded in their cells. One of the most notable forms it takes is epigenetic memory: the ability of a tree to record its life experiences and allow them to define its future, without changing the sequence of its DNA.
As Membra (full name: Understanding the memory of UK treescapes for better resilience and adaptation), we have studied a number of ecologically vital and culturally significant UK species such as oak, ash, hazel, beech and birch. Together, they helped us understand how trees record and respond to environmental stresses, offering deep insight into how their memories are transmitted through forests.
At the heart of this process is DNA methylation, where chemical tags known as methyl groups are added to the tree’s DNA over time. Although they do not rewrite the genetic code, they do alter its reading. These chemical signatures can turn genes on or off, increase or decrease responses, and fundamentally change the way a tree grows, adapts, or defends itself. In oaks, for example, prolonged exposure to drought over decades is associated with changes in DNA methylation, suggesting that trees can adjust their gene expression in response to repeated stress.
These epigenetic memories may allow trees to respond more quickly to drought, disease or climate extremes, and could even be passed on to the next generation. In some plant species, this type of inheritance is well documented, but in long-lived trees, it remains an open question, with crucial implications for forest regeneration and resilience.
So far, our research has shown that trees respond to stress in ways that can extend far beyond the immediate event. Exposure to drought or high levels of CO₂, for example, can leave lasting marks on a tree’s growth and internal chemistry, and could determine its response to future conditions. However, the strength of this memory seems to depend on the nature of the stress: it is more pronounced when it is particularly intense, such as an illness, or when it is repeated over time, such as a chronic drought.
A surprising result came from oak, where we observed that DNA methylation changes depending on the time of year: methylation levels are lowest in early spring and then increase as the seasons progress. This suggests that memory imprinting in trees may be much more dynamic than previously believed, and that the timing of stress events within the growing season could influence the intensity of memory encoding.
All the species studied and the associated environmental conditions were sequenced. In all cases, we found evidence of these memories of past stresses. In ash trees, for example, we are beginning to detect methylation changes related to ash dieback pressure, offering clues about how trees regulate their defenses over time as a disease progresses.
Trees are certainly resilient. They bend, adapt and resist, keeping the memory of storms and seasons within. But even his deep-rooted strength has limits. The challenges they face now are faster, more frequent and more severe than at any time in their evolutionary history.
This means that what we are learning from their memories is not just a story of survival, but a warning. They warn us that there may come a time when they can no longer bear it.
Also read: The importance of urban trees to mitigate high temperatures in cities
Even young trees remember
It is easy to get carried away by a century-old oak tree. But what often goes unnoticed is the silent crisis beneath its canopy. In many UK forests, the next generation has disappeared.
Studies show sharp declines in most young tree species (seedlings and saplings) due to a growing list of pressures: prolonged droughts, rising temperatures, changes in herbivore populations, and a rising tide of pests and pathogens.
According to a study of nine sites in England and Scotland, co-written by one of us (Bruno) and currently under review, the mortality rate of young trees has increased from 16.2% in the period to 2000 to 30.9% two decades later.
In some species, such as elm and now ash, diseases have driven populations almost to the point of non-regeneration, when a forest can no longer sustain itself. To counter this threat, young trees must be highly adaptable, not only in their shape, but also at the molecular level. At Membra, scientists are exploring whether young trees absorb environmental stress more easily than older ones, and whether that memory, recorded through changes in DNA methylation, influences their survival.
One way to test these transgenerational changes is to expose trees (oaks and hazelnuts) to the high levels of CO₂ expected in the UK by 2050. This was carried out at the Birmingham Institute of Forestry Research (Bifor) facilities in a Staffordshire forest, one of the world’s largest climate change experiments, where groups of trees (circular forest plots) are exposed to 150 parts per million (ppm) CO₂ above environmental concentrations.
Membra’s research found that tree saplings exposed to these levels of CO₂ respond very differently to other environmental stressors, which may increase their resilience. For example, acorns from oak trees exposed to CO₂ were noticeably larger and their seedlings showed faster growth and greater resistance to pathogens such as powdery mildew, a clear sign that the environmental conditions experienced by parent trees can influence the resilience of saplings.
To date, molecular analysis shows that the inherited memory of this exposure is imprinted in the trees’ genes involved in defense mechanisms. The direct link to resilience should be identified in the coming years as our data analysis progresses.
Surprisingly, these beneficial effects were most pronounced during peak growing years, when trees produce an abundant seed crop, suggesting that the reproductive cycles of mature oaks, as well as resource availability, are key for oaks to successfully inherit their stress-adaptive traits. Similarly, seedlings from oak trees repeatedly exposed to drought showed greater drought tolerance, suggesting that some trees may prime their offspring to be more resilient to repeated climate stress.
*Estrella Luna-Diez is an associate professor of Phytopathology at the Faculty of Biosciences at the University of Birmingham; Anne-Marie Culhane is a visiting researcher at the Global Systems Institute at the University of Exeter; and Bruno Barcante Ladvocat Cintra is a researcher in Geography, Earth and Environmental Sciences at the Birmingham Forestry Research Institute at the University of Birmingham.
This text was originally published in The Conversation
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