DataPDF Available
Wijesundara, S. (2010): Invasive alien plants in Sri Lanka. In: I nvasive Alien Species in Sri Lanka Strengthening Capacity to Control Their
Introduction and S pread (Eds: Marambe, B., Silva, P., Wijesundara, S. and Atapattu, N.), pp 27-38. Biodiversity Secretariat of the Ministry
of Environment, Sri Lanka.
Invasive Alien Plants in Sri Lanka
Siril Wijesundara
Royal Botanic Gardens, Peradeniya, Sri Lanka
Invasiveness of a species is generally understood as the ability to spread beyond its introduction
site and become established in new locations where it may cause a deleterious effect on
organisms already exists. There are various definitions to invasive alien species (IAS), which are
described elsewhere in this publication (see Chapter 1). From among the definitions described in
Chapter 1, the information provided in this Chapter is based on the definition for IAS given by
the SCBD (2009), i.e. species whose introduction and/or spread outside their natural habitats
threaten biological diversity.
Invasions are a basic characteristic of nature and have occurred ever since life first appeared on
the Earth. Invasion can be considered as an integral part of evolution as any other mechanism or
process. However, the unprecedented and accelerating rate of species invasions caused by the
removal of natural impediments to dispersal, deliberate introductions and ecosystem changes
caused by man have devastated ecosystems and caused enormous ecological and economic
Deliberate plant introductions date back to the early days of human civilization, that the origin
of some of the most useful crops of the world is unknown. For example, according to historical
information, nuts of the coconut palm (Cocos nucifera) have been used even in the 2nd century.
The Department of National Botanic Gardens (DNBG) and the Department of Agriculture (DOA)
Chapter 4
Siril Wijesundara
have played a major role in early plant introductions. It would be impossible to estimate what Sri
Lanka owes to plants that have been introduced from other countries and successfully
acclimatized. Our principal economic crops, our tastiest fruits, our best shade trees, our most
beautiful flowering trees, our major vegetables and our best fodders have all been introduced
from other countries. Our most venerated tree, the sacred bo tree (Sri Maha Bodhi) at
Anuradhapura, was also introduced to Sri Lanka 2,300 years ago from India (MacMillan, 1908).
However, some of the plants introduced have become noxious weeds or invasive plants. The
Royal Botanic Gardens, Peradeniya played a major role in many such introductions. One of the
best examples is Water Hyacinth (Eichhornia crassipes). That aquatic plant species was first
introduced in 1905 to the Royal Botanic gardens, Peradeniya by Lady Blake, the wife of the
Governor from Hong Kong as an ornamental plant. By June 1912 it was reported from
Wattegama in the central province, in 1914 it appeared near Tangalle in the southern province,
and two years later in Chilaw in the north western province. By 1917 it was found in
Sabaragamuwa Province. By 1930, four ordinances were in action to control this weed, namely
Water Hyacinth Ordinance No. 4 of 1909, Plant Protection Ordinance No. 10 of 1924, Village
Communities Ordinance No. 9 of 1914 and Irrigation Ordinance No. 45 of 1917 (Wijesundara,
1999). Table 1 gives some of the notable IAS introduced to Sri Lanka through the botanic
Table 1. Invasive alien flora introduced through botanic gardens.
Country of Origin
Year of
Ageratina riparia
Tithonia diversifolia
Clusia rosea
West Indies
Dillenia suffruticosa
Myroxylon balsamum
Prosopis juliflora
Tropical America
Ulex europaeus
Aristea ecklonii
Clidemia hirta
Tropical America
Miconia calvescens
Antigonon leptopus
Tropical America
Eichhornia crassipes
Hong Kong
Cestrum aurantiacum
Cape of Good Hope
Lantana camara
Tropical America
ca 1826
Types of Invasive Plants
Invasive alien plants can be herbs (e.g. Alternanthera philoxeroides), shrubs (e.g. Cestrum
aurantiacum), creepers (e.g. Wedelia trilobata) or trees (e.g. Prosopis juliflora). They may invade
terrestrial or aquatic ecosystems. Some of these species such as Cuscuta are parasitic
(Wijesundara et al., 2001). According to current knowledge almost all invasive alien plants
reported from Sri Lanka are vascular plants (Angiosperms or Pteridophytes). Although a green
alga, Caulerpa taxifolia has been reported as a sea weed, data on invasive lower plants are
scanty in Sri Lanka.
Invasive alien plants in Sri Lanka
Invasive Alien Plants in Sri Lanka and Their Extent of Spread
A few researchers have previously attempted to compile lists of invasive alien flora in Sri Lanka
(Wijesundara, 1999; Bambaradeniya, 2002; Marambe et al., 2003a). The main drawback of these
attempts is the lack of proper criteria to determine the invasive nature of the listed species.
Others have either documented the spread of several invasive alien plants in a specific locality
(Ratnayake, 2008), or the spread of a single invasive alien plant species in different localities
(Marambe et al., 2000a, 2000b; Hitinayake et al., 2000; Jayasuriya, 2001; Pushpakumara et al.,
2001; Medawatte et al., 2008). Even though there are no accurate information on the degree of
infestation, Amarasinghe and Ekneligoda (1997) reported that about 8,000 ha of rice fields were
infested with Salvinia in 1988. Area invaded by A. philoxeroides was reported to be more than
200 ha of land in the southern province of Sri Lanka (Marambe et al., 2003a). This has now been
reported in the montane areas of the island. too.
Sri Lanka is blessed with a wide array of vegetation types distributed in diverse climatic zones.
Some IAS are specific to certain ecosystems or climatic zones while others are widely distributed.
Some of the common IAS and their current distribution are given in the Table 2.
Table 2. Common invasive alien flora and their distribution in Sri Lanka
Alstonia macrophylla
sub-montane zone
degraded forests, forest
up- / low-country
wet zones
fallow fields, marshy/
riparian areas
Annona glabra
lowland wet zone
coastal lagoons, marshes
montane zone
Montane grassland/
forest ecotone
Cestrum aurantiacum
montane zone
montane forests
Clidemia hirta
sub-montane wet
Open areas in lowland
rain forest edges
Clusia rosea
sub-montane zone
Rock outcrops/forest
Colocasia esculenta
wetlands, marshes
Cuscuta campestris
island-wide except in
upper montane zone
wastelands, agricultural
land in low country
Dillenia suffructicosa
low-country wet
forest edges, open
Eichhornia crassipes
reservoirs, ponds,
marshes, streams
Ageratina riparia
montane zone
Open areas in montane
forests, roadsides
Hydrilla verticillata
streams, canals, marshes
Siril Wijesundara
Table 2. Contd…
Mode of Introduction and Spread of Invasive Plants
Introduction of invasive alien plant species may be deliberate or accidental. Deliberate
introduction of an alien species applies to a collection of plants, which are useful, interesting or
ornamental, and also imported (through institutions such as Royal Botanic Gardens). Such plants
need to be treated with special care and propagated by artificial aid. A plant is said to be
naturalized when, having become independent of artificial aid of any kind, escaped from
cultivation and thrives in a wild state. Some plants, which have been deliberately introduced for
a specific purpose, have escaped from cultivation and become invasive.
Lantana camara
scrubland, degraded
open forests
Miconia calvescens
sub-montane zone
forest edges
Mimosa invisa
wastelands, agricultural
Mimosa pigra
dry and intermediate
river banks, fallow fields,
irrigation canals
Myroxylon balsamum
wet and
intermediate zones
sub-montane forests
Opuntia dillenii
arid zone
thorn scrublands
Panicum maximum
wastelands, dry patina
grassland, agricultural
dry and intermediate
wastelands, irrigation
dry and intermediate
Wastelands, dry patina
Prosopis juliflora
arid zone
thorn scrublands, edges
of dry mixed evergreen
forest, sea shore
Pteridium revolutum
montane zone
grasslands, riparian areas
Salvinia molesta
reservoirs, ponds,
marshes, streams, paddy
Tithonia diversifolia
Wet, sub montane
and intermediate
wastelands, roadsies
Ulex europeaus
montane zone
montane forests, wet
patana grasslands
trilobata (Wedelia
wet and
intermediate zones
wastelands, roadsides,
abandoned paddy fields
Invasive alien plants in Sri Lanka
For example, Salvinia (S. molesta) was introduced to Sri Lanka in the late 1930's as educational
material, but appears to have escaped and is currently a one of the most troublesome aquatic
invasive plants, blocking irrigation canals and water bodies and also invading aquatic ecosystems
and rice fields in the dry and intermediate zones of Sri Lanka (Marambe et al., 2003a).
It is believed that giant mimosa (M. pigra) was introduced in to Sri Lanka in the early 1980s to
strengthen the river banks in the Mahaweli areas. That species has now introduced into other
parts of the country by irrigation water, machinery, river sand used for construction purposes,
and lopping branches with mature pods, as a result of the use of the stems of the plant as fuel
wood by people (Marambe, 2000b).
Many other invasive species are spread by irrigation water. In some instances even the control
measures can cause further spread of the plant meant to be controlled. For example, mechanical
removal of water hyacinth has resulted in its spread due to contamination of the machinery
used for this purpose (Marambe, 1999b). According to Jayasinghe (2004) the parasitic invasive
plant, Cuscuta campestris is distributed by irrigation water in the Mahaweli areas.
Mesquite (P. juliflora) was first introduced by the Royal Botanic Gardens, Peradeniya in 1880. It
is reported that it was introduced to the Hambantota district in southern province of Sri Lanka in
early 1950s to improve saline soils, and as a form of ground cover (Algama and Seneviratne,
2000). Prosopis juliflora has become a very serious invasive plant threatening the ecosystems in
Bundala National Park, a Ramsar wetland site in southern province. The seeds of this plant are
dispersed by cattle as well as by elephants that eat the pods.
One of the best examples for accidental or non-deliberate introductions of an invasive plant is
the Congress weed (P. hysterophorus). This plant was believed to have entered the northeast of
the country in the late 1980s, through goats imported from India by the Indian Peace Keeping
Force (IPKF). Seeds of P. hysterophorus have also entered the island along with seeds of onion
and chillies imported from India as a contaminant. Since the colonial times many plant species
introduced into the island have become invasive. Several IAS have been reported during the last
few decades. Some plants show invasive characteristics after a considerable time since the first
introduction. For example, the Guinea grass (P. maximum) was not considered a weed in 1908
(MacMillan, 1908) even though it is believed to have been introduced around 1801-1802
(Wisumperuma, 2008). Similarly, there may be some species which may become invasive in the
future. A list of such species with invasive potential is given in Table 3.
It has been reported that climate change could result in both range expansion and contraction of
invasive plants (Bethany et al., 2009; Kriticos et al., 2003; Dukes et al., 1999). Although there are
no quantitative ecological studies comparing the population sizes at different intervals, some
invasive species such as Austroeupatorum inulifolium, Clidemia hirta and Dillenia suffruticosa
have shown a marked increase in population sizes during the last three decades in Sri Lanka. It
was also observed that Pinus caribaea, a plantation tree species, which did not regenerate
naturally before, has shown invasive behavior (Medawatte et al., 2008) in the Knuckles forest
region. Whether these are due to the changes in climate needs to be investigated.
Nature of Threats
The IAS can cause significant changes to ecosystems, disturb the ecological balance, and cause
economic harm to agricultural and recreational sectors. These IAS compete with native species
Siril Wijesundara
for space, resources and plant-animal interactions. Few researchers have documented the
harmful impacts of invasive alien flora on native biodiversity in Sri Lanka.
Table 3. A list of potential invasive alien plant species.
Myriophyllum aquaticum (Vell.)
(Parrot feather)
Montane zone. Native of the Amazon
River in South America. Only
reported in Gregory’s Lake at Nuwara
Eliya Lake (Sujith Ratnayake,
Biodiversity Secretariat, Ministry of
Environment (ME), Sri Lanka - Pers.
Com.). Invasive in many countries
including USA, Pacific Islands, Japan,
New Zealand, South Africa and
European countries.
Mayaca fluviatilis Aubl.
(Stream bogmoss)
Wet zone. Ornamental aquatic.
Escaped into some water bodies in
the western province near Gampaha.
Invasive in some countries.
Tibouchina urvilleana Cogn.
(Glory bush)
Montane zone. Native to Southern
Brazil. Small population in Horton
Plans near Anderson Bungalow.
Invasive in Hawaii and some pacific
Ludwigia sedoides (Bonpland) H.
(False Loosestrife, Mosaic Plant)
Wet zone. Native to South America.
Ornamental aquatic. Escaped into
some water bodies in the western
province near Gampaha. Invasive in
some countries.
Panicum trichocladum K. Schum.
(Donkey grass, creeping guinea
Wet zone. Native to Africa. Probably
imported as a pasture grass.
Spreading in Hanguranketha area.
Observed around 2002.
Setaria barbata Kunth.
(bristly foxtail grass)
Wet zone. Native to Africa.
Spreading in the mid country.
Clerodendrum quadriloculare
(Blanco) Merr.
(Philippine fireworks, Valentine
All zones. Native to Phillippines.
Ornamental plant grown in many
parts of the country. Invasive in the
Cissus rotundifolia (Forssk.) Vahl
(Arabian wax cissus)
Dry Zone. Native to Africa. Cultivated
ornamental. Invasive in some
The flowers of C. aurantiacum are pollinated by an endemic bird, the Sri Lanka White Eye and
the fruits of this species are dispersed by another endemic bird, the Yellow eared bulbul. Due to
the abundance of Cestrum plants in the forest fringe, these two bird species are now found
mostly in those areas and the pollination and dispersal of native species in the montane forest
may be affected by the altered feeding habits of them.
Invasive alien plants in Sri Lanka
The spread of P. juliflora in the Bundala area has deprived large mammals such as elephants of
important habitats. It is now spreading in the lagoon shore areas of Bundala National Park,
reducing the feeding area for wading birds (Bambaradeniya et al., 2002).
As documented by Bambaradeniya et al. (2006), a rapid increase in the spread of Thorny cactus
(O. dillennii) in the coastal scrubland and seashore habitats in Tangalle and Ambalanthota areas
subsequent to the December 2004 tsunami has resulted in the loss and/or deterioration of
nesting habitats of globally threatened marine turtles that visit these areas annually. The spread
of the invasive cactus has also hindered the regeneration of coastal vegetation destroyed by the
tsunami, such as Pandanus odoratissimus, Scaevola takkada, and Spinifex littoreus
(Bambaradeniya et al., 2006).
As stated in the 2007 National Red List of Threatened Species, the spread of invasive alien plants
such as Annona glabra, Dillenia suffruticosa, and Eichhornia crassipes has led to further
degradation of the remaining marshy habitats of threatened blind eels (Monopterus desilvai and
Ophisternon bengalense) in the western province of Sri Lanka (IUCN and MENR, 2007).
According to the research findings of Gunaratne et al. (2008), the preferred habitat types of
native aquatic birds such as the Little grebe and the Pheasant-tailed Jacana are adversely
affected by the spread of S. molesta and E. crassipes in tanks and reservoirs. Similarly,
Weerakoon and Athukorala (2008) have stated that the feeding habitats of globally threatened
spot-billed pelicans in Sri Lanka are adversely affected by these aquatic invasive plants.
A large area in the natural montane grassland in Horton Plains was cultivated with potato in
1961 to 1978 period. The cultivation was abandoned in late1970s. Those areas were later
invaded by exotic, pasture grasses such as Pennisetum clandestinum, P. thunbergii and Vulpia
bromoides escaped from the nearby cattle farm in Ambewela. The original montane grassland
vegetation in the Horton Plans comprised of tussock grasses such as Chrysopogon, Cymbopogon
and Andropogon. The change in physiognomy and composition due to potato cultivation
followed by invasive alien grass species benefited the local population of sambhurs. The
presence of nutritious pasture grasses and the increased safety due to absence of tussock grass
cover for predators (leopards) may have caused the apparent increase in sambhur populations
in Horton Plains (Wijesundara, 1997). On the other hand, lack of tussock grasses may have
negatively affected the survival of leopards that used them for cover in hunting sambhur.
As Sri Lanka is an island with sensitive ecosystems consisting of a unique biodiversity it is very
important to mitigate factors affecting regeneration of species. Impact of IAS on pollination and
dispersal of native species is worth studying. Data on the statistics of distribution or economics
of the damages due to IAS in Sri Lanka is scarce. The goat weed or white weed (Ageratum
conyzoides) is said to have cost the planters 250,000 a year to control it during the time of
coffee cultivation (MacMillan, 1908).
Control and Management Strategies Adopted
Control and management of IAS need a strategic approach that encompasses prevention,
eradication, control and containment. Several legislative provisions have been enacted in Sri
Lanka (see Chapter 6 in this book). These legislative acts and ordinances can be used to prevent
Siril Wijesundara
and control introduction of IAS to a considerable extent. However, there are many areas to be
improved in accordance with the current needs.
In 2007 (MENR, 2007), as a part of the Addendum to the Biodiversity Conservation in Sri Lanka -
a framework for action, the Ministry of Environment (ME) of Sri Lanka has proposed to
formulate a National Action Plan for the Control of IAS in protected areas. A National Invasive
Species Specialist Group (NISSG) has also been proposed to be appointed to deal with the issues
related to the alien invasions. The Biodiversity Secretariat of the ME has conducted many
awareness programmes to educate the general public on the adverse impacts of IAS. Research
on biology, impact and control of IAS is also receiving attention. About five national level
workshops and symposia have been conducted on IAS in Sri Lanka since 1999, where useful
information related to management and control of IAS were presented (Marambe, 1999a;
Marambe, 2000a; Kotagama et al., 2001; Ranwala, 2008; MENR, 2009). Marambe et al. (2003a)
presented a draft national list of IAS, and recently, Marambe (2008) has highlighted the research
priorities on IAS.
The ME, together with the DOA, implemented a one year project on management of aquatic
weeds in 2005/2006, with funding from the FAO. This project involved awareness raising
activities and pilot scale control programmes targeting S. molesta, E. crassipes and P. stratiotes.
The Department of Wildlife Conservation (DWLC), in collaboration with the private corporate
sector has implemented a programme to manage the spread of P. juliflora and O. dillennii in
Bundala National Park.
The DOA is engaged in a biological control programme for S. molesta using the weevil
Cyrtobagus salviniae. This has been successful and it was introduced into many parts of the
country, especially in the low-country wet zone. This species has been declared as a serious pest
under the Plant Protection Ordinance. The DOA is also rearing the bio-control agents Neochetina
eichhorniae and N. bruchi and releasing the organisms as a measure to control E. crassipes.
Recently, the DOA launched a chemical control programme for E. crassipes in the northwestern
province in collaboration with the Irrigation Department. The DOA, together with ME,
universities and other governmental, non-governmental and private organizations is actively
involved in programmes to control P. hysterophorus. An extraordinary gazette notification was
released by the government of Sri Lanka in December 2000, prohibiting the movement of
materials contaminated with any part of P. hysterophorus from the infested areas (Marambe et
al., 2003a). Marambe et al. (2000b; 2003b) also attempted the control of Mimosa pigra by using
glyphosate, which is a total killer systemic herbicide.
Many NGOs, in collaboration with the Ministry of Environment and Natural Resources, are
actively involved in campaigns to eradicate IAS. Some of the programmes conducted to
eradicate IAS have become complicated due to the interactions with wildlife. For example, the
eradication programmes on U. europaeus, were aborted due to the fact that endemic lizards and
amphibians seek protection from their natural enemies in this thorny plant (Bambaradeniya et
al., 2001). Programmes conducted by the DWLC to remove L. camara from the Uda Walawe
National Park were also not successful due to various practical difficulties.
In some instances the control measures are affected by conflicts in the policies. For example, the
Forest Department is reported to promote planting C. rosea in the Knuckles reserve as a fire
prevention measure (as a biological barrier). Similarly the DWLC has been promoting the
planting of P. maximum as a food source for elephants.
Invasive alien plants in Sri Lanka
Many alien plants that have been introduced deliberately or accidentally have become invasive
as they have escaped human management. The measure adopted to control them have mostly
being through a piece-meal approach rather than being comprehensive. Early detection of and
rapid response to new invasive alien plants (species), identifying the factors that may influence
their spread, and application of control strategies requires a well coordinated participatory
approach. Several strategies, which are discussed below, could be adopted to achieve effective
control of invasive alien plants (or IAS in general) to minimize their impacts on the ecosystems of
Sri Lanka.
A central coordinating committee (CCC) including all relevant stakeholders such as the
government departments and institutes dealing with wildlife, forests, biodiversity, agriculture,
botanic gardens, customs, marine environment protection, coast conservation, and scientists
from the universities, should be established under the ME. The CCC should coordinate existing
and future efforts on prevention and control of IAS. It could also enhance information exchange
among scientists, government and non governmental agencies, and private sector. Integration of
university`-based research to optimize management and prevention activities, effective
communication techniques for wider and more effective delivery of public education about
biological invasions would be some of the important role plays of the CCC to effectively deal
with issues related to IAS.
Geographical distribution and areas of spread needs to be recorded for all known IAS in Sri
Lanka. This information could be collected at grass root level using Global Positioning System
(GPS) and Geographic Information Systems (GIS). Up-to-date information needs to be collected
using the Grama Niladharis and other officers at village level and at Divisional Secretary level. All
data should be recorded and updated in a central data base maintained at the CCC. Lists of
potential invasives and information on their invisibility, vulnerability of sensitive ecosystems and
environmental factors that affect spread of IAS need to be maintained at the CCC.
As discussed elsewhere in this book, there are many gaps in the knowledge of IAS in Sri Lanka.
Some of the problems could be solved by conducting appropriate research, where it becomes a
necessity to improve facilities in the universities and other relevant institutions involved in IAS
research. Capacity building of scientists and the necessary infrastructure facilities should be
provided to the relevant institutions.
One of the main obstacles to IAS control is the lack of access to current knowledge. In many
developed countries Invasion Ecology is given a special attention. It is essential to facilitate local,
regional and international co-operation on information exchange through workshops, symposia,
seminars, public lectures, exhibitions, poster campaigns at local level and supporting the local
scientists to participate and get involved in regional and international events related to IAS.
Transboundary collaborations with relevant international knowledge networks such as the IUCN
Invasive Species Specialist Group (ISSG) and the Global Invasive Species Programme (GISP) would
also enable to share and acquire new knowledge on IAS.
Programmes such as press conferences, TV and radio documentaries, and publishing informative
articles in the print media at the national level for building awareness among the stakeholders
should be designed and carried out by the CCC. There can also be seminars, workshops,
exhibitions, poster campaigns, and public lectures at local level. Universities, agricultural schools
Siril Wijesundara
and technical colleges can also be encouraged to accommodate IAS in their curricula at an
appropriate level.
The main obstacle for capacity building and infrastructure development in any discipline is lack
of funding. There should be a mechanism to channel adequate funding for human resource
development and improving infrastructure facilities at relevant institutions. It can also be helpful
if the leading research organizations such as the National Science Foundation (NSF), Council for
Agricultural Research Policy (CARP) and National Research Council (NRC) recognize IAS as a
priority area for providing research funding. The relevant private sector organizations should
also be encouraged to initiate an endowment for IAS research.
Amarasinghe, L. and Ekneligoda, I.A. (1997): Some recent observations on the biological control of salvinia.
Krushi, 16: 44-50.
Bambaradeniya, C.N.B. (2002): The status and implications of invasive alien species in Sri Lanka. Zoos’ Print
Journal, 17: 930-935.
Bambaradeniya, C.N.B., Ekanayake, S.P., Fernando, R.H.S.S., Perera, W.P.N. and Somaweera, R. (2002): A
biodiversity status profile of Bundala National Park A Ramsar wetland in Sri Lanka. Occ. Pap.
IUCN Sri Lanka., 2: iii+ 37 pp.
Bambaradeniya, C.N.B., Ekanayake, S.P., Gunawardena, J. (2001): Preliminary observations on the status of
alien invasive biota in natural ecosystems of Sri Lanka. In: Report of the Workshop on Alien
Invasive Species (Ed: P. Balakrishna). Global Biodiversity Forum, South and Southeast Asia
Session, October 1999, Colombo, Sri Lanka. IUCN Publication. pp 67-76.
Bambaradeniya, C.N.B., Perera, M.S.J., and Samarawickrama, V.A.M.P.K. (2006): A rapid assessment of
post-tsunami environmental dynamics in relation to coastal zone rehabilitation and development
activities in the Hambantota District of Southern Sri Lanka. Occ. Pap. IUCN Sri Lanka., 10: iv+ 27
Bethany B., Oppenheimer, M., and Wilcove, D. (2009): Climate change and plant invasions: restoration
opportunities ahead? Global Change Biology, 15: 1511-1521.
Davis M.A. and Thompson, K. (2000): Eight ways to be a colonizer; two ways to be an invader: a proposed
nomenclature scheme for invasion ecology. ESA B 81: 226230.
Doeleman, J.A. (1989): Biological control of Salvinia molesta in Sri Lanka. An assessment of cost and
benefits. ACIAR Technical Report. Canberra, Australia. 14 pp.
Dukes, J., Harold, A. and Mooney, A. (1999): Does global change increase the success of biological invaders?
TREE, 14: 135-139.
Gunaratne, A.M., Jayakody, S. and Bambaradeniya, C.N.B. (2008): Spatial distribution of aquatic birds in
Anawilundawa Ramsar wetland sanctuary in Sri Lanka. Biological Invasions, 11: 951-958.
Hitinayake, H.M.G.S.B, de Costa, W.A.J.M., Dharamawardena, M.I.U.D.S. and Wedathanthri, H.P. (2000).
Key ecological features and distribution of plant species showing apparent invasive behavior at
Udawattakele forest reserve. Proceedings of the Symposium on Alien Invasive Species in Sri
Lanka: Impact on Ecosystems and Management (Ed: B. Marambe), pp 51-57. Joint Publication of
the Ministry and Forestry and Environment of Sri Lanka and the National Agricultural Society of
Sri Lanka, Peradeniya, Sri Lanka.
IUCN and MENR (2007): The 2007 Red List of Threatened Fauna and Flora of Sri Lanka. IUCN-Sri Lanka and
the Ministry of Environment and Natural Resources, Sri Lanka. Xiii+148 pp.
Jayasinghe, J.L.D.H. (2004): Identification, distribution and host specificity of Lowland Cuscuta in Sri Lanka.
M.Phil Thesis, University of Peradeniya.
Jayasuriya, M. (2001): New invasive weed in Sri Lanka: Parthenium hysterophorus L. (Asteraceae).
Proceedings of the Silver Jubilee Seminar Series of the Postgraduate Institute of Agriculture (Ed.
H.P.M. Gunasena), 14 pp. University of Peradeniya, Sri Lanka.
Kotagama, H.B., Wijesekara, A. and Wijesundara, D.S.A. (Editors) (2001): Sri Lankan Biodiversity Review, 1:
63 pp.
Invasive alien plants in Sri Lanka
Kriticos, D.J., Sutherst, R.W., Brown, J.R., Adkins, S.W. and Maywald, G.F. (2003): Climate change and the
potential distribution of an invasive alien plant: Acacia nilotica ssp. indica in Australia. Journal of
Applied Ecology, 40: 111-124.
MacMillan, H.F. (1908): Acclimatization of Plants. Circulars and Agricultural Journal of the Royal Botanic
Gardens, Ceylon. IV: 55-73.
Marambe, B. (Editor) (1999a): Proceedings of the First National Workshop on Alien Invasive Species.
Ministry of Forestry and Environment, Sri Lanka. 73 pp.
Marambe, B. (1999b): Factors affecting the spread of alien invasive plants on Sri Lanka. Proceedings of the
First National Workshop on Alien Invasive Species (Ed: B. Marambe,), pp. 29-34. Ministry of
Forestry and Environment, Sri Lanka.
Marambe, B. (Editor) (2000a): Proceedings of the Symposium on Alien Invasive Species in Sri Lanka: Impact
of Ecosystems and Management. Joint Publication of the Ministry of Forestry and Environment
and the National Agricultural Society of Sri Lanka, Peradeniya, Sri Lanka. 63 pp.
Marambe, B. (2000b). The need for a coordinated strategy to control alien invasive plants in Sri Lanka.
Proceedings of the Symposium on Alien Invasive Species in Sri Lanka: Impact of Ecosystems and
Management (Ed: B. Marambe), pp. 13-23. Joint Publication of the Ministry of Forestry and
Environment of Sri Lanka and the National Agricultural Society of Sri Lanka, Peradeniya, Sri Lanka.
Marambe, B., Amarasinghe, L., Dissanayake, S. and Balasooriya, A.H.K. (2000): Distribution of the alien
invasive plant Mimosa pigra L. in Sri Lanka. Proceedings of the Symposium n Alien Invasive
Species of Sri Lanka: impact on ecosystems and management (Ed: B. Marambe), pp 69-63. Joint
Publication of the Ministry of Forestry and Environment of Sri Lanka and the National Agricultural
Society of Sri Lanka, Peradeniya, Sri Lanka.
Marambe, B., Amarasinghe, L. and Gamage, G. (2003a): Sri Lanka Country Report. Invasive Alien Species in
South-Southeast Asia: National Reports and Directory of Resources (Eds: N. Pallewatta, J.K.
Reaser, and A.T. Gutierrez), pp. 91-100. Global Invasive Species Programme, Cape Town, South
Marambe, B., Amarasinghe, L, Silva, A., Gamage, G., Dissanayake, S. and Seneviratne, A. (2003b):
Distribution, biology and management of Mimosa pigra L. in Sri Lanka. Manual on Biology and
Management of Mimosa pigra (Eds: M. Julien, G. Glanagan, T. Heard, Q. Paynter, and C. Wilson),
pp. 85-90. CISIRO, Australia.
Marambe, B. (2008): Research priorities on Invasie Alien Species in Sri Lanka. Proceedings of the National
Symposium on Invasive Alien Species (Ed: S. Ranwala), pp. 7-12. Sri Lanka Association for the
Advancement of Sciences.
McNeely, J. A. (Editor) (2001): The Great Reshuffling: Human Dimensions of Invasive Alien Species. IUCN,
Gland, Switzerland and Cambridge, UK. vi + 242 pp.
MENR (2009): Abstract Booklet of the National Symposium on Invasive Alien Species in Sri Lanka. A Joint
Publication of the Ministry of Environment and Natural Resources, Agriculture Education Unit of
University of Peradeniya, and Institute of Biology of Sri Lanka.
Medawatte, W.W.M.A.B., Tennakoon, K.U., Hulme, P.E., and Gunatilleke, I.A.U.N. (2008): Spread of
Caribbean pine into the grasslands of the Knuckles range, Sri Lanka. Proceedings of the National
Symposium on Invasive Alien Species. 11th November, Colombo. p 5 (Abstract).
Pushpakumara, D.K.N.G. and Hitinayake, H.M.G.S.B. (2001): Invasive tree species in Udawattakele forest
reserve. Sri Lankan Biodiversity Review, 1: 53-63.
Rabinowitz, D. (1981): Seven forms of rarity. In: The Biological Aspects of Rare Plant Conservation (Ed: H
Synge). Wiley, New York, 205218.
Ratnayake, R.M.C.S. (2008): Dominant alien invasive plants of Hantana ecosystem. Proceedings of the
National Symposium on Invasive Alien Species. 11th November, Colombo. pp 21 (Abstract).
SCBD (2009): Invasive Alien Species A Threat to Biodiversity. Secretariat to the Convention on Biological
Diversity. Montreal, Canada. 45 pp.
Weerakone, K. and Athukorala, H. (2008): Invasive plant species: Is it a threat to the existence of globally
threatened Spot-billed pelicans in Sri Lanka? Proceedings of the National Symposium on Invasive
Alien Species. 11th November, Colombo. p 24 (Abstract).
Wijesundara, S. (1997): Leopards in Horton Plains (long).
Siril Wijesundara
Wijesundara, S. (1999): Alien invasive species in Sri Lanka and their history of introduction. Proceedings of
the First National Workshop on Alien Invasive Species (Ed: B. Marambe), pp 25-27. Ministry of
Forestry and Environment, Sri Lanka.
Wijesundara, D.S.A., Jayasinghe, C., Marambe, B. and Tennakoon, K.U. (2001): Host-parasitic association of
Cuscuta chinensis Lam. in Sri Lanka. Annals of the Sri Lanka Dept. of Agriculture, 3: 343-351.
Wisumperuma, D. (2008): First known record of guinea grass cultivation in Sri Lanka, 1801-1802. Journal of
the Royal Asiatic Society of Sri Lanka, Colombo, LIII (New Series): 219-226.

File (1)

Full-text available
Changes in the climate have worsen the problems caused by weeds and invasive alien plants (IAPs) in agro-ecosystems at global scale resulting from their changes in the range and population densities. Over the past six decades, Sri Lanka has experienced a slow but steady increase in annual environmental temperature by 0.01–0.03°C. Increasing extreme events of rainfall, wetter wet seasons, and drier dry seasons are some of the characteristic features of the changes in the climate observed in Sri Lanka over the years. The Ministry of Environment (MOE) in Sri Lanka has established a National Invasive Species Specialist Group (NISSG) in 2012 and adopted the National Policy on Invasive Alien Species (IAS) in Sri Lanka, Strategies and Action Plan in 2016. Further, the MOE has developed and adopted protocols to assess the risk of IAS at pre- and post-entry level to the country while incorporating climate change concerns. Periodic risk assessments have being carried out to prioritize actions against IAS in Sri Lanka. The Ministry of Agriculture as adopted a National Weed Strategy (NWS) and has identified the Weeds of National Significance (WONS) under different priority crops. A study done in 2014 has clearly shown that weed control costs in agricultural lands in several district of Sri Lanka were nearly doubled during the years that experienced El Niño Southern Oscillation (ENSO). Further, studies have clearly indicated that IAPs also survive, expand and impact the continuously disturbed environments in agro-ecosystems. Panicum trichocladum, a species listed as a potential invasive based on the risk assessment done in 2016, has shown an increase in its population density and distribution in Sri Lanka during the last 2–3 years. However, weeds and IAPs in agro-ecosystems have drawn less attention of policy makers, scientists, and practitioners in relation to impact of climate change in island ecosystems. This paper focuses on the scientific evidence reported in agro-ecosystems in Sri Lanka on climate-related impacts on agriculturally important weeds and IAPs, and the efforts made to manage their introduction and spread across the country.
Full-text available
Alien invasive species (AIS) is one among the various threats to the biodiversity of Sri Lanka. A survey was carried out to establish the present status of AIS in Sri Lanka. Wetland and terrestrial ecosystems of different climatic zones were surveyed randomly for the presence of AIS and their threats. Among the 59 AIS identified, 10 species of fauna and 13 species of flora are included in the list of 100 of the world's worst AIS. The alien invasive fauna of Sri Lanka includes 15 vertebrates and 5 invertebrates. The paper discusses the impact of alien invasive fauna and flora on the native species and stresses the need for a proper management strategy.
Full-text available
In 1981, Deborah Rabinowitz wrote an article entitled "Seven forms of rarity," in which she presented a simple classification scheme of spe-cies rarity based on three dichoto-mous criteria—species range (large or small); habitat specificity (wide or narrow); and local population size (large or small). The paper, still regu-larly cited in textbooks and research articles, has become a minor classic, and Rabinowitz clearly succeeded in accomplishing her stated goal, which was to "contribute some clarity" to the investigation of rarity and encour-age "new perspectives for people en-gaged in more practical concerns." We believe that the investigation of biological invasions could benefit from a similar contribution of clar-ity and new perspectives. Recent evaluations of the field of invasion ecology (Williamson 227 Lonsdale 1999) have concluded that little progress has been made in the more than 40 years since Charles S. Elton (1958) initiated the modern dis-cipline of invasion ecology with his book, The Ecology of Invasions by Animals and Plants. We believe that inconsistent and imprecise use of in-vasion terminology is one factor that is contributing to the ongoing diffi-culties of the field. Thus, in a clear, unabashed imitation of Rabinowitz' efforts, we propose a similar classifi-cation scheme for invasion nomen-clature in an attempt to provide some clarity to the field of invasion ecol-ogy and to promote new perspectives. Depending on the author, a spe-cies in the invasion literature might be referred to as alien (Crawley et al. 1996), exotic (Green 1997), inva-sive (Daehler 1998), nonindigenous (Pimentel et al. 2000), imported (Williamson and Fitter 1996), weedy (Fox 1990), introduced (Lonsdale 1994), non-native (Davis et al. 2000), immigrant (Bazzaz 1986), colonizer (Williamson 1996), native (Meyer and Florence 1996), naturalized (Hussey et al. 1992), endemic (Williamson 1996), or indigenous (Sauer 1988). In many cases, these terms are not defined, or if they are defined, they are not always defined consistently. Until a commonly accepted vocabu-lary is adopted by invasion ecolo-gists, we think the field will continue to have difficulty developing reliable generalizations, partly due to misun-derstandings and misinterpretations among investigators. Because species invading a new region and successional species mov-ing into a habitat following a distur-bance are both colonizing new sites, the development of a nomenclature scheme based on types of colonizers might clarify communication within the field of invasion ecology. Just as important, we believe such a scheme may help bring to an end the notion that invasions and invading species are unique ecological phe-nomena, thereby requiring unique ex-planations. We acknowledge that not all colo-nization events are alike. For ex-ample, some colonizations occur over a short distance, some over a very long distance; some colonizers are new to the region, some are not; some colonizers have a negligible effect on the new environment, whereas some have very large im-pact. We think it would be useful to distinguish among different types of colonizers while recognizing the fun-damentally similar ecological pro-cesses that govern all colonization episodes. To this end, we propose a simple classification scheme for colonization terminology modeled after Rabinowitz's (1981) classifica-tion of rarity forms. The organizing criteria for this classification scheme are based on strictly ecological and geographical concepts. The scheme is organized around three distinctive aspects of the colonizer: dispersal distance (short or long), uniqueness (novel or common to the region colonized), and impact in the new environment (small or great). According to this scheme, there are 2 3 combinations of catego-ries, or "eight ways to be a colonizer" (Fig. 1). The three different criteria will be described in more detail.
Full-text available
Mimosa, Mimosa pigra L., was first reported in Sri Lanka in 1997. The species is mainly confined to the central and north-western provinces of Sri Lanka. The plant has colonised along the river banks of the Mahaweli River, which is the main supplier of irrigation water to the agriculture-dominant dry zone of the country. Use of river sand for construction work was identified as a major method of seed dispersal, apart from seeds being trans- ported with river water flow. GPS technology is currently being used for monitoring the extent of spread of this species. Mimosa seeds were 100% viable after four years of storage at room temperature (28±2°C) and also at 8°C. The onset of flowers was first observed at 12-14 weeks after planting. The initial growth of the weed was slow, but the height increased at a rate of 2.4-2.6 cm day -1 during the first 8-12 weeks. From 12 weeks, the stem dry weight of mimosa increased at a more rapid rate than the root dry weight. The relative growth rate (RGR) increased until onset of flowers and then decreased. The soil seed-bank density within the canopy diam- eter of the naturally grown mimosa plants varied from 2,336 to 46,410 seeds m -2 . Glypho- sate at the dosage of 1.44 kg active ingredient ha -1 effectively controlled mimosa seedlings less than six months old, when applied three times repeatedly at four-month intervals on the same set of seedlings. Mimosa seeds did not germinate in the presence of one-month old Panicum maximum Jacq. at a population density of 16 plants m -2 . Awareness programs conducted for the communities in the infested areas have resulted in several community participatory activities to eradicate small patches of mimosa from the Central Province.
Full-text available
Biotic and abiotic factors that influence the avian distribution in a dry zone wetland was investigated by studying the distribution of Asian Openbill (Anastomus oscitans), Cotton Pygmy-goose (Nettapus coromandelianus) and Pheasant-tailed Jacana (Hydrophasianus chirurgus) in Anavilundawa Ramsar sanctuary in Sri Lanka in 2006. Their distribution was recorded in Anavilundawa, Suruwila and Maiyawa reservoirs, their catchments and respective paddy fields, through line transects. The floral cover of surface water was recorded by floating quadrates. Water lily (Nymphea spp.) was the dominant flora in Anavilundawa reservoir, invasive water hyacinth (Eichhornia crassipes) in Suruwila reservoir and a native lotus (Nelumbo nucifera) in Maiyawa reservoir, respectively. Anavilundawa area had a higher distribution of birds than in the other two areas. Among the three species observed, Asian Openbill distribution was mainly restricted to Anavilundawa whereas Pheasant-tailed Jacana was present in all three areas. Nesting of Asian Openbill occurred only in Anavilundawa while nesting of Pheasant-tailed Jacana was only observed in Maiyawa. Among the three species recorded, Cotton Pygmy-goose numbers were the least. Asian Openbill preferred dead trees and trees with no leaves for nesting and perching over live trees. It is concluded that the spread of invasives such as Water hyacinth and Salvinia (Salvinia molesta) forming mats over surface water have reduced the abundance of habitat specialists like Cotton Pygmy-goose.
Rather than simply enhancing invasion risk, climate change may also reduce invasive plant competitiveness if conditions become climatically unsuitable. Using bioclimatic envelope modeling, we show that climate change could result in both range expansion and contraction for five widespread and dominant invasive plants in the western United States. Yellow starthistle (Centaurea solstitialis) and tamarisk (Tamarix spp.) are likely to expand with climate change. Cheatgrass (Bromus tectorum) and spotted knapweed (Centaurea biebersteinii) are likely to shift in range, leading to both expansion and contraction. Leafy spurge (Euphorbia esula) is likely to contract. The retreat of once-intractable invasive species could create restoration opportunities across millions of hectares. Identifying and establishing native or novel species in places where invasive species contract will pose a considerable challenge for ecologists and land managers. This challenge must be addressed before other undesirable species invade and eliminate restoration opportunities.
1. Acacia nilotica is a spinescent woody legume that has become highly invasive in several parts of the world, including Australia where it has been declared a weed of national significance. Understanding the likely potential distribution of this notorious plant under current and future climate scenarios will enable policy makers and land managers to prepare appropriate strategies to manage the invasion. 2. CLIMEX was used to synthesize available information from diverse sources to model the invasion potential of A. nilotica and gain insights into the climatic factors limiting its range expansion. The model identified areas at risk of further invasion so that early preventative or ameliorative measures could be undertaken in a timely manner. 3. The potential distribution of A. nilotica in Australia under current climatic conditions is vast, and far greater than the current distribution. 4. Global climate change is likely to increase markedly the potential distribution of A. nilotica in Australia, significantly increasing the area at risk of invasion. The factors of most importance are the expected increases in water-use efficiency of A. nilotica due to increased atmospheric CO2 concentrations, allowing it to invade more xeric sites further inland, and increased temperatures, allowing it to complete its reproductive life cycle further southward (poleward). 5. Synthesis and applications. Simple paddock quarantine procedures may provide a means of limiting the range of A. nilotica within its potential distribution under current, as well as future, climate scenarios. The projected increased growth potential of A. nilotica throughout its current range suggests that if future management patterns result in seed pods lying unconsumed on the ground, heightened vigilance may be required to identify and eradicate new invasion foci arising from flood dispersal. The increased growth potential may also result in an alteration of the economic balance, in favour of harvesting A. nilotica for agroforestry or local bioenergy projects. A crucial component in containing this invasion will be raising public awareness of the invasion threat posed by A. nilotica, its identification and suitable control techniques.