Bio-Invaders

Similar to bickering of the Social scientists pertaining the issue of migration conservation biologists are at war of words over the migration of flora and fauna from their native place of origin to exotic lands. These alien or migrating species have different patterns of adaptation in the new lands. In some cases, migrating species remained innocuous and often failed to proliferate into sustainable populations and thus perished. Others have become beneficial.  While those of which that managed to colonise were incorporated into existing ecosystem and were responsible for change balance of the native ecosystem. Few of them started out-competing the native competitors and emerged as greater threats to the local dwellers.

Invasive species are the alien or exotic or introduced non native species that have brought about a significant change in the native ecosystem which they began to colonize. Such species can be plants, animals, microbes and other organisms which have migrated to new niches through natural migration or by allied human activities. Invasion Biology encompasses study of these organisms and the process of species invasion. This discipline has recently registered a sudden spurt of interest among biologists with its own journals, academic centres and graduate programs.

In an article published in Nature recently, a thorough investigation of such species has been clearly elucidated. The process of migration is as old as the human civilisation itself. Globalisation and rapid economic activity has enhanced the movement of men and material across different continents. Conservation biologists are now seriously concerned over the issue of invasion/spread of species both flora and fauna. While a majority of them view that new change is an impending threat to the native ecosystem, other believe that theory of evolution would eventually balance out any change. The later are least intimidated by the enormous expansion of foreign species.

The term invasion implies any act that infringes or intrudes the native state. Human beings are the most invasive species that ever in habited the earth. In the long course of evolution this species began its journey from the inner fringes of African continent and slowly spread to each and every corner of the world and to every possible kind of climate and colonised the new places. At every new place of settlement, they have successfully displaced the native habitants and often led to their obliteration. Over the course of time, humans shaped the global ecosystem by pumping green-house gases upending the delicate balance of the very earth we live. The epitome of all invasive species- human beings are now imperilled by the swarming invasive species.

History is replete of examples where introduced species have changed the balance of the native ecosystem. The most significant invasions have occurred during Pliocene Epoch (5.3 to 2.6 million years ago) after the formation of narrow isthmus between North and South America.  It was believed that migration several predators from North America in this period had led to extinction of many South American mammalian populations. Subsequently, during the course of exploration of new lands, men intentionally or unintentionally had played a significant role in introduction of alien organisms into the new lands. Particularly Australia and Oceania were hard hit during the early days. In the past two centuries North America is greatly affected by the invasive species.

The introduction of Zebra mussel, a filter-feeding mollusc;  native of Aral, Black and Caspian seas into the Great Lakes and other rivers causing severe economic and ecological losses. These were carried in the ballast water by the ocean going ships and spread beyond Great Lakes and to all other rivers by attaching themselves to the bottom of the boats. Now, these began out-competing the native species for food. They grow rapidly and clog the water in-take pumps of the power plants and also remove the aquatic algae.  Power plants are now spending $800,000 a year to monitor and control it. Similarly, Asian carp and Silver carp native of south East Asia got introduced into the rivers of Mississippi by the fish farmers in 1960’s. These are voracious filter feeders and are competing with native marine life for food incurring $200 million loss annually. These constitute nearly 90% of biomass in some stretches in Mississippi.

The Burmese Python native of South East Asia got introduced into the wetlands of South Florida by the Hurricane Andrew. It now threatens the dominance of the American Alligator. Growing to 6ft it predates on Key Largo Wood rat and wood stork as a result the numbers of both have declined significantly. Appalled by its huge damage, government is organising workshops for volunteers in this region to capture pythons. Giant African Snail native of East Africa which got accidentally introduced into forests of Florida has become a new threat. It eats more than 500 kinds of plants and carries a parasite that can cause meningitis in humans.

Brazilian pepper trees were imported as ornamentals in mid-1800, now dominate 700,000 acres in Florida. Its huge canopy shuts out sunlight to its competitors consequently out-competing the natives. Species of Feral hogs, Lion fish, Asian Long-horned beetles, snake head fish, Cuban tree frog and emerald ash border continue to excise their control in the new habitats threatening to destroy the composition of the native population. These invasive species are now treated by conservationists as enemy combatants in a biological war. Government is expending huge amounts of money to prevent, control and eradicate these species. It was estimated that 50,000 of alien species are in US out competing native flora and fauna.

But against this background, some scientists believe that nature has been never balanced and often there isn’t any particular trait that makes an alien inherently bad or native species inherently good. Sometimes the distinction between native and alien is arbitrary. Scientists believe that in the age of globalisation, it is impossible to guard the migration of species. To sum up, nativeness has little intrinsic value while spread of invasiveness can increase the diversity. But on a different note, just as globalisation resulted in spread of brands like Mc Donald’s and Walmart around the world, unchecked invasiveness might lead to homogeneity.  In the course of evolution the epithet of survival of the fittest always reigned supreme. Even in the era of Global Swarming it will wield its power in restructuring the global ecosystem.

 

 

 

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