The Ecological and Socio-Economic Impacts of Invasive Alien Species on Island Ecosystems: Report of an Experts Consultation Contents

5. CLOSURE OF THE MEETING

After concluding remarks by the meeting Chair and the Facilitator in which they thanked the donors and the organizers of the meeting and the participants for their efforts and most valuable contribution, the Expert Consultation was declared closed by the Chairperson at 4 p.m. on Saturday, 19 October 2002.

Délégation à la Recherche

Ministère de la Culture, de l’Enseignement Supérieur et de la Recherche

B.P. 20981 Papeete, Tahiti, French Polynesia.

It was introduced as a garden ornamental to Tahiti (Society Islands) in 1937, and was not recognized as a problem until the early 1970’s when U.S. and French botanists first documented its invasiveness. Today, Miconia is present over 70% of the island of Tahiti (more than 70,000 ha) and found in all the mesic and wet habitats between 10 m and 1300 m elevation, including the montane cloud forest, where it forms dense monospecific stands. In Tahiti, Miconia is directly endangering 40 to 50 endemic plants by overtopping, shading, and crowding them. Terrestrial rare endemic orchids belonging to the genera Calanthe, Phaius, and Moehrenhoutiana; shrubby understory species belonging to the genera Ophiorrhiza and Psychotria (Rubiaceae), Cyrtandra (Gesneriaceae), and Sclerotheca (Campanulaceae: lobelioidae), as well s small trees such as Fitchia (Compositae), Meryta (Araliaceae) and Myrsine (Myrsinaceae), are among the most vulnerable. On steep slopes, pure stands of Miconia promote landslides and increase soil erosion.

The “Green Cancer,” as it is popularly called in Tahiti, has also spread to the neighbouring islands of Moorea, Raiatea and Tahaa (Society Islands) and more recently to Nuku Hiva and Fatu Hiva in the Marquesas with soil contaminated by seeds. Miconia is also invasive in the Hawaiian islands (Hawai’i, Maui, Oahu and Kauai) where it was first introduced in the early 1960’s as an ornamental, and now considered as the highest priority for control and eradication.

A number of ecological and biological characteristics make the species particularly competitive. It grows rapidly, up to 1.5 meters per year, and is adapted to low-light conditions. It flowers after 4-5 years of vegetative growth, and self-pollinates. Panicles of fleshy berries (up to 500) are produced and contain up to 230 seeds. There are at least three flowering and fruiting seasons per year. A single isolated tree has the capacity to produce millions of seeds annually. Fruits are eaten by frugivores (especially the introduced silvereye, Zosterops lateralis, and the red-vented bulbul, Pycnonotus cafer). Seeds are actively dispersed over long distances. The large soil seed bank (up to 50,000 seeds per square meters) can persist more than eight years, giving Miconia a formidable reservoir of regenerative capacity even if all plants are removed from an area.

Active control efforts have been conducted in the Hawaiian Islands and in French Polynesia since the early 1990’s. In French Polynesia, a governmental inter-agency effort has been mobilized on the island of Raiatea (Society Islands) where small (350 ha) well-localized and accessible Miconia populations were first discovered in 1988. A total of about 1,220,000 plants including 1190 reproductive trees were destroyed between 1992-2002 during control and public education campaigns using hundreds of volunteers (schoolchildren, nature protection, religious groups, and the French army). The spread was checked on that island but eradication was not attained as new reproductive trees and small isolated populations were found during helicopter and ground searches.

A biological control fungal agent (Colletotricum gloeosporioides f. sp. Miconiae), discovered in Brazil in 1996 was tested for host-specificity and then first released in the Hawaiian Islands in 1997. It causes the development of necrotic leaf spots, followed by premature defoliation. The C. gloeosporioides was released in two test-zones of Tahiti in 2000 and 2002, and monitoring of its impact on Miconia and its dispersal is in progress. Other natural enemies (especially insects) are currently being sought in Costa Rica.

University of Hawai’i, Dept. of Oceanography

1000 Pope Road

Honolulu, HI 96822

Tel: (808) 956-8668

Fax: (808) 956-9516

Mangroves have had a negative impact on indigenous Hawaiian fauna (Allen 1998, Cox and Allen 1999, Steele et al. 1999, Drigot 2001), and have altered coastline hydrodynamics and patterns of near shore sedimentation (Allen 1998). Mangroves in Hawai’i provide a habitat for exotic marine species such as the crab Scylla serrata, the barnacles Chthamalus proteus and Balanus reticulatus, and the fish Oreochromis sp. and Poecilia sp. (Demopoulos and Smith unpublished data). Mangroves are also colonized by other root encrusting and sediment-dwelling fauna, including a variety of sponges and polychaete species.

But more unfortunately, the introduction and spread of mangroves throughout the islands has led to habitat loss for the Hawaiian stilt (Himantopus mexicanus knudseni) and other wetland birds including the Hawaiian coot (Fulica americana alai) and Hawaiian duck (Anas wyvilliana) (Allen 1998, Cox and Allen 1999, Rauzon and Drigot 2002). This continued habitat loss is being mitigated by restoration of wetland refuges for both native and migratory bird species (e.g., Nuupia Ponds Wildlife Management Area, Kaneohe Bay; Cox and Allen 1999, Drigot 2001). As part of the restoration effort, the U.S. Fish and Wildlife Service plans to remove mangroves from the Waiawa Wildlife Refuge, located in Middle Loch, Pearl Harbor.

While mangroves reduce available bird habitat for migrants, the trees provide refuge for shorebirds from predators including the introduced mongoose (Herpestes javanicus) and rats (Rattus norvegicus and Rattus rattus). Despite mangrove removal and bird habitat restoration, little work has been conducted to evaluate the impact of mangroves and their removal on Hawaiian coastal communities. Preliminary data indicate that a rich group of organisms utilize mangrove habitat. However, it appears that most organisms do not use mangroves as a food source (Demopoulos and Smith, unpublished data). Thus, there is a great deal to learn about the food web and community structure of these mangrove systems. The continued presence of mangroves in Hawai’i provides scientists with the opportunity to investigate the impact of a highly invasive opportunistic plant on coastal ecosystems, including the role of mangroves in reducing coastal erosion and enhancing water quality.

Allen, J.A. 1998. Mangroves as alien species: the case of Hawai’i. Global Ecology and

Cox, E.F. and J.A. Allen. 1999. Stand structure and productivity of the introduced

Degener, O. 1940. Flora Hawaiiensis. Honolulu, HI (privately published document).

Degener, O. 1946. Rhizophora mangle L. Flora Hawaiiensis. Book 1-4. The Pattern Co., Honolulu, Hawai’i.

Drigot, D. 2001. An ecosystem-based management approach to enhancing endangered

water bird habitat on a military base. in J.M. Scott, S. Conant, and C. van Riper, III, eds. Studies in Avian Biology no. 22, Evolution, Ecology, Conservation, and Management of Hawaiian Birds: A Vanishing Avifauna, Allen Press, Cooper Ornithological Society, p. 330.

MacCaughy, V. 1917. The Mangrove in the Hawaiian Islands. Hawaiian Forester and

Rauzon, M.J. and D.C. Drigot. 2002. Red mangrove eradication and pickleweed control

in a Hawaiian wetland, water bird responses, and lessons learned. in Eradication of Island Invasives: Practical Actions and Results Achieved,. C.R. Veitch, ed. International Union for the Conservation of Nature, Auckland, New Zealand. pp. 94-102.

Steele, O.C., K.C. Ewel, and G. Goldstein. 1999. The importance of propagule predation

in a forest of non-indigenous mangrove trees. Wetlands 19:705-708.

Wagner, W.L., D.R. Herbst, and S.H. Sohmer. 1990. Manual of the flowering plants of

Hawai’i, Vol. 1,2. Bishop Museum Special Publication 83, University of Hawai’i Press and Bishop Museum Press, Honolulu, HI.

Wester, L. 1981. Introduction and spread of mangroves in the Hawaiian Islands.

Association of Pacific Coast Geographers Yearbook. 43:125-137.
Achatina Fulica: the Giant African Snail¹
Written by Robert Cowie

South Pacific Regional Environment Programme

Dr. Lucius Eldredge

Pacific Science Association

Bishop Museum

1525 Bernice Street

Honolulu, HI 96817

Tel: 808-848-4139

Fax: 808-847-8252

psa@bishopmuseum.org
The giant African snail (Achatina fulica) species has been introduced widely, both deliberately (e.g., for food; Clarke et al. 1984) and accidentally. Characteristically, its populations may remain relatively low and more or less innocuous for some time, and then explode dramatically, with the snails becoming both agricultural and garden pests, threats to human health, as well as a public nuisance. In Hawai’i, as with many IAS, however, their populations subsequently decline to a low level (e.g., Eldredge 1988), for reasons that are not understood, although disease has been strongly suggested (Mead 1979, Waterhouse and Norris 1987, Cowie 1992).

Large population sizes and invasion of native ecosystems result in impacts such as eating native plants, modifying habitats, and likely out-competing native snails (e.g., Tillier 1992). However, the more insidious conservation problem is that they tempt agricultural officials to initiate a number of putative biological control measures. The best publicized is the introduction of predatory snails, most notably Euglandina rosea (see below). The first attempts at such biological control were made in Hawai’i. Fifteen carnivorous species were deliberately introduced (Cowie 1998a). Of these, nine did not become established; the fate of three is unknown but they are certainly not common and do not appear to be causing serious problems. However, three have become established and are discussed below: Euglandina rosea, Gonaxis kibweziensis, G. quadrilateralis. There is no scientific evidence that the predatory snails are the reason for the decline in numbers of A. fulica (Christensen 1984).

Similar ill-conceived attempts at biological control involving Euglandina rosea in particular have been implemented in French Polynesia, American Samoa, Guam, and a number of other places in the Pacific and Indian Oceans (Griffiths et al. 1993) (see below under Euglandina rosea).

In addition to the deliberate introduction of predatory snails, the predatory flatworm Platydemus manokwari has also been introduced, although as yet less widely (Eldredge 1994a, 1995). It is reported that this flatworm can indeed cause populations of Achatina fulica to decline (Muniappan 1983, 1987, 1990; Muniappan et al. 1986; Waterhouse and Norris 1987), but the evidence is only correlative, not convincingly causative. However, the flatworm has also been implicated in the decline of native species on Guam (Hopper and Smith 1992). The flatworm has been seen in Hawai’i (Eldredge 1994a, 1995) but as yet does not appear to be present in large numbers (M.G. Hadfield, unpublished observations).

These introductions of putative biological control agents against A. fulica are extremely dangerous from the perspective of the conservation of native snail species. And in any case, there is no good evidence that they can control A. fulica populations.

Achatina fulica continues to spread both intentionally and accidentally; for instance it was first reported on ‘Upolu (Samoa) in 1990 and in Kosrae (Federated States of Micronesia) in 1998. Some islands remain free of it, such as Ofu (American Samoa), yet seriously at risk. Once established on one island of an archipelago, the risk of local dispersal to other islands in the group is very high (Waterhouse and Norris 1987). People still see A. fulica as a potential food source. An effort has been made to promote it as a food resource on ‘Upolu as a method of controlling them. However, promoting a pest, for whatever seemingly positive reason, seems fundamentally counterproductive, as it will likely encourage the further deliberate spread of the snails around the island and possibly into other regions.
History of A. fulica introductions

Hawaiian Islands.

Kaua‘i - 1958 (Mead 1961); O‘ahu - 1936 (Mead 1961); Moloka‘i - 1963 (Mead 1979); Maui - 1936 (Mead 1961); Läna‘i - 1963-1972 (Mead 1979; possibly not established); Hawai‘i - 1958 (Mead 1961).

French Polynesia.

Marquesas Islands: Nuku Hiva, Hiva Oa - before 1984 (Pointier and Blanc 1984).

Society Islands: Tahiti - 1967 (Mead 1979); Moorea, Huahine, Raiatea, Tahaa, Bora-Bora - after 1967 but before 1978 (Clarke et al. 1984; Mead 1979).

Tuamoto Archipelago: Moruroa - 1978 (Mead 1979); Hao - 1978 (Mead 1979); Apataki - (Pointier and Blanc 1984).

Samoa.

American Samoa.

Tutuila - 1977 (Cowie 1998c); Ta‘ü (Eldredge 1988, Cowie 1998c).

Wallis and Futuna.

Wallis Islands - (Anon. 1998a).

Tuvalu.

New Caledonia. 1972 (Gargominy et al. 1996; Mead 1979).

Vanuatu.

Efate - 1967 (Mead 1979); Espiritu Santo - (Mead 1979).

Solomon Islands. (Anon. 1999).

Papua New Guinea. pre-1945 (Mead 1961; Dun 1967).

Port Moresby - early 1960s (Mead 1979); Lae - 1976-1977 (Mead 1979); Madang - before 1972 (Mead 1979); Bougainville - 1970 (Mead 1979); Bismarck Archipelago (New Britain, New Ireland) - pre-1945 (Mead 1961); Manam Island - (Lambert 1974).

Marshall Islands.

Kwajelein - (Anon. 1996, 1998a).

Federated States of Micronesia.

Kosrae: 1996 (Anon. 1998a).

Pohnpei: 1938 (Mead 1961, 1979; Smith 1993b).

Truk - (Mead 1979; Smith 1993c): Dublon - pre-1940 (Mead 1961); Moen, Romonum - pre-1945 (Mead 1961); Uman, Fefan - 1948 (Mead 1961).

Belau (Palau).

Babeldaob - 1938 (Mead 1961; Cowie et al. 1996); Oreor (Koror) - 1939 (Mead 1961); Ngerekebesang (Arakabesan), Ngemelachel (Malakal) - pre-1950 (Lange 1950); Ulebsechel (Auluptagel), Ngeruktabel (Urukthapel) - 1949 (Mead 1961); Beliliou (Peleliu) - pre-1946 (Lange 1950); Ngeaur (Angaur) - pre-1950 (Lange 1950).

Guam. 1943 (Bauman 1996; Mead 1961; Eldredge 1988).

Northern Mariana Islands.

Rota, Tinian, Saipan - 1936-38 (Mead 1961; Bauman 1996); Aguijan - pre-1939 (Mead 1961); Pagan - 1939 (Mead 1961).

South Pacific Regional Environment Programme

Dr. Lucius Eldredge

Pacific Science Association

Bishop Museum

1525 Bernice Street

Honolulu, HI 96817

Tel: 808-848-4139

Fax: 808-847-8252

psa@bishopmuseum.org
Ampullariidae are freshwater snails predominantly distributed in humid tropical and sub-tropical habitats in Africa, South and Central America and South-East Asia. They include the largest of all freshwater snails (Pomacea maculata can exceed 15 cm) and frequently constitute a major portion of the native freshwater mollusk faunas of these regions. Among the seven to ten genera usually recognized, the two largest are Pomacea, with about 50 species, and Pila, with about 30. Snails in these two genera in particular are frequently known as ‘apple snails,’ because many species bear large, round, often greenish shells. They have also become known as ‘mystery snails,’ ‘miracle snails,’ ‘golden snails’, among other common names (‘kuhol’ in the Philippines, ‘bisocol’ in the Filipino community in Hawai’i). The comprehensive review of Cowie (in press a) focuses on the increasing impact of ampullariids as agricultural pests, but also discusses their potential environmental impacts. Some species have been used to control aquatic plant pests such as water lettuce (Perera and Walls 1996). Many species appear to be extremely voracious and generalist in their food preferences and concern has been expressed (Simberloff and Stiling 1996) that they could seriously modify native ecosystems.

The genus Pomacea is centered in South and Central America, extending into the Caribbean and the southeast of the US. One or perhaps more species have been taken from their native South America to Southeast Asia to be cultured for food (Mochida 1991). The market for the snails never developed. The snails were released or escaped into the wild, becoming major pests in rice paddies (Cowie, in press a; Naylor 1996). Other species have been developed as aquarium snails (Perera and Walls 1996) and have been moved around the world via the aquarium trade.

At present, P. canaliculata is not widespread in the region (only the Hawaiian Islands, Guam, and Papua New Guinea). It has also probably been introduced to Belau (Palau) but was eradicated (Cowie, in press a). However, the lesson from south-east Asia is that people in some countries (e.g., Cambodia) have ignored the negative experiences of other countries (e.g., Vietnam, Philippines) and have persisted in trying to establish aquaculture operations, despite advice to the contrary (Cowie 1995b). They have then come to regret this course as the snails inevitably escaped or were released when the aquaculture operations did not become profitable and are now serious pests. Therefore, despite the negative experience in the Hawaiian Islands particularly, people from other islands may yet be tempted to introduce this species. Pomacea canaliculata should be considered a potentially serious threat and every effort should be made to prevent its further spread into the Pacific region.

Hawaiian islands.

Kaua‘i - 1991; O‘ahu - 1990; Maui - 1989; Läna‘i - 1995; Hawai‘i - 1992 (Cowie 1995a, 1996c, 1997).

Papua New Guinea. 1990 (Laup 1991; Anon. 1993; incorrectly identified as Pomacea lineata).

Guam. 1989 (Eldredge 1994b; Smith 1992a).
Other introduced ampullariids recorded in the Pacific are:

Pomacea bridgesii. Hawaiian islands (Kaua‘i, O‘ahu, Hawai‘i) -- Cowie 1995a, 1997, in press a.

Pomacea paludosa. Hawaiian islands (Maui) -- Cowie 1995a, 1997, in press a.

Pila conica. Hawaiian Islands (O‘ahu, Moloka‘i, Maui) -- Cowie 1995a, 1997, in press a; Belau (Palau) (eradicated) -- Eldredge 1994b; Guam -- Smith 1992.
None of these species seems to pose as serious a threat as does Pomacea canaliculata. However, all four are difficult to distinguish from each other, even by experts, and there are a number of other potentially voracious ampullariid species so far not recorded in the Pacific (e.g., Marisa cornuarietis). Therefore the best approach would be to guard against the introduction of all species of Ampullariidae.
¹ These case studies originally appeared in the following: Cowie, R. H. 2000. Non-indigenous land and freshwater mollusks in the islands of the Pacific: conservation impacts and threats. Invasive species in the Pacific: a technical review and draft regional strategy. South Pacific Regional Environment Programme. For complete citations please refer to this document at www.sprep.org.ws.

Salvinia Molesta in Sri Lanka
Dr. Soetikno Sastroutomo

CAB International

Senior Project Officer, SE Asia Regional Centre

Glasshouse No 2, Opposite Block G

Mardi Complex, P.O. Box 210UPM Serdang, Selangor

Malaysia 43400

Tel: 64-3-8943-2921/3641

Fax: 60-3-8943-6400

s.soetikno@cabi.org
Salvinia (Salvinia molesta) is one of four species that are members of the S. auriculata complex (Forno, 1983). Other members include S. auriculata, S. biloba, and S. herzogii. On the upper surface of mature leaves, members of this complex all have hairs on the tip of each papilla that are joined to form a bird cage-like structure. Other species in the genus have hairs on the tip of each papilla, and each hair divides at the end into three or four free arms not joined into a cage. Within the S. auriculata complex, all species are very similar in their vegetative morphology. Therefore, reproductive structures should be used for identifying species within the complex whenever possible. Other common names for S. molesta are giant salvinia, kariba weed, velvet weed, or water fern. Salvinia propagates vegetatively by division and is capable of colonizing large areas of stagnant fresh water in very short periods. Under ideal conditions, the plant grows at a doubling rate as brief as 2 days.

The native range of this species is southeastern Brazil. However, it is distributed throughout the tropics and subtropics. It has been described as one of the world’s worst aquatic weeds and its spread has posed major problems in a number of tropical and subtropical countries, including Australia, Botswana, Kenya, Papua New Guinea, India, Indonesia, Malaysia, the Philippines, and Sri Lanka.

Sri Lanka is an agricultural country with estimated population of 18.73 million people (census in July 2001). Farmers and farming communities rely on a multitude of reservoirs for water because the country is prone to prolonged dry periods. Salvinia, observed in Sri Lanka since the early 1940’s, has spread to a number of these reservoirs and the associated distribution and drainage systems. Water buffalo (Bubalus bubalis) may have been an important vector. Salvinia has caused a serious problem to the production of rice, which forms part of the staple diet. Rice production is affected because salvinia enters the rice fields and because it interferes with irrigation. In 1986, approximately 25% of Sri Lanka’s 50,000 reservoirs (often referred to as tanks) were invested by salvinia.

The economic losses caused by salvinia in Sri Lanka were reported in 1989 by Doeleman as a result of study on “Assessment of costs and benefits of salvinia’s biological control program in Sri Lanka.” The program was sponsored by the Australian Centre for International Agricultural Research (ACIAR) and implemented by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in collaboration with the National Resources and Science Authority of Sri Lanka (NARESA).

Agricultural and other output, public health, and aquatic ecosystems in Sri Lanka have been adversely affected by salvinia. The economic losses caused by salvinia are categorized in terms of: (1) losses in rice production, (2) fishing losses, (3) other commercial losses, (4) human health costs, (5) environmental costs, and (6) abatement expenditure.
(1) Fishing losses

Salvinia’s dense growth reduces light and oxygen, creating anaerobic conditions characterised by high concentrations of carbon dioxide and hydrogen sulphide that inhibit aquatic life. Salvinia contributes to fishing losses in affected reservoirs in two ways: 1) placing constraints on fish breeding sites which reduces population sizes and 2) reducing the effectiveness of gill netting. Fortunately, salvinia has not caused the relocation of fishermen and their families in Sri Lanka as it has in the Sepik River, Papua New Guinea in the early 1980s, where half of the 500 km² of lakes in the lower floodplains have been covered by impenetrable mats of salvinia.

In Sri Lanka, fishing accounted for 1.9% of 1987 GNP (113 billion Rp) and 19% of the fish supply was comprised of inland catch. River fisheries in Sri Lanka were not affected by salvinia but a quarter of reservoirs were affected in various degrees. It has been estimated that about 5% of the inland catch may have suffered losses due to salvinia and that on average the catch may be reduced from 20 to 40%. Accordingly, a low estimate of fishing losses would be 0.019 x 0.19 x 0.05 x 0.2 x 113,000 million Rp = 4.1 million Rp. The high estimate yields a figure of 8.2 million Rp.
(2) Losses in rice production

Amongst agricultural crops, only rice production appears to have suffered from salvinia. Salvinia is commonly introduced by irrigation water into irrigated rice fields. Rain fed rice cultivation may also be affected by salvinia, but only during wet periods.

The value of rice production in 1987 was estimated as 5.7% of GNP (113 billion rupees) or 6400 million rupees (Rp). The average area under rice cultivation in this year was estimated as about 418,000 Ha and the range of areas under salvinia infestation are 30,000 to 50,000 Ha. Crop losses in salvinia-invested areas were approximately 2-3%. On this basis, the low estimate of rice production loss was 30,000/418,000 x 0.02 x 6400 million Rp = 9.19 million Rp. The corresponding high estimate was 50,000/418,000 x 0.03 x 6400 million Rp = 22.97 million Rp.
(3) Other losses

Salvinia does impinge on activities other than rice production and fishing. These activities include power generation, water transport, washing and bathing. Due to the challenges in determining costs for these activities, only coarse-scale estimates are possible: 200,000 Rp for a low estimate and 500,000 Rp for a high estimate for 1987.

Sri Lanka, as with many other tropical countries, is suffering from a resurgence of vectored diseases, e.g., malaria, filariasis, dengue fever, and encephalitis. Chemical controls, widely and successfully used in the 1950s, have resulted in resistant strains of mosquitoes. Salvinia increases breeding opportunities for the mosquitoes because the formation of vegetative mats reduces wave action and creates the shallow conditions the mosquitoes prefer for breeding.

The full extent of salvinia’s contribution to mosquito-borne diseases is not known. However, salvinia plays a major role in filariasis. Filariasis is transmitted by the Mansonia genus of mosquitoes which favors salvinia. Unfortunately, there are no field studies to provide guidance on the costs of salvinia for filariasis and other human diseases. Assuming that salvinia, by providing a breeding ground for the mosquitoes, will add between 1 and 2% to the incidence of vector disease, the cost of the increase in disease incidence is crudely measured as the % increase in the health budget spent on this type of disease (around 30% of the total budget of 1,935 million Rp in 1987). In 1987, a low estimate of the health costs of salvinia was 0.01 x 0.30 x 1,935 million Rp = 5.8 million Rp. The high estimate doubles these costs to 11.6 million Rp.
(5) Environmental costs

No estimates have been made for environmental costs. Unlike the salvinia problems that developed in the Sepik Delta in Papua New Guinea, there has been no relevant research and thus there are no records of salvinia threatening natural communities in Sri Lanka. However, it is clear that salvinia can rapidly reduce a complex ecology to monoculture. Thus, as salvinia has spread in Sri Lanka, aquatic plants and animals must have suffered as a result.

In addition to the economic costs associated with loss of rice production due to salvinia infestations, management costs are incurred (termed “abatement costs”).

Abatement measures for salvinia in Sri Lanka are mostly done by mechanical control, for example, physical removal, using booms and occasionally a major clean-up exercise organized by relevant authorities. The Department of Agriculture estimated that 2-3 hours of labour on average per month per hectare is needed for the affected farmers to keep irrigation and drainage channels free from salvinia and pumps protected. Based on the estimate that 30,000 to 50,000 Ha of rice fields might be affected by salvinia and using 1987 agricultural wage per hour of 7.5 Rp, a low abatement cost can be calculated, at 30,000 x 2 x 12 x 7.5 Rp = 5.4 million Rp. The high abatement cost estimate is 50,000 x 3 x 12 x 7.5 Rp = 13.5 million Rp.
References:

Dias G. 1967. Eradication of water weed (Salvinia auriculata) in Ceylon. World Crops 19:64-68.

Doeleman, J.A. 1989. Biological control of Salvinia molesta in Sri Lanka: an assessment of costs and benefits. ACIAR Technical Reports No. 12, 14 pp.

Forno, I. 1983. Native distribution of the Salvinia auriculata complex and keys to species identification. Aquatic Botany 17:71-83.

Fowler S. and A. Holden. 1994. Classical biological control for exotic invasive weeds in riparian and aquatic habitats - practice and prospects. in L. deWaal, L. Child, P. Wade, and J. Brock, eds., Ecology and management of invasive riverside plants. John Wiley, Chichester, U.K, pp. 173-182.

Holm L.G., D.L. Plucknett, J.V. Pancho, J.P. Herberger. 1977. The world's worst weeds. Distribution and biology. University Press of Hawai’i, Honolulu, Hawai’i, USA.

1. 
   Conveners
   

Dr. Richard Mack (Chair)

Co-Chair, GISP Evaluation and Assessment Working Group

School of Biological Sciences

Washington State University

Pullman WA 99164-4236 USA

Tel: 509 335 3316

Fax: 509 335 3184

rmack@wsu.edu
Dr. Jamie K. Reaser (Facilitator)

Executive Director, Global Invasive Species Programme

U.S. Office of the Secretariat

c/o Smithsonian Institution

P.O. Box 37012

NHB MRC 105

Washington, DC 20013-7012 USA

Tel: 202 633 9800

Fax: 202 357 1453

sprgpeeper@aol.com

AAAS Environmental Fellow, US EPA NCEA

Coordinator, Assessment and Evaluation Working Group

Global Invasive Species Programme

U.S. Office of the Secretariat

c/o Smithsonian Institution

P.O. Box 37012

NHB MRC 105

Washington, DC 20013-7012 USA

Tel: 202 737 6307

Fax: 202 357 1453

meyerson.laura@nmnh.si.edu

2. 
   Experts