Drivers of biodiversity loss -III - Invasive species

Drivers of biodiversity loss - III - Invasive species 

The five important drivers of biodiversity loss are

1.      Habitat loss and degradation

2.      Pollution

3.      Invasive species

4.      Over-exploitation

5.     Climate change associated with global warming

3.      Invasive species

Invasive species are organisms that enter into an ecosystem where they are not native.  Generally this occurs as the result of human activities.

Many alien species blend into their new habitat and actually increase biodiversity there. A few damage the local ecosystem

Species naturally enter new environments frequently, but the number and rate at which they are introduced has increased dramatically around the world.

When members of an alien species are introduced into a new ecosystem, there are three possible outcomes.

• The habitat is inhospitable and the invader perishes
• The habitat is suitable for the invader and it develops a population and increase the ecosystem’s biodiversity
• The habitat is suitable for the invader and it outcompetes the native species, its population explodes wiping out the native population – resulting in a decrease in biodiversity.

Invasive species may cause harm to native organisms in three ways

• Predation:  The Australian brown tree snake has eliminated several native bird species by eating them.
• Spreading disease: Birds introduced to Hawaii are less susceptible than the native birds.to the avian malaria parasite (this parasite is also an introduced species)
• Altering the environment: The Australian melaleuca tree is spreading through the Everglades; oil in the tree’s leaves burns easily which results in spreading fires that kill native plants.

Invasions of Aquatic Ecosystems

Alien species have damaged both marine and freshwater ecosystems.  The alien species are introduced into an aquatic ecosystem through the ballast water of a ship. Ships suck water into tanks as counterbalance to heavy loads.  This water contains as many as 300 species of organisms or their larvae.  When the ship dumps the ballast water, these organisms are expelled with it.

An example for such an alien species is the zebra mussel, a small mollusk, from the Caspian Sea which reached United States. The organism is a voracious filter feeder and reproducer and drive out native species and clog drain pipes.

Aquarium dumping is another common path for the invasion of an aquatic system by alien species.

Milfoil, a lovely aquarium plant that was released into the eastern United States formed very dense mats at the surface of a lake.  It interferes with recreational activities and power generation and prevent dissolving of oxygen into the water there by destroying the fish population.

Invasions of Terrestrial Ecosystems

Terrestrial ecosystems are also suffering from invasive species. Island animals are highly susceptible to invasive species.    Example is the dodo, a large, flightless bird lived on the island of Mauritius in the Indian Ocean had no predators to fear. When the Dutch arrived, 400 years ago, their dogs and pigs and the rats that had sneaked on their ships consumed the easy to obtain dodo eggs and in less than 100 years, the Dodo was extinct.

Invasive Species Control

We can control invasive species before they enter a new environment, early during their invasion or after they have become a serious problem.

The most effective way to keep down alien species damage in a location is to stop the aliens from entering

Once they enter a new habitat, most alien species blend into the ecosystem. Mechanical methods such as pulling off weedy plants, chopping of trees, use of herbicides to stop seedlings, etc may be adopted. Animals may be stopped by trapping or hunting.  Chemical controls such as the use poisons such as herbicides and insecticides may be employed.  Biological control, or biocontrol which uses a pathogen or a predator to control invasive species may be used to reduce the alien population density.

After habitat destruction, invasive species is the second greatest cause of biodiversity loss. The best way to avoid destruction by alien species is to stop the organisms from entering the new environment. Once they are integrated into the ecosystem, most invaders are very difficult or impossible to remove.

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References

• Emerging Consequences of Biotechnology - Biodiversity Loss and IPR Issues, Krishna Dronamraju, World Scientific Publishing Co. Pte. Ltd.
• Biosphere - Ecosystems and Biodiversity Loss, Dana Desonie, Chelsea House