Species that are nonnative to a specific location are called invasive species. Invasive species have the ability to spread at a level that proves harmful to the human economy, environment, and human health.
The term that is used to define the species that is not native to a specific location and affect the bioregions and habitat, they can also affect the environment ecology and economy.
It may be an animal or a plant that overcrowd a region and disrupt that habitat wilderness area. Invasive species are defined by the European Union as“ those species that now threaten the biological diversity were firstly out of this area of natural distribution”.
They termed as “noxious weeds” by the researchers, land managers, horticulturalists, botanists, conservationists, and the public.
Causes of Invasive species
Scientists have to include ecosystem factors and species in the mechanisms that cause the introduced species to become invasive species.
Species based mechanisms
These species have a combination of specific traits that make them able to compete with native species. Sometimes the competition is for reproduction and for growth rates, sometimes the species are more directly interact with each other. From the list of noninvasive and invasive species, 86% of invasive species can be determined from their traits.
Traits of the invasive species
- fast growth rate
- high rate of reproduction
- the ability of wide dispersal
- high plasticity to phenotype, which means that they have the ability to change their growth which suits the present condition
- can tolerate environmental conditions on a wide range
- generalist which means that they can feed on a wide variety of food.
- They have also Association with humans
- They have previously successful invasions
Usually and introduce species have to survive at a low population density until in a new location it becomes an invasive species. In a new location to maintain and reproduce itself will be a difficult task for the introduced species.
If and introduce species successfully compete with the native species for resources, for example, light, nutrients, physical space, food, and water, it will allow the introduced species to multiply rapidly.
A coexistence is present between the native species and an invasive species for a long period of time until the population of the invasive species becomes denser and larger and the invasive species successfully adapt in a new location and competitive abilities become Apparent.
An invasive species can create negative or positive effect on native species because it can change the environment by modification of abiotic factors, or by the release of chemical compounds, or by the effect of herbivores’ behavior.
The available resources amount and their utilization by organisms will determine the effect of invasive species on the ecosystem. A stable ecosystem has equilibrium between the use of the resources that are available. when changes occur in an ecosystem, for example, forest fire it will favor the normal succession of forbs and grasses that are native to that location.
An introduced species will utilize the resources that were the resources of native species, so that introduced species will grow faster and squeeze the native species. In this situation, Phosphorus and nitrogen are often considered as a limiting factor.
In an ecosystem each species have its specific niche, so the invasive species will fill the niches that were not occupied by native species by creating new niches. E.g edge effects show the disturbance of an ecosystem part when a piece of land is cleared for agricultural use, a distinct habitat is formed between the boundary of a newly cleared piece of land and the remaining undisturbed habitat.
It will create new losers and winners and hopefully host the species that were not survived outside that habitats boundary, the populations of newly introduced species have a great rate of adaptations, in this way the in a new environment the newly introduced species become invasive.
These Rapid adaptations include the alters in phenology, morphology, plasticity, and Physiology, so their offspring will be fitter and better adapted for this environment,
Effects of invasive species
The invasive species have affected the ecology, geomorphology, and economy.
The local areas are pressurized by human habitation and land clearing. The habitats. that are disturbed by human activities are very sensitive to invasive species, that have harmful effects on the ecosystem because it can alter the functions of an ecosystem. e.g a pest plant species known as “ae ae” In the Hawaiian wetlands had covered the wetlands that were made artificially for the waterfowls as a refuge, it has made the undesired feeding areas for endangered Hawaiian waterfowls.
Ecosystems functions are changed by the influence of invasive species because invasive species can change the nutrient cycle and the native ecosystem hydrology.
Sometimes hybridization occurs between the native species that are rare in nature and the invasive species that are closely related to that of native species creating adverse effects on the native species by causing their extinction, e.g the hybridization of native California’s cordgrass with introduced invasive cordgrass has to threaten native California’s Cordgrass.
Bio protection and bio construction are the geomorphological effects of the plant’s species that are invasive. While bioerosion, bioturbation, bio construction is the primary geomorphological effects of animal species that are invasive.
Some invasive species create some negative effects on the local area’s economy. E.g the sea lamprey which is an invasive species in the Great Lakes region act as a Predator, while the sea lamprey in its original Habitat act as a parasite that does not kill the host organisms.
Sea lamprey can feed on all types of fishes like Salman and trouts by adding destructive effect on the fish industry.
- The invasive species provide food resources and suitable habitats for other organisms, when a native species are endangered or extinct the invasive species fill their place.
- For the restoration, the invasive species act as a catalyst, because the invasive species can increase biodiversity and heterogeneity in an ecosystem.
- For an existing engineer of an ecosystem, the non-native species can play the role of a substitute.
- The invasive species can also be introduced to fill al niche that was niche of native species previously.
- Service is also provided by non-native species e.g As a pollinator, in the rainforest the Honey Bee was introduced to pollinate landscapes because the native species cannot do this.