Field Trip to Brockham Quarry

Its the first time we have tried to do an evening event, but judging by feedback from the 16 participants, it was a great success. Brockham Quarry Nature Reserve, is one of the jewels in the 4Bs biodiversity crown. 90 years ago it was a busy and noisy industrial site, now its a peaceful haven for wildlife. It teaches us a lesson in how, given time, nature reclaims even the most damaged environments. We are grateful to local ecologist Paul Rictchie for his excellent guided tour and Paul shares some of his thoughts in the rest of this post.

Paul's Notes
These notes reflect the main topics we considered on our guided walk of the quarry. At the end of the notes you will find a short movie I made with the 4Bs Biodiversity team about the wildlife habitats in the quarry.

We talk about biodiversity - but what do we mean?
Biodiversity is the variety of life, including species, habitats, ecological processes the natural environment around us. Historically in the UK we tended to conserve species (Giant Panda, Blue Whale etc) until we realised that without the right habitats these species will not survive. Our focus then shifted to managing habitats or homes of species. More recently nature conservation is concerned with whole ecological systems - how biodiversity works in an area because of the interaction and interdependencies of all organisms and their environment. Attention is now focused on understanding environments and exploring ecological processes, such as rewilding, as the way to protect, sustain and enhance biodiversity.

Ecological processes
In the UK all ecological processes and conservation activity is targeted at semi-natural habitats and ecosystems because there is no natural environment left in Britain. The flora and fauna we see today arrived after the last Ice Age and with the melting glaciers came humans (Homo sapiens) and we are a key species affecting everything we touch and not always for good. Our impact on the environment changed dramatically once we ceased being nomadic hunter-gatherers and became farmers.

The first process I talked about at Brockham Quarry was the human activity of quarrying, an industrial process that extracted chalk to burn for lime and left behind exposed chalk cliffs, scree slopes of chalk debris and spoil heaps on the quarry floor. Although highly destructive at the time this commercial activity left a wonderful space for nature to colonise and a legacy of dynamic ecological processes that are leading to the creation of diverse semi-natural habitats.

Read more about Brockham Lime Works  http://www.brockhamhistory.org/business-and-industry/lime-works/​

Next we considered the ecological process of natural succession, which is a dynamic progress from open ground through a series of changes in habitat and plant and animal communities living there, to close canopy woodland in the UK. Nature does not favour bare ground, so bare flower beds, or allotment plots, or in this case bare chalk slopes, scree and rubble get colonised by ruderal plants, which change soil conditions so that other plants such as wildflowers, trees and shrubs can colonise.

The final ecological process we considered is grazing by large herbivores such as cattle, horses, goats, sheep and pigs, which are generally missing from most semi-natural habitats in the UK. Historically auroch (wild cattle), bison, red deer, wild ponies and wild boar had a key physical impact on vegetation cover, grazed or browsed on plants and created bare ground habitats. The ‘modern’ concept of rewilding is all about restoring natural ecological processes such as grazing to ecosystems such as at the Knepp Estate near Horsham.

Habitats & species
The outcome of these industrial and ecological processes in Brockham Quarry is a dynamic ecosystem based on chalk rock covered in places by thin, poor, free-draining alkaline soils. This is reflected by four key semi-natural habitats – rocky slopes (with scree), chalk grassland, scrub and lowland mixed-deciduous woodland. The chalk cliffs provide home to a variety of large nesting birds of prey and crows and are topped by three types of woodland – dominated by yew, beech and oak & ash trees.

Where trees and shrubs have managed to get a foot-hold the mixed deciduous woodland has spread down into the quarry with areas of closed canopy woodland and scrub. The scrub comprises young yew, oak, ash, birch, field maple and sycamore trees, as well as whitebeam, dogwood, hazel, hawthorn, blackthorn and holly bushes. Scrub is a maligned habitat, often seen as a nuisance or threat to grasslands but it provides important shelter and food for insects and songbirds.

The poor alkaline soils of the chalk grassland do not favour coarse vigorous grasses often found in open habitats, which provides space for a variety of wildflowers such as thyme, wild marjoram, vipers bugloss, hemp agrimony and scabious. These plants are all important food sources for a variety of bees, beetles, bugs, butterflies and moths. The absence of mowing on the quarry floor has resulted in the development of lots of anthills.

Management
These key semi-natural habitats contribute to the quarry being a Site of Special Scientific Interest but they require human management in the absence of wild herbivores and the large carnivores that control them. To stop or turn back the process of natural succession to closed canopy woodland requires the introduction of domestic herbivores such as the feral goats or human volunteers armed with bowsaws and loppers.

4Bs Nature Movie - Paul Rictchie describes the wildlife habitats of Brockham Quarry