Stunted oaks
Stunted oaks in Wistman’s Wood, Devon © Mike Hill/Alamy

A few years ago, as my wife and I enjoyed our post-wedding supper in a Las Vegas restaurant, I witnessed the strangest of exchanges. The chef/patron, Joël Robuchon, was in town that evening and dutifully cruising the restaurant floor glad-handing his customers. One couple – regulars, we surmised – were especially excited to meet Robuchon. Had they ever been to his restaurant in Paris, he inquired through his interpreter? “Paris?” they exclaimed. “Why would we; we have our own Paris right here in Vegas!”

Last November, the UK House of Commons’ environmental audit committee issued a less than glowing report on the coalition government’s “biodiversity offsetting” green paper. The paper’s proposals – green in colour alone – were designed to help developers cut through the bureaucratic red tape that can plunge projects into planning limbo, by enabling them to measure the value of wild habitats and, if necessary, offset any loss from a proposed development through the creation of new habitats elsewhere.

The benefits of greasing the wheels a little would come from economic stimulus to the construction industry, and much needed new homes being built more rapidly. But in an interview with The Times just before Christmas, the environment secretary, Owen Paterson, suggested that any and all habitats could potentially be at risk – including ancient forest.

The notion that habitat lost through development can be mitigated by creating new habitats (and that planting more trees than those that are set to be felled offers a net gain) may seem seductive, and let’s be honest – convenient. Paterson used the construction of the M6 toll road around Birmingham as a positive example of offsetting, where the 10,000 mature trees that were felled were offset by 1m new saplings. His choice of that contentious development was an interesting one; during construction it was a hotspot for demonstrations, with protesters tunnelling under the route of the roadway in a bid to halt the diggers. Ten years after it opened the road carries only half the vehicles it was designed for and, according to the Campaign for Better Transport, it has “produced no net benefit for drivers, whilst causing huge and irreversible environmental damage”.

Tawny owl
Tawny owl © Brian Bevan/Alamy

Environmental groups, including the Campaign to Protect Rural England, have been largely united in their concerns. The CPRE stated that biodiversity offsetting should be used “only as a last resort” but that as the plans stood they could be used to set “unacceptably low standards of protection”. If environmentalists were angered by Paterson’s comments, the cross-party environmental audit committee was not too impressed either. Acknowledging that “biodiversity offsetting could improve the way the planning system accounts for the damage developments do to wildlife”, the proposals were denounced as “too simplistic”, and risked “giving carte blanche to developers to concrete over important habitats”.

Although the proposals are potentially applicable to any and all habitats, it is the threat to ancient woodlands that has raised the ire of environmentalists and caught the attention of the wider public. The still smouldering fire that was set by the coalition government’s attempt to sell off the nation’s publicly owned forest shortly after it came to power, has been reignited. Woodland preservation is always likely to be a touchstone. Britain is one of the least wooded countries in Europe – deforestation started in the Neolithic era – with the total percentage of wooded land as low as 5 per cent by the end of the industrial revolution in the 19th century. Commercial forestry and subsidy incentive schemes to farmers and landowners have led to an increase in woodland to about 8 per cent of the total landmass – still hopelessly small compared with other countries with similar landmass and climate. Of that 8 per cent, ancient woodland (which has been in existence for 500 years or more) is a tiny fraction.

Biodiversity offsetting relies on one central proposition; that an administrative exercise can be used to assess the value of a habitat and the cost of its loss. In its current form it is a flawed proposition. As the chair of the environment audit committee, Joan Walley MP, noted: “How do you put a value on 1,000 years of woodlands? You can’t wait 1,000 years for a new woodland to grow.”

Two hazel dormice
Two hazel dormice © Gerard Lacz/FLPA

The assessment method proposed requires only a 20-minute box-ticking exercise that does not adequately cover individual species, the effect on pollination, flood protection or the way in which different habitats link together to form ecosystem networks. The lack of emphasis on individual species is especially troubling – the equivalent of going into the Sistine Chapel and never looking up.

A single mature English oak (Quercus robur) can host up to 25,000 individual animals, from tiny invertebrates to birds such as tawny owls and small mammals like dormice. As many as 280 species of insect live on English oak. The green oak moth caterpillar (Tortrix viridana) feeds on the oak leaves, and in pupa stage can be parasitised by species of ichneumon wasp. When the ichneumon wasp egg hatches, the larvae eat the still live but parasitised moth pupa.

The life cycle of the oak is long and fascinating; loosely divided into three phases, juvenility, maturity and decrepitude, with each phase lasting anything from about 100 years to 300 years. Dead and rotting wood are a feature of oaks from early middle age, and the distinctive “stag’s head” – formed from dead wood at the ends of branches – are important habitats.

The older the oak, the more significant it is to biodiversity, not least because in the final stage, when the tree becomes a “veteran” (a period that can last as long as three human lifespans) the slow disintegration provides even more food and habitat opportunities. Oaks are so slow out of the blocks they do not even become sexually mature until they are 50 years old, at which point they begin to produce acorns.

Herb Paris
Herb Paris in bloom © Woody Stock/Alamy

Large trees are not the only significant species in ancient woodland. Ground-level flora and fauna achieve a richness and complexity that can only come about through hundreds of years of annual enrichment from leaf litter, and the absence of human “improvement”. The interaction between plant roots, mycorrhizae and soil fauna is still not adequately understood. Rare species of invertebrates, fungi and plants are reliant on old woodland. The stag beetle (Lucanus cervus), the UK’s largest, needs dead oak for its larvae to feed on, while one of the most graceful and rare of woodland plants, herb Paris (Paris quadrifolia), can only be found in old calcareous woodland.

We had an Elvis impersonator at our Vegas wedding. He was really rather good, but he wasn’t the real thing. The idea that a field full of knee-high saplings can replace even one 500-year-old oak must surely be specious. Ancient woodland is as priceless as the real Paris. A field full of saplings in plastic sleeves is rather like the “Paris” on the Vegas strip; no substitute for the real thing.

Matthew Wilson is managing director of Clifton Nurseries in London

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