Wednesday, December 25, 2013

What are invasive species?
  • Invasive species are usually non native in nature and appear to have specific traits or specific combinations of traits that allow them to out-compete native species. 
  • Fast growth, rapid reproduction, high dispersal ability, phenotypic plasticity etc are the major traits exhibited by the introduced species which may turn themselves out to be invasive with their capability to out compete the native species for resources, such as nutrients, light, physical space, water or food.
  • Human interference in the form of water ballasts or transmittal of species for pest control or aesthetics provide repeated chances for establishment of the introduced species with its low population in the new environment. 
  • According to IUCN, Alien invasive species" means an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity.

Why invasive species pose a problem to the 

  • Invasive species can change the functions of ecosystems. 
  • For example, invasive plants can alter the fire regimen (cheatgrass, Bromus tectorum), nutrient cycling (smooth cordgrass Spartina alterniflora), and hydrology (Tamarix) in native ecosystems. 
  • Invasive species can impact outdoor recreation, such as fishing, hunting, hiking, wildlife viewing, and water-based activities. 
  • Invasive species will adversely affect agricultural productivity, health and economy as a whole apart from its deleterious effects on bio diversity. 
  • Encroachment of humans into previously remote ecosystems has exposed exotic diseases such as AIDS virus to the wider population.

Introduced birds (e.g. pigeons), rodents and insects (e.g. mosquito, flea, louse and tsetse fly pests) can serve as vectors and reservoirs of human afflictions. Genetic pollution is another after effect as the invasive species tend to hybridize the filial generations. Once introduced, it is very difficult to control the expansion of invasion and hence prevention is the most desired step in managing the invasive species. Eradication is a tedious task involving huge cost constraints and sometimes may not be successful.

Guidelines provided by IUCN for management at international level

#  Implement the provisions of international treaties, whether global or regional, that deal with alien invasive species issues and constitute a compulsory mandate for respective Parties. Most prominent among these treaties is the Convention on Biological Diversity, and a number of regional accords.

# Implement decisions taken by Parties to specific global and regional conventions, such as resolutions, codes of conduct or guidelines related to introductions of alien species, for example the International Maritime Organisation's guidance on ballast water.

# Consider the desirability, or as the case may be, necessity, of conducting further agreements, on a bilateral or multilateral basis, or adapting existing ones, with respect to the prevention or control of introduction of alien species. This includes, in particular, consideration of international agreements related to trade, such as those under the auspices of the World Trade Organisation.
# For neighbouring countries, consider the desirability of cooperative action to prevent potential alien invasive species from migrating across borders, including agreements to share information, through, for example, information alerts, as well as to consult and develop rapid responses in the event of such border crossings.

#  Generally develop international cooperation to prevent and combat damage caused by alien invasive species, and provide assistance and technology transfer as well as capacity building related to risk assessment as well as management techniques.

Indian Scenario

  • India with its vast biodiversity is threatened by invasive species like Acacia farnesiana (Tropical America), Lantana camara (shrub), Mimosa pudica (herb), Cryptostegia madagascariensis (vine, climber) and Cabomba caroliniana (aquatic plant). 
  • Actions to prevent, detect and manage Invasive Alien Species (IAS) are categorized into three themes-biodiversity, human health, and economic. 
  • In line with these themes India has formulated National Biodiversity Action Plan. 
  • In order to reduce the impact of invasive species, India has enacted much legislation and has constituted many organizations and nodal ministries to deal with the issue.

Why Jellyfish proved a problem, if native to Mediterranean?

Jelly fish in the coast lines of Mediterranean is a non native species. This rise in the population of non native species is attributed to species invasion rather than natural growth in a native population.


What is the difference between Exotic and 

Invasive species?

• Both are non-native species occurring in a particular area, but exotic species may or may not raise

 concerns, while invasive species always raise serious concerns on many aspects.

• Exotic species could be either wild or captive, while they would become invasive in wild.

• Exotic species may or may not have natural competitors and enemies, whereas invasive species do not have any danger of such barriers.


Role of Exotic Vegetation in Coastal Protection

  • Casuarina (casuarina equisetifolia L) trees of Australian origin have been planted along Indian coasts as bioshields for protection from cyclones, tsunamis, tidal water damage, and the like. 
  • The data from the "super cyclone" of October 1999 that devastated 12 districts of Odisha is compared with the storm protection afforded by other native species such as mangroves and mixed cashew nut forests found along the coast. 
  • It is seen that while native vegetation provided storm protection and saved human lives, casuarina did not have such an impact. 
  • The findings question the policy of planting casuarina as storm buffers in all cyclone-prone areas irrespective of the topography.

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