Invasive Alien Plant Species in Nepal

Full text

269
Frontiers of Botany, 2016, pp. 269-284
Eds.: P.K. Jha, M. Siwakoti and S. Rajbhandary
Publisher: Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu
Invasive Alien Plant Species in Nepal
Bharat Babu Shrestha
Central Department of Botany
Tribhuvan University, Kirtipur, Kathmandu, Nepal
Email: bb.shrestha@cdbtu.edu.np
Introduction
Biological invasion has been considered as an important component of global
environmental changes (Vitousek et al. 1997) and a leading cause of decline and/or
loss of native biodiversity (Ricciardi et al. 1998, Kohli et al. 2004) and ecosystem
services (Pejchar and Mooney 2009). With steady increase in human movement and
global trade, the intensity of biological invasion has been increasing in all
ecosystems and landscapes. The negative impact of invasive species is further
exacerbated by ongoing climate change because the later has been projected to
increase both frequency and intensity of biological invasion (Simberloff 2000). The
problem of invasive species is prevalent both in developed as well as developing
countries, but their impact is likely to be higher in developing countries like Nepal
due to lack of expertise and limited resources available for their management.
Nepal lies at the cross-road of six floristic provinces of Asia (Sino-Japanese,
Southeastern Asiatic, Indian, Sudano-Zambian, Irano-Turranean and Central
Asiatic) and the floral elements of all provinces are represented in Nepal (Dobremez
1976, as cited in TISC 2002). With the widest elevation gradient and heterogeneous
geomorphology, organisms from anywhere of the world may find suitable habitat
and climatic condition in Nepal. There are at least 219 alien species of flowering
plants (Tiwari et al. 2005, Siwakoti 2012, Sukhorukov 2014) and 64 species of
animals (Budha 2015) that are naturalized in Nepal. An assessment of invasive alien
plant species (IAPS) was undertaken for the first time by IUCN Nepal during 2002-
2003 and reported 21 naturalized (i.e. alien species with self sustaining population)
flowering plant species to be invasive in Nepal (Tiwari et al. 2005). Community
consultation and field observations showed that at least four additional naturalized
plant species can be considered invasive in Nepal (Table 1). Though the Nepalese
scientific community was aware of the arrival of IAPS since long, scientific study of

270
the problems related to them got momentum only after 2000 and the Central
Department of Botany, Tribhuvan University is playing a leading role in IAPS
related research in Nepal (Poudel and Thapa 2012). In this communication, an
overview of diversity of the IAPS in Nepal, their distribution, dispersal, impacts,
management, legal provision, and future prospects have been presented.
Diversity
In an assessment undertaken by IUCN Nepal during 2002-2003, 21 naturalized
plant species have been reported as invasive in Nepal (Tiwari et al. 2005). In
addition to them, four naturalized species Ageratum conyzoides, Erigeron
karvinskianus, Galinsoga quadriradiata and Spermacoce alata Aubl (Syn. Borreria
alata) have been also found to be invasive in agro-ecosystems and rangelands (BB
Shrestha, personal observation). A. haustonianum is spreading rapidly in Tarai,
Siwalik and Mid Hills from east to west while E. karvinskianus is problematic
mainly in Mid Hills and Low Mountains of western Nepal (e.g., Darchula district).
G. quadriradiata is a serious weed of agro-ecosystem in Mid Hills and Low
Mountains from east to west. S. alata is commonly invading agro-ecosystems and
rangelands of Siwalik and Mid Hills, and, according to the local community of
Begnas lake area of Kaski district, it has significantly reduced forage production.
Therefore, the total number of IAPS in Nepal becomes 25 which belong to 13
families (Table 1). Asteraceae is the largest family with 10 species, followed by
Amaranthaceae (2 species) and Caesalpiniaceae (2 species); remaining 11 families
are represented by single species.
Table 1. Invasive alien plant species (IAPS) of Nepal.
Name of IAPS Common
name Local name Family Native
range
$
First
Report*
Minimum
residence
time (Yr)#
Ageratina
adenophora L. Crofton
weed Kalo Banmara Asteraceae Mexico 1952 63
Chromolaena
odorata
(Spreng.) King
and Robinson*
Siam weed Seto Banmara Asteraceae Mexico,
C & S
America
1825 190
Eichhornia
crassipes
(Mart.) Solms.*
Water
hyacinth Jalkumbhi Pontederiaceae S
America 1966 49
Ipomoea
carnea ssp.
fistulosa (Mart.
ex Choisy) D.F.
Austin
Bush
morning-
Glory
Besaram Convolvulaceae
Mexico,
C & S
America
1966 49

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Lantana
camara L.* Lantana Kirne kanda Verbenaceae C & S
America 1848 167
Mikania
micrantha
Kunth*
Mile-a-
minute weed Lahare
banmara Asteraceae C & S
America 1963 52
Alternanthera
philoxeroides
(Mart.) Griseb.
Alligator
weed Jalajambhu Amaranthaceae S
America 1994 21
Myriophyllum
aquaticum
(Vell.) Verdc.
Parrot’s
feather Holaragaceae South
America – –
Parthenium
hysterophorus
L.
Parthenium Pati jhar Asteraceae Southern
USA to S
America
1967 48
Ageratum
conyzoides L. Billygoat Raunne/Gandhe
Asteraceae C & S
America 1910 105
Amaranthus
spinosus L. Spiny
pigweed Kande lude Amaranthaceae Tropical
America 1954 61
Argemone
mexicana L. Mexican
poppy Thakal Papaveraceae Tropical
America 1910 105
Senna tora (L.)
Roxb. Sickle pod
senna Tapre Caesalpiniaceae
?? 1910 105
Hyptis
suaveolens (L.)
Poit.
Bushmint Tulsi Jhar Lamiaceae Tropical
America 1956 59
Leersia
hexandra
Swartz.
Southern Cut
grass Karaute ghans Poaceae ?? 1820 195
Pistia stratiotes
L. Water
lettuce Kumbhika Araceae S
America 1952 63
Bidens pilosa
L. Black
jack/Hairy
Beggar-tick
Kalo kuro Asteraceae Tropical
America 1910 105
Senna
occidentalis
(L.) Link.
Coffee
Senna Panwar Caesalpiniaceae
Tropical
America 1910 105
Mimosa pudica
L. Sensitive
plant Lajjawati Mimosaceae Mexico
to S
America
1910 105
Oxalis latifolia
Kunth. Purple wood
sorel Chari amilo Oxalidaceae C and S
America 1954 61
Xanthium
strumarium L. Rough
cockle-Bur Bhede kuro Asteraceae America 1952 63
Ageratum
haustonianum
Mill.
Blue
Billygoat
Weed
Nilo gandhe Asteraceae Mexico
& C
America

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Erigeron
karvinskianus
DC
Karwinsky’s
Fleabane Phule Jhar Asteraceae Mexico
& C
America
Galinsoga
quadriradiata
Ruiz &Pav.
Shaggy
Soldier Jhuse Chitlange
Asteraceae Mexico
Spermacoce
alata Aubl Broadleaf
bottonweed Alu Pate Jhar Rubiaceae West
Indies
and
Tropical
America
*Species listed in world’s 100 worst invasive species (Lowe et al. 2000).
** This includes both first scientific report as well as collection of first herbarium specimens
whichever is earlier.
# Minimum residence time is the number of years since first record. It is obtained by
subtracting year of first record from the current year (2015).
$ Based on database of CABI’s Invasive Species Compendium (http://www.cabi.org/isc)
[except Ageratum haustonianum which is based on http://keys.lucidcentral.org/keys/v3/
eafrinet/weeds/key/weeds/Media/Html]. Assessed on 17 August 2015.
Among 25 IAPS, four species (Chromolaena odorata, Eichhornia crassipes,
Lantana camara and Mikania micrantha) are included in world’s 100 worst invasive
species (Lowe et al. 2000). In addition, six plant species found in Nepal are also
included in the list. However, five of them (Arundo donax L., Hedychium
gardnerianum Sheppard ex. Ker Gawl., Hiptage benghalensis (L.) Kurz., Imperata
cylindrica (L) P. Beauv. and Rubus ellipticus Sm.) are native to Nepal. The
remaining one Leucaena leucocephala (Lam.) de Wit., a medium sized tree, was
introduced as fodder plant in Nepal and now it is naturalized within agro-ecosystem.
Invasive status of this species in natural habitat has not been reported yet.
Distribution
There is high concentration of IAPS on the southern half of the country (which
includes Tarai, Siwalik and Mid Hills running east-west) with tropical to subtropical
climate (Table 2). This is not surprising because more than 3/4
th
of the naturalized
plant species (which also includes IAPS) of Nepal are native to tropical and
subtropical region of the world (Tiwari et al. 2005, Bhattarai et al. 2014). Until now,
the most troublesome species such as Chromolaena odorata, Eichhornia crassipes,
Lantana camara and Mikania micrantha are confined to this region. However,
northward movement of these species cannot be ruled out. Some species of tropical
origin like Ageratina adenophora and Parthenium hysterophorus started their

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invasion from the southern part and have already reached to northern border
crossing through Low Mountain region. Only a few invasive species like Erigeron
karvinskianus and Galinsoga quadriradiata are confined to Mid Hills and Low
Mountains, and absent in warm regions such as Tarai and Siwalik. The IAPS has not
been reported from High Mountain regions of Nepal.
Table 2. Distribution of invasive alien plant species (IAPS) in Nepal.
Name of IAPS Elevation
range
(m asl)
Ecological
Division
Physiographic
regions Major Habitats
Ageratina
adenophora 400-2600 E, C, W T, S, H, M
L
Forest, shrubland,
grassland, agro-
ecosystem
Chromolaena
odorata 75-1700 E, C, W T, S, H Forest, shrubland,
grassland, agro-
ecosystem
Eichhornia
crassipes 75-1500 E, C, W T, S, H Wetland
Ipomoea carnea
ssp. fistulosa 75-1350 E, C, W T, S, H Wetland
Lantana camara 75-1700 E, C, W T, S, H Forest, shrubland,
grassland, agro-
ecosystem
Mikania
micrantha 75-1200 E, C T, S, H Forest, shrubland,
grassland, agro-
ecosystem
Alternanthera
philoxeroides 80-1350 E, C, W T, S, H Wetland
Myriophyllum
aquaticum 1350 C H Wetland
Parthenium
hysterophorus 75-1935 E, C, W T, S, H, M
L
Shrubland, grassland,
agro-ecosystem,
residential area
Ageratum
conyzoides 75-2000 E, C, W T, S, H Grassland, agro-
ecosystem
Amaranthus
spinosus 75-1800 E, C, W T, S, H Residential area, agro-
ecosystem
Argemone
mexicana 75-1400 E, C, W T, S, H Agro-ecosystem

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Senna tora 75-1300 E, C, W T, S, H Shrubland, grassland
Hyptis suaveolens 75-1000 E, C, W T, S, H Shrubland, grassland
Leersia hexandra 100-300 E, C T, S Wetland
Pistia stratiotes 75-1350 E, C, W S, H Wetland
Bidens pilosa 100-2300 E, C, W T, S, H, M
L
Shrubland, grassland,
agro-ecosystem
Senna
occidentalis 75-1400 E, C, W T, S, H, M
L
Shrubland, grassland
Mimosa pudica 75-1500 E, C, W T, S, H Grassland, agro-
ecosystem
Oxalis latifolia 600-2200 E, C, W H Agro-ecosystem
Xanthium
strumarium 75-2500 E, C, W T, S, H Shrubland, grassland
Ageratum
haustonianum 400-1350 E, C, W S, H Shrubland, grassland,
agro-ecosystem
Erigeron
karvinskianus 700-2300 E, C, W H, M
L
Forest, shrubland,
grassland, agro-
ecosystem
Galinsoga
quadriradiata 1200-2200 E, C, W H, M
L
Agro-ecosystem
Spermacoce alata 200-2000 E, C S, H Agro-ecosystem,
shrubland, grassland
Ecological division: E – Eastern, C – Central, and W – Western; Physiographic regions: T –
Tarai, S – Siwalik, H – Hills, M
L
– Low Mountain, and M
H
– High Mountain
After introduction, the dispersal and establishment of IAPS at local scale depend
on resources availability and human activities. Frequent availability of unused
resources increases vulnerability of a habitat to invasion (Davis et al. 2000) while
human activities increase propagule pressure of invasive species (Simberloff 2009).
Therefore, most of the IAPS in Nepal are concentrated in anthropogenic landscape
such as agro-ecosystem, residential area and rangeland (e.g., shrub land, degraded
forests) while they are less common in intact forests. For example, Parthenium
hysterophorus was present in 80% of the sampling locations in fallow and grazing
land while it was present only in 24% of the sampling locations in forests (Shrestha
BB, unpublished data). Out of 25 IAPS found in Nepal, 4 species are found in
wetland and Eichhornia crassipes is the most problematic among them. Species like
Ageratum conyzoides, A. haustonianum, Erigeron karvinskianus and Oxalis latifolia

275
are problematic in agro-ecosystems. In forest and shrublands, the major problematic
species include Ageratina adenophora, Chromolaena odorata, Lantana camara and
Mikania micrantha while the species like Parthenium hysterophorus is threatening
grass/grazing lands.
Dispersal
Introduction of alien species exclusively depends on human activities while the
subsequent dispersal of naturalized species occurs both by natural process as well as
human activities. The IAPS that belongs to Asteraceae such as Ageratina
adenophora, Chromolaena odorata and Mikania micrantha are mostly dispersed by
winds but some other species of the same family are dispersed by animals (e.g.,
Xanthium strumarium, Bidens pilosa), vehicles and agriculture produces (e.g.,
Parthenium hysterophorus). Dispersal by vehicles and as contaminant of transport
materials often result in the formation of satellite populations at isolated geographic
locations (e.g., valley with warm climate amid high hills). Seeds of Lantana camara
is mainly dispersed by birds but this species is still being transported to new
locations for ornamental purposes due to its attractive flower. Wetland IAPS are
mostly dispersed by water but species like Eichhornia crassipes and Pistia
stratioites are also transported to new locations for their ornamental values. Ipomoea
carnea ssp. fistulosa, a wetland species common in Tarai region has been introduced
to hilly region for controlling soil erosion along roadside and also as hedge plant in
agroecosystem. However, this species is less likely to be problematic in hilly region
due to lack of suitable habitat. Species that is dispersed mainly by natural process
(e.g., Chromolaena odorata) often has low spread rate than other species which is
dispersed by human activities (e.g., Parthenium hysterophorus). For example,
Chromolaena odorata with minimum residence time (MRT) of 190 years has not
been reported from the Tarai region west of Karnali river but Parthenium
hysterophorus with only 48 years MRT is found not only from eastern to western
Nepal but also from southern border with India to northern border with China
(Timbure of Rasuwa district).
Impacts
Because of the inherent linkage with human activities, the IAPS are more
common, and hence have more impacts in anthropogenic landscape than in intact
natural landscape. The impact of IAPS in anthropogenic landscape mainly includes
the economic losses due to decline in agriculture production, increased labor to
remove the weeds, suppression of useful species, and health hazard to human and

276
livestock. From anthropogenic landscape, some of the IAPS expand to natural
landscape such as forest, grassland and wetland where they not only compete with
native species for resources but also degrade the habitats thereby making the
ecosystems hostile to native species and increasing the rate of human-induced
biodiversity loss. Therefore, globally the biological invasion has been considered as
the second major cause of biodiversity loss next to habitat degradation (Glowka et
al. 1994).
In Nepal, the IAPS are already common and spreading rapidly both in
anthropogenic as well as in natural landscape but their impacts – economical,
ecological and evolutionary – have not been evaluated comprehensively. Limited
researches and case studies have shown that the impacts of IAPS ranges from habitat
degradation of endangered wildlife (e.g., one-horned rhinoceros, Murphy et al.
2013) to negative effects on the livelihood of rural communities (Rai et al. 2012).
Murphy et al. (2013) reported that 44% of the habitat of endangered one-horned
rhinoceros in Chitwan National Park has been negatively affected by Mikania
micrantha by suppressing growth of grasses and regeneration of trees. Another IAPS
Parthenium hysterophorus has significantly altered species composition and soil
chemistry of grasslands (Timsina et al. 2011). The cases of bitter taste in milk
produced by cattle that grazed in P. hysterophorus invaded grassland, and allergic
dermatitis due to this weed to human have been also reported (Shrestha et al. 2015).
Other IAPS of the terrestrial ecosystems such as Ageratina adenophora, Lantana
camara and Chromolaena odorata are also widespread and form monoculture stands
displacing native species and disrupting ecosystem processes. They have reduced
carrying capacity of rangelands, increased the risk of fire damage, and prevented
regeneration of other species including trees. However, these impacts are largely
anecdotal due to lack of risk assessment and impact study. In wetlands of Tarai,
Siwalik and Mid Hills, Eichhornia crassipes is the most troublesome IAPS
threatening all the Ramsar sites and most of the other lake systems. This species not
only smothers the wetland biodiversity but also negatively affects the livelihood of
wetland dependent local communities. For example, in Begnas lake of Pokhara
valley, boating and fishing are important economic activities of the local
communities residing near the lake. Boating is both means of transportation as well
as source of income from tourism, and about 200 individuals are involved in boating
profession (Buddhi Sagar Kandel, staff of Boat Entrepreneur’s Association of
Begnas Lake, personal communication, Nov 15, 2015). Similarly livelihood of at
least 60 households depends on fishing in the lake. Livelihood of both these boating
and fishing communities has been threatened due to rapid expansion of the E.
crassipes in the lake since last 8-10 years.

277
Review of available references showed that a limited number of studies have
evaluated the impacts of a few IAPS (e.g., Timsina et al. 2011, Rai et al. 2012,
Murphy et al. 2013) while most of the perceived impacts of IAPS is largely
anecdotal. There is a need of systematic and comprehensive studies on the
ecological and economic impacts of invasive alien species in Nepal. The
Government of Nepal has targeted to evaluate ecological and economic impacts of at
least five invasive alien species by 2020 (MFSC 2014a). Some research activities
are being initiated in this direction by different institutions such as the Central
Department of Botany (Tribhuvan Unversity), International Center for Integrated
Mountain Development (ICIMOD), and National Trust for Nature Conservation
(NTNC).
Management
Management of invasive species involves three basic strategies: prevention,
eradication and control (Radocevich et al. 2009). Prevention involves restriction to
the introduction of potentially invasive alien species and requires strict quarantine
and regular monitoring. It is the first and the best strategy for invasive species
management but its implementation, even partial at best, cannot be effective in the
context of globalization of trade and increasing human mobility. Because of the
open border with India and high trade dependency, prevention of the entry of
invasive species to Nepal is almost impossible. Eradication is the complete removal
of invasive species from the habitat or region and this is possible only when the
species occurs in a small area. However, in most of the cases, by the time when
managers acknowledge the problem and prepare for action, it is often too late for
eradication to be possible due to rapid spread of the invasive species covering large
areas. Control involves reducing the abundance of invasive species in the invaded
habitat or region and preventing further spread, thereby minimizing their impacts to
ecosystem and economy. It does not necessarily result in elimination of species from
any particular region. Due to a large number of IAPS and their widespread
occurrence, ‘control’ is the only strategy left to manage them across landscapes.
The control of the IAPS requires the integration of physical, chemical and
biological methods. One important lesson learned from the management efforts of
IAPS is that a single method is no more effective in controlling these weeds. A
carefully selected set of intervention methods is required to successfully manage the
IAPS. Before any strategy is developed to manage IAPS, their ecological and
economic impacts need to be analyzed, and the underlying mechanisms need to be
understood. In Nepal, the number of IAPS, and their ecological and economic
impacts – which are often irreversible – are increasing over the time. These facts are

278
reflected in the recently prepared biodiversity related national documents such as the
Nepal Fifth Report to Convention on Biological Diversity (MFSC 2014b) and Nepal
National Biodiversity Strategy and Action Plan 2014-2020 (MFSC 2014a).
Unfortunately, systematic and science-based management of the IAPS has not been
initiated yet in Nepal. However, some efforts have been made by communities and
development partners to manage a few IAPS by using their biomass to meet demand
of energy and organic manure. For example, Ageratina adenophora and
Chromolaena odorata have been used as animal bed and subsequently for preparing
organic manure by farmers in Nepal. In districts like Makawanpur (Hetaunda area)
and Bajhang (Rayal village), the stem of Lantana camara is used as fire wood.
Biomass of all these three IAPS has been also used for preparing bio-briquette to
substitute fire wood. Community Forest Users’ Groups near Kathmandu valley have
initiated commercial production of bio-briquette and supply to the Valley. Biomass
of Ageratina adenophra and Eichhornia crassipes has been also used, together with
animal dung, in biogas plant. At some locations fire is also used to control IAPS in
grassland and shrub lands.
In wetlands, physical removal of IAPS has been practiced. For example,
Eichhornia crassipes is being periodically removed from Bishajari lake system (a
Ramsar site) of Chitwan, Taudaha of Kirtipur Municipality in Kathmandu valley,
Phewa and Begnas lakes of Pokhara valley, etc. with limited success. In Pokhara
valley, the biomass of E. crassipes has been used for preparing handicraft items
(e.g., pen holder, hand-bag, dust bin, etc.) by local women’s group (Anonymous
2015a). Biomass removal has been also practiced for other species such as Leersia
hexandra in Bishajari lake (Chitwan) and Myriophyllum aquaticum in Taudaha
(Kirtipur). The Hario Ban Program, which is being implemented by WWF Nepal,
has supported local communities to remove E. crassipes and Pistia stratioites from
Tikauli lake (a part of Bishajari lake system) of Chitwan (WWF Nepal 2013).
One important approach of biological method of IAPS management is the use of
biological control agents. In Nepal, biological control agents are present only for
two IAPS: leaf feeding beetle Zygogramma bicolorata Pallister and winter rust
Puccinia abrupta var. partheniicola (Jackson) Parmelee for Parthenium
hysterophorus (Shrestha et al. 2015), and stem galling fly Procecidochares utilis
Stone and leaf spot fungus Passalora ageratinae Crous and A.R Wood for
Ageratina adenophora (Winston et al. 2014). However, these biological control
agents were not introduced officially after quarantine screening but spread naturally
into Nepal from India and other Asian countries. Recently, Nepal Agriculture
Research Council (NARC) has imported two weevils Neochetina eichhorniae
Warner and N. bruchi Hustache from USA (Florida) as an effort to biological
control of Eichhornia crassipes and both these weevils are under laboratory trial

279
(Anonymous 2015b). It is not clear whether a standard quarantine screening will be
performed before releasing them into natural habitats as was done by India when N.
eichhorniae was released there in 1984 (Jayanth 1988).
Effectiveness of the biological control agents in controlling target IAPS has not
been evaluated systematically but field observations showed that the effect is only
marginal. Distribution of fungal control agents (Puccinia abrupt var. partheniicola
and Passalora ageratinae) of both species is much localized with apparently no
effect to the target species. Zygogramma bicolorata seems to be the most effective
biological control agent of IAPS present in Nepal but its population is still small and
their effectiveness is erratic with year to year variation (Shrestha et al. 2015). For
effective control of P. hysterophorus, it seems necessary that the control by Z.
bicolorata need to be complemented by other biological control agents,
displacement by competitive plant species, and other cultural, physical and chemical
measure (Adkins and Shabbir 2014). Procecidochares utilis entered Nepal naturally
from India and established population by 1972 in eastern part of Nepal (Ilam,
Terhathum and Dhankuta districts) (Sharma and Chhetri 1977, as cited by
Muniappan et al. 2009). The fly, originally from Mexico, has already established its
populations in Hawawii (USA), Asia, Africa, Australia, New Zealand, etc.
(Muniappan et al. 2009). In Nepal, the fly has reached to almost all areas where A.
adenophora is present but its impact on the weed is insignificant (BB Shrestha,
unpublished data). In China and Africa too, the damaging effect of the fly on A.
adenophora is only marginal (Xiao-yu et al. 2004, Heystek et al. 2011).
Legal instruments
Legal instruments related to IAPS aim to prevent the entry of potential invasive
species to a particular territory. Major international conventions and treaties related
to biodiversity conservation and health have called upon to the Parties to develop
mechanisms for preventing entry and spread of invasive species. For example,
Article 8 (h) of the Convention on Biological Diversity (CBD) states that “Each
contracting Party shall, as far as possible and as appropriate, prevent the introduction
of, control or eradicate those alien species which threaten ecosystems, habitats or
species” (
https://www.cbd.int/convention/articles/default.shtml?a=cbd-08
). In addition
to CBD, there are a number of international conventions and other legal instruments
(e.g., Cartagana Protocol on Bio-safety to CBD, The Convention on International
Trade in Endangered Species of Wild Fauna and Flora, Convention on Migratory
Species of Wild Animals – Bonn Convention, Convention on Wetlands – Ramsar
Convention, International Plant Protection Convention, Sanitary and Phytosanitary
Measures (Quarantine) of World Trade Organization, International Health

280
Regulation) which are related to invasive alien species, and to which Nepal is a
signatory (Siwakoti and Shrestha 2014). In line with international conventions and
treaties, and acknowledging the increasing impacts of invasive species a few
national policies of Nepal such as National Wetland Policy 2003 (MFSC 2003) and
Agro-Biodiversity Policy 2008 (First amendment 2014) (www.moad.gov.np,
accessed on Nov 10, 2015) call upon for controlling invasive species which threaten
native biodiversity and ecosystems. The Plant Protection Act (2007) has included a
number of provisions to regulate the import of plants, plant products and biological
control agents (www.lawcommission.gov.np), however, effective implementation of
these provisions remain always a challenge due to porous border and weak
regulatory mechanisms at entry points. Similarly, National Seed Vision 2013-2025
also identified uncontrolled flow of and increased dependency to seeds of exotic
crop, fruits and vegetable species and varieties as a threat to seed sector
development of Nepal (Seed Quality Control Center 2013). However, some other
pertinent national acts (e.g., Forest Act 1993, Seed Act 1988 – First Amendment
2002) and policies (e.g., Rangeland Policy 2010) remain silent on the issues of
invasive species. For example, the IAPS like Lantana camara, Chromolaena
odorata, Ageratina adenophora, Mikania micrantha, Hyptis suaveolens have
severely invaded rangelands of Tarai, Siwalik and Mid Hills of Nepal with obvious
negative impacts to productivity and biodiversity of this important ecosystem.
Nepal’s Rangeland Policy 2010, however, has not identified invasive species as a
threat to the pastureland (http://www.npafc.gov.np/content.php?id=261, accessed on
Nov 9, 2015).
In Nepal’s first Biodiversity Strategy (MFSC 2002), invasive alien species was
identified as a threat to all levels of biodiversity but management strategy was not
specified. In second version of the National Biodiversity Strategy and Action Plan
2014-2020 (MFSC 2014a), the threats due to invasive alien species to biodiversity
and ecosystem functions of wetlands, agro-ecosystems, rangelands, etc. have been
adequately acknowledged. To manage these alien species, the Strategy has included
a number of activities such as nation-wide distribution survey of five most
problematic IAPS, development of atlas for the identification and early detection of
invasive species, enhancement of the capacity of custom and quarantine offices, use
of appropriate biological control agents, and public education and community
participation.
Way forward
Biological invasion has emerged as a new environmental problem for Nepal with
direct implications to biodiversity conservation, ecosystem services and economic

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development. In recent decades, the number of invasive species, and their abundance
in Nepal have been increasing rapidly. This can be attributed to local level drivers
such as land use change (e.g., conversion of agro-ecosystems to urban area), infra
structure development (e.g., road construction), etc. and regional/global drivers such
as globalization of trade and transport, increased human movement, etc. Although
the issue of biological invasion has not been addressed adequately in most of the
national level legal instruments of Nepal (Siwakoti and Shrestha 2014), the recently
prepared National Biodiversity Strategy and Action Plan (MFSC 2014a) has fully
acknowledged the problem of invasive aliens species and included a number of
strategies to manage them. Effective execution of these strategies within the
stipulated time (by 2020) will be an important first step towards the management of
invasive species. The second important step can be the evaluation of ecological and
economic impacts of the invasive species. Most of the ‘impacts’ of the invasive
species is anecdotal. Unless empirical and quantitative data on the invasive species’
impact is generated, the government will be reluctant to invest resources for their
management. This is relevant in the context of climate change too, because the
intensity of biological invasion is likely to increase under anthropogenic climate
change (Simberloff 2000). The third step is the preparation of national strategy for
the management of invasive species. One important lesson learned so far while
managing invasive species is that ‘eradication’ is virtually impossible and
‘management’ requires integration of all approaches at different levels of both
temporal and spatial scales. This kind of consolidation of management approaches
and available limited resources is possible only through the national strategy for the
management of invasive species. The fourth step is up-scaling the national strategy
to regional level. Biological invasion is obviously a trans-boundary issue and
effective management of invasive species requires harmonization of the approaches
implemented among the countries sharing borders. For example, a common regional
strategy can be developed for south Asian countries associated with South Asian
Association for Regional Cooperation (SAARC). ‘European Strategy on Invasive
Alien Species’ is already in place for European region (Council of Europe 2004).
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