Insect re-establishment - a code of conservation practice

Invertebrate Link - Joint Committee for the Conservation of British Invertebrates


The use of re-introductions and re-establishment of animals and plants, as part of projects aimed at re-creating habitats and communities, is widely accepted as constructive for the conservation of the countryside.

The Joint Committee for the Conservation of British Insects has been concerned at the lack of coordination, documentation or advice available on appropriate techniques for the reestablishment of insects. Accordingly, it has produced this code of conduct, which it hopes will have wide application. It has consulted with other conservation organisations and is currently pressing the Nature Conservancy Council to produce a nationally accepted policy with guide-lines for re-establishment and re-introduction.

This code of conduct has been agreed by the members of the Committee, representing the Royal Entomological Society, the British Butterfly Conservation Society, The British Entomological and Natural History Society, the Amateur Entomologists' Society, the British Museum (Natural History), the WCN (SSC) Butterfly Specialist Group, and by observers of the Nature Conservancy Council, National Trust, Forestry Commission, Agricultural Development and Advisory Service and the Ministry of Defence on the Joint Committee.

  1. Cautionary Foreword

    Entomologists and conservationists are by no means agreed about the role establishment of invertebrates (see 'Definitions', 2. below) should play in the conservation of species and sites. Indeed, some insect conservationists believe that establishment of species may do more harm than good. Others are convinced that, under due safeguard, establishment of species has an increasingly important role in conservation. It is for these that this code is written. The Committee recommends that no specific proposal for insect re-establishment be condemned or approved without full discussion and consideration.

    Any proposal to establish a population of insects must consider the objectives of doing so, together with the points for and against, including theoretical and practical ones. These cannot be set out fully in a code of practice, but the Committee is always willing to advise on particular cases.

    However, the Committee believes that some ecological principles have been misunderstood in relation to establishment, and it urges that a thorough ecological assessment be made when considering the points for and against any establishment.

  2. Definitions

    Re-establishment means a deliberate release and encouragement of a species in an area where it formerly occurred but is now extinct. It is recommended that no species should be regarded as locally extinct unless it has not been seen there for at least five years.

    Introduction means an attempt to establish a species in an area where it is not known to occur, or to have occurred.

    Re-introduction means an attempt to establish a species in an area to which it has been introduced but where the introduction has been unsuccessful,

    Reinforcement means an attempt to increase population size by releasing additional individuals into the population.

    Translocation means the transfer of individuals from an endangered site to a protected or neutral one. Translocation is of less importance to insects than to longer-lived animals, such as mammals.

    Establishment is a neutral term used to denote any attempt made artificially and intentionally to increase numbers of any insect species by the transfer of individuals.

  3. Objectives

    Objectives in establishing insect populations are many and varied. The three most important objectives are pest control, scientific research and wildlife conservation.

    Biological, natural and integrated control are three types of pest management aimed at the establishment of insect populations. Biological control uses introductions, specifically Establishments for pest control are not considered further in this code, though it may be helpful in planning them. Attention is drawn to the provisions of the Wildlife and Countryside Act 198 1, which prohibit the introduction of alien species to the United Kingdom (Part 1, Section 14).

    Establishments of insect populations for scientific research are often temporary, being mad to elucidate some principle of scientific theory or practice. In most of its provisions, this cod is relevant to this type of establishment.

    Establishments of insect populations for conservation are arguably acceptable in principle, but are affected by individual circumstances, by the aims of conservation, and by consideration of geographical scale. Establishments cannot replace biotope conservation, or ensure conservation of species over their natural range.

    Establishment of insect populations for conservation should focus particularly on the re-establishment of nationally threatened species, but the establishment of a particular resource, such as-an attractive butterfly, for the enhancement of human enjoyment can also be considered. Re-establishments are particularly important because of recent trends in land-use (see 4. below)

    It is recommended that for any proposed re-establishment, its objectives are clearly formulated, in detail, and made freely available for examination by responsible organisations (e.g. NCC, this Committee, BRC, BBCS). The need for confidentiality in particularly sensitive cases is recognised.

  4. Trends in wildlife conservation

    Whilst it is not the purpose of this code to advocate the use of re-establishments for conservation, the trend over the last 30 years has at least shown that they must be increasingly considered.

    In the past, wildlife in some areas has been able to survive only because agriculture and forestry have been relatively inefficient in maximising yields of crops and timber.

    Intensification of agriculture (and, to a lesser degree, forestry) has destroyed wildlife habitats over a wide area, leaving nature reserves as the most important wildlife refugia.

    Nature reserves are a series of isolated and fragmented areas. Virtually all need to be managed to preserve their wildlife interest, but some have lost species through the lack of appropriate management. Some species may be particularly vulnerable to extinction in small reserves.

    Although local extinctions and recolonisations have been the usual pattern in nature, the isolation of nature reserves makes recolonisation uncertain and unreliable.

    The rehabilitation of nature reserves, and their creation from disused or abandoned land, may suggest the intervention of Man to establish wildlife in them.

    Contrary to a widely held belief, many successful re-establishments have been made over the last few decades.

  5. Planning for re-establishment

    Re-establishment for conservation may be species-orientated or site-orientated.

    Species-orientated re-establishments are primarily aimed at endangered or vulnerable species whose very existence in the country is threatened by habitat destruction and change. Such species obviously merit particular attention. In some instances, it is appropriate also to consider introduction, in which case the risk of displacing other organisms should be considered.

    Site-orientated re-establishments are usually aimed at enhancing the wildlife of a site (usually a nature reserve) by providing a showy, or otherwise valuable, species that was formerly present but has become extinct.

    In practice, both site-orientated and species-orientated re-establishments are dependent on adequate preparation of the site, or sites, to receive the species selected.

    There is little point in attempting to re-establish a species if its ecological requirements are not known or understood. It is recommended that every proposal for re-establishment states the detailed ecological needs of the species concerned and how they are to be met.

    Although local extinctions may occur from a variety of events, a very common cause is simply lack of, or inappropriate, habitat management. Virtually no reserve (or other site) consists of 'climax' vegetation, and most are changing with time in the absence of management. It is recommended that no re-establishment be attempted unless the cause of extinction is well understood, and can be reversed. This is the counterpart to the paragraph above.

    Before proceeding to prepare a site for re-establishment, it must be considered whether objections, theoretical and practical, have been given due weight. Is the proposed receiving site large enough? Will the re-established colony require constant reinforcement? Have genetic implications been fully thought out?

    In the planning stage, an assessment of the impact of the proposed re-establishment on the receiving site should be prepared. Possible effects on other wildlife, especially species of conservation value, should be considered.

  6. Preparing the receiving site

    Permission to re-establish any species must be obtained from the owner-occupier of the designated site.

    The adequacy of resources for the species on the receiving site should be determined, preferably through research.

    The ecological conditions necessary for the re-established species must be imposed on the site before the re-establishment is attempted. Where continuous, regular or periodic management is required, this must be to an agreed, detailed plan, and the body attempting the re-establishment must be satisfied that management will proceed in accordance with the plan.

    Re-establishment of any species, and the re-creation of its habitat, must be compatible with the objectives of management for the receiving site, and conform to the provisions of the management plan. Apparently incompatible objectives can often be achieved by suitable rotational management.

    It is recommended that the attempted re-establishment be discussed fully with the site owner/occupier, and with the full reserve committee and scientific committee, as well as the warden, in the case of nature reserves.

    It is important to consult NCC because an SSSI may be involved. There are implications under the Wildlife and Countryside Act, 1981, if this is the case.

  7. The source of stock for re-establishment

    An attempt at re-establishment must not weaken or harm the source population from which the stock is obtained. (Most colonies of insects, with a high rate of intrinsic natural increase, are able to withstand the removal of stock, if their habitat is in a satisfactory condition.)

    Permission to take stock for re-establishment elsewhere must be obtained from the owner/occupier of the source site. The provisions of the Wildlife and Countryside Act, 1981, must be complied with. Advice can be obtained from regional officers of the Nature Conservancy Council.

    The community of which the species for re-establishment is a part must be considered, and reproduced as far as possible on the receiving site. Specific parasites should be introduced with the source stock, if possible, as these are inevitably rarer, and therefore in even greater need of conservation than their hosts. An exception should of course be made where the purpose of the establishment is biological control rather than species conservation.

    Stock of an ecological type most similar to that formerly inhabiting the receiving site should be chosen. Usually this will mean a source close to the receiving site, but not to the exclusion of other factors. Stock from a similar biotope should be preferred to a geographically closer but dissimilar biotope.

    Consideration should be given to breeding in captivity stock for later release. In this way, numbers may be increased with less damage to the source.

    The stage (egg, larva, pupa, imago) for release depends on circumstances; there is no generally applicable rule. Species with sedentary adults may be released with the exception that eggs will be laid in the most appropriate sites. Active adult insects may leave the site before oviposition. Larger numbers of immature stages than adults should be used in re-establishment, to allow for mortality between release and reproduction.

    Numbers of released insects must be adequate to achieve re-establishment. Small numbers are often ineffective.

    Detailed records of the exact procedures used in the attempt at re-establishment should be kept.

  8. Monitoring re-establishments

    All attempts at re-establishment, whether successful or not, should be reported to the Biological Records Centre (ITE, Monks Wood), and to this Committee. Confidentiality, if required, is assured. Secretive attempts can confuse others and result in lost information.

    A standard form for recording re-establishments has been produced by this Committee, is available gratis from the Biological Records Centre, and should be sent, when completed, to the Committee's Surveys Officer. The relevant addresses are at 10. below.

    Detailed assessment of the success of any attempt at re-establishment should be made, with continual re-assessment at frequent and regular intervals. Such assessment should consider resources and other species.

    In the case of butterfly re-establishments, success can be monitored using transect 'walks', undertaken during the adult flying period and compared with regional and national trends derived from the Butterfly Monitoring Scheme. Details may be obtained from this Committee or the organiser of the Scheme, Dr E. Pollard (ITE, Monks Wood Experimental Station).

    As far as possible, re-establishments should be written up and published, so contributing to a common store of expertise.

  9. Summary of main recommendations
    1. Consult widely before deciding to attempt any re-establishment.
    2. Every re-establishment should have a clear objective.
    3. The ecology of the species to be re-established should be known.
    4. Permission should be obtained to use both the receiving site and the source of material for re-establishment.
    5. The receiving site should be appropriately managed.
    6. Specific parasites should be included in re-establishment.
    7. The numbers of insects released should be large enough to secure re-establishment.
    8. Details of the release should be meticulously recorded.
    9. The success of re-establishment should be continually assessed and adequately recorded.
    10. All re-establishments should be reported to the Biological Records Centre and this Committee.
  10. Useful addresses

    Biological Records Centre, Monks Wood Experimental Station, Huntingdon, PE1 7 2LS.

    Butterfly Monitoring Scheme, address as above.

    JCCBI, c/o Royal Entomological Society of London, 41 Queen's Gate, London, SW7 5HU

    Nature Conservancy Council, Northminster House, Peterborough, PE1 1UA.

    British Butterfly Conservation Society, Tudor House, Quorn, Loughborough, Leicestershire, LE12 8AD.

    Amateur Entomologists' Society, PO Box 8774, London, SW7 5ZG

Originally printed in Antenna 10 (l): 13-18 (1986), by the Royal Entomological Society of London and with generous financial assistance from the Entomological Club.