Kathir2016

INVASIVE ALIEN PLANT SPECIES OF KERALA

                                                          Bennett Thomas. K , College of agriculture Padannakkad

               Vasco  da  Gama  – the Portuguese, the Britain, the Arabs, Japanese and so on the first people to invade india for marketing and conquering purpose. Is it true that people from other countries were the only ones to invade our kerala or our country? No. we can’t say that humans were the only ones. Some group of plants , animals or microbes are also invaders  to other parts of the worlds beyond the boundaries. In other words we can call them as ‘Alien species’ or ‘invasive exotics’. They might be /not economical ,harmful /not harmful to human health.

Common features of invasive exotics include:

·          The ability to reproduce both asexually and sexually

·           Fast growth

·           Rapid reproduction

·           High dispersal ability

·          Tolerance of a wide range of environmental conditions

·           Ability to live off of a wide range of food types

            Most of the plant species we see around us were not of kerala orgin, inspite they’re really ‘foreigners’. Generally they invade a variety of ecosystems, spread quickly, displace native variety of plants, monopolize resources, upset ecological equilibrium, change hydrological regimes, reduce biodiversity, and forms a monoculture. They might be intentionally or accidently inhabiting the new areas. The ecological damage caused by them have influenced and affected ecosystem processes, hydrology, primary productivity, decomposition, nutrient cycling, soil structure and profile. Kerala's plant biodiversity faces a severe threat from 89 alien invasive species, which were recorded in a survey commissioned by the Kerala State Biodiversity Board. Out of these, 19 present a high risk; many were found displacing and destroying a large number of native species, causing environmental and economic loss. Around 40 per cent of the varieties belonging to Brazil, Trinidad, Costa Rica, Chile, and Mexico were believed to have reached the State mostly through timber and food grain imports, said K. V. Sankaran, director of the Kerala Forest Research Institute, Peechi, Thrissur, which conducted the survey and risk assessment.

Pollinating insects usually preferred these species as they produced more pollen grains and nectar than the native ones. The resultant fall in the pollination rate of the native plants would affect the local biodiversity and its regeneration. Dr. Sajeev pointed to earlier reports of pollen grains of Acacia and Parthennium having caused allergy among humans.

Here are some of the highly riskful invasive exotic plants in  kerala,

Mikania micrantha (Mile-a-minute weed)

Native : Central and  South America

Threat: Fast growing, perennial ,climber with vigorous and rampant growth habit. It grows where fertility, organic matter, soil moisture, and humidity are all high and damages or kills other plants by cutting out the light and smothering them.

Occurs in:  Agricultural areas, coastland, natural forests, planted forests

Distribution: Australia, Bangladesh ,China, Fiji etc

Acacia mearnsii (Black wattle)

Native: Australia

Threat: Evergreen shrub/tree, threatens native habitats by competing with indigenous vegetation, replaces grass communities, reduces native biodiversity and increase water loss from riparian zones.

Occurs in: Natural forests, range/grasslands, riparian zones, ruderal/disturbed lands and  urban areas, water courses

Chromolaena odorata (Siam weed)

Native: Tropical America

Threat: This fast growing perennial  shrub is a aggressive competitor which forms dense stands that prevent the establishment of other plant species.This plant has allelopathic  effects  and  it is also nuisance to forests, agricultural land and commercial plantations.

Occurs in: Agricultural areas, natural forests, planted forests, range/grasslands

Distribution: Australia, Bangladesh, Bhutan, Cambodia, China,  India, Indonesia, Malaysia, Myanmar, Nepal, Papua

Lantana camara (Lantana)

Native: Central and northern South America and the Caribbean

Threat: In disturbed native forests  can become the dominant under storey species, disrupting succession and decreasing biodiversity. As the density of lantana in forest increases species richness decreases

Occurs in: agricultural areas, coastland, natural forests, planted forests

Distribution: Australia, Cambodia, China, Fiji, India, Indonesia, Kiribati, Malaysia etc

Prosopis juliflora (Mesquite)

Origin: Central and South America

Threat: This tree grows gregariously in its preferred habitats, forming dense impenetrable thickets, The carrying capacity of many habitats has been seriously reduced due to the spread of the species

Occurs in: Degraded lands, deserts, wasteland, agricultural lands, grass lands

Distribution: Australia, India, Sri  Lanka, Pakistan etc

Pueraria phaseoloides

Native: Tropical Asia

Threat: Twining and climbing legume which can smother and displace native plants.

Occurs in: Vacant lands and along margins of cultivated areas.

Distribution: Asia-Pacific

Sphagneticola trilobata (Singapore daisy)

Origin: Central America

Threat: The creeping herb forms a dense ground cover, crowding out or preventing regeneration of other species. Cultivated as an ornamental.

Occurs in: Agricultural areas, coastland, natural forests, planted forests, range/grasslands

Antigonon leptopus (Railway creeper)

Origin:  Mexico

Threat: Invades disturbed areas and forest edges, smothers native plants in the wet season outcompeting native vines and understory plants.

Occurs in: Along roadsides, vacant lands and open areas

Distribution: Asia - Pacific

Pennisetum polystachyon (Kothapullu)

Origin:  Africa

Threat: Competes with native plants species, alters fire regime and can be a potential seed contaminant

Occurs in:  Disturbed mostly dry low land areas and cultivated fields

Senna spectabilis (Manjakonna)

Origin:  America

Threat:  Capable of invading natural habitats grow into thickets and displace indigenous flora

Occurs in:  Vacant lands, river banks, plantations, parks and along roadsides

Distribution: Asia – Pacific and South Africa

Merremia vitifolia

Native: Indo-Malesia and China

Threat: An ornamental climber which can smother native flora

Occurs in: Vacant lands, forest  edges and plantations

Distribution: Asia-Pacific

Mimosa diplotricha var. diplotricha (Giant sensitive plant)

Origin:  S.America

Threat: A major weed of cultivated areas and waste lands; has the ability to climb over other plants forming a thorny mat; prevents animals from accessing the area and utilize natural vegetation

Occurs in: Agricultural areas, fringes of natural forests, plantations

Mucuna bracteata

Native: Asia

Threat: Fast growing perennial climbing vine which can choke and pull down native plants.

Occurs in: Vacant lands, road sides, forest boundaries.

Distribution: Asia-Pacific

                   

                                 Currently ,there is no cohesive policy to deal with invasive species in India. MoEF is still in the process of developing policies and strategies for their management. The possibilities include early detection and rapid response, pest risk assessments, surveys. International and regional collaborations training and sharing of expertise. Early detection and prevention are the most effective and cost efficient strategies to combat invasive species. Direct control of existing populations are rarely successful unless combined with cultural practices. Ecological restoration of the weed free habitat is  the key to successful eradiation of invasive plants

How to prevent new incursions and manage those already invaded ? That’s the next question that should arise in innovative minds.Check all plant and soil samples for transportation to forest areas for seeds, plant parts and other propagules of IAS (Invasive Alien Species). New introductions of plants  may be done after risk assessment and observing proper quarantine measures .Tourist destinations inside forests should be under constant surveillance to avoid unintentional transportation of IAS through baggage, vehicles; detect and eradicate any new introductions. Restrict movement of soil and plant parts from infested areas to un-infested areas; control IAS in infested areas before flowering and fruiting. Adopt restoration policies by planting fast growing native species in the infested areas and assist natural regeneration.

References

·         ww.thehindu.com/sci-tech/energy-and-environment/89-invasive-plant-species-present-a-threat-to-keralas-biodiversity/article3470290.ece

·         http://www.upsbdb.org/pdf/invasive_alien_species.pdf