Invasion by Alien Macrophytes in Freshwater Ecosystems Of

Invasion by Alien Macrophytes 1 in Freshwater Ecosystems of India Manzoor A. Shah and Zafar A. Reshi Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir, India Introduction struction, etc. (Rahel, 2007), flowing river waters act as natural conduits for the Freshwater ecosystems support almost 6%transport of propagules of alien species of all described species (Hawksworth and (Lavoie et al., 2003) across geographical and Ka lin-Arroyo,1995),despitecomprisingpolitical boundaries. The relatively higher only a tiny fraction of the world's watervulnerability of aquatic systems to plant (0.01%) and terrestrial(0.8%)surfacesinvasions is attributed mainly to water being (Gleick, 1996). Although freshwater bio-an efficient vector for dispersal and the diversity provides a wide variety of valuable relatively weaker restrictions on establish- economic goods and irreplaceable ecosystem ment and spread of plants. Aquatic habitats, services for humanity,itisincreasinglysuch as lakes and wetlands, being mostly threatened by overexploitation, pollution,resource rich are especially more vulnerable water flow changes, habitat degradation andto spread of invasive alien species (Zed ler invasion by alien species (Dudgeon et al.,and Kercher, 2004). Besides, anthropogenic 2006). Of these threats, the spread ofdisturbance of established vegetation in invasive species appears the most severethese habitats further facilitates invasion (Zed ler and Kercher, 2004; Olden et al.,meltdown, allowing aliens to compete with 2006) and causes considerable damage, withand displace useful native plant species, cascading effects on structural organizationsome of which are important sources of food andfunctionalintegrityoffreshwaterand shelter for avifauna and other wildlife. ecosystems. There is a relatively greaterMoreover, manyaquaticplantsare degree of decline and extinction of species in characteristicallyinvasiveduetotheir freshwater ecosystems than in terrestrial orimmense potential for rapidly increasing marine environments (Johnson et al., 2008),their spatial spread (Richardson et al., 2000) mainly due to hydrologic alterations andand, once established, these invasive species biological invasions. It is for these reasonsimpair ecological processes such as water that freshwater biodiversity comprises atable levels, fire regimes, soil quality and priority conservation concern during thenutrient cycling, thereby influencing both UnitedNations'InternationalDecade the flow and chemistry of water, blocking (2005-2015) for Action - 'Water for Life'drainage pipes, impeding navigation and (Dudgeon et al., 2006). hinderingcommercialandrecreational While the human species has greatlyfishing.Thus,invasivespeciesaffect facilitated the invasion of aquatic alienaesthetics, wildlife and avifaunal habitability species through intentional shipping and- and theoverallecology and socio- trade, aquarium releases and canal con-economics of infested waterbodies. For © CAB International 2012. Invasive Alien Plants: An Ecological Appraisal for the Indian Subcontinent (eds J.R. Bhatt et al.) 199 200 M.A. Shah and Z.A. Reshi thesereasons,governmental and non-country, has provided opportunities for the governmentalagencieshavetospendintroduction, establishment and spread of millions of dollars annually to control thesome alienspecies.India's fast-growing spread of invasive plants and reverse theirtrade links in the globalized world have impacts in affected habitats. further accentuatedtherateof plant invasion. Notwithstanding the well-known invasion-inducedalterationofaquatic Status of Freshwater Ecosystems in ecosystems,studiesonaquaticplant India invasions in India are inadequate, scattered and disorganized, leaving large information India, owing to its characteristic geologicalgaps on the taxonomic status of alien species history,geographicalsettingandeco- and their current and potential distribution, climatic regimes, abounds in complex andand priority invasive species and their diverse freshwater ecosystems that are richimpact. Although several studies have been repositories of native biodiversity. Aquaticcarried out on macrophytic diversity in habitats in India include 14 major, 44 different lentic and lotic freshwaterbodies of medium and hundreds of minor riverIndia (Mirashi, 1954; Chavan and Sabnis, systems; many natural Himalayan and1961; Unni, 1971; Zutshi, 1975; Gopal and floodplain lakes and wetlands of diverse Sharma, 1979; Billore and Vyas, 1982; Dey origin(Zutshietal.,1980); numerousand Kar, 1989; Gopal, 1990; Gopal and thermal springs in the Himalaya, WesternChamanlal, 1991; Gopal and Zutshi, 1998; Ghats and other hills (Rao, 1975); a few salt Kar and Arbhuiya, 2001), very little is known lakes in the arid region of Rajasthan andabout the extent of invasion (Reshi et al., cold desert of Ladakh; and several coastal2008). A rich body of literature documents lagoons. Moreover, the Indian landscape isthe widespread invasionof non-native dotted with over 4290 large(>15 mspecies and their impacts in aquatic systems maximum depth or >1 million m3 storage) elsewhere, however (Stromberg et al., 1997; and innumerable smaller man-made water-Strayer, 1999; Gollasch, 2002; Genovesi and bodies (Sugunan 1995). In India, freshwaterShine, 2004; Gollasch and Nehring, 2006; wetlands alone occupy 58.2 million ha Lodge et al., 2006; Minchin, 2007a). (Directory of Indian Wetlands, 1993) and Lack of any systematic effort towards support 20% of the known biodiversity indocumenting alien plant species in the the country (Deepa and Ramachandra,freshwater ecosystems of India has multi- 1999). farious ecological and economic implications. The total number of aquatic plant speciesIt is in this context that an attempt, based in Indian freshwaters exceeds 1200 (Gopal, on primary and secondary data sources, has 1995). These aquatic plants are characterizedbeen made to compile a conspectus of alien by a variety of life forms and functionalplantspeciesharbouredbydifferent groups, such as emergents, rooted- andfreshwater ecosystems. For the present floating-leaf types and submersed types thatstudy, alien species were considered as those adapt to diverse habitat conditions, depend-that have been introduced intentionally or ing on the level, quality and availability ofunintentionally in areas outside of their water during the growing season. natural distributional range. Based on the The freshwater ecosystemsinIndia,available literature, herbarium material and together with their biodiversity, representfield surveys, we tried to include all the alien anevolutionarymosaicofinteractingplant species that have naturalized in India. ecological,socio-economic,culturaland Speciesoccurringadjacenttoaquatic geopolitical factors. However, alteration inenvironments with a dependency on water the natural disturbance regimes, mainly duehave also been included. Nativity of the to a shift from traditional, value-based tospecies was established through all possible modern, market-driven social settings in thesources, both published and unpublished, Alien Macrophytes and Freshwater Ecosystems 201 and presented continent-wise as suggested2005; Pradhan et al., 2005; Adhikari and by Pygek et al. (2002). The important sourcesBabu, 2008) and field study surveys carried included Anonymous (1883-1970); Tutin etout in the Kashmir Himalaya, India. al. (1964-1980); Weber (2003); and Khuroo The majority of the alien aquatic species et al. (2007), in addition to consulting somein Indian waters are native to either Europe relevant internet sources (www.efloras.org; (37.16%) or Asia (25.28%), with those from Panov, 2004; Panov and Gollasch, 2004). For either north or South America each -10% species of Asian nativity, Asia excludes the(Table 16.2; Fig. 16.1) followed by Africa Indian subcontinent but includes the other(8.42%) and Australia (6.51%). The highest Asian countries, including Central Asia, theproportion of European and North American Far East and South-east Asia. Nativity ofnative species among the Indian alien flora those species traced to more than threeare found in the Kashmir Himalaya region, continents was considered cosmopolitan.which may partly be attributed to the close The documented plant species, in additionclimatic matching of these biogeographical to a few trees, were classified into emergents, regions; India's colonial past would have rooted floating-leaf types, submersed typesfacilitated propagule transport from Europe andfree-floatingtypes.Despitebeingto this region (Khuroo et al., 2007) in the preliminary in nature, this would providelate-19th and early-20th century. Although informationonbroadtaxonomicandneither mode nor purpose of introduction of ecological patterns exhibited by alien aquatic the listed alien species was explored, most plant species, and would also identify thewere probably introduced through frequent potentialgapsinknowledgerequiringintercontinental voyages driven by economic urgent attention in order to acquire a moreinterests.Besidesincreasedtradeand complete assessment and characterizationtourism activities, the construction of new of alien species - which is pivotal to theircanals and tributaries have also facilitated management. the exchange of global species. In addition, the possible role of migratory birds in alien introductions can not be ruled out, because Aquatic Alien Plant Species in India thousands of such birds from different countries annually visit different Indian The present study demonstrates that 223freshwater habitats; these birds can con-

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