Much of the heavy London clay underlying the Blean woodlands has a superficial layer of more gravelly, sandy soil, which is acidic and with low levels of nutrients. Timber trees such as oaks tend not to flourish so well in these conditions, whereas silver birch can become abundant and, if tree regeneration is inhibited by grazing or other habitat management, typical heathland plants such as ling (a common species of heather), gorse and broom can quickly become established. We know that in the past some livestock did graze parts of the Blean and that heather was harvested to thatch cottages, so it is likely that open heath, or at least heathy pasture woodland with widely spaced trees, was a feature of the Blean.
In recent years land managers within the Blean (RSPB, Kent Wildlife Trust, Forestry Commission and Woodland Trust) have all played a part in recreating aspects of a former heathland landscape, with wide-open skies where buzzards now soar above vivid yellow torches of spring-flowering gorse and broom, or great sheets of purple ling in high summer. Today there are around 20 hectares of heathland within the Blean, and Kent Wildlife Trust’s work will shortly increase this to about 30 hectares. Left to itself, any area of heath will quickly revert to birch woodland, losing all of its special wildlife value in the process. This succession is halted in the Blean through a combination of grazing, mowing and chemical treatment of regenerating birch saplings. The livestock used to control the woody regrowth varies from site to site, but includes konik ponies, Soay sheep, feral goats and Highland cattle, all of which are hardy animals able to subsist on a tough, nutrient-deficient diet.
A visit to one of these heaths at dusk from May to July may well be rewarded by the eerie churring of the nocturnal nightjar, a summer visitor from Africa. Around ten pairs of these enigmatic birds nest in the Blean each year, which is about 20% of the known Kent population. Other heathland birds that may be found here include tree pipit (fast declining), whitethroat and linnet. Dartford warblers have overwintered at least twice in recent years, but are not yet known to have nested in the Blean, and although there are records of woodlarks pausing here in spring, none have stayed to breed, and they remain an extremely scarce Kent species.
Patches of bare ground that heat up in summer are attractive to tiger beetles, mining bees and wasps, and basking common lizards, but adders have not been recorded in the Blean.
The Blean heaths have also proved very rich in invertebrates. This is most evident in summer when flowering heather is visited by huge numbers of bees, hoverflies and other insects; bush crickets leap away from your every footstep and, in a good year, clouds of butterflies erupt from the heather as you pass. Gatekeepers and meadow browns are easily the commonest butterflies, but other species occur, including the gorgeous little green hairstreak, whose underwing coloration makes it a true metallic emerald gem. Heathland within the Blean has also been shown to be exceptionally good for spiders, with a number of local species found only in a few southern counties of England being present: included in this category are Phrurolithus minimus, Dipoena tristis (Blean is the only known Kent site for this species), and Gonatium paradoxum (the only other Kent site is on chalk grassland).
Heathland is an extremely scarce habitat in Kent, the nearest extensive patch to Blean being in the Kent Wildlife Trust’s reserve at Hothfield Common, near Ashford. Consequently, as a result of its isolation, and perhaps the ephemeral nature of the habitat, which would have rapidly reverted to woodland whenever grazing pressure was relaxed, the Blean heathland does not support the full range of plants and animals to be found on the much more extensive, longer-established Surrey heaths. Dwarf gorse, bell heather and cross-leaved heath, for example, are all absent from the Blean, as are specialist species of boggy heath such as round-leaved sundew, but a number of characteristic heathland plants do occur here, including heath bedstraw, wavy hair grass, purple moor grass and heath milkwort.
Written by Michael Walter