How to Rewild

Shoreline Cliffs and Slopes

Habitat Management Plan

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Shoreline Cliffs and Slopes
Habitat Guide

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About 2500 miles of the British coastline has been designated as ‘cliff’ habitat, but the definition is a bit sloppy. Anything from a modest outcrop or muddy bank to a towering rock face gets lumped in under the same category. These ecosystems may be liberally sprayed with salt or get only a light dusting depending on the prevailing wind direction, height and foreshore conditions.

Nevertheless, the vertical rock face, harsh winds and frequent mud- or rockslides make it hard for trees to get established here, so the dominant vegetation is low-growing, with some salt-tolerant scrub mixed in. The rock type will have an influence on which plant community will thrive, as well as the form of the cliff itself – soft rock results in slumping slopes while hard rock creates huge vertical walls. Harder cliffs are more suitable for nesting, and they may be home to huge colonies of breeding seabirds, with enormous biodiversity value.

Sub Habitats

All cliffs and slopes which fall within the zone that is affected by sea spray. This includes a very wide range of geological formations, from huge, hard rock sea cliffs to slumping mudstone slopes.

Value

Maritime Cliffs and Slopes are not only of value to the species living in this habitat, but also to the ecosystems below and above. At sea level, the eroded sediment from sea cliffs enriches beach sediment, while this large surface area absorbs salt spray and protects the land from climate change-caused sea level rise. The inaccessibility of these vertical habitats, which often have dangerous sea and rocks at the base, has made them ideal refuges for a wide range of wildlife, turning them into biodiversity hotspots along our shorelines.

In hard rock, the cliff is fractured and pitted by holes, crevices and caves which create refuges for bats, seabirds and a hardy community of plants, lichens and bryophytes (mosses and liverworts). In soft rock, the slow slumping of the slope creates a dynamic habitat which favours pioneer species, creating a diverse ecosystem with high variability in soil moisture levels (including springs, seeps and pools), exposure and sunlight. This ‘undercliff’ ecosystem can in turn support a range of microhabitats from scrub to reedbed, while also being home to an abundance of specialist invertebrates. The ephemeral ponds created during slumps can even be important habitats for threatened amphibians like Great Crested Newts.

Cliffs have not just biodiversity value, but also strong cultural value, with certain areas benefiting from tourism due to their fossiliferous rocks, their cultural resonance or their beauty. At the intersection of sea and land, their erosion creates conflict between the interests of biodiversity (and long term coastal protection), and the shorter term protection of property and infrastructure.

Sandstone cliffs
When cliffs are eroded, the resulting rock falls get broken up into smaller and smaller chunks, forming boulders, then shingle, then sand.

Protect

Protecting a sea cliff is not as simple as installing a sea wall at its base. In fact, hard engineering will degrade the quality of this ecosystem and the resilience of the coastline. Cliff erosion is a key contributor to beach sand – when cliffs are walled-off from wave action, this reduces the input of new sediment into the system by as much as 50%, leaving beaches vulnerable to erosion. Beyond the benefit of new beach sand, wave action also creates structural diversity in the face of the cliff, as rockslides alter its shape over time. New niches and crevices become colonised by pioneer vegetation, which slowly succeeds to scrub and may briefly turn to patches of woodland or isolated trees before sliding down to the beach below.

This dynamic (‘seral’) ecosystem is what the community of cliff-dwelling organisms have evolved to expect. Rare pioneer species rely on the rapid turnover of cliff habitat – as one niche is lost, another appears elsewhere. But a stabilised cliff, with rock armour and a sea wall at the base, bolts and netting covering the face, will lead to the development of a stable, unnatural habitat, with valuable nesting opportunities becoming lost over time and specialist plant communities swamped by scrub and woodland. Therefore, protecting a cliff means avoiding hard infrastructure at the base where possible, but this is clearly not going to be an option in developed locations where property is at risk.

The ever-changing community of a cliff is also influenced by human activity from the top down. Non-native invasive species like Holm Oak, Buddleia and Sycamore can take over these habitats and reduce biodiversity. Runoff of fertilisers and pesticides from agriculture can destroy or shift sensitive plant communities towards a system dominated by agricultural weeds. Overgrazing can erode cliff edges, but when herbivores are removed entirely from the system, valuable cliff top grassland and undercliff habitat can revert to rank grasses and scrub.

Britain doesn’t have a native goat or sheep species, so it’s hard to know what level of grazing pressure would have existed in some of these precarious habitats in the past (particularly the undercliff). However, short sward clifftop lawns appear to be essential habitat for our native Chough (a fancy Crow), suggesting that wild horses may have maintained this type of ecosystem in our ancient past.

Some leisure activities can damage cliff ecosystems, particularly in areas with high tourism. Fossil hunters climb cliff faces and access sensitive undercliff habitats in areas with soft rock such as the Isle of Wight. Access paths may create damage to clifftop grassland and increase erosion of these areas, creating public pressure for hard protection measures at the cliff base. Climbing and coasteering are known to have negative impacts on coastal vegetation and animal life, disturbing and destroying communities through trampling and ‘gardening’ of rocks and ledges to clear detritus. Chalk residue from heavily-climbed routes may impact ferns and mosses, while access trails at the cliff base may also destroy biodiverse sites. However, given the approximately 2,500 miles of cliff habitat in Britain, and the localised nature of most leisure activities, a balanced response may be most appropriate – educational signs, marked paths and access restrictions at sensitive sites are likely to be effective.

Lundy Island
In some cases, protecting the base of sea cliffs is considered essential to protect infrastructure, such as the dock access road on Lundy Island.

Restore

While restoration of cliffs is difficult to achieve without removal of hard protection at the base, it is not impossible to create a similar effect with livestock. In Bournemouth and elsewhere on the south coast, goats are being used to restore lower vegetation height and an earlier successional stage on miles of undercliff habitat. Here, hard protection is still in place, and the cliff face is not permitted to erode further due to the impact this would have on valuable property situated at the cliff edge. However, the non-native goats can recreate the same kind of conditions that might have been found in the undercliff habitat while it was still dynamically eroding. This will allow threatened species of wildflower and specialist communities of invertebrates to thrive, without scrub and woodland dominating this ecosystem.

Elsewhere, the restoration of cliff ecosystems also requires restoring livestock at the top – Natural England is partnering with landowners across the Southwest of England to create a grassland buffer zone along clifftops. This zone is ideally grazed by animals similar to the wild horses which would have existed here in the past and created short grazed lawns that favoured certain wildflowers, invertebrates and the Chough. And indeed, Exmoor Ponies (a close relative of these ancient wild horses) are being used in some places, like on the Lizard in Cornwall. However, in these narrow coastal strips with public access and a high cultural value placed on horses, there can be issues with this system. Welfare concerns have been raised about this practice by concerned members of the public fearful of the cliff edge proximity, and feeding of the animals is common, which can affect their health and ability to keep the habitat in good condition. As ever, interpretation boards and public signs are a good, though not foolproof, way to address these issues.

Removal of hard protection at the cliff base will inevitably lead to erosion of the cliff itself, but could protect communities further down the coastline. Armouring one section of the coast against erosion prevents eroded sediment from the cliff (i.e. sand/shingle) entering the system, leaving the next section downwind exposed. Over time, the area in front of the hard infrastructure is also ‘scoured’, requiring artificial replenishment of sediment. This double-whammy creates high erosion hotspots beyond hard structures, and leaves beaches or sand spits downwind vulnerable to disintegration due to a lack of inputs. By removing cliff reinforcements where they are not essential, and sacrificing some property to the sea, we can restore the health of the rest of the coastline, including a biodiverse and beautiful ecosystem on the eroded section of cliff.

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