Content uploaded by Buddhi Marambe
Author content
All content in this area was uploaded by Buddhi Marambe
Content may be subject to copyright.
Pak. J. Weed Sci. Res., 18: 863-871, Special Issue, October, 2012
POST-ENTRY RISK ASSESSMENT OF INVASIVE ALIEN FLORA
IN SRI LANKA - PRESENT STATUS, GAP ANALYSIS, AND THE
MOST TROUBLESOME ALIEN INVADERS
S. Ranwala1, B. Marambe2, S. Wijesundara3, P. Silva2,
D. Weerakoon1, N. Atapattu 4, J. Gunawardena5, L. Manawadu1
and G. Gamage6
ABSTRACT
The paper reviews the existing situation on risk assessment
processes carried out globally to regulate introduction, early detections
and management strategies for IAS globally and in the Sri Lankan
context, and provides results of important activities carried out to
develop a post-entry risk assessment protocol for invasive alien flora.
The national lists of invasive alien species developed previously in Sri
Lanka have not gone through a rigorous risk assessment process. The
present study has led to the development of a post-entry risk
assessment protocol for invasive alien flora in Sri Lanka through a
participatory approach and based on a scientifically sound procedure.
This has resulted in identification of 12 species of invasive alien flora in
each category of National List (significantly threatening the
environment) and Priority List (require urgent attention to tackle the
problem) in Sri Lanka. The results are expected to foster an enabling
policy, institutional and planning environment towards effective and
informed-decision making, and to coordinate actions in tackling this
major environmental issue. Steps need to be taken to generate and
share knowledge about the rationale, need and specific techniques and
best practices to tackle IAS in Sri Lanka through the use of valid risk
assessment protocols.
INTRODUCTION
The significance of invasive alien species (IAS) as a global
problem is widely recognized and the adverse effects of these species
have been well described, including the situation in Sri Lanka
(Marambe et al., 2001; Marambe et al., 2003; Marambe, 2008). The
identification and characterization of the adverse effects associated
with IAS is crucial, not only to prevent their introduction to new areas
1 Faculty of Science, University of Colombo, Sri Lanka, 2 Faculty of Agriculture, university
of Peradeniya, Sri Lanka, 3 Royal Botanic Gardens, Peradeniya, Sri Lanka, 4 Canadian
High Commission, Colombo, Sri Lanka, 5 Stanlkey Tilakaratne Mawathe, Nugegoda, Sri
Lanka, 6 Biodiversity Secretariat, Ministry of Environment, Sri Lanka
Corresponding author’s email: bmarambe@pdn.ac.lk
S. Ranwala et al., Post-entry risk assessment of...
864
but also to prioritize management and control measures for already
established IAS.
Risk assessment is a tool that can be used to support the
exclusion of potential IAS from being introduced, as well as to assess
the potential impact of those invasive species that have already
become established. Risk assessment is one of the three components
of risk analysis (Anderson et al., 2004), and should be closely linked to
the other two components; risk management and risk communication.
Risk assessment protocols related to impacts of IAS on native biota
and natural landscapes have been developed and implemented by
various international bodies such as the International Plant Protection
Convention (www.ippc.int/id/13399), World Organization for Animal
Health (www.oie.int) and Pacific Island Ecosystem at Risk
(www.hear.org/pier/), and countries such as Australia (Downey,
2006), New Zealand (Williams et al., 2000), Hawaii (Denslow et al.,
2000), Japan (Yoshioka, 2005), Canada (Anonymous, 2003), USA
(www.plant_materials.nrcs.usda.gov/technical/invasive.html) etc., for
regulation of alien species introductions, early detection and
implementation of control/eradication measures. Risk analysis for
issues related to entry, establishment and spread of IAS have been
addressed through species- or habitat-based approaches in theoretical
ecological studies such as pathway analysis, population viability
analysis and by use of various mathematical models. Risk
assessments, especially on weeds, are not only being conducted at
country borders to forecast the consequences of a particular species
introduction but also at post border level for those already present in
the country or region, or which are likely future incursions so as to
prioritize species for control and management processes (FAO, 2006).
Sri Lankan Context
At present, there are some legislative provisions directly
addressing the prevention of introduction and control of spread of IAS
in Sri Lanka (Marambe and Gunawardena, 2010). Pest risk assessment
conducted at the National Plant Quarantine Services (NPQS) at
Katunayake and the Seed Certification Center, Gannoruwa qualitatively
investigates the likelihood of the entry, establishment and spread of
aquatic or terrestrial pests including invasive plants, pathogens,
nematodes and agricultural insects via imports of plants and planting
material for non consumption and consumption purposes. These risk
assessments comply with the International Standards for
Phytosanitary Measures (ISPM standards) and often other institutions
are consulted especially with regard to the prevention of introduction
of invasive plant species to the country. At present, a more
comprehensive protocol for screening of invasive species at the port of
entry is being drafted by the NPQS of Sri Lanka.
Pak. J. Weed Sci. Res., 18: 863-871, Special Issue, October, 2012
865
Currently, risk analysis for already established IAS in Sri Lanka
has been poorly addressed and has not been incorporated to IAS
management strategies of the country. However, two preliminary post-
entry risk assessment protocols for invasive alien flora have been
developed, aimed at prioritization of IAS for management strategies: a
protocol for prioritization of established invasive alien flora prepared
by Hafiz et al. (2006), and one developed by Weerakoon (2007) for
the Protected Area (PA) Management and Wildlife Conservation Project
of the Department of Wildlife Conservation, Sri Lanka. Implementation
of risk assessments for the control of introduction, establishment and
spread of IAS in Sri Lanka is currently neglected primarily due to the
lack of an acceptable assessment scheme to characterize risks
associated with IAS in Sri Lanka. Gaps in knowledge, access and
sharing of data and lapses in policies, responsibilities and applications
are also attributed to this situation.
Gap Analysis
As in other risk assessment schemes developed for IAS in
various countries, the risk assessment protocol for IAS in Sri Lanka
could also address the economical, ecological and social impacts,
invasiveness, distribution, spread and management options of the
known or potential invasive species. The principal state organization
mandated for biodiversity conservation (the national focal point of
CBD), the Biodiversity Secretariat of the Ministry of Environment, Sri
Lanka, has a major role to fill gaps in risk assessments to manage the
entry, establishment, spread and control measures for IAS in Sri
Lanka.
Knowledge gaps
Risk analysis of IAS is totally based on existing scientific
knowledge and risk assessment protocols assume that information on
the target organism is readily available. Limitations in existing
knowledge, especially on ecological aspects of IAS, often hamper
identification and characterization of the ‘invasiveness’ of a species.
Many species of invasive aliens at the early lag phase of invasions or
that may be future/potential invaders, have still not been subjected to
adequate scientific studies. Taxonomic relationships, invasiveness of
relatives and history of invasiveness elsewhere are integral
components of prediction of invasiveness. High ecological and
taxonomical diversity of noxious species may result in difficulties in
such investigations. The limited available information on growth rates,
length of juvenile period, habitat requirements, dispersal patterns,
behavioral studies etc, also constrains the identification of
invasiveness. Further, knowledge of economical aspects related to IAS
has been poorly explored and integration of economics with
management and control programmes of IAS has occurred only for a
S. Ranwala et al., Post-entry risk assessment of...
866
few well known species. These limitations are a gap in risk assessment
and risk analysis processes.
Data gaps
Information needed for assessment of invasiveness of a species
and its impacts are often obtained through published and unpublished
literature, scattered throughout different institutions, including
personal communications. The lack of a repository of relevant
information in an accessible and updated form, and of an adequate
information management system for IAS, often causes problems in
completing risk assessments.
Limited institutional facilities for quick retrieval of IAS
information also create difficulties and has become a major problem
especially for stakeholders conducting risk assessments at national
borders. Limited data can lead to arbitrary decisions even on sanitary
and phytosanitary measures, increasing the risks of noxious invaders
being intentionally imported. Inefficienct data sharing mechanisms
among relevant stakeholders is another major reason for the gaps in
data related to IAS.
Gaps in policies and applications/responsibilities
Lack of government policy on IAS is another constraint
resulting in weak implementation of risk assessments for IAS in Sri
Lanka. Poor understanding and awareness of impacts of IAS among
politicians, policy makers, administrators, and lack of collaboration
among relevant stakeholders also limits applications of risk
assessments at border and post border levels. Structural and
management deficiencies in organizations/institutions, usually due to
shortages in financial and/or human resources, can disable the
institutional capability to conduct effective risk assessments for IAS.
In certain situations deficiencies in international regulatory
frameworks relating to international standards can contribute to a lack
of policies for application of a risk analysis process. The International
Convention for the Control and Management of Ships’ Ballast Water
and Sediments (2004) highlights management options to control the
spread of marine organisms and pathogens during ballast water
exchanges. However, it does not specifically emphasize invasive alien
planktonic organisms or the need for a risk analysis of ballast water
exchange processes. Deficiencies in international regulatory
frameworks are also present in IPPC as there is no direct provision to
address IAS, which are not considered as pests. There is also a
concern about the exotic pathogens and parasites that could pose risks
to wildlife but that are not listed by the OIE (www.oie.int).
Post-entry Risk Assessment for Invasive Alien Flora in Sri Lanka
The implementation of risk assessment protocols to prevent
further introduction of IAS to Sri Lanka was first highlighted a decade
Pak. J. Weed Sci. Res., 18: 863-871, Special Issue, October, 2012
867
ago, at the First National Workshop on IAS (Marambe, 1999). Later,
the urgent need to establish a standardize surveillance and a threat
assessment of IAS in protected areas was emphasized in the proposed
policy on control of invasive species in protected areas of Sri Lanka
(Weerakoon, 2007). The addendum to the Biodiversity Conservation
(MENR, 2007) also recommended the preparation of risk assessment
protocols for prioritization of established invasive species in Sri Lanka.
Although risks associated with alien plant introductions are
considered at the points of entry by the quarantine authorities, IAS
have not been specifically addressed in standard regulations for
species introductions. Prevention is considered the most economical
and effective management strategy against alien invaders (Wittenberg
and Cock, 2001). Hence, a better prediction of whether or not a
species is likely to be invasive should be conducted at the national
borders, to reduce subjectivity in judgments, and minimize both over
and under-estimates of risks associated with IAS.
Risk assessments for IAS are used to select species that
warrant immediate control as most aggressive species are identified by
the screening process. Current lists of invasive plants and animals in
Sri Lanka (Bambaradeniya, 1999, 2000, 2002; Marambe et al., 2001,
2003) have not been developed through risk evaluation, and there is a
need for a (qualitative and/or quantitative) assessment scheme to
measure relative risks of IAS in Sri Lanka. An attempt at this was
made in 2009-2010, through a broad stakeholder consultation and
with technical expertise provided by the United Nations Development
Organization (UNDP) – Sri Lanka and the Global Environmental Facility
(GEF). The protocol presented has been accepted by the Ministry of
Environment of Sri Lanka and will be used for prioritization of the
invasive alien flora in order to develop management strategies and
decide on financial allocations in the future.
The risk assessment protocol was designed to include four main
themes, each divided into segments covering important areas (Table-1).
Each sub-section was addressed in detail with a set of questions with 3-
5 potential responses per question, scored from least likely (0) to most
likely (4). The questions were designed to ensure minimum occurrence
of the response ‘unknown’.
The scoring was done by 63 people actively involved in IAS
activities in Sri Lanka, including academics, policy makers, scientists,
researchers, and extension officers in the state, private sector and
international and national non-governmental organizations. The input of
15 practitioners were also used in determining the final scores, and
selected questions from themes 1-3 were given double weight. The
invasive alien flora from previous lists prepared without a risk
assessment protocol (Bambaradeniya, 2002; Marambe et al., 2003)
S. Ranwala et al., Post-entry risk assessment of...
868
were evaluated individually according to the listed criteria, and the total
scores for each species for each section calculated. The maximum
possible score for each section was determined and the scores obtained
expressed as a percentage of this.
Table-1. Major themes and sub-themes in the post-entry risk
assessment protocol for invasive alien flora
Theme
Sub sections
No.of
questions
(1) Potential of
Ecological and
Socio-Economic
Impacts
Potential impacts on ecosystem processes
1
Potential impacts on community structure
1
Potential impacts on community composition
1
Potential impacts on other trophic levels
1
Potential impacts on genetic integrity
1
Social nuisance and potential injuries to human
health/injury risks
1
Potential impacts on landscape diversity and aesthetic
aspects
1
Any beneficial use
1
If used commercially, could it lead to harmful impacts
1
Potential detrimental impacts on
agricultural/forestry/fishery productivity
1
Any socio-political, religious, or ethical considerations
1
(2) Invasive potential
Propagation
5
Establishment and/or spread due to disturbances
2
Competitive ability
5
(3) Distribution
Current global distribution
Known level of impact in natural areas at global scale
The species domesticated and/ or reported as a weed
elsewhere
Distributions in Asia as an exotic species
Potential distribution in Sri Lanka
1
1
1
1
1
(4) Management
options
Chances of re-introduction in future
Likelihood of entry through unintentional introductions
Possibility of detection if escaped from manageable
areas
Level of effort required for management if escaped
1
1
1
1
Preparation of National and Priority lists for invasive alien flora
in Sri Lanka
Development of the National List was based on impact severity
of the species, using only the rating from themes 1-3 (impacts,
invasive potential and distribution), with the overall severity score
calculated as a weighted percentage. Species with a score >70% were
placed in the National List of Invasive Alien Flora, those that
significantly affect environmental values of the country. Species with a
score 40-70% were considered Potential Invasive Species. The Priority
Pak. J. Weed Sci. Res., 18: 863-871, Special Issue, October, 2012
869
List of invasive alien flora, where management strategies are urgently
needed, was based on the severity score obtained above and the total
score obtained for section 4 (management option), expressed as a
percentage of the maximum. Species with a score > 70% were
considered priority species that requires immediate action. The results
were validated by a broad stakeholder group of administrators and
scientists involved in IAS control in Sri Lanka. The resulting National
list and the Priority invasive alien flora list for Sri Lanka, totalling 12
species in each category (dirty dozen), are given in Table-2.
Table-2. National and Priority lists of Invasive Alien Flora of Sri
Lanka from post-entry risk assessment
Species
National List (scores
for themes 1, 2 and 3)
Priority List
(scores incl. theme 4)
Priority Invasive Alien Flora
Panicum maximum
1
1
Pennisetum polystachion
2
2
Eichhornia crassipes
3
7
Salvinia molesta
4
5
Lantana camara
5
3
Mimosa pigra
6
8
Prosopis juliflora
7
6
Opuntia dilenii
8
4
Clidemia hirta
9
9
Dillenia suffraticosa
10
12
Austroeupatorium inulifolium
11
10
Ageratina riparia
12
11
Potential Invasive Alien Flora
Mikania micrantha
13
Clusia rosea
14
Miconia calvescens
15
Sphagneticola trilobata
16
Pennisetum clandestinum
17
Parthenium hysterophorus
18
Chromolaena odorata
19
Alstonia macrophylla
20
Cuscuta campestris
21
Myroxylon balsamum
22
Tithonia diversifolia
23
Swietenia macrophylla
24
Cestrum aurantiacum
25
Aristea ecklonii
26
Psidium littorale
27
Ulex europaeus
28
The order of priority in the National List differed in some cases
to that of the Priority List, however, as a group, the dirty dozen
remained the same. Variation within the group is mainly due to the
management strategies adopted at present and related experiences of
the stakeholders in the consultative process who identified some
S. Ranwala et al., Post-entry risk assessment of...
870
species as more invasive than others based on unpblished information.
The final lists have given due recognition to the views of stakeholder
organizations actively involved in management of IAS in different
ecosystems.
The absence of scientifically valid risk assessment protocols and
properly constituted National and Priority Lists has been a hindrance to
efforts to control IAS in Sri Lanka. Ad hoc national lists prepared in the
past have hampered the efforts of IAS control, diverting interest away
from the actual situation. The risk assessment protocol developed in
this study followed a participatory approach for post-entry risk
assessment to identify invasive alien flora in Sri Lanka, which will
foster an enabling policy, institutional and planning environment
towards effective and informed joint actions, at the same time taking
steps to generate and share knowledge about the rationale, need and
specific techniques and best practices to tackle IAS in Sri Lanka.
Similar efforts need to be extended to invasive alien fauna and for pre-
border risk assessment of IAS if Sri Lanka to safeguard its unique
environments from the detrimental impacts of IAS.
REFERENCES CITED
Anderson, M., H. Adams, B. Hope and M. Powell. 2004: Risk analysis
for invasive species: General Framework and Research Needs.
Risk analysis. 24:893-900.
Anonymous. 2003. Criteria for categorizing invasive non-native plants
that threaten Wildlands. California Exotic Pest Plant Council,
USA and Southwest Vegetation Management Association,
Canada.
Bambaradeniya, C.N.B. 1999: Alien invasive fauna in natural habitats
and their impact on indigenous biota. Proc. 1st Nat. Workshop
on Alien Invasive Species in Sri Lanka (Ed: B. Marambe),
Ministry of Forestry and Environ. Sri Lanka. pp 45-51.
Bambaradeniya, C.N.B. 2000: Alien invasive species in Sri Lanka.
Loris, J. wildlife & nature Prot. Soc. Sri Lanka. 22:3-7.
Bambaradeniya, C.N.B. 2002: The status and implications of invasive
alien species in Sri Lanka. Zoos’ Print J. 17:930-935.
Denslow, J., B. Waterhouse, J. Space, and D. Nelson. 2000: Weed risk
assessment for Hawaii and Pacific Islands.
http://www.botany. hawaii.edu/
Downey, P.O. 2006. The weed impact to native species (WINS)
assessment tool for NSW, Australia. Plant Prot. Quarterly,
21:109-116.
FAO. 2006: Procedures for Post Border Weed Risk Assessments. Plant
Prod. & Prot. Div., FAO, Rome.
Pak. J. Weed Sci. Res., 18: 863-871, Special Issue, October, 2012
871
Hafiz, R., S.M.W. Ranwala, and S. Somaratne. 2006: Development of a
criteria for prioritizing invasive plants of Sri Lanka, Proc. 26th
Annual Sessions of the Institute of Biol. Sri Lanka, pp. 21.
Marambe, B. 1999. Proc. 1st Nat. Workshop on Alien Invasive Species in
Sri Lanka. Ministry of Forestry and Environ., Sri Lanka. 73 pp.
Marambe, B., C. Bambaradeniya, D.K. Pushpakumara and N.
Pallewatta. 2001. Human dimensions of invasive alien species
in Sri Lanka. In: The Great Reshuffling-Human Dimensions of
Invasive Alien Species (Ed: J.A. McNeely), pp. 135-142.
Marambe, B., L. Amarasinghe and G. Gamage. 2003. Sri Lanka
Country Report. In: 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.
Marambe, B. 2008. Research priorities on Invasie Alien Species in Sri
Lanka. Proc. Nat. Symp. Invasive Alien Species (Ed: S.
Ranwala), pp. 7-12.
Marambe, B. and J. Gunawardena. 2010. Institutional coordination,
legal regime and policy framework for management of invasive
alien species in Sri Lanka. In: Invasive Alien Species–
Strengthening Capacity to Control Introduction and Spread in
Sri Lanka. Pp. 63-76.
MENR 2007. Biodiversity Conservation in Sri Lanka– A Framework for
Action (Addendum). Biodiversity Secretariat, Ministry of
Environment and Natural Resources, Sri Lanka. 52 pp.
Weerakoon, D.K. 2007. Unpublished Report, Protected Area
Management and Wildlife Conservation Project of the
Department of Wildlife Conservation, Sri Lanka.
Williams, P.A., E. Nicol and M. Newfiold. 2000. Assessing the risk to
indigenous New Zealand biota from new exotic plant taxa and
genetic material, Science for Conservation, Land Care
Research, Dept. of Conservation. New Zealand.
Wittenberg, R. and M.J.W. Cock. 2001. Invasive Alien Species: A
toolkit of best prevention and management practices. CAB
International Wallingford, Oxon, UK. Xii +228 pp.
Yoshioka, T. 2005. Preliminary Weed Risk Assessment of Landscaping
Plants, Landscape Res. Japan, 68:296-300.
