By Daniel Greenwood, Conservation Project Officer, London Wildlife Trust
Separated by a line of crumbling green posts, Dulwich and Sydenham Hill Woods make up the largest remaining fragment of the Great North Wood, a stretch of ancient woods, commons and pasture which stretched from Selhurst to Deptford. The Great North Wood was originally a product of the wildwood, a landscape made up of naturally occurring trees that colonised in the wake of retreating glaciers 10,000 years ago, as the climate warmed and became more hospitable. The wildwood no longer remains in the UK, its gradual clearance enacted by Neolithic farmers 6,000 years ago. Dulwich and Sydenham Hill Woods are still here with us because they provided a lifeline for local people living in the Great North Wood and beyond. Both woods, though joined, differ in structure and species present. This article aims to explore some of the differences between the two and why that may be.
Sydenham Hill Wood
Sydenham Hill Wood is a Local Nature Reserve, a Site of Metropolitan Importance for Nature Conservation and is designated as Metropolitan Open Land. Before the Crystal Palace High Level railway and the adjacent Victorian villas were built (1860s), what has been known as Sydenham Hill Wood since the 1980s was broken up into coppices – Lapsewood, Ambrook Hill Wood and Peckamins Coppice, the latter making up much of what is now Dulwich Wood. Coppicing is a craft which dates back thousands of years and meant that many British woods were open and bright, and the oldest woods remaining in Britain today are old coppices. Coppicing is now mostly extinct economically but is enacted by London Wildlife Trust at Sydenham Hill Wood to diversify habitat structure and reignite the lost practice. The timber is used for dead hedging, handrails, other vital woodland infrastructure and as deadwood log piles. Historically this form of management provided timber for small scale industry as well as fuel for charcoal burning. But it was great for wildlife, too. The coppices of Dulwich and the Great North Wood were once a place to hear the song of the nightingale, a migratory bird which is now long gone from London and relies on coppices and scrub to breed where it still resides in England. Coppicing also meant sunlight met the woodland floor offering warmth and nourishment to bluebells, primroses and violets, and the butterflies, moths and other invertebrates dependent on those particular wildflowers. Across the country the collapse of coppicing and darkening of woods has meant a national decline in woodland wildflowers and associated species, particularly once common butterflies like the silver-washed fritillary. Thankfully this species made a return to Sydenham Hill Wood in 2014.
The sunny channel created by the railway will have encouraged plant species which utilise wind to spread their seeds. It is likely that rosebay willow herb, now dominant in the Sydenham Hill Wood glade, made its way down the railway line in the twentieth century. Rosebay willow herb is a non-native plant which colonised Second World War bombsites in London. This is a plant which is generally absent from Dulwich Wood, shielded from the railway line by a screen of oak, holly and hornbeam. On the western boundary of Sydenham Hill Wood runs the Ambrook stream, once a tributary of the River Effra. Before the 1860s, when the railway and housing was complete, Sydenham Hill Wood will have been much richer in ground flora, fungi and their associated species. The disruption caused by the movement of soil and building work will have led to the loss of a number of sensitive plant species and the complete removal of fungal mycelia, the web of fungal roots which produces the mushrooms we see most splendidly in the autumn and which proves vital in the ecosystem of woods. A fungal mycelium links with a wood’s network of tree roots to pass nutrients back and forth in symbiosis.
The impact of the Victorians is a key part in understanding the ecology of Sydenham Hill Wood. Rhododendron was widely planted as a garden ornamental shrub in the 1800s but in oak woodlands its presence is highly destructive. The evergreen rhododendron adds a toxin to the soil in its attempts to maintain dominance and as it grows it begins to shade out everything it overcomes. Over time it will kill oak woodland. Therefore it is one of our target species for removal. Another plant which is disruptive to broadleaved woodland ecosystems like those of the Dulwich Woods is cherry laurel. This poisonous plant, introduced from the Balkans, is planted still today as a hedge plant due to its vibrant, evergreen foliage and low-maintenance nature. It can grow rapaciously, gradually lowering and thickening its boughs to send down more roots when they become so heavy that they travel horizontally rather than upwards. Some large laurels in Dulwich Wood have nothing growing underneath them and the Dulwich Estate plan to undergo clearance work to aid native species. At Sydenham Hill Wood we actively reduce laurel, pulling new saplings which appear each year, often after birds pass the seeds. But we are keen to retain part of the wood’s heritage and manage it without complete removal in certain areas of historical interest, whilst stopping the plant from spreading where possible.
Dulwich Wood is owned and managed by the Dulwich Estate, with the main management tasks being the clearance of paths, maintenance of boundary trees and perimeter fencing, the removal of ivy from mature trees and the emptying of bins and maintenance of signage. Dulwich Wood is not a registered or recognised nature reserve. Unlike Sydenham Hill Wood, Dulwich Wood has remained untouched by development and retains larger spreads of wood anemone, English bluebell and wild garlic. Dulwich Wood’s structure comprises standard sessile oak, ash and hornbeam trees with a holly, hazel and bramble understorey. It has a typical coppice-with-standards woodland structure where mature sessile oaks were harvested for their timber and the tannin residing in the bark, and the hazel understorey coppiced on rotation. There are signs that the oaks were replanted and abandoned after the collapse of woodland industry in the UK which is why there are some dense stands. In recent decades the Dulwich Estate have acted upon the degree of shade in Dulwich Wood by selectively felling an area of trees to allow more light in and an understorey to regenerate. This has had some success with growths of willow, ash, bramble and black bryony present in 2012 and butterflies like the speckled wood being observed on the wing. A botanical survey for the London Naturalist in the 1960s showed a more open wood pasture style landscape, with grassy swards and standard oaks dotted throughout. Many of the species seen then are now lost due to the shade, with species such as common cow wheat disappearing completely. Many of the wildflower species flourishing along the sunnier banks beside pathways in Dulwich Wood are showing a decline from accidental damage through trampling. The woods are experiencing numbers of visitors that their wildlife will not have had to cope with before.
The Dewy Pond in Dulwich Wood
In 2011 London Wildlife Trust enacted a three year programme of regeneration at the Dewy Pond with funding from the Dulwich Estate and the SITA Trust. During those three years the Dewy Pond and Ambrook was de-silted, fenced, and replanted with native aquatic and riparian plants like marsh marigold, yellow flag iris, watermint water avens and hemp agrimony. Volunteers constructed a pond dipping platform from seasoned oak for use with schools and public events. The works involved the clearance of a number of trees and shrubs and has proved highly beneficial for the wildlife which depends on the aquatic environment – aquatic invertebrates, dragonflies, frogs, newts and foraging bats. It has also added another layer of diversity to the structure of both woods, as well as a break from the dense shade of Dulwich Wood’s holly understorey.
Understanding the impact of visitors
One of the biggest challenges to the Dulwich and Sydenham Hill Woods is managing the impacts of visitors. Footfall erodes soil over time and so clear, well maintained pathways are key to protecting the woods in the long term. Soil compaction degrades soil, reduces biodiversity through trampling and prevents tree roots from gathering the oxygen required to sustain it. Responsible dog walking is not a problem but the impacts of dog fouling are, on many levels. The nutrients added to the soil from faeces raises the level of nitrogen which increases the dominance of bramble, nettle and other vigorous plants. English bluebell and many other important wildflowers are known to be lost when soils become too rich. London Wildlife Trust enjoys a good relationship with dog walkers at Sydenham Hill Wood and the majority of visitors pick up after their pets when visiting. However, the problem does persist. With the impact of visitors in mind, we are attempting to get a sense of how many people are visiting the woods. Between April 2014 and January 2015 we have conducted 24 hours of site transect walks on Monday mornings in 45-60 minute visits between 9:00 and 11:00am. Over this period we have observed 269 people and 122 dogs. This is just a snapshot of visitors to Sydenham Hill Wood. It’s vital for people to visit both woods for the wellbeing of our community and so that the woods are appreciated and their wild inhabitants not forgotten. People have lived and worked in woods for thousands of years and it’s a relationship which is adapting to twenty-first century living. It is only in recent decades, as the scale of woodland loss has been understood, that people are again turning to woods for exercise, fresh air, a sense of solitude and the most important thing of all: a connection with the natural world.