I’m fortunate to be the temporary custodian of a 250-year-old oak in my garden, a true city in the sky that is home to an astonishing variety of life.
A tree of this age and stature is more than just a feature of the landscape—it’s a fully functioning ecosystem. Its vast network of branches, standing high above, may contain 20–25 tonnes of dry wood and another 20–30 tonnes of water above ground, not to mention an extensive underground root system.
Ancient oaks are biodiversity hotspots, supporting more species than any other native UK tree. Protecting these trees is crucial, and ensuring their preservation means safeguarding an entire web of life. Here’s why they matter:
The Oak as an Ecosystem
- Likely species: English oak (Quercus robur) or sessile oak (Quercus petraea)
- Features a massive canopy, deeply textured bark, hollow trunks, and deadwood, providing diverse habitats
- Produces acorns, a key food source for numerous animals
Invertebrates: Over 2,300 Species!
Ancient oaks are a lifeline for an astonishing array of insects, including:
- Oak processionary moth
- Stag beetle, whose larvae feed on decaying wood
- Gall wasps, which create unique formations on leaves and twigs
- Many species of spiders, ants, and beetles, all playing vital roles in the ecosystem
Birds: A Canopy for Nesting and Feeding
Oaks provide essential nesting sites and food sources. Residents of my own tree include:
- Tawny owls, their calls echoing across the woodland at night
- Woodpeckers, both great spotted and green—the latter easier to hear than to see (listen to their calls here)
- Treecreepers, nuthatches, and jays, the latter playing a crucial role in dispersing acorns
Mammals: Roosting, Nesting, and Foraging
- Bats (e.g., pipistrelles, noctules) roost in oak hollows and church towers, emerging at dusk to hunt
- Squirrels and dormice nest in tree hollows, with dormice sometimes moving into nearby houses for winter shelter
- Deer benefit from the oak’s cover; roe deer and muntjac are common, though the latter—an introduced species—can wreak havoc on gardens
Fungi & Lichens: The Oak’s Hidden World
- Fungi decompose deadwood, enriching the soil (e.g., oak polypore, beefsteak fungus)
- Lichens colonize bark, with some species serving as indicators of ancient woodland health
Plants & Mosses: Flourishing Beneath the Canopy
- Mosses thrive in the oak’s shaded, damp bark crevices
- Woodland understory plants, such as snowdrops and bluebells, flourish beneath its protective canopy
Carbon Storage & Climate Impact
- Oaks play a crucial role in carbon sequestration. Trees are roughly 50% carbon by dry weight, meaning a 250-year-old oak stores around 8 tonnes of carbon—equivalent to 29.4 tonnes of CO₂, the annual emissions of approximately three UK citizens.
Why We Must Protect Our Ancient Oaks
A 250-year-old oak is an irreplaceable living monument—a keystone species supporting an intricate web of life. While it takes centuries to grow, it can be lost in seconds. Protecting these trees is not just about preserving a landscape feature; it’s about safeguarding a vital component of our biodiversity and climate resilience.
We must ensure these trees stand for another 250 years and beyond. Whether by advocating for their protection, monitoring their health, or simply appreciating their role in our ecosystem, each of us has a part to play. Let’s keep our oaks standing.
Do you have an innovation that could help conserve biodiversity? Whether it’s a technology, a new business model, or a bold idea, we’d love to hear from you.
