Managing Woodland for Butterflies and Moths

Managing woodland for butterflies and moths Why manage woodland at all? Surely a natural woodland, without (or with minimum) intervention would best supply sustainable habitat for butterflies and moths? The answer lies in the processes cleared woodland habitats. The For many species, the speed and that have formed our present natural processes that produce such extent of this change has made it landscape. Almost no woodland habitats within woodland (such as very difficult to adapt and landscape in Britain today can be considered fires, storms and the natural collapse changes have reduced opportunities wholly natural. We have inherited a of aging trees) typically occur too to relocate to suitable habitat long history of forestry use that has infrequently to provide the continuous elsewhere. substantially modified even our most cycle of clearings needed by these ancient woodlands. We have, and species. Woodlands would also have Overall objectives still are, continuously changing the been subject to regular, extensive This guide outlines specific woodland composition and structure of woods grazing and browsing by large management options designed to to meet our needs. The woodland herbivores which are now absent, benefit butterflies and moths. These wildlife we see today is a product of and these effects are not replicated options are designed to achieve the that history and many Lepidoptera by the increasing number of deer following overall objectives: survive in woodland habitats only now browsing our woods. The small because of repeated human use of size and fragmentation of most • Structural complexity woodland resources. woods in the UK also prevent natural • Habitat diversity processes operating at a sufficient scale to conserve the full range of • Foodplant diversity woodland wildlife. Low-intervention • Management continuity management strategies can make • Landscape connectivity David Green a contribution to the mosaic of habitats within a landscape, but need The single most important factor to be complementary to an active that makes a woodland good for management process that maintains butterflies and moths is a diverse, and enhances the valuable habitat uneven structure. This should features found in our woods. include some mature or tall trees, Our current suite of woodland some dense regrowth, numerous species coexisted in the past sunny rides and glades (both large alongside often extensive active and small) and patches of recently management of woodlands. So cleared and regenerating open areas why is woodland management now with sparse ground vegetation and considered a conservation issue? The warm unshaded conditions. This diverse woodland structure creates a Sustainable removal of timber and reason lies in the extreme speed and firewood is an important part of woodland the huge scale of recent changes. variety of habitats necessary for the management The usage of woodland has always various life stages of Lepidoptera, changed over time, but change has including larval foodplants growing In Britain, applying a non- happened very rapidly in the last in appropriate conditions, a limiting intervention approach using only hundred years. This has occurred not factor for many species. natural processes within most of just within one type of woodland or Such a varied structure, with a diverse our woodlands will not create the one region of Britain, but across the range of tree and plant species, habitats needed by many of our whole landscape. At the same time not only provides good habitats for butterflies and moths. For example, urbanisation and intensive agriculture Lepidoptera, but also for a wealth many of our rarest butterflies are has removed or highly fragmented of other insects and forest wildlife. highly dependent on open, newly much of our woodland network. 14 | Woodland management for butterflies and moths Specific requirements for specialist Managing across patch is likely to undergo regular species requiring deadwood, lichens, local extinctions and regular re- mosses or wetland features can be the landscape colonisations. Problems arise when integrated with this overall aim. Looking beyond the survival of the breeding patches become species on single sites, conservation isolated, either by distance and/or Continuity of management is the must operate at the landscape scale because the intervening landscape is next vital factor to consider. Species to be effective in the long-term. There hostile. usually occur on a site because its is now considerable evidence that past use has created the habitat they the populations of many if not most Managing habitats at the landscape need, and periodically repeating that butterflies and moths function as scale is essential given the evidence management will be necessary for metapopulations. This is defined as a that some species are already them to persist. This is particularly collection of local populations which shifting their geographical range, important at sites with a long history occupy discrete habitat patches but their habitat use and the timing of of a specific management regime. which are connected by occasional their life cycles in response to climate Where woodland landscapes have dispersal of individuals. Each habitat change. Enabling species to move become fragmented management continuity is essential as it is harder for species to move to alternative habitats elsewhere. What butterflies and moths need Continuity of management is also Indeed, adult butterflies may important because habitats are be encountered in parts of the dynamic: they will constantly change, woodland away from the vital often over very short time periods. breeding habitat, especially when Fundamentally, most woodland searching for nectar. In general, management for Lepidoptera is Lepidoptera require sheltered, about working within a cycle of warm sunny places as adults, often habitat succession rather than trying with a nectar source, as well as to maintain areas in a fixed state a suitable place to lay their eggs. over time. In particular, trying to hold The larvae will then require plentiful a permanent open area at an early foodplants, often growing in specific stage of woodland succession (such conditions, and will move to a as that used by Heath Fritillary) is sheltered or inconspicuous spot almost impossible. Regular cutting to pupate before emerging as an or grazing may keep the site open, Peter Eeles adult. For highly threatened species but will usually cause the woodland A Purple Emperor emerging from its in particular, understanding where ground flora to be replaced by a chrysalis on the underside of a sallow leaf they spend each of these stages, grassland community which may and at what time of year, can be the not support the target species. Understanding the life cycles of key to effective conservation. Land Most sites will require a shifting and butterflies and moths provides managers sometimes concentrate diverse habitat mosaic, created and an insight into what they need on providing the nectar-rich areas maintained by regular management from woodland habitats. All frequented by adult butterflies on different parts of the site to butterflies and moths go through (where they are most often seen) produce younger growth stages a complex lifecycle from egg to at the expense of other habitat (clearings or short, herb-rich swards) larva (caterpillar) and then pupa features. In fact it is rare that nectar which will in turn provide other (chrysalis) and adult. Some species is the factor limiting population habitats as they re-grow through spend much longer as an egg, growth, and suitable habitat for egg- woodland succession. Regular larva or pupa than as an adult, laying and larval development is management provides continuity of and the habitat requirements of usually crucial. Details of individual short-lived habitat conditions. each stage may be very different. species requirements are given in Section 4. Woodland management for butterflies and moths | 15 Careful planning allows you to work out what is possible and to set Sam Ellis priorities. The stages are: • Assess what you have (consider what habitats and species are represented, in a local and/or regional context) • Decide your objectives and priorities (incorporate the needs of butterflies and moths alongside other interests) • Decide how these objectives are to be achieved over time, given your resources and any legal requirements (including felling licences, site designations and protected species) • Monitor progress and examine how both vegetation and your target species respond to management (incorporating what you learn into future management) Once management is underway, be flexible and consider revising management prescriptions if they do not meet your objectives. It may be best to trial new management on only a proportion of the site, until monitoring results show that it does deliver the anticipated conservation Open space as part of the wooded landscape at Whitbarrow, Cumbria outcomes. through the landscape and between Management planning Felling licences habitats gives them a better chance As part of the management plan it Management for butterflies and of adapting to future changes. must be noted that a felling licence moths often requires a long-term The aim should be to restore and from the Forestry Commission is commitment to produce a diversity construct landscape networks with generally required for the felling of habitats that will meet the interconnected, varied habitats. of trees, even if

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