Invasion in India: an Overview

R.K. Kohlii, D.R. Batishi,J.S. Singh2, H.P. Singh3 and J.R.Bhatt4

1Department of Botany, Panjab University, Chandigarh, India; 2Department of Botany, Banaras Hindu University, Varanasi, India; 3Department of Environment Studies, Panjab University, Chandigarh, India; 4Director, Ministry of Environment and Forests, CGO Complex, Lodi Road, New Delhi, India

Introduction introduction to an alien environment is not a new phenomenon but has been an important The Earth's flora is dynamic and has been part of our history. A number of economically constantly changing over a period of time.importantplantssuchascropsand Changes may be natural or human-aided,ornamentals are introduced that have although in the recent past the latter hasproved especially beneficial and non-harmful played a vital role. In fact, the movement ofto the human race. However, many intro- plants from one part of the earth to theduced plant species initially considered to be other has become very common and fre-valuable have become a nuisance and difficult quent owing to better trade and transport to manage. Example include Lantana camara, facilities. Plant species that move from onea South American shrub now known to be a geographical region to the other (eithervery troublesome invader but now introduced accidentally or intentionally), establish and to several parts of the world as an ornamental. proliferatethereandthreatennativeThere are also examples of accidental entry of ecosystems, habitats and species are knownsome invasive plants as contaminants of as invasive alien plants (hereafter referredimported food grains or agricultural/horti- to as invasive plants) (Richardson et al.,cultural material or in ships' ballast water. 2000). An invasiveplantsuchasParthenium The problem of invasive plants has become hysterophorus - one of the most serious global and is largely human-aided (Vitousekinvasive plants - is an example of accidental et al., 1997). Invasive plants are responsibleentry. forglobalenvironmentalchanges,bio- Environmental problems such as climate diversity crisis, species endangerment andchange, disturbances and changing land- disruption of ecosystem processes essential scape patterns have further escalated the for human welfare (Drake et al., 1989; Parker process of biotic invasion. The harms caused et al., 1999; Mack et al., 2000; Mooney, 2005; by biotic invasions are enormous as they Charles and Dukes, 2007; Herron et al., 2007,interfere with the socio-economic system, Pejchar and Mooney, 2009). The impact ofhuman and animal health and food security invasive plants on global biodiversity isof the region. Various international and second only to habitat fragmentation and isnationalorganizations,suchasWorld a major globalissue.Furthermore, theConservation Union (WCU, formerly IUCN economic costs due to are- International Union for Conservation of also enormous, though not widely studiedNature and Natural Resources), Convention (Pimentel et al., 2005). Plant movement oron Biological Diversity (CBD) and Global

© CAB International 2012. Invasive Alien Plants: An Ecological Appraisal for the

Indian Subcontinent (eds J.R. Bhatt et al.) 1 2 R.K. Koh li et al.

Invasive Species Programme (GISP), areknown invasive plants in India, there is no concerned with the prevention and controlcomplete listing of the status of invasive of this global problem. plants. According to one source, around 18% of Indian flora are adventive aliens, of which 55% are from America, 30% from Asia and Status and Vulnerability of the Indian 15% from and Central Asia (Nayar, Region to Plant Invasion 1977). More recently, Reddy (2008) has identified 173 invasive plants belonging to The Indian region, because of its diverse117 genera and 44 families, based on his climatic and environmental conditions, is comprehensivework.TropicalAmerica highlyvulnerabletobioticinvasion. (74%) and tropical Africa (11%) have con- Moreover, a burgeoning population, hightributed most to the invasive flora of the rate of trade and transport, coupled with country. greater movement of people favour the Besides, there are several other reports accidental and intentional entry of plantavailable that provide information on the species in this region. The recent fast rate ofinvasive flora of a particular region/area. For economic growth of the country is alsoexample, Kohli et al. (2004, 2006) have pro- expected to leave its mark on loss of plantvided information on the status of invasive diversity and increased invasion of alienplants in the north-western Himalayan species. Three hot spots of biodiversity,region and have stated that three invasive although supporting rich floral and faunalweeds - Ageratum conyzoides, Parthenium diversity including endemic species, alsohysterophorus and Lantana camara - found in reflect a high rate of habitat degaradationthis region have caused considerable harm where opportunist invasive species canto the fragile biodiversity. Several reasons, easily establish themselves. Consequently, asuch as fragile soil, anthropogenic activity, numer of invasive species have made theirtourism, pollution, rapid industrialization/ abode in the region. The three main reasons urbanization and the livestock-dependent for the greater invasibility of this regionlifestyle of the aboriginals such as the Gaddi could be listed as follows: or Gujjar communities, are responsible for the establishment of invasives and declining excessive humanpopulationsthatbiodiversity (Kohli et al., 2009). Khuroo migrate frequently and carry oret al. propagules of invasive plants from one (2007) reported 571 alien species belonging to 352 genera and 104 families place to another; from the Kashmir Himalayas, their origins availabilityoffragmented/disturbed habitats or species-poor regions due totraceable from Europe, Asia and Africa. Negi and Hajra (2007) reported 308 woody and habitat fragmentation and degradation128 herbaceous exotic species from the that provide habitat for alien species; and Doon Valley of the north-western Himalayas favourable environmental and climatic conditions owing to the diversity ofof which many are harmul invasives that have created several environmental, socio- seasons and climatic variations that give economic and health problems. invasivespeciesanopportunityto establish. Invasive plants such as Ageratum cony- Major Invasive Plants and their zoides, Eupatorium adenophorum, Eupatorium Attributes odoratum, Lantana camara, Mikania micrantha and Parthenium hysterophorusBased on the available databases and some have caused havoc in terrestrial ecosystems,regional reports, nearly 60 invasive plants and , Ipomoea spp. andhave been identified from the Indian region Salviniamolestainaquaticecosystems(Table 1.1), the majority from South and (Raghubanshi et al., 2005). Despite severaltropical America and ,Africa, Plant Invasion in India 3

Europe and even the Asian region. Table 1.1 (National Focal Point for APFISN, 2005), includes Arundo donax - a grass of Indianand this is also included in the list of the top origin that can pose a major threat to100 worst invaders (GISD, 2010). It is also biodiversity owing to its capacity to invadeone of the most obnoxious weeds in the huge areas around water bodies. Most of theWestern Ghats, north-eastern parts of the invasive plants, irrespective of their origin,country and impacts on coconut, rubber, belong to the family , whilecoffee and teak plantations (Singh, 1998). families such as Poaceae, Solanaceae andMikania micrantha (Asterceae), commonly also predominate. Furthermore,known as mile-a-minute, was introduced for invasive plants belong to a variety of lifecamouflaging airfields during the Second forms such as , shrubs, , climbers/World War (Randerson, 2003). It is now a vines, grasses and aquatic plants (Table 1.1).very noxious weed inplantations and Important invasive plants that have created forests,especially in the southern and havoc in a number of habitats includenorth-westernpartsofthecountry terrestrial herbaceous weeds (e.g. Ageratum(Muniappan and Viraktamath, 1993). Trees conyzoides and Parthenium hysterophorus),such as leucocephala and Prosopis shrubs (e.g. Lantana camara and Chromolaenajuliflora introduced under various forestry odorata), trees(e.g. Prosopis juliflora andprogrammes arealso now of invasive Leucaena leucocephala), vines (e.g. Mikaniaproportions. micarantha) andaquaticplants (e.g. Of species introduced accidentally to the Eichhornia crassipes). These have entered the region, Parthenium hysterophorus is one of alien environment by one of two main path-the most harmful weeds and the best-known ways - either intentionally to serve someexample (Koh li and Rani, 1994). It grows human purpose or accidentally (throughrapidly in vacant areas, agricultural land, import of agricultural/horticultural material,pastures, urban areas and natural and man- human beings, ballast water, etc.). made forests, whereitformsits own Lantana camara is perhaps the best-monoculture stands. It is found in every known example of a serious weed havingstate and union territory of India except at been intentionally introduced for orna-higher altitudes and has now covered nearly mental value, in this case from tropical2,025,000 ha of land (Aneja et al., 1991). It America to other parts of the world. Lantanaspreads mainly through its minute seeds, camara is now rated as one of the worstwhich are blown easily by wind and water. invasive species identified by the Global Likewise, Ageratum conyzoidesisa fast- InvasiveSpeciesDatabase andisalsospreading weed, is the most serious invader included in the top 100 invasive species ofof agricultural land and is a problem in hilly the world (GISD, 2010). In India, it wastracts.The weed alsospreads through introduced at the beginning of 19th centuryits seeds, which are minute and are carried as an ornamental plant, and is now foundby wind and water,asisParthenium widespread in almost the whole of thehysterophorus. Eichhornia crassipes, Salvinia subcontinent and has encroached even at molesta,Alternantheraphiloxeroidesand high altitudes (> 1700 m) in the HimalayasIpomoea sp. are invaders of aquatic eco- (Koh li et al., 2006). Lantana is a serioussystems and wetlands; these have done invader of forests, grasslands, agriculturalmuch harm to the biodiversity of aquatic land and vacant urban areas, and also inecosystems (Reddy, 2008). protected areas, and this has implications There are several attributes of invasive for the vegetation structure and dynamicsplant species that enable them to spread in (Koh li et al., 2004; Sharma and Raghubanshi, alien environments (see Tables 1.2 and 1.3, 2007; Sahu and Singh, 2008; Love et al.,respectively, for established invasive plants 2009). and those in the process of establishment). Another weed introduced in India as anSome of the key features of invasive plants ornamental plant is Chromolaena odorata are discussed below. 4 R.K. Koh li et al.

Table 1.1. Prominent invasive alien plants of the Indian subcontinent. Family name Botanical name (common name) Nativity Life form

Amaranthaceae Chenopodium album (lamb's-quarters) Europe Alternanthera philoxeroides (alligator weed) Aquatic herb Amaryllidaceae Zephyranthes citrina (yellow rain lily) Central, S. America Herb Apocynaceae Cryptostegia grandiflora (rubber vine) Madagascar Vine-climber Araceae Pistia stratiotes (tropical duckweed) South America Aquatic plant Asparagaceae Asparagus densiflorus (asparagus fern) Herb Asteraceae Ageratum conyzoides (billy goat weed) Tropical America Herb Ambrosia artemisiifolia (small ragweed) USA, Canada, Herb Anthemis cotula (stinking mayweed) Europe Herb Chromolaena odoratum (Siam weed) Central, S. America Shrub Cirsium arvense (creeping thistle) Europe Herb Eupatorium adenophorum (Crofton weed) Shrub Eupatorium cannabinum (-agrimony) British Isles Herb Gymnocoronis spilanthoides (Senegal tea plant) South America Aquatic plant Leucanthemum vulgare (ox-eye daisy) Europe Herb Mikania micrantha (mile-a-minute weed) Central, S. America Vine/climber Parthenium hysterophorus (ragweed parthenium) Tropical America Herb Sphagneticola trilobata (Singapore daisy) Central America Herb Synedrella Walls (straggler daisy) South America Herb minuta (Mexican marigold) South America Herb Azollaceae Azolla pinnata (mosquito fern) Non-specific Aquatic plant Bignoniaceae Macfadyena unguis-cati (cat's claw vine) Central America Climber Cabombaceae Cabomba caroliniana (green cabomba) South America Aquatic plant Convolvulaceae Ipomoea aquatica (water spinach) China Climber Merremia peltata (merremia) Africa Climber Elaeagnaceae Elaeagnus umbellata (Japanese silverberry) China, Korea, Japan /shrub Euphorbiaceae Ricinus communis (castor bean) North-eastern Africa Tree/shrub Sapium sebiferum (Chinese tallow) China Tree Fabaceae Acacia farnesiana (sweet acacia) Trop. America Tree/shrub Acacia mearnsii (black wattle) Australia Tree Acacia melanoxylon (blackwood acacia) Australia Tree Leucaena leucocephala (wild ) Trop. America Tree Mimosa diplotricha (giant sensitive plant) South America Climber/shrub Mimosa pudica (touch-me-not) South America Herb Prosopis juliflora (mesquite) Central, S. America Tree Ulex europeus (gorse) Europe Tree Hydrocharitaceae Hydrilla verticillata (water ) Asia, North Australia Aquatic plant Limnocharitaceae Limnocharis flava (yellow velvetleaf) South America Aquatic plant Melastomataceae Clidemia hirta (Koster's curse) South America Shrub Miconia calvescens (velvet tree) Tropical America Tree Moraceae Broussonetia papyrifera (paper mulberry) China Tree Myrtaceae Eugenia uniflora (Surinam cherry) South America Tree Psidium guajava (apple guava) Central, S. America Tree Onogranaceae Ludwigia peruviana (Peruvian primrose willow) South America Aquatic plant Poaceae Arundo donax (giant cane) Indian subcontinent Grass Imperata cylindrica (Cogon grass) Asia/Africa? Grass Paspalum vaginatum (seashore paspalaum) North America Grass Pennisetum clandestinum (Kikuyu grass) Tropical Africa Grass Phalaris arundinacea (reed canary grass) Europe Grass Spartina altemiflora (smooth cord grass) South America Grass Pontederiaceae Eichhornia crassipes (water hyacinth) South America Aquatic plant Coffea arabica (Arabic coffee) Africa Shrub Rubiaceae Coffea canephora (robusta coffee) Africa Shrub Salviniaceae Salvinia molesta (water fern) South America Aquatic plant Solanaceae Physalis peruviana (cape gooseberry) South America Shrub Solanum mauritianum (wild tobacco tree) South America Tree Solanum sisymbriifolium (sticky nightshade) South America Herb Solanum viarum (tropical soda apple) South America Shrub Plant Invasion in India 5

Table 1.2. Attributes of selected established invasive plants in India. Country of Pathway of Plant origin invasion Invasive potential Ageratum Tropical Unknown, probably Fast-growing herb; aggressive stolon conyzoides America as ornamental formation; high regenerative and reproductive potential through large number (ay. 94,772/plant) of minute, lightweight seeds, bearing pappi that help in dispersion through wind; wide ecological amplitude; strongly allelopathic Parthenium Tropical Food grains Fast-growing herb; wide ecological hysterophorus America amplitude; high regenerative and reproductive potential through large number of minute seeds (15,000/plant) dispersed through wind, water, biotic factors and transport; strongly allelopathic Lantana camara Tropical Introduced as Shrubby habit; flowers exhibit genetic America ornamental variations; forms suckers; high reproductive and regenerative potential; produces numerous seeds disseminated by birds, animals and even humans; wide ecological amplitude; strongly allelopathic Chromolaena Tropical Introduced as Highly vigorous; high regenerative and odorata America ornamental reproductive potential; prolific producer (260,000/m2) with prolonged viability Mikania macrantha South America Brought for Vigorous, rampant growth; produces camouflaging 40,000 seeds/year; spreads army during WWII vegetatively by rooting at nodes Eichhornia crassipesTropical Ornamental aquaticSpreads fast due to quick vegetative America plant (stolons) and sexual reproduction in water bodies Alternanthera South America Accidently, as Aquatic herb, spreads through vegetative philoxeroides contaminant reproduction by formation of fragmentation and axillary buds Salvinia molesta South Accidental/ Reproduces very fast, mostly vegetatively America, ornamental by fragmentation Tropical America

Fast growth and reproduction: invasive Ability to adapt to diverse environmental alien plants often have better growth and conditions:invasive plants have high reproductive traits, and thus they spread ecologicalamplitudeandthushave very fast in the invaded region. They enormous adaptability to a wide range of oftenhaveeitherhighregenerative environmentalconditions.Thesecan potential (Parthenium hysterophorus) or survive under stressed conditions and specialorgansforvegetativerepro- they also have the ability to modify growth duction, such as stolons (Ageratum cony- patterns in response to changing environ- zoides), root suckers (Lantana camara), ments such as soil condition, moisture rhizomes, bulbs or turions. status or limited space availability. 6 R.K. Koh li et al.

Table 1.3. Attributes of selected potential invasive plants in India in the early stages of establishment. Country of Pathway of Plant origin invasion Invasive potential Leucaena South America Agroforestry/social Self-fertile and produces large number of leucocephala forestry seeds growing in vicinity of parent plant forming monoculture; ability to re-sprout after cutting; seed production through year Broussonetia China, Japan Avenue tree Prolific growth, multiplying rapidly papyrifera vegetatively by suckering activity of root system Tagetes minuta South America Essential oils Spreads very fast by seeds and forms huge populations showing vigorous growth Prosopis juliflora Tropical Timber Spread rapidly due to aggressive growth America Sapium sebiferumChina, Japan Avenue tree Spreads very fast by suckers, re-sprouts very rapidly and produces large number of seeds over a year with effective dispersal Synedrella Tropical Spreads through seed dispersal nodiflora America Anthemis cotula Europe, S. Spreads through seed dispersal Africa Potamogeton Eurasia, Aquatic weed Tolerance to low light and low water crispus Africa, temperature allows it to outcompete native Australia, N. plants; spread by plant fragments attached America to water craft Imperata cylindricaSE Asia Unknown Aggressive and invasive nature is attributed to its rhizome, which produces numerous buds that sprout into new shoots Galinsoga ciliata Tropical Unknown Rapid establishment of weed is due to: (i) America production of large number of seeds in a wide range of environmental circumstances; and (ii) vegetative reproduction Mimosa invisa Tropical By tea gardeners Spreads very fast through seeds that remain America for soil dormant for up to 50 years enrichment Tithonia Tropical Ornamental Spreads through seed dispersal and diversifolia America vegetatively from basal stem Eupatorium Tropical - Spreads through seed dispersal riparium America

Absence of natural enemies or predators: are allelopathic. In other words, they invasive alien plants in new geographical release toxic chemicals to the environ- areas are devoid of their natural predators ment that in turn hamper the growth or pests that co-evolved with them in andestablishmentofnativeflora. their native environment. In the absence Parthenium hysterophorusisa potent of these enemies their populations grow allelopathic plant (Kohli and Rani, 1994). unchecked. Consequently, these form Lantana camara and Ageratum conyzoides huge monocultures. In fact, absence of are likewise reported as being strongly natural enemies forms the basis of the allelopathic (Ambika et al., 2003; Kohli et Natural Enemies hypothesis, as proposed al., 2006). In fact, the allelopathic nature by Heirro and Callaway (2003). of many invasive alien plants forms the Competitive advantage on account of basis for the Novel Weapon hypothesis allelopathy: many invasive alien plants (Heirro and Callaway, 2003). Plant Invasion in India 7

Efficientseeddispersalmechanism: measuresare required to control them. invasive alien plants have a better andThere are separate ways of dealing with more efficient mechanism of dispersal ofthose already established and those pos- their seeds or propagules, by virtue ofsessing the potential to be invasive but not which these spread very rapidly from oneof immediate risk. Above all, preventive place to another. measures are of utmost importance and require great attention at every level to prevent the entry of invasive species. Potential Invasive Plants in the Process of Establishment Management of potential invasive species There are several plants that have not proved especially harmful to date but which possess EnvironmentImpact Assessmentof the potential to become serious invaders. introduced plants could be very useful in Early warnings regarding these species may managing invasive species in the initial help in managing them well before they stages of their establishment. damage natural ecosystems. Tagetes minuta, Gathering information regarding the a native of South America, was introduced pathways of invasion of potential in- to various parts of the world, including vasive species; appropriate steps can be India, for essential oils and medicinal value. taken to prevent the entry of potential However, it has been reported to be a invasive plants based on thisinfor- noxious and invasive weed at many sites mation. (Soule, 1993; Holm et al., 1997). In India it Following the international standards seems to have spread from cultivated areas, and quarantine measures based on the as it can be seen growing luxuriantly in InternationalPlantProtectionCon- disturbed sites in the north-western parts of vention (IPCC) or the Convention on the country (personal observation of the InternationalTradeonEndangered authors). Anthemis cotula, an ornamental Species of Flora and Fauna (CITES) to plant from Europe, is now spreading fast in prevent the entry of potential plant the Kashmir valley - a Himalayan bio- invaders. Further information regarding diversity hot spot (Shah and Zafar, 2007). these can be obtained from international Leucanthemum vulgare, another ornamental organizations on invasive species such as plant from Europe, is also spreading rapidly The Global Invasive Species Programme in this valley and inhibiting the regeneration (www.gisp.org), IUCN's Invasive Species of the native forest floor vegetation (Khuroo Specialist Group (www.issg.org) and its et al., 2010). Jaryan et al. (2007) reported Global Invasive Species Database (GISD). that Sapium sebiferum, a woody perennial, Creating adequate awarenessof the has the tendency to become invasive, public about potential invasive plants particularlyintheHimalayanregion. and their management. To this end, Broussonetia papyrifera, commonly known as online websites,scientific documents paper mulberry -a shrubby deciduous tree and books containing information on of Asianorigin,possesses an invasive invasive plants could be quite useful. character and is spreading rapidly in the city Success stories on control of weeds like of Chandigarh, India (personal observation Parthenium hysterophorus can also be of the authors). used for dissemination of information (Batish et al., 2004).

Management Tools Management of established species When looking at the alarming rate at which invasive plants are spreading in IndiaManagement of established invasive plants and also worldwide, effective management is very difficult. Based on the local situation, 8 R.K. Koh li et al.

geographic region and climatic conditions, Determine the environmental and socio- various methods such as physical, biological, economic impact of the invasive plants chemical or cultural methods have been and devise management tools for their suggested, but these are of limited use. It is control. thus very important to follow an integrated approach and common interactive protocols for the management of invasive plants across the world. Some suggestions that References may help in the management of invasive Ambika, S.R., Poornima, S., Palaniraj, R., Sati, S.C. plants are listed below. and Narwal, S.S. (2003) Allelopathic plants. 10. understanding the life history of invasive Lantana camara L. Allelopathy Journal 12, 147- plant species and their phenology, to 162. help in devising control measures for Aneja,K.R., Dhawan, S.R. and Sharma, A.B. (1991) Deadly weed Parthenium hysterophorus their management; L. and its distribution. Indian Journal of Weed studying the ecology and biology of Science 23, 14-18. invasive plants, with special reference to Batish, D.R., Singh, H.P., Kohli, R.K., Johar, V. and theirreproductivebiology,dispersal Yadav, S. (2004) Management of invasive exotic ability and efficiency; weeds requires community participation. Weed understanding various biotic and abiotic Technology 18, 1445-1448. factors limiting the growth of such Charles, H. and Dukes, J.S. (2007) Impacts of plants; invasive species on ecosystem services.In: pests/pathogens of such plants can be Nentwig, W. (ed.) Biological Invasions explored from their native countries for (Ecological Studies, Vol. 193). Springer-Verlag, Berlin, pp. 217-237. their biological control; Drake, J.A., Mooney, H.A., di-Castri, F, Groves, mass awareness programmes through R.H., Kruger,F.J. and Rejmanek, M. (1989) booklets/pamphletscontaininginfor- Biological Invasions: A Global Perspective. John mation on established localinvasive Wiley and Sons, Chichester, UK. speciestodiscouragetheirfurther GISD (2010) Global Invasive Species Database. spread; and Available online at http://www.issg.org/database management, in a coordinated manner, Heirro, J.L. and Callaway, R.M. (2003) Allelopathy through involvement of thegeneral and exotic plant invasion. Plant and Soil 256, public and government officials or policy 29-39. makers. Herron,P.M.,Martine, C.T.,Latimer, A.M. and Leicht-Young, S.A. (2007) Invasive plants and theirecologicalstrategies:predictionand explanation of woody plant invasion in New Conclusions and the Way Forward England. Diversity and Distributions 13, 633- 644. From the above discussion, it is clear that a Holm,L.,Doll,J.,Holm,E.,Pancho,J. and number of invasive plants have become Herberger,J.(1997) World Weeds. Natural established in India and several others are in Histories and Distribution. John Wiley and Sons, the process. These cause major environ- Inc., New York. mental, socio-economic and health-related Jaryan, V., Chopra, S., Uniyal, S.K. and Singh, R.D. (2007) Spreading fast yet unnoticed: Are we in harms to the native people, and it is thus for another invasion?Current Science 93, important to take the following steps. 1483-1484. Prepare a list of invasive plant species Khuroo, A.A., Rashid, I., Reshi, Z., Dar, G.H. and and gather comprehensive information Wafai, B.A. (2007) The alien flora of Kashmir Himalaya. Biological Invasions 9, 269-292. on their status, pathways of entry and Khuroo, A.A., Malik, A.H., Reshi, Z.A. and Dar, G.H. spread. (2010) From ornamental to detrimental: plant Determine means of spread of invasive invasionofLeucanthemumvulgare Lam. plants in order to prevent their further (Ox -eye Daisy) in Kashmir valley, India. Current spread. Science 98, 600-602. Plant Invasion in India 9

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