Four main factors threaten swallowtails, as well as other terrestrial forms of wildlife: habitat destruction, pollution (which might be considered as a special form of habitat destruction), the introduction of exotic species and commercial exploitation. In general these threats are either the direct result of increasing human population pressure or else are enhanced by it. It is now internationally recognized that conservation efforts can only reach long-term fruition in partnership with policies for population planning and control. A full consideration of the global problem of human populations outstripping their resources, and of the political, economic and social causes, are beyond the scope of this book and other publications should be consulted for more detailed studies.
Each of the four types of threat will be briefly reviewed, with examples drawn from the swallowtails.
Habitat alteration and destruction
As demonstrated in the companion lUCN Red Data Books for plants, mammals, amphibians, reptiles and invertebrates, the primary threat to wild species throughout the world is the destruction and alteration of the biotopes and habitats in which they live. All species depend for their survival upon the integrated network of physical and biological factors that make up their environment. Most are able to withstand a small degree of disturbance and manipulation, but human activities have steadily modified wilder- ness areas into man-made landscapes of settlement, agriculture and industry that are altered to an extent that precludes coexistence with many wild creatures.
Habitat alteration has a universal impact on swallowtails and other wildlife, but the effects are more noticeable in biomes and ecosystems that are restricted in area. Hence the extensive destruction and alteration of African savannas has certainly caused great reductions in distribution patterns, but no swallowtail species are regarded as threatened there. Even in the more restricted rain forests of the Zaire basin only Papilio antimachus is recognized as threatened (category Rare), and this species is still widespread. A similar situation prevails in the massive forest block of the Amazon basin. Conversely, islands are particularly prone to extinctions because they tend to have rich endemic faunas in very restricted areas. Mauritius for example, has suffered the extinction of many species of animals and plants, largely because of deforestation followed by extensive cultivation of sugar cane. The endemic swallowtail Papilio manlius has been fortunate in successfully adapting to Citrus for its foodplant, but Libythea cinyras (Libytheinae) is now believed to be extinct there and Cyclyrius mandersi (Lycaenidae) may be seriously threatened. Similarly, Papilio phorbanta has adapted to Citrus on Reunion, but the subspecies nana from the Seychelles has not been seen since 1890. A number of endemic taxa in Taiwan are under threat, including Papilio maraho (Vulnerable) and Troides aeacus kaguya. In Jamaica Eurytides marcellinus is now extremely rare and populations of the Homerus Swallowtail (Papilio homerus) have been split up and endangered as a result of coffee production and timber extraction. Graphium epaminondas may be under similar pressures in the Andaman Islands, as may Graphium levassori on Grande Comore. Many other examples of island-living swallowtails are at risk, including amongst others the birdwings of South East Asia, Papilio hospiton from Corsica and Sardinia and Papilio neumoegeni from Sumba.
Montane species suffer many of the same problems as those on islands. In the tropics there are many swallowtails restricted to a habitat that may have been more extensive during the cooler climate of the last Ice Age, but is now found only on mountains. In Sabah and Sarawak Papilio acheron and particularly Graphium procles have restricted ranges in montane regions. Mt Kinabalu, the only place where G. procles flies, is a protected area, but economic considerations have taken high priority there and the region has suffered incursions by mining companies and recreational developments. In Indonesia the little known species Graphium stresemanni is possibly confined to the Manusela range in Seram and Atrophaneura luchti has a very restricted montane range in eastern Java. Graphium sandawanum is found only on Mt Apo in the Philippine island of Mindanao, and both Papilio chikae and P. benguetanus are relict species in the Cordilleras of Luzon.
In Africa the effect of the last Ice Age on vegetation patterns is still contentious, but whatever the historical causes, there is no question that the string of relict forests running from Mt Kulal in northern Kenya to Mt Mulanje in Malawi now all have their own endemic subspecies of butterflies, if not species, and all are under threat from deforestation for agriculture and plantation forestry. Of particular note is the now highly Endangered Taita Blue-banded Swallowtail (Papilio desmondi teita) from the Taita Hills in southern Kenya. Other Kenyan montane papilios of interest include Papilio dardanus flavicornis from Mt Kulal and P. d. ochracea from Mt Marsabit and Mt Nyiru. In Tanzania Papilio sjoestedti flies only in montane forests in the regions around Mt Kilimanjaro, Mt Meru and the Ngorongoro range, much of which is fortunately protected inside national parks. Many more butterflies from East Africa’s montane forests could be listed here, particularly from the nymphalid genus Charaxes.
The forms of habitat alteration of most importance to swallowtail butterflies are 1) deforestation, 2) agricultural conversion and intensification, 3) alteration of pastures and 4) industrialization and urbanization.
As a result of the ecology and distribution of swallowtail butterflies, forestry practices in temperate latitudes have little impact on their populations. An exception is the Japanese Luehdorfia japonica, which is discussed below.
In 1981, following an extensive survey of 76 tropical countries, the Food and Agriculture Organization (FAO) and the United Nations Environment Programme (UNEP) jointly published an assessment of the global tropical forest resources. These documents have supplied an extremely valuable framework within which to discuss the conflicts between conservation and exploitation of forest resources, conflicts that must be resolved if sustainable economic growth is to be achieved. When combined with data on protected areas and the distribution patterns of animals, plants and, in the present case, swallowtail butterflies, it becomes possible not only to assess current conservation problems, but also to predict which regions and species are likely to be of particular concern in the future.
Tropical forests in the broadest sense are estimated to cover 2970 million hectares, i.e. 20 per cent of the land surface of the globe. The main forest formations are closed broadleaved forest (including rain and monsoon forests, 40 per cent), open forest types (including the cerrados of South America and the wooded savannas of Africa, 25 per cent), coniferous forests (1 per cent) and shrubland (21 per cent). These ecosystems include by far the most important swallowtail habitats. The majority of swallowtail species use larval foodplants that are vines, shrubs or trees, although there are important exceptions in the Parnassiinae. Exploitation of tropical forests by man will inevitably disturb swallowtail populations, but the extent of the impact depends on the level of disturbance, the extent of the biotope and its ability to recover, and the willingness of people to allow it to do so.
Tropical forests may be altered in two ways: 1) through complete deforestation followed by non-forestry usage such as agriculture, or 2) by selective felling for industrial use (mainly rain and monsoon forests) or fuel production (mainly drier forest formations). However, it is usual for logged over forests eventually to become completely deforested so that for all practical purposes deforestation becomes the major factor altering tropical forests.
The most important single cause of deforestation is shifting cultivation, accounting for70 percent, 50 percent and 35 percent of the total areas that have been deforested in Africa, Asia and the Americas respectively. Thus, the division of threats between deforestation and agricultural conversion in this discussion is to some extent artificial. Other significant causes of deforestation are clearance to create grazing lands (particularly in South and Central America) and settlement of agriculturalists along new logging roads with subsequent expansion into the forest (particularly in Africa and Asia).
Logging can damage forests to varying extents . In South East Asia for example , the ‘volume actually commercialized’ (VAC), an index of production from the point of view of commercial exploitation, ranges from 15 cu. m/ha in Burma to 90cu. m/ha in Sabah, i.e. from less than 10 per cent to more than 30 per cent of the corresponding standing volume of timber. This may mean that whereas Burmese swallowtails like the Kaiser-I-Hind (Teinopalpus imperialis) could survive logging, native birdwing species in Sabah would be unable to withstand the rapid degradation and complete loss of habitat which can result from such intensive logging rates. Another variable is the extent to which logging roads are subsequently used as access roads to new farms by land-hungry people. This problem is most apparent in Africa and Asia where 70 per cent of the deforestation occurs in areas of closed forests that have been previously logged. In the Americas the comparable figure is only 44 per cent because most logs are transported along rivers or existing roads.
In the drier regions of the tropics, particularly of Africa and Asia, the accelerating demand for fuelwood and charcoal is causing severe deforestation of open woodland. The technology is available to meet these demands through plantation forestry and Brazil produces 29 per cent of its fuelwood needs from Eucalyptus plantations. In Africa and Asia however, the low levels of investment in plantations to meet these basic demands of the rural poor must eventually have dire consequences in socio-economic and resource conservation terms.
The global rate of clearance of tropical closed broadleaved forest is now believed to be lower than was previously feared. However, this is no cause for complacency, it simply means that there is a little more time in which to implement sound conservation and management strategies. A large proportion of those remaining forests will be disturbed to some degree.
There are considerable differences between the rates at which countries are utilizing and altering their closed forest resources. Whereas Zaire and Brazil will still have extensive forest resources in the year 2000, the forests of Peninsular Malaysia, Ivory Coast, Nigeria, Sri Lanka and Java will be virtually gone. If present trends continue, nine countries will have used practically all their closed broadleaved forests within 30 years, and a further 13 will join them within 55 years. All 22 of these countries between them only account for 11 per cent of the world’s tropical closed forest, but some, such as Jamaica and Sri Lanka have important swallowtail faunas.
What impact is tropical deforestation having on swallowtail butterflies? Considering in the first place the loss of tropical closed forests, the Asian sector is of greatest concern . About one quarter of the world’s closed tropical forest area is found in Asia, 61 per cent of this being in the islands of South East Asia including New Guinea. This is the world’s richest area for swallowtail butterflies. Indonesia has 121 species of swallowtails, over 20 per cent of the world total. It has also emerged as the world’s most important producer and exporter of tropical hardwoods. Rain forest species from the South East Asian islands that have been given threatened status include Graphium idaeoides, G. megaera, G. sandawanum, Papilio osmana and P. carolinensis in the Philippines, Graphium stresemanni, Ornithoptera aesacus and O. croesus in the Moluccas, O. rothschildi, O. chimaera, O. paradisea and particularly the Endangered Queen Alexandra’s Birdwing, O. alexandrae, in New Guinea and Graphium meeki, G. mendana and Papilio toboroi in Bougainville and the Solomon Islands.
In continental Asia the threats from deforestation are less serious because most swallowtails are more widespread in their distribution. However, deforestation throughout its range, but particularly in India and Nepal, is placing the Kaiser-I-Hind, Teinopalpus imperialis at risk. Numerous species are locally at risk in Peninsular Malaysia, including Troides helena, T. aeacus, T. amphrysus, T. cuneifer, Papilio agestor, P. mahadeva, P. palinurus, Graphium empedovana, Meandrusa payeni, Lamproptera meges and L. curius.
African rain forests are still poorly studied and the two Insufficiently Known species, Graphium weberi and G. aurivilliusi from the main Cameroon-Congolese block, require further research . There are few endemics in the much-depleted forests of the western block, but Graphium maesseni is only known from the Ghanaian type series. The Giant African Swallowtail, Papilio antimachus, is now very scarce in this western part of its range but although it is confined to primary forests, its future may be assured in the forests of the Zaire basin.
In the South American rain forests the swallowtail fauna also remains poorly known. There are few seriously threatened species but the narrow ranges of Parides hahneli, P. pizarro, P. steinbachi, P. coelus, P. klagesi, P. burchellanus and Papilio garleppi are cause for concern . There are many other poorly known rain forest species..
Turning to the loss of tropical open woodlands, a number of threats to swallowtail butterflies can also be identified. Of the Asian fauna, Papilio jordani is a Rare species from possibly open formations of semi-deciduous forest in northern Sulawesi and Troides dohertyi is Vulnerable in the nearby Talaud and Sangihe Islands. Two Vulnerable species, Papilio neumoegeni from Sumba and Atrophaneura schadenbergi from Luzon, probably fly mainly in open woodlands. Eurytides is a genus of kite swallowtails that fly in the open woodlands of the Neotropics. Both the Yellow Kite, Eurytides iphitas, and Harris’ Mimic Swallowtail, E. lysithous harrisianus, are in serious decline in Brazil, and the Jamaican Kite, Eurytides marcellinus is now a great rarity in Jamaica. As already noted, there are few threatened species in the extensive savanna formations on the African mainland. A number of threatened island species have already been mentioned; two others that are confined to open woodland, Graphium levassori from the Comores and Graphium pelopidas (possibly a subspecies of G. leonidas) from Pemba Island and Zanzibar, are at risk.
Agricultural conversion and intensification
The spread of subsistence farming has been cited as the biggest single cause of forest clearance, soil degradation and loss of wildlife in the world today. Landless labourers, sharecroppers and marginal farmers now form a majority in rural areas of Latin America and Asia, and in Africa the recent and rapid rise in human population levels is imposing severe pressure on land unsuitable for settlement. Approximately 3.8 million hectares of open woodland are being cleared every year, mainly as agriculture extends into marginal lands. Much of Africa is too infertile and dry for crops or even grazing, but farmers are moving further into semi-arid areas in their search for land and food. Pastoralists are being squeezed into desert margins, causing overstocking and overgrazing which in turn lead to degradation of soils and an increasing proportion of plants unpalatable to domestic animals. Inevitably the wildlife suffers too and land in national parks throughout Africa, and to a lesser extent other continents, is under pressure for grazing and development. In Kenya for example, where the population growth rate of about 4 percent is one of the highest in the world, sections of the Masai Mara, Tsavo and Lake Nakuru reserves have already been excised.
Many examples of threats to swallowtails from deforestation followed by agriculture have already been cited. A few more that specifically concern agricultural pressure may also be mentioned. In the central African countries of Rwanda and Burundi agricultural land is so overcrowded that pressures on the few relict forests are intense. Encroachment into these forests is depleting forest wildlife such as the Vulnerable Cream-banded Swallowtail, Papilio leucotaenia. Papilio morondavana, P. grosesmithi and P. mangoura, all endemic to Madagascar, are threatened by uncontrolled burning, the spread of shifting agriculture and the failure to sustain adequate fallow periods. In Sri Lanka the few remaining forests are under severe pressure from agriculturalists and logging companies. The Vulnerable clubtail Atrophaneura jophon has its last stronghold in the island’s Sinharaja Forest Reserve, until recently severely encroached by agriculturalists and fuel-gatherers but now under full legal protection.
In temperate latitudes where agricultural conversion is already extensive, emphasis in recent decades has been on intensification of farming practices. Many traditional forms of land use are compatible with butterflies, e.g. coppicing and moderate grazing, but the demand for higher food production and living standards has resulted in much more intensive and exhaustive exploitation of the fertile areas. In Great Britain, the U.S.A. and many other parts of the northern hemisphere, this has caused severe reductions in butterfly populations. Factors detrimental to virtually all forms of wildlife are involved in these processes of intensification, including use of insecticides and herbicides, destruction of hedgerows, drainage, short fallow periods and heavy use of fertilizers. With the very limited swallowtail fauna in the north temperate regions, the family has suffered less than many other forms of wildlife. Nevertheless, drainage has severely reduced the range of the British Swallowtail (Papilio machaon britannicus), and in Japan Luehdorfia japonica is becoming more scarce as its previously lightly managed open woodland haunts are destroyed in favour of agriculture or intensive forestry.
In tropical regions problems associated with intensification of agriculture on the main continental blocks are of much less significance to conservation than the extension of agriculture into virgin lands. However, in eastern Asia human population levels are such that intensive agriculture is already very widespread and incompatible with wildlife, notably in the subtropical parts of China, parts of Indochina and Thailand, Peninsular Malaysia and Java. In Brazil drainage and development of coastal swamps and thickets is threatening the Vulnerable species Parides ascanius. Its mimic Eurytides lysithous harrisianus is now seriously Endangered and has been proposed for Brazil’s protected list, an action which will only be successful if suitable habitat for the mimic and its model can be set aside and maintained.
Alteration of pastures
Permanent grasslands are important habitat for many butterflies, particularly in the families Lycaenidae and Hesperiidae, but they are of less significance to the Papilionidae. The swallowtail foodplants are generally shrubs, vines or trees and most species fly in woodlands or forests. An important exception is the north temperate subfamily Parnassiinae, many of which use herbaceous species that grow in open situations. Luehdorfia feeds on the aristolochiaceous herb Asarum, which grows in open woodland, and the foodplant families used by Parnassius are all herbs of alpine meadows. In the mountains of the Hindu Kush, the Himalaya and western China there are very many species of Parnassius that are poorly known and may be at risk from pasture degradation. Some are in such inaccessible regions that their future may be assured, but others, such as Parnassius autocrator, are certainly coming under new pressures. This particular species lives in the Hindu Kush of Afghanistan and the Pamir mountains. In certain parts of the southern Himalaya, particularly in Nepal, there are reports of heavy tourist foot traffic resulting in pollution, trampling, erosion and degradation of vegetation through firewood collecting. Such impacts are not in the best interests of either the wildlife or the tourist industry.
Also Endangered is Papilio hospiton from Corsica and Sardinia, primarily as a result of alteration and destruction of pastures. The umbelliferous foodplants are poisonous to sheep and are destroyed by fires started by local farmers. Pressures from recreational developments are reducing the butterfly’s range, particularly on Corsica.
Industrialization and urbanization
Since the Papilionidae is a mainly tropical group, there are relatively few examples of conservation problems resulting from these factors. However, the range of Papilio himeros in south-eastern Brazil is declining as a result of development in Rio de Janeiro and coastal regions in general. Schaus’ Swallowtail (Papilio aristodemus ponceanus) from the Florida Keys is Endangered because of demand for building land and the consequent destruction of the hardwood hammocks in which the butterflies live.
The effects of atmospheric pollution on butterflies are rather poorly understood. An assessment of Europe’s threatened butterflies has reported that a number of widespread species have suffered severe declines in Fennoscandia, northern Germany, Poland, Czechoslovakia, Netherlands, Switzerland, Austria, Hungary and the Italian Alps. All these areas are to the north and east of the principal industrial zones in western Europe from which atmospheric pollution is carried on the prevailing south-westerly winds. The decline of Parnassius apollo in Norway has, for example, been attributed to ‘acid rain’ – a weakly acidic solution of sulphur and nitrogen oxides in rainwater. It seems likely that acid rain has deleterious effects on a wide variety of butterflies and possibly also their foodplants, as well as other invertebrates and wildlife. Ozone has been implicated as a particularly toxic component of acid rain but further research is needed to demonstrate its effects. In Europe there are widespread demands to instigate and increase international efforts to improve anti-pollution measures.
Pesticides are not generally hazardous to butterflies when applied in the recommended manner directly to the target species. However, there is a significant risk in the effects of wind drift, particularly with the growing trend towards aerial application of pesticide to rice, wheat and other extensive monocultures. When spraying is carried out in a cross-wind pesticide may drift into adjacent natural habitats. Although no serious conservation problems have been reported directly from this cause, there is still a need for vigilance in the responsible use of pesticides.
While in the industrialized countries of the northern hemisphere pollution control is showing valuable results, there is little evidence of similar efforts in the developing world. Here, serious pollution may result from forest and savanna fires as well as industrial effluent and incorrect or excessive use of pesticides. Serious threats to all forms of wildlife may be expected from such sources in the future.
Introduction of exotic animals and plants inevitably upsets the balance of natural communities to some extent. There are no documented cases of severe effects on swallowtail butterflies but the spread of Papilio demodocus (Orange Dog) from the African mainland to Madagascar, Mauritius and Reunion is a matter for concern. Apart from being a minor pest of Citrus, P. demodocus is an aggressive species that is capable of ousting less vigorous native species. Research is needed concerning the impact P. demodocus has had on the Indeterminate Mauritius endemic P. manlius during the three-quarters of a century since demodocus was introduced. No effects on the closely related Madagascar endemics Papilio morondavana (Vulnerable) and P. grosesmithi (Rare) have been noted, nor on the Vulnerable Reunion endemic Papilio phorbanta.
The level of commercial exploitation of swallowtails and other butterflies has never been estimated globally. With butterfly trade in Taiwan worth about US $20-30 million per year, a speculative figure in the order of $100 million per year worldwide may not be unrealistic. As has been noted in the above discussion of swallowtails and mankind, exploitation can be anything from the capture, sale or barter of a single specimen for the sake of interest or decoration, to large-scale commercial ventures employing hundreds of local collectors.
Invertebrates can frequently, but not invariably, withstand a considerable level of harvest because of their high reproductive capacities. However, heavy exploitation can have serious effects under three circumstances: 1) if the population is already critically depleted by other factors like habitat destruction, e.g. Papilio hospiton may be seriously at risk in Corsica and Sardinia, 2) if the population is small and has a high value per individual, e.g. the highly prized species Papilio chikae from Luzon, 3) if the species has a low reproductive rate and low juvenile recruitment, e.g. the Ornithoptera birdwings of Indonesia, New Guinea and the Solomon Islands.
The need for self-restraint in the collecting of butterflies and other insects was first formally recognized by the Royal Entomological Society of London, which set up a Protection Committee in 1923. In 1968, the Society replaced this with the Joint Committee for the Conservation of British Insects, which includes representatives from all parts of Britain and all the major entomological societies. In 1972 the Committee published “A Code for Insect Collecting” which has been reproduced and adopted not only in Britain, but also in many parts of Europe and throughout the world. The Xerces Society, a U.S. organisation devoted to conservation of insects, responded with its own policies in 1975, and the Lepidopterists’ Society of America published guidelines in 1982. The only code adopted by commercial entomologists is the Entomological Suppliers Association of Great Britain “Code of Conservation Responsibility”, published in 1974. In this document, the trade in a number of British and exotic species was restricted to specimens already in circulation.
Transcribed, adapted and abbreviated, with permission, from Threatened Swallowtail Butterflies of the World: the IUCN Red Data Book by N.M. Collins & M.G. Morris. The full volume, with references, is available from the IUCN Library System.