G.A.M. Scott, T.J. Entwisle, T.W. May & G.N. Stevens
Environment Australia, May 1997
ISBN 0 6422 1399 2
G. Nell Stevens
Lichens are significant in Australia because of their ecological importance, aesthetic value, and usefulness to humanity. A lichen is one of the most remarkable alliances in nature. It can be regarded as a community rather than an organism because it always consists of at least one species of alga and one species of fungus. The algal portion of the lichen is its photosynthetic component and is very sensitive to sulphur dioxide in the atmosphere. The fungal portion usually makes up the bulk of the plant; it is drought resistant and able to withstand periods of hot and cold temperatures and dryness with no ill effect to the lichen which remains dormant. This makes the lichen a useful monitor for both pollution and water relations, that is, assessing the amount of water absorbed through the surface of the lichen in relation to the available moisture in the atmosphere.
The association formed by these partners is so successful that it can grow in widely diverse habitats, e.g. wet tropical rainforest, wet temperate rainforest, dry sclerophyll forest, semi-arid soil, stony desert, desert scrub, alpine high plain, mangrove swamp and coastal heath. The substrate can be trees, rocks, charred wood, mosses, soil, walls and many other man-made substrates.
Fossil lichens are recorded back to the Mesozoic era (135–225 million years ago), but no extensive fossil lichen flora is known. Their long history implies complex interactions with other organisms during the evolution of the plant kingdom.
Reasons for lichen conservation:
- Lichens play an important role in the water cycle of the ecosystem, and their loss can upset this process; they are also important in nutrient cycling in some communities.
- Where they occur on rock, lichens form a pioneer vegetation, creating soil by breaking down the rock. Soil-crust lichens bind the topsoil and prevent erosion and so play an important role in the ecology of semi-arid and arid lands.
- Lichens are utilised by some birds and insects; e.g. birds collect foliose and fruticose lichens to make or decorate their nests; some insects or their larvae cover themselves with pieces of lichen or with the vegetative spores of lichens. Mites feed on lichens and some gastropods include lichens in their diet.
- Lichens produce a wide range of unique secondary metabolites. In other countries these substances are being examined for new pharmaceuticals and agrochemicals, as well as commercially valuable enzymes for use in biosensors, biotransformation reactions and diagnostic kits. Recent work has identified compounds with marked anti-tumor properties (terpenes), and anti-amoeba activity (fatty acids) and nematocidal activity.
- Lichens can be used as environmental indicators for pollution monitoring around cities and factories (e.g. G.N. Stevens & C. Scarlett, Gladstone Lichen Survey, unpublished report, Fisheries Dept, DPI, Brisbane, 1980). Their potential has not been realised in Australia as yet because there are so few lichenologists to carry out surveys using lichens as bioindicators.
- As part of the biodiversity of the Australian flora, they contribute aesthetic value to all plant communities.
In the past, lichens have not been recognised specifically as flora to be conserved. At present there is no legislation pertaining especially to lichen conservation in any State, although conservation policies in some States include non-vascular plants with vascular plants without specific mention of lichens.
Checklist of Australian Lichens (McCarthy 1991) recorded 2494 accepted lichen species names, of which 945 (38%) are presently known only from Australia. The checklist covers the eight States and mainland Territories. Some names will be placed in synonymy with further revision of genera, but new taxa are being found as each genus is revised and it is assumed that the total number of taxa in Australia will be between 2500 and 3000.
Flora of Australia Vol. 54: Lichens – Introduction Lecanorales 1 (George 1992) recorded 307 genera of lichens for Australia. It is estimated that about 70 genera have been revised recently, which leaves 77% not revised. Volumes 54 and 55 treat 59 genera, providing distribution maps of each species described and an indication of how rare or common each is, though allowance must be made for lack of collecting in areas where the species may occur. Also, some of these revisions have been based mainly on collections held in overseas herbaria and so lack first-hand information on actual distribution. All scientific literature pertaining to Australian lichens has been listed by McCarthy (1992).
In Australia, there is only a small group of lichenologists; they keep in touch through the Australasian Lichenological Newsletter and by a biennial meeting and field trip. Only one Australian herbarium employs a lichenologist (the Tasmanian Herbarium, Dr G. Kantvilas). At the Australian National Herbarium Mr H. Streimann curates lichens and at the Western Australia Herbarium Mr Chang Sha Fang oversees curation of lichens.
Currently, knowledge of lichen distribution depends on data in herbarium records, including recent collections by lichenologists revising genera. From this it can be assumed that a lichen found in one or at most a few locations should be regarded as rare. If the habitat to which it is confined is threatened, it follows that the species must be termed endangered.
The list of X, E, V, and P species in Appendix B was compiled from information obtained from recent revisions of some of the lichen genera and from personal communications with the lichenologists involved in those revisions. It is impossible to assess the rarity of taxa that belong to genera which have not been revised recently.
Fire is the greatest threat to lichens, whether they grow on bark, dead wood, leaves, soil or rocks. Lightning strikes or man-made fire can wipe out a lichen population. Today, fire is used as a management tool in fuel reduction, forest regeneration and maintenance of fauna habitats, and fire regimes are planned to suit the vascular flora and its response to the effect of fire, but the vulnerability of non-vascular plants has not been considered. Each State and Territory has a fire management policy (Burrows, McCaw & Friend 1989) which encompasses impacts and effects on the environment, but when a habitat is burnt it means that lichen recovery will take much longer than vascular plant regeneration since non-vascular plants have no special mechanisms for fire resistance as do many of the vascular plants, e.g. fire-resistant fruits and seeds, epicormic buds etc.
Fire results in the loss of many critical habitats for lichens such as dead wood, old trees, and the understorey shrubs in eucalypt sclerophyll forest. It also destroys emergent shrubs and trees in graminoid heathlands, and vegetation at the margin between sclerophyll forest and rainforest. Fire has the potential to wipe out all lichens in an area.
Air pollution close to cities, highways and around factories denudes these areas of sensitive lichens. The renowned sensitivity of lichens to air pollution derives from an ability to concentrate air- or water-borne compounds in the plant body, potentially to lethal levels. Sulphur dioxide, fluoride, lead and zinc are common causes of death in lichen populations. Aerial application of fertilisers, fungicides and insecticides is also likely to have a significant impact on the non-vascular flora. But in Australia this is a largely unstudied problem.
Grazing in particularly sensitive areas can be a threat to lichens. In arid and semi-arid Australia, grazing by sheep and cattle destroys the prolific cover of soil surface lichens which ultimately leads to soil degradation, loss of top soil and therefore lack of a suitable substrate for recolonisation of the soil crust lichens that stabilise the soil. In Tasmania, it has been found that trampling and browsing by domestic animals in native bushland opens up the vegetation with drastic changes in the cryptogamic flora.
In coastal areas, clearing for housing development and shoreline activities destroys a vegetation that is rich in lichen species. In the Buckenbowra River area near Batemans Bay, N.S.W., much of the Casuarina vegetation has been cut. Along the Queensland coastline, many communities of mangroves have been destroyed to build marinas for the increase in boating.
Drainage and reclamation of coastal areas for shoreline development and pollution of streams with sewage or fertilisers can kill stands of mangroves, resulting in the death of all lichens that grow on the bark of these trees. As mangrove forests are noted for their rich diversity of lichens, any destruction of mangroves means a drastic reduction in numerous lichen taxa.
Farming in the mallee area of inland New South Wales, western Victoria, South Australia and Western Australia destroys the mallee scrub together with the prolific number of tree and soil lichens. The application of fertilisers and insecticides to these areas threatens the survival of all cryptogams.
Clear-felling practices destroy whole lichen habitats, resulting also in alteration of the microclimate in the surrounding vegetation as drier conditions prevail. In Tasmania, Kantvilas, James & Jarman (1985) and Kantvilas & Jarman (1993) found that reduction in the size of native forest stands, especially in the case of rainforest disturbance, could have a destructive effect on the cryptogamic flora due to change in habitat including the replacement of rainforest trees with species that are poor substrates for lichens.
Quarrying rock in areas where the outcrop is covered in lichens results in the elimination of the whole population that occur on the rocks. In Western Australia, Mount Willyung is the type area for Usnea pulvinata but most of the hill has been quarried, eliminating the lichens. In South Australia, quarrying granite tors on Eyre Peninsula could cause serious depletion of the crustose lichens.
Recreational areas in reserves and State Forest may contain lichens that would be under threat through public over-use, e.g. from excessive trampling over rock outcrops, or by removal of decorative species. For example, at Yilliminning Rock, W.A., two rare lichens – Paraparmelia sammyi and Paraparmelia sargentii – occur on rock in a Crown reserve used as a picnic site and for local recreation. Mount Monster, S.A., is a recreational area where Usnea maculata and Cladia corallaizon grow. Although these lichens do occur in other States they could be eliminated by people-pressure if some form of protection is not given to the area. In Aldinga Scrub Conservation Park, South Australia, a raised walkway has been constructed to assist viewing the lichen ground cover of Cladia ferdinandii.
Landscaping firms promote 'mossy rocks' (lichen-covered boulders) for gardens. The change in environment commonly results in death of these lichens. Rare species of Xanthoparmelia on rocks used for landscaping in the Canberra district could become endangered. This practice occurs in other States.
Collecting lichens for use in dyeing is an extremely destructive activity. Although at present on a small scale, the activities of wool dyers can cause depletion of lichen numbers because of the large volume of material required. Local populations can be destroyed, and elimination of rare species can occur as dyers collect indiscriminantly rather than selecting particular species.
Collecting specimens for science may be a threat when over-enthusiastic collection of selected species could place local populations or rare species at risk. The amount of material collected of any one species (particularly exsiccatae sets) should to be curtailed.
Lichens occur in diverse habitats. Those listed below are the major ones, some of which are already conserved by State, Federal or international legislation.
Rainforests: tropical, subtropical, warm-temperate, cool-temperate
Logging in the tropical rainforest of Queensland has now stopped, but sclerophyll forests that abut rainforests are prone to fire. Whether started deliberately or naturally, fires that burn to the rainforest margin destroy the lichen populations on the rainforest trees. The interior of a rainforest is too dark for lichens but they occur either in the canopies of the trees or along the forest margin where there is ample light and constant humidity. On the Mount Windsor Tableland, N Qld, rainforest margin is the habitat of two rare lichens (Usnea hossei var. squarrosa and U. misamisensis), both of which extend south to this area from South-East Asia.
Subtropical and warm-temperate rainforests are also prone to forest fire, spreading from adjoining dry sclerophyll forests, which then destroys the marginal vegetation of the rainforest. A number of these rainforests are on private property and are in danger of being cleared for pasture etc.
Nothofagus spp. of cool-temperate rainforests are host to some substrate-specific lichens. In the Border Range area of south-east Queensland, the rare lichen Sagenidiopsis merrotsii occurs in this habitat, and in Tasmania Conotremopsis weberiana occurs in similar habitat. Also in Tasmania, Rocellinastrum lagarostrobi grows on the leafy twigs of Lagarostrobos franklinii at the edge of cool-temperate rainforest north of Greystone Bluff, and fire could quickly eliminate this rare species.
Many of these are State forests managed by State and Territory forestry agencies or on private or leasehold property.
Lichens grow on the branches, twigs and trunks of many trees in this habitat. In the tropics and subtropics, they do not occur on the eucalypt overstorey but prefer the understorey shrubs, e.g. Acacia and Casuarina spp. This position in the forest affords a relatively cool microclimate with adequate humidity, but when fire sweeps through the eucalypt forest it is the understorey that is destroyed. Felling large trees commonly results in severe damage to the understorey and the reduction of usually large lichen populations.
This habitat occurs at intervals along the whole coastline of eastern Australia but many areas are under threat by development. The mangrove community provides several distinct habitats for lichen species, from the exposed seaward fringe through the sheltered, humid, middle zone to the landward fringe abutting terrestrial forest or claypan. Each habitat is colonised by distinct associations of lichens of all three growth forms (crustose, foliose, fruticose) so that destruction of the mangroves results in destruction of many species of lichens from that area. The mangroves that most often act as host to lichens are Rhizophora spp., Ceriops spp., Bruguiera spp., and Avicennia marina.
Bulbothrix apophysata grows on Rhizophora stylosa and has a restricted distribution in Moreton Bay (Mud Is. and North Stradbroke Is.), Qld, and at Hastings Point, N.S.W., areas that are more and more in demand for development. Bulbothrix microscopica grows on Rhizophora stylosa in Tin Can Bay, Qld, and has not been found elsewhere. With the sale of private land, development of this area is likely in the near future.
Relicina terricrocodila grows on Rhizophora sp. only at Portland Roads, Cape York, north Qld. Three rare species of Relicina occur on Hinchinbrook Is., Qld (R. subabstrusa, R. ramosissima and R. conglutinata). Hinchinbrook Is. is a National Park and therefore offers protection for these species.
Pertusaria melaleucoides has been found only at Buckenbowra River, N.S.W., growing on Avicennia marina, but the land in this area is being developed rapidly for housing.
Local and State government laws pertaining to protection of mangroves must be rigorously upheld, otherwise the destruction of these trees will result in a great loss of lichen species. The taxonomy of many crustose species on mangroves is still unknown.
The areas above the treeline in the Australian Alps and Tasmanian highlands contain abundant ground lichens. Rock outcrops here act as substrate for many species of crustose, foliose and some fruticose lichens. Alectoria nigricans occurs in small populations in restricted areas at Mount Stilwell, N.S.W., and Cradle Mountain plateau, Tas. Usnea torulosa grows prolifically in this environment but is scarce in other habitats. Neuropogon acromelanus has been found only once in Victoria on the Bogong High Plains; it also occurs at several localities in Tasmania. Although such areas are nominally protected, their conservation could be enhanced by adoption of appropriate management practices, e.g. by the erection of walkways.
This habitat occurs in semi-arid areas of Australia, including north-western Victoria, south-eastern South Australia, southern Western Australia and southern Northern Territory. In these areas a rich soil crust lichen flora exists, e.g. Psora decipiens, Endocarpon spp., Dermatocarpon spp., Heppia spp., Peltula spp., Collema spp. and Chondropsis semiviridis.
The mallee areas of Victoria, South Australia and Western Australia are used extensively for rangeland grazing and cereal growing, and the destruction of soil crust lichen flora results from both practices. In bluebush and saltbush communities trampled by stock and feral animals (rabbits and goats), the lichen cover is totally destroyed or may be restricted in occurrence to pedestals of soil beneath the bushes. David Eldridge, Department of Conservation and Land Management, N.S.W., is researching this problem (R. Rogers, pers. comm.).
Rock outcrops and boulders
Although a particularly exposed habitat, many species of lichen grow exclusively on rock substrate and protection of this habitat is important, especially where rare species are known.
Threats in this habitat are damage by fire; disturbance due to boulders being removed from a field for pasture or development; or the more recent habit of removing rock for landscape gardening by firms selling 'mossy rocks' for gardens. Xanthoparmelia nebulosa and Xanthoparmelia xanthofarinosa grow on sandstone and porphyry in the Canberra area and if they continue to be removed with the rocks they will become endangered.
Quarrying can result in the elimination of species. Usnea pulvinata has disappeared at its type locality at Mount Willyung, W.A., because of quarrying.
Roadsides and banks
Species of soil lichens that grow in the disturbed habitat of road cuttings and banks are particularly susceptible to destruction by road maintenance. Protection for these may be secured by notifying local authorities so that they may place 'markers' along the road at the appropriate location, as is already done in some States for rare vascular plants. The Tasmanian endemic Siphulella coralloidea colonises road cuttings, and although at present it is a common lichen in such habitats, repeated road maintenance over a period could eventually eliminate it.
2.6.1. Impediments to improved conservation
Because lichens occupy a subordinate ecological role in the plant community, their welfare has not been taken into consideration when developing conservation strategies for vascular plants. Management techniques adopted for vascular plants are not necessarily appropriate for non-vascular plants and may need modification. The use of fire may have little perceived deleterious effect on some vascular plant communities but can be disastrous for cryptogams; e.g. fires lit for the management of forests can be fatal for the lichens in adjacent rainforest margins. In some States, forest agencies' policies do not presently include non-vascular plant preservation in their conservation management.
Until more taxonomy is carried out on Australian lichens, many species will remain poorly defined or unknown; many areas have yet to be searched systematically for lichens and therefore the single record of some species may reflect simply lack of collecting. An effective conservation strategy is difficult to devise under these circumstances. The current amount of lichenological research is not sufficient to produce taxonomic revisions of all genera, or to classify those lichens still unknown. This will be a slow process.
There is a lack of specialists in lichenology in Australia. Currently there are four working lichenologists, four retired but still working on lichens, three postgraduate students (two of whom are mature age), and three lichen curators. As undergraduate lectures include no more than a sketchy account of lichens, and there are no jobs to go to, there is no incentive for students to look towards lichenology as a career. This is quite different from the situation in European universities where lichenology is taught at both undergraduate and postgraduate levels.
Where rare species are known to occur on private land, whether in forest or on rock outcrops, their conservation is in danger through burning off, tree felling, animal disturbance or removal of rocks. Protection of a rare species by fencing off an area may be the best suggestion to the land owner. In Tasmania, Pyxine nubila is restricted to a few localities on private land in the south-east (G.Kantvilas, pers. comm.).
2.6.2. Future priorities for research and management
A database of Australian lichens is needed to collate published information on lichen species and recently-verified herbarium specimens. This would form a basis for indicating distribution and habitat of lichens. The information supplied would have to be as accurate as possible since it would form the basis of management decisions as well as influence research directions and funding priorities. The Australian National Herbarium, Canberra (CANB), would be the most suitable herbarium to undertake this task as they already have a large proportion of their collections on a database. Care must be taken to exclude herbarium collections that have not been identified by specialists (or if included they should be given a distinguishing mark). Species can then be classified according to conservation and reservation status and those species in the categories E, V and P can be indicated. General information regarding land tenure should be included to provide a good reference for formulating appropriate management strategies.
The database would require continual upgrading as new information became available, and lichens initially listed as rare may be found later to be common and should then be downgraded accordingly.
Basic research into taxonomy and ecology of the lichens is paramount for conservation management. The Flora of Australia project has helped enormously in this direction and has laid the foundation for recent revisions of lichen genera, but the scarcity of specialists will always result in slow progress in taxonomy. Funding at the training level is crucial if more lichenologists are to emerge.
At present, very little lichenology is taught at University level. To stimulate an interest in lichenology, the use of lichens in applied research, e.g. chemistry and physiology, could be stressed in lectures, together with basic taxonomy. At present the Australian National University is the only one equipped to carry out this type of practical work. Some students have been given air pollution projects in their capital cities and their findings could be used as a basis for further studies on air pollution.
Very few ecological studies have been carried out in Australia to identify the physiological reactions of lichens to climate and habitat. Although arid-land water relations in Chondropsis semiviridis were tested by Rogers (1971), no other experimentation has been undertaken on lichens in open or closed woodland habitats to learn more about the responses that occur with disturbance of the habitats. General observations suggest death due to alteration in the water regime and humidity change (G.Kantvilas, pers. comm.).
There should be an aim towards greater understanding of the ecological factors that determine lichen distribution, e.g. the relationship between vascular plant communities and the lichens that occur in their microhabitats. In Tasmania, much work has been undertaken recently by Kantvilas (1988) and Kantvilas & Minchin (1989).
Lichen identification and distribution should be incorporated in plant resource surveys undertaken to provide distribution and habitat data for higher plants. This would give greater support for reservation of a particular plant community, where it could be shown that the vascular plants provide suitable microhabitats for lichens.
The non-vascular component must be incorporated in all fire management policies.
Protection of the lichen flora in areas set aside for higher plant conservation (e.g. National Parks and State Forest reserves or refuges) seems assured, but a species list of E, V, and P lichen taxa should be incorporated with the list of vascular species. In some cases it could be found that the reserves would need to be extended to include samples of vegetation not normally targeted for conservation, e.g. ecotones, and communities that are cryptogamically rich but not necessarily the most highly representative of vascular species.
During preparation of this overview, lists of E, V, and P taxa for each State and Territory were forwarded to members of the ANZECC Endangered Flora Network so that non-vascular species could be incorporated into the appropriate conservation listings of plants in specific areas.
The outlook for lichen research is bleak on the Australian front, but many European lichenologists are becoming more and more interested in our obscure crustose species. With ABRS funding for the Flora of Australia lichen volumes, grants are being given to Europeans for research on our flora. At least this is ensuring that Australian lichenology will progress. The aim for the future, however, should be to fund the training of more Australian lichenologists to carry out research on lichens.
Lichen brochures could be produced for public distribution in national parks. Illustrated brochures showing the lichens to be seen within the park would make the public aware of lichens if they carried self-guiding brochures when walking along trails. Coloured posters or postcards of lichens could be made available at park information centres.
Lectures could be given to national park and forestry rangers to introduce them to ways of identifying lichens so that they would then have a working knowledge of the lichens in their area and could pass on the information to the public.
Educational kits and junior computer programs could be assembled for use at primary and secondary school levels, to introduce children to the beauty and usefulness of lichens.
Scientific media programs should be encouraged to include mention of lichens, whether the program is a documentary on plant life and the ecology of forests, or in the format of 'Beyond 2000' format. The usefulness of lichens could be presented, showing them as indicators for monitoring environmental pollution, or discussing the many uses that the unique acids of lichens are currently being examined for.
The usefulness of some lichens in stabilising the soil and preventing erosion in semi-arid regions of Australia should be publicised. The Murray-Darling Basin Travelling Exhibition, which visits rural and regional centres throughout the Murray-Darling Basin and reaches many people, could include a lichen content so that private land owners and lease holders could be made aware of the existence and importance of soil crust lichens. The general public could also be made aware that it is the destabilisation of inland soils that ultimately results in the dust storms experienced in some capital cities.
Public awareness could be stimulated by introductory lichenology being taught in a continuing education program and U3A (University of the Third Age) classes. Fieldwork in this connection would stimulate adult interest and could lead to voluntary support of fieldwork through Earthwatch or the National Threatened Species Network.
The publication of a field guide to lichens (similar to The Observer's Handbook to Lichens in England) would bring lichens to the attention of field naturalists, bushwalkers, conservation groups and other outdoor movements.
Vacation workshops could be held at some universities for the instruction of herbarium staff and interested students.
The public should be encouraged to look at the beauty in the structure of the lichen plant and the intricacy of detail in lichens on tree trunks. Enlarged photographs could show the benefit of using a magnifying glass or microscope.
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