Veteranisation Saves Ancient Trees

The Art of Ageing: How Simulating Damage Could Save Britain's Ancient Woodlands 

Deep within Sherwood Forest, a giant commands attention. The Major Oak stands immense, even surrounded by the lush green of early summer. Its trunk measures a colossal 36 feet around. Its canopy stretches wider than several buses parked end-to-end. Precisely fitted metal props act like supportive canes, holding up the tree's vast, dish-shaped crown. A fence keeps the many visitors from treading too close to its ancient base. 

This oak began life as an acorn at least 800 years ago. Its precise age remains unknown. Some experts estimate it has seen over a thousand summers pass. The tree likely reached its maximum height around the time Columbus sailed to the Americas. Its highest branches fell away long ago. Now, in its advanced years, it possesses a thick, gnarled trunk. Storms have scarred its bark. Large, knotty burrs mark injuries from centuries past. 

A Living Monument 

Touching the Major Oak's mossy exterior reveals a cool, solid structure, like touching aged cathedral timbers. Closer inspection shows signs of decay and insect activity between protective patches applied by previous generations of tree surgeons. The current metal supports replaced an older system of chains. Some chains remain embedded forever within the wood. They prevent the tree splitting under the immense weight of its spreading limbs. Centuries ago, a slow process of self-consumption began. The decaying heartwood was gradually absorbed. This formed a huge hollow inside the trunk. 

Few people have entered this fungal, insect-filled space. Arborist Reg Harris described remnants of lead lining inside. He noted reinforced hollows within lower branches. He compared the interior shape to the bow of a ship. Yet, this strange, almost macabre sight does not evoke sadness. Harris views the Major Oak as a model. It provides inspiration for innovative methods designed to replicate its complex array of imperfections. Scars, cracks, hollows, and decay define such ancient trees. These "veteran characteristics" are now the focus of conservation efforts. 

Forging Veteran Features 

Harris and fellow arborists face a daunting challenge. They aim to artificially create features that usually take centuries to develop naturally. Across the globe, ecologists, woodland managers, and fungi specialists are pioneering new research. They seek ways to mimic the characteristics of old trees. Techniques include using LIDAR technology to map tree structures. Some introduce beneficial microorganisms into younger saplings. Others fabricate artificial tree limbs and supports. Initial results show considerable promise. Harris jokingly calls their work an attempt to create an "arboreal time machine." They strive to accelerate the ageing process, not for the tree itself, but for the habitats it provides. 

The need for such intervention is urgent. Biodiversity is declining rapidly worldwide. Extinction rates are soaring. The United Kingdom's protected natural areas face a critical new role. Historically, areas like the national parks, established 75 years ago, focused primarily on human recreation. They often failed to adequately support the diverse creatures needing them for food and shelter. Consequently, the UK now ranks among the world's most nature-depleted countries. It sits in the bottom 10% globally for biodiversity intactness. Environmentalists and scientists urge legal changes. They want parks formally recognised and managed as interconnected ecological systems.

The Oak's Ecological Empire 

Britain's oak trees stand as powerful symbols of national heritage. They also form vital hubs within woodland ecosystems. Oaks collectively support an estimated 2,300 wildlife species. Bats roost within the Major Oak's fractured trunk. Countless life forms find niches specifically within aged trees. They feed on organisms thriving in dark crevices and damp hollows, features developed over many human lifetimes. Squirrels build dreys in branches and trunks. Woodpeckers excavate nesting holes. Later, other birds like the pied flycatcher and tawny owl occupy these abandoned cavities. A recent sighting confirmed the rare Lesser Spotted Woodpecker near the Major Oak. 

Trees like the Major Oak function as intricate networks of microhabitats. Sadly, such ancient specimens are astonishingly rare. The UK boasts around 170 million oak trees. However, University of Oxford data reveals only about 115 truly enormous, ancient examples comparable to the Major Oak survive. Within Sherwood Forest itself, approximately 380 trees exceed 400 years old. This age generally marks the threshold for developing significant old-growth characteristics and earning the title "ancient". Across continental Europe, such ancient trees are even scarcer. The total number across the rest of Europe likely falls short of the UK's count alone. 

A Legacy of Protection and Loss 

This relative abundance in the UK partly stems from historical land practices. Large estates were often set aside as royal hunting grounds. Sherwood Forest gained protected status early. It became William the Conqueror's royal hunting forest in the 11th century. Subsequent centuries saw immense human impact. Countless Sherwood oaks were felled. They provided timber for naval ships during the Napoleonic Wars. Many others built London landmarks like St Paul’s Cathedral. Further waves of logging took many more trees. The survivors, like the Major Oak, often escaped because they seemed too old, misshapen, or decayed for profitable timber extraction. Their perceived flaws ultimately saved them. 

Despite Sherwood Forest being enveloped in pollen during a recent visit, indicating peak growth, Reg Harris focused attention on time and decay. He pointed enthusiastically towards a leafless oak skeleton, its branch structure still distinct. "That one's dead, but it's teeming with life," he declared. Maintaining standing deadwood, harnessing the peculiar persistence of trees even after physiological death, is crucial. Certain organisms depend entirely on this decaying matter. Columns of rotting wood, termed "tree earth," form vital nutrient sources. Harris calls them "deadwood tubes," attractive homes for beetles and other invertebrates. 

Nature's Intricate Designs 

Moving deeper into Sherwood, Harris highlighted other features. Dead branches, known as stag-heads, protruded from living limbs. Moths hiding beneath loose bark favour these areas. He explained "ram's horn recovery growth". This occurs as rippling wood forms to seal wounds. It creates desirable roosting spots for bats. Cracks splitting tree trunks, often caused by storms, expose the inner wood. Uprooted trees sometimes survive, re-rooting nearby. Each feature serves a specialised ecological role. Many support complex communities, including fungal networks largely invisible to the naked eye. A broad consensus now exists among ancient tree specialists. They agree that the health of veteran trees underpins the stability of the entire forest ecosystem. 

As ancient trees decline naturally, the myriad organisms relying on them need alternative homes. The vast majority of Sherwood's other oaks are much younger, perhaps one or two centuries old. They lack the complex features of their ancient counterparts. This creates a monotonous landscape from an ecological perspective. Harris described these younger stands as uninteresting and uniform. He worries about a critical habitat gap developing. As the oldest trees eventually die, unique forest life could become stranded. The situation mirrors the plight of species losing habitat in shrinking polar regions. At Sherwood, Harris estimates a gap of roughly 500 years separates the oldest trees from the next generation capable of developing similar features naturally. This represents an extraordinary interruption in the forest's natural cycle. Current efforts aim to bridge this gap, creating suitable habitats much sooner. 

Simulating Nature's Scars 

An hour's walk brought us to an otherwise unremarkable oak. About three feet up its trunk, a peculiar square cavity appeared, like a vertical letterbox. Healing tissue ringed the opening. Harris looked pleased. He reached inside, pulling out leaf litter to reveal composting wood and insect life. Previous checks of similar artificial cavities yielded darkling beetles. These insects typically inhabit wood in advanced stages of decay. Normally, an oak as relatively young and modest as this one might take 300 years or more to develop natural cavities capable of supporting such communities. To accelerate habitat creation, Harris and his colleagues use chainsaws and other tools. They carefully inflict simulated damage on younger trees. 

Sherwood Forest hosts the UK's largest programme for artificially creating veteran features. This work supports vulnerable wildlife populations. The interventions focus exclusively on younger, healthy trees. Arborists design the damage to mimic natural processes while ensuring the tree's overall stability. Chainsaws create patterns resembling lightning strikes. They carve out hollows suitable for nesting or roosting. Other, less precise techniques also fast-track ageing features. Harris described pulling limbs off with ropes attached to vehicles to simulate storm damage. Striking trunks near the base can induce decay higher up. This mimics damage once caused by large herbivores like wild horses or aurochs, missing from the UK landscape for centuries. 

An Ethical Dilemma Resolved 

For those unfamiliar with this field, deliberately wounding trees as a conservation strategy can seem counter-intuitive, even alarming. Witnessing features normally associated with extreme age appear on relatively young trees might feel unnatural. Yet, these artificial wounds represent successful interventions. Encouraging faster habitat development in younger trees helps close the age gap. It supports specialised wildlife that might otherwise vanish from the landscape as the truly ancient trees naturally senesce. These small-scale efforts offer hope for significant long-term benefits for Sherwood's threatened species. Vikki Bengtsson, a leading tree conservation consultant who trained Harris, recalled initial scepticism when the idea was first proposed. However, veteranisation quickly gained traction. 

The techniques provide significant ecological benefits at relatively low cost. Bengtsson carried out some of the earliest tree veteranisation work near Heathrow Airport in the late 1990s. She now advises on projects across Europe. The largest systematic trial began in 2012. It involved around 1,000 trees across the UK, Norway, and Sweden. Results confirmed minimal tree mortality from the interventions. More importantly, evidence indicated wildlife readily adopted the artificial features. Bird nesting material, insect frass (droppings), and fragments of bark suggested colonisation by target species. Ants and bats showed particular attraction to artificially created cavities. These findings provide a strong rationale for using veteranisation to support threatened species and address the lack of old trees elsewhere. 

Supporting Creatures of Decay 

Sherwood Forest serves as an excellent case study. Its relatively high number of natural ancient trees supports diverse populations dependent on decaying wood. These established populations can potentially colonise newly created artificial habitats nearby. This contrasts with areas lacking ancient trees, where such species may already be locally extinct. Sherwood's veteran trees act as vital reservoirs for insects like the Cardinal click beetle and various longhorn beetles. These creatures, collectively termed saproxylic invertebrates, play essential roles in the ecosystem. They break down deadwood, recycle nutrients, and provide food for birds and mammals. They also transport smaller organisms like mites and fungi across the woodland. 

Declines in ancient tree populations inevitably lead to declines in the specialist insects dependent on them. These species face the greatest risk in woodlands with few ancient trees remaining. As the last veterans die, a critical habitat gap emerges. Younger trees cannot naturally develop the necessary features quickly enough. In areas without intervention, populations crash. This occurs through natural attrition of old trees combined with the inability of younger trees to provide continuity. Nearly 20% of Europe's catalogued saproxylic invertebrates now face some level of threat. Certain beetles living deep within mature trunks struggle to disperse. They often rely on interconnected decay columns persisting across generations of trees. Population declines reflect these dispersal limitations and the lack of suitable younger trees without targeted human action. 

Early Signs of Success 

Researcher Adrian Dutton conducted surveys at Sherwood Forest. He found that half of the 350 target species previously recorded were clustered around trees subjected to artificial veteranisation. Such early indicators encourage further development of these techniques. However, Dutton cautioned that while the work is likely beneficial, more long-term monitoring is essential. Confirming definitive, lasting benefits requires continued observation and data collection. The initial signs suggest the interventions are providing valuable resources for target species, helping bridge the critical habitat gap identified by Harris and others. This offers a proactive strategy rather than simply waiting centuries for nature to take its course. 

South of Sherwood lies Windsor Great Park. This former royal hunting ground now serves as another ecological laboratory. Here, mycologist Matthew Wainhouse focuses on a different aspect of veteranisation: harnessing fungi. Using a sterilised drill bit, he carefully introduced a rare fungus into an oak tree's core. This organism specialises in breaking down inner heartwood. Trees constantly battle fungi, insects, and animals attacking their leaves, bark, and wood. At Windsor, Wainhouse and colleagues aim to enlist these natural antagonists. They hope to accelerate the formation of internal hollows, a key goal in veteranisation projects. These moist, decaying chambers provide vital microhabitats for rot-dependent invertebrates. 

Fungal Allies Speed Decay 

Wainhouse explained that hollows naturally expand over time. Larger creatures then colonise them. In North America, bears eventually use large tree hollows. Nesting activities deposit organic matter rich in microorganisms. This provides specialised food sources for other inhabitants. Hollows also act as crucial insulators. They buffer extreme temperatures, helping animals survive harsh weather or maintain stable conditions for raising young. Wainhouse's technique, developed with fellow mycologist Lynne Boddy, bypasses the tree's natural defences. Researchers insert small wooden dowels colonised with specific decay fungi directly into the target tree's heartwood. This delivers the desired organisms precisely where they can initiate decomposition most effectively. 

The Windsor team carefully selected fungi isolated from naturally occurring ancient trees within the park. They expected the dense heartwood to resist decay for a considerable time. Surprisingly, initial assessments revealed significant progress much faster than anticipated. Within just a few years, the inoculated areas showed decay patterns normally found only in centuries-old trees. This demonstrated the potential for fungal inoculation to rapidly create complex internal habitats. Understanding oak woodland ecology remains a complex challenge. Interventions like fungal inoculation often reveal the limits of current knowledge in fields like entomology and mycology. Emma Gilmartin, a specialist in fungal ecology working with UK tree managers, highlights the need for better collaboration. 

Technology Enhances Understanding 

Restoring ancient woodland characteristics requires pooling expertise. Arborists, mycologists, entomologists, and ecologists must share detailed knowledge. This fosters a holistic understanding of forest systems like Sherwood's. New technologies facilitate this collaboration. Sensor networks deployed in some woodlands monitor environmental conditions and tree health. Individual trees can relay data about their status. This helps conservationists assess the impact of management programmes in near real-time. These "smart forest" approaches provide unprecedented insights. At Sherwood, remote sensing techniques like LIDAR (Light Detection and Ranging) created detailed 3D digital models of trees, including the Major Oak. 

These digital twins allow researchers to calculate carbon storage accurately. They help assess structural integrity and inform management decisions. The models also serve as powerful educational tools. Advanced image analysis, potentially using artificial intelligence, can reveal hidden information. Patterns in tree form or growth rings might offer clues about past conditions or future risks. AI could help analyse wildlife camera trap data to understand how different species use veteran features. Gilmartin noted that these tools reveal the relative ecological value of different trees. They show how quickly hollows develop and indicate overall woodland health. This allows for more precise, targeted interventions, focusing efforts where they are most needed, especially for rare or sensitive species. 

Global Efforts, Local Solutions 

Around the world, teams employ digital technology and innovative designs to aid forest management and support wildlife impacted by habitat loss. Near Canberra, Australia, mature eucalyptus woodlands provide vital habitat for diverse bird species. However, historical clearing and ongoing development have reduced the number of large, old trees with complex structures. This loss negatively impacts bird populations needing specific features for nesting and roosting. Fewer large, hollow-bearing trees limit breeding success and survival. An Australian National University team, including architect Stanislav Roudavski, is designing novel structures. These aim to enhance habitat complexity in younger forests, bridging the gap until trees mature naturally. 

The project uses detailed wildlife tracking data and AI analysis. Researchers study how birds use eucalyptus trees, particularly focusing on microhabitat preferences. One key finding revealed birds favour flatter, horizontal branches over thicker, vertical ones for perching and nesting. This insight informs AI-driven designs for lightweight, flexible structures made of rods and wires. These artificial additions simulate the complex canopy architecture and specific features found in old-growth trees but absent in younger stands. They aim to provide immediate habitat improvements for vulnerable bird communities while the forest slowly recovers its natural complexity over decades. This demonstrates a global trend towards proactive, technologically informed habitat creation. 

Reassembling Nature's Work 

Decades ago, the poet W.S. Merwin wrote movingly about the imagined reassembly of a felled tree. His poem described meticulously putting back every splinter, leaf, and piece of bark. It envisioned rejoining severed limbs and replacing nests exactly as they were. The poem highlighted the impossible intricacy of restoring what was lost, comparing the final, fragile state to a dream: "You cannot believe it will hold." This imagery resonates with modern conservation efforts in places like Sherwood and Windsor. Human interventions, however sophisticated, attempt to replicate processes perfected over millennia. They aim to accelerate features like decay columns, fungal communities, and complex cavities. 

Harris emphasized that these planned interventions represent just the latest chapter in humanity's long relationship with woodlands. People shaped Sherwood Forest for centuries before conservation laws existed. Local inhabitants gathered firewood, grazed livestock, and even drilled into trees to assess timber quality. Archaeological evidence points to human activity influencing the landscape for millennia. In the UK, most woodlands showed signs of human management long before the Norman Conquest – around the time Sherwood's Major Oak likely sprouted. Many visitors expect pristine wilderness. They are often surprised to find open, wood pasture landscapes rather than dense, closed-canopy forests. 

Shaped by History, Guided by Science 

Louise Hackett, a senior conservation manager, explained Sherwood's mixed character. It features dense woodland patches alongside open areas with scattered trees. Acidic soils and historical clearing created conditions allowing some oaks to grow large and ancient. Removing competition allowed trees like the Major Oak to develop their massive crowns and survive for centuries. Sherwood's unique history and terrain fostered the persistence of its remarkable veteran trees. Across the planet, few forests remain truly untouched by human influence. Areas like Sherwood offer glimpses of ancient ecosystems, but they exist within a human-modified world. Recognition is growing that some interventions, once considered harmful, can be beneficial. Controlled burning, for example, is increasingly used to manage certain woodland types. 

If the veteranisation work in England and elsewhere proves durably effective, these techniques should become standard practice. Introducing specific fungi, as Wainhouse does, or creating artificial habitat structures, like Roudavski's team, could become vital tools. Those working closely with ancient trees often report a profound connection. The trees inspire awe through sheer endurance. Efforts to mimic natural ageing processes underscore the limitations of human ingenuity compared to evolutionary time. Current tools cannot fully replicate the complexity developed over centuries. Artificial methods cannot construct a Major Oak from scratch. Instead, experts aim to imbue younger trees with some veteran qualities. This provides life-support for species dependent on features found only in the oldest trees. 

A Long View, An Affirmative Act 

Merwin explored similar themes after embarking on a massive personal project. He spent nearly half a century restoring degraded agricultural land in Hawaii into native forest. He transported seaweed and manure to enrich the soil. He painstakingly planted thousands of native and diverse trees, recreating a semblance of Maui's pre-industrial landscape. Amid today's converging ecological crises, experts hope targeted actions can sustain vulnerable ecosystems. Trees live long lives; the ecosystems they support operate on equally vast timescales. People initiating projects today may not see the ultimate results. Bengtsson acknowledged this long perspective, a common theme among forest ecologists. 

The vast timescales involved inevitably raise questions. Does the effort justify the investment, given the uncertainty and the long wait for outcomes? Harris provided an answer. Gazing into an artificially created cavity, observing the nascent insect life and early signs of wood mould forming within, his response was simple, grounded in immediate, tangible evidence of life taking hold: "Yes." The interventions offer not a perfect replica of the ancient, but a vital bridge across a dangerous ecological gap, providing hope for continuity in these precious woodland realms.