13 March 2013 ~ 0 Comments

Who Bothers Hawaii?

waipio valley

Hawaii archipelago is one of those lands suffering not only from human activity, but from alien species as well. For many centuries there were no predators or invasive species that could threat to conventional livelihood of Hawaiian ecosystem.

Long before European settlers, there were only two mammal species distributed over the islands – hoary bats, apparently brought by winds from America, and monk seals. The population of seals declined significantly in the 19th century, as colonists started to hunt them for skin and eat, and to date conservation of monk seals is one of the primary environmental issues on Hawaii.

All in all, the diversity of Hawaiian fauna was enlarged a lot, as numerous species of domestic animals (sheep, feral pigs, wild boars, deer), ants (big-headed and Argentine ants), plants (the Velvet tree) found a perfect place on Hawaii to be dispersed, therefore, signifying about the end of Eden.

Negative Alien Species

One of the recent zoological researches, enclosed by Proceedings of the National Academy of Sciences, featured bees, imported from North-American continent, as invasive and distrustful species on the archipelago.

It is one of the examples of how alien species might modify lifestyle and habits and thereupon cause severe damages for a new habitat. In particular, this research is referred to revived bees’ abilities to consume any variety of food and to form larger colonies.

In normal conditions, Pennsylvania bees gather in small colonies for one season, while on Hawaii they gather in large colonies (about 600 thousand bees) for long-term periods. In this way, bees obstruct essential development of forest areas and sub-alpine vegetation.

Positive Alien Species

However, there some examples of invasive species that promote natural advancement of Hawaiian ecosystem. To be more précise, the biggest achievements are attained by alien terrestrial birds, which include 58 species.

They play an important role in reproduction of many indigenous plants. For instance, birds distribute seeds of Lehua trees (Eugenia plants), known for its reddish wood and bright red flowers.

Unlike native birds, consuming exclusively nectar or invertebrates, alien birds eat fruit of trees and, therefore, disperse plant seeds over the area. This is a nice example of how invasive species cannot just push out the native, but also take on their functions, often coping with them no worse than their predecessors.

Potential Alien Species

For many centuries Hawaiian archipelago was free from reptiles, especially snake species. Notwithstanding in recent years there were some notices about potential threat of snakes’ distribution to the islands, preconditioned by illegal snakes trade and keeping some as pets.

Having no natural enemies, snakes might embed themselves deeply into the Hawaiian ecosystem, if they happen to be out of human control. In this case, the fate of Guam Island is imminent, where imported brown tree snakes ate all the birds and, therefore, caused severe ecological damage.

On Hawaii snakes can eat bird eggs and small chicks, including representatives of 34 species of Hawaiian forest birds at risk of extinction. If birds disappear, there will be more spiders that create webs over the trees and so darken the wood; insect populations may get bigger.

In this case, the list of consequences might be prolonged, eventually ending up in completely new vision of Hawaiian environment.

Creative Commons License paul (dex) bica via Compfight

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