LOWLAND HEATHLAND - BIODIVERSITY ACTION PLAN SPECIES

The Convention of Biological Diversity, signed by 159 governments at the Earth Summit in Rio de Janeiro in 1992, provided a legal framework for biodiversity conservation and called for the creation and enforcement of national strategies and action plans to conserve, protect and enhance biological diversity.

In 1993, the British government consulted widely on the subject and in 1994 Biodiversity: the UK Action Plan was launched. Species and types of habitats of conservation concern were identified and action plans for 391 species and 45 habitats were published. Predictably, the number of species in the list has risen since that initial assay, with 1,149 species and 65 habitats in the latest version published in the summer of 2007. These consist of 59 species of bird, 14 fish, 10 herptiles, 337 lower plants and fungi, 212 vascular plants, 88 marine flora and fauna, 411 invertebrates and 18 terrestrial mammals.

The Biodiversity Action Plan (BAP) was a means of providing support for the UK government's bold commitment to halt biodiversity loss by 2010 by way of : 1. protecting, enhancing and aiding recovery of threatened species and habitats; 2. protecting our finest wildlife sites and ensuring appropriate management; and 3. providing space for biodiversity through making all habitats wildlife friendly. In 2012 it was succeeded by the Post-2010 Biodiversity Framework, covering the period up to 2020, which in some respects is the same thing by a different tag.

Considering that in 2002 a third of the UK's BAP habitats and a quarter of species were still declining, and that many national policies such as incessant development and encouragement of air transport do nothing to help wildlife, this may seem a ludicrously optimistic intention, always assuming it was genuine in the first place.

Lowland heathland is one of the habitats, and a number of species there have a BAP, all of which are under the aegis of Natural England, which covers the subject in depth on its website www.naturalengland.org.uk.

The Sand Lizard (Lacerta agilis), whose males turn a marvellous shade of green in the breeding season in May, is larger than the Common Lizard (Lacerta vivipara) , measuring up to 20cm. (The latter can also carry some green colouring.)

The species is under threat throughout its international range. In the UK, natural populations have disappeared from some coastal dunes, the Wealden heaths and the New Forest, and despite reintroductions, the dry heaths of south Dorset are the only area where they seem safe.

Sand Lizards feed mainly on invertebrates and their eggs are laid under sand. In a rather unhelpful arrangement of nature for both species, Sand Lizards are one of the principal prey items of another BAP species, the Smooth Snake (Coronella austriaca, up to 75cm).

Silver-studded Blue butterflies (Plebeius argus, wingspan 30mm) have undergone an 80 per cent decline in recent years. They are single brooded, with adults flying from July to August on heathland and from June to mid-July on calcareous sites. In all habitats the butterfly requires short or sparse vegetation and the presence of Lasius sp ants, which tend the larvae. Early successional stages are best, with some bare ground, and the pictured regeneration of Heather (Ericaceae) at Thursley National Nature Reserve in Surrey is ideal. They feed on Heather (Calluna vulgaris), Bell Heather (Erica cinerea), Cross-leaved Heath (Erica tetralix) or Gorses (Ulex spp).

Since 1970 the Heath Tiger Beetle (Cicindela sylvatica, 15mm) has been very localised in Surrey, Sussex, Hampshire and Dorset. It is found on open, dry and sandy soils with heather, feeding on surface-active invertebrates including ants and caterpillars. They fly readily and breed in spring and summer, with the larvae found in vertical burrows in the soil. The Heath Tiger Beetle shares its habitat with the Green Tiger Beetle (Cicindela campestris, 14mm), which is much commoner and not covered by a BAP.

Human ideas of beauty are ridiculous when applied to the natural world, but the Hornet Robberfly (Asilus crabroniformis, 25mm), shown in all its glory on the menu page of the website, would be pretty low down an uninformed person's list of handsome creatures.

Found in unimproved grassland as well as heathland, they are large, in the region of 35mm, hairy and ferocious predators of almost anything, including crickets, grasshoppers, flies and beetles. They are athletic and fast-moving hunters, able to jump up to 10cm and using the stout proboscis to drain victims dry. The eggs are laid in dung and the larvae are believed to prey on the larvae of large dung beetles. Unfortunately the species is in decline.

Cerceris quinquefasciata, an uncommon digger wasp preying on weevils, is dealt with in full detail on the Solitary Wasps page of this section (see below). Altogether rarer, and certainly harder to find, is the cuckoo wasp Chrysis fulgida (10mm), which preys on another scarce wasp, the eumenid Symmorphus crassicornis. Both species are dealt with in the Solitary Wasps section in Woodland in this website.

Mottled Bee-flies (Thyridanthrax fenestratus, 10mm) are purely southern and confined to Dorset, Hampshire, Surrey, West Sussex and, possibly, Berkshire. This species, too, is declining and has gone from some former sites. They are found in open, heather-dominated heathland, usually along sandy paths and in other sparsely vegetated areas.

The Bee-fly is considered to be a parasitoid of either the solitary wasp Ammophila pubescens or of the caterpillars the wasp collects to feed its larvae. However, as with so many parasites, they are not found in anything like all the locations inhabited by the host species.

The large mounds of stems, dried leaves and other plant detritus which make up the nest of another BAP species, the Southern Wood Ant (Formica rufa, 8mm), are familiar to anyone walking through a woodland clearing, mostly in heathland but also in deciduous forests.

The nest can contain several queens and around 100,000 workers (a fair-sized group is shown on the menu page in this section), who forage widely along paths they make snapping up caterpillars, flies and beetles among others as both predators and scavengers. Honeydew is a key part of their diet so they require trees with Homoptera (aphids) nearby. Their defensive tactic at the nest of projecting formic acid in bulk was vividly shown by Sir David Attenborough in Life in the Undergrowth on BBC television.

Dangers to individual locations of the species include poor woodland management and a succession of bad summers - not a likely event at the time of writing. However, while the Wood Ant remains quite common in lowland England, its range appears to be contracting elsewhere.

The most-pictured bird associated with lowland heath is not the Wood Lark (Lullula arborea), which has a BAP, but the more colourful Dartford Warbler (Sylvia undata, wingspan 16cm), usually perched atop a gorse bush unless it's windy - they dislike such conditions.

This species, which feeds exclusively on invertebrates, suffered a decline for most of the last two centuries, but was recovering and expanding up until 2009, to the extent that its population had more than doubled over the previous 25 years. In 2006 there were 3,208 breeding territories, up by 70 per cent compared with 1994, while the Wood Lark's tally of 3,084 was up by 89 per cent on 1997.

At this point there were 100+ pairs of Dartford Warblers in Suffolk, where there were none in the 1930s. A succession of mild winters and proper heathland management undoubtedly helped the expansion, but Dartford Warblers are still vulnerable if conditions change. Their numbers fell to 11 pairs after the harsh 1963 winter and counts in the Thames Basin and Wealden Heaths Special Protection Areas in 2009 indicated that the population had fallen from around 1,000 pairs the year before to just 117.

Heavy snowfall in the area in early February 2009 apparently contributed to this crash, and the even harder winter of 2009-2010 might well have placed the species in yet greater difficulty all over lowland England. If this is the case, renewal is almost certain in time but so long as Dartford Warblers remain on the edge of their range in Britain a stable presence is not guaranteed.

Images © Jeremy Early. All rights reserved.

In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.