Invasive species are living organisms that are introduced to new environments where there are no existent natural predators. These species grow and reproduce quickly hence aggressively spreading to an extent of causing severe environmental harm, if they survive such new habitat. They are spread through unintentional human activities as people move from different parts of the world to other areas (Simberloff, 2013).
Aquatic invasive species are spread through ballast water discharge from transoceanic ships, short distance travels between fresh waterways, and recreational boats. If the recreational boats from infested waterways are not thoroughly cleaned and dried, the invasive species that might be deposited on the boats are transferred to other freshwater bodies. Moreover, some species, such as zebra and quagga mussels can survive for up to 5 days out of water thus increasing their chances of invasion. Invasive species, for instance the mussel populations increase because of their reproductive cycle. As water heats to 54 0F, egg production begins with a mature female being estimated to produce more than a hundred thousand eggs a season (Simberloff, 2013).
After the eggs are fertilized, they develop into free-swimming larvae, which are moved by currents to other areas. The invasive species colonize the areas, covering the undersides of boats, anchors and water pipes. Zebra mussels invade other mussels’ species and kill them. The colonies formed become too big, thus reducing their ability to move, feed and breed leading to their death and eventual reduction in their populations (Raiter, Possingham, Prober & Hobbs, 2014). The populations are also reduced as the species are transported to other areas. Further, when their hide outs are exposed to the sun, the mussels die.
The mussels filter large amounts of phytoplankton from the water, thus depriving fish species of their nutrition. As the smaller fish die, their predators fall suit, therefore collapsing the fisheries industry. Moreover, as the zebra mussels feed, they deposit contaminants by way of waste. The invasive species increase toxic algal blooms that affect the fish and wildlife. Recreational activities are also affected as the invasive species, such as mussels cut people’s feet. The increasing numbers in one place also affect the survival of fish eggs. However, invasive species accelerate the growth of aquatic vegetation by cleaning the water thus letting sunlight through.
Introduction of new species that use disproportionate share of the ecosystem’s resources causes widespread problems, such as devastation of forests and farms, blockage of waterways, fouling of freshwater bodies, replacement of native species, as well as adversely effecting human health (Ganpat & Isaac, 2014). The introduction of invasive species is costly to the taxpayer and is estimated to cost billions of dollars annually, in addition to extinction of native species.
Studies show that 25 percent of agricultural gross national product is lost annually to invasive pests, such as boll weevil and leafy spurge, and the cost of containing the invasive species (Raiter et al., 2014). Moreover, some of the species are disease vectors. The Asian tiger mosquito transmits encephalitis and dengue fever while rainbow trout once led to an outbreak of whirling disease.
Ganpat and Isaac (2014) further assert that melaleuca species has replaced cypress and other native plants in forests with consequential effects to animals in those forests. Further, some species cause adverse effects to the ecosystem without biomass or number domination, for instance the Myrica faya have nitrogen fixing characteristics thus modifying plant colonization and favoring other introduced species. Introduced species can mate with the native species leading to a hybrid breed hence leading to an extinction of the native species (Simberloff, 2013).
Invasive species result from human activities and multiply beyond their accepted normal distribution thus posing a threat to the environmental, and agricultural resources. They affect the biodiversity and reduce the abundance and diversity of species in the environment they invade.