Any living organism can be an invasive species, be it a plant, bacteria, seeds, insect, amphibian, or even fish. Human beings are also invasive species. They move into new areas and clear all the plantations to pave the way for urbanization and settlement. For a species to be invasive, first, it must be introduced to an ecosystem that is not its original ecosystem (pain et al., 2016). However, we have species that are termed intrusive even if they are in their natural habitat, like the lake trout, which are native to the Great Lakes but are classified as invasive species in Yellowstone Lake in Wyoming. Also, not all species that are native to a place are termed as intrusive; an example is most of the crops grown for food worldwide, like maize, rice chilies, tomatoes, and wheat. They were once introduced to the places they are being planted now, but they are not termed as invasive.

For a species to be termed invasive, it has to adapt to the new area quickly, spread destructively, reproduce, and increase. It must cause harm to the species in the native environment in which it has been introduced.

Invasive species can cause both economic harm and ecological harm in the new environment they get into. They can threaten human activities in the area they invade, like the water hyacinth in Lake Victoria, and can harm natural resources in a new ecosystem (Russel et al., 2017).  Invasive species threaten the extension of native animals and plants since they compete with native organisms for limited natural resources.
How do invasive species spread?

The leading cause of the spread of invasive species is human activities. Human beings spread the spices unintentionally, while other times, they spread the species knowingly. Human beings and the commodities that we use to travel all over the world. While touring the world, human beings carry a lot of unwanted species with them. Unwanted insects can be spread by getting into shipping crates and palettes or even wood and being transported across the world to places where they are not native, are unwanted, and become invasive (Reaser et al., 2020).

Quite a large amount of invasive species are introduced to a new area by accident. An example is Zebra mussels; they spread to the lakes in North America by accident. They stuck to the ships that voyaged from the Caspian and Black seas located in Central Asia to North America’s Great Lakes.

Other species are brought to a new habitat intentionally. They can be introduced to the new habitat as decorative displays like flowers or a specific type of grass, and they can also be presented as pets. Other times, a species can be introduced as a form of pest control. The species that are brought to a new habitat intentionally are referred to as introduced species. The introduced spices later become invasive by multiplying too quickly. They spread quickly because they lack natural predators in the new habitat that they have been subjected to (Reaser et al., 2020).  

Often, human beings carry firewood when they go camping; by so doing, they help spread invasive species. The firewood brought has many species within, and by moving them from one point to another, we as humans unknowingly act as agents of introducing invasive species to new ecosystems. Buying hay from a different ecosystem also poses a threat of introducing invasive species (pain et al., 2016).

Improper disposal of garden waste is another way in which invasive species are introduced to new ecosystems. The garden waste contains seeds and insects that might not be native to the area they are being taught. The sources might germinate and later become invasive.

Invasive species and the threats posed to the local environment.

For an invasive species to flourish in a new habitat, it has to compete with the native species for food. Mostly, the invasive species outcompete the native species, thus causing threats to the native species’ survival.  An example is the silver and bighead carp; they are a species of fish that are large by nature. They are very common in the Missouri River, yet that is not their native habitat; they were introduced from fish farms in the 1990s. These fish feed on tiny organisms called plankton that float in the water, and many of the native species of fish also feed on them. (Russel et al., 2017) Since they have a higher feeding cycle than the native fish, they are now more than the native species, making the native species not acquire enough food.

Invasive species cause a significant threat to the new habitat since they don’t have predators that feed on them. They reproduce rapidly, and within a short time, they cannot be controlled, and they overfeed in the new habitat and disrupt the food chain in the new habitat. An example is the brown tree snakes; the snakes were introduced to Guam, which is in the southern Pacific. No animal fed on the snake on the island since it was filled with rodents, birds, and other small animals. Since no predators were feeding on the snakes, they rapidly multiplied, and they fed on the birds, making nine of the eleven bird species on the island extinct.

Native species are at risk from invasive species since they may not have developed a defensive mechanism against the invasive species. The invasive species can, in turn, prey on the native species for food or carry a disease that may affect the native species, thus leading to their extinction. The invasive species can alter the native environment; they can change the food web by either replacing the native food source or even destroying the food source. Aside from the food web, an invasive species can even destroy the natural habitats where other plants and animals live (Reaser et al., 2020).

Invasive species can also cause significant harm to the economy of the people living around the native area. An example of this is the water hyacinth that invaded Lake Victoria in East Africa. It is a plant that is originally from South America. It is an introduced species, and it is presented for its pretty flowers (pain et al., 2016).

The introduction spreads quickly and covers the water, thus choking out the native aquatic wildlife. In the Lake Victoria region, the plant has spread and prevents fisherman’s boats from passing through the water. This makes it hard for them to get their daily bread, affecting the area’s economy, which is majorly reliant on fishing. In the region, the water hyacinth has also led to the closure of some ports.

How to curb the spread of invasive species.

To curb invasive species, we should replant and reintroduce more native plants and eliminate invasive plants in our surroundings. We should make sure that the plants we buy for our farms are all native. We should also not purchase animals or pets from a different ecosystem and bring them to our ecosystems; by doing this, we will accidentally reduce the chances of introducing an invasive species. We should also not release pets into the wild.

Another way to curb the spread of invasive species is by making sure that we thoroughly clean any tools and gear that we use for outdoor activities. We should clean the shoes we use when hiking before going to walk a new area to avoid any chances of spreading a seed that might have been stuck in the shoe trends. We should also clean boat propellers and the boat generally before using it in a different body of water.

Containers, pallets, and other materials used in shipping goods need to be inspected for any seeds, insects, and any other organisms that might have been attached during transit (Reaser et al., 2020). By doing so, many invasive species might be stopped from spreading.

We are eradicating invasive species.

In eradicating invasive species, several approaches can be used. The manual process involves burning invasive plants, destroying invasive birds’ nests, killing their young ones, and digging and physically uprooting invasive plants. This method works well in places where there is a small infestation of the invasive plant or animal (Russel et al., 2017). It is more labor-intensive but effective. The downside is that it cannot be effective in large areas and larger populations.

The chemical approach involves the spreading of insecticides, herbicides, pesticides, and fungicides. It is less labor-intensive and effective since it can target a specific invasive species and is guaranteed to kill the species. The downside of the Chemical approach is that it has environmentally damaging options; it might affect the natural plantation in the ecosystem. Invasive animals can be exposed to a particular virus that will ensure their extension. For instance, the cats that had invaded Marion Island were exposed to a virus that eradicated them.

The mechanical approach to eradicating invasive species includes tilling, cutting, drilling, and even constructing barriers to prevent invasive species from invading a particular area. This method is most effective in medium infestation (pain et al., 2016). It involves using a machine and can be a little expensive compared to the chemical approach. This method works well in areas with favorable terrain and is preferred to the chemical process in environmentally sensitive regions.

The biological control method involves using other living species to control the spread of invasive species. This method works best in areas that have large infestations. Since invasive species are not native to the ecosystem they have infested, this method involves bringing in their natural predators to curb their spread and even wipe them out of existence (Sakai et al., 2001). This method is preferable since it can be used in environmentally sensitive areas and is suitable for large infestations.

To eradicate invasive species, new species can be introduced to feed on the invasive species and keep them in check. An example is introducing cactus moth caterpillar in Australia to control the spread of prickly pear cactus, which had grown out of control.  However, this is not the right solution since the introduced species can also destroy other native plantations in the area, becoming invasive species themselves.

Examples of invasive species.

Asian carp is a fish species that was introduced from Asia to be raised by fish farmers near the Mississippi region. The fish escaped the farms and found their way into river Mississippi during a flood, since then it has become one of the major invasive species since they eat up to forty percent of their weight in a day. 

A photo of the Asian Carp in the Great Lake.

Brown marmorated stink bug is an invasive species that originates from Asia and has spread across almost all states in America. They were introduced accidentally to the United States and spread because there were no natural predators.

Zebra mussels are invasive mollusks; they are native to Eastern Europe and were first discovered in the Great Lake in the 1980s (Sakai et al., 2001). They spread quickly since they have free-floating larvae; hence, they spread quickly, settling in large colonies, and they produce threads that allow them to attach to hard surfaces.

Water Hyacinth is an invasive plant that floats on water; it originated in South America and is a significant problem for riparian communities worldwide. It is an introduced species (Reaser et al., 2020). It is an ornamental plant that people submit to their ponds for their beautiful flowers. It later found its way to lakes and has caused significant problems, especially in Lake Victoria.  

Cogon grass is an invasive plant that originates from Asia; it was introduced in the United States to inform seeds in some packaging materials. However, it has displaced the native plants and is spreading across the southeast. It contains no food value for native wildlife and poses a significant threat of wildfire since it quickly burns and is hotter than the native grass.

References.

Paini, D. R., Sheppard, A. W., Cook, D. C., De Barro, P. J., Worner, S. P., & Thomas, M. B. (2016). Global threat to agriculture from invasive species. Proceedings of the National Academy of Sciences, 113(27), 7575-7579.

Reaser, J. K., Simpson, A., Guala, G. F., Morisette, J. T., & Fuller, P. (2020). Envisioning a national invasive species information framework. Biological Invasions, 22(1), 21-36.

Russell, J. C., & Blackburn, T. M. (2017). The rise of invasive species denialism. Trends in Ecology & Evolution, 32(1), 3-6.

Sakai, A. K., Allendorf, F. W., Holt, J. S., Lodge, D. M., Molofsky, J., With, K. A., … & McCauley, D. E. (2001). The population biology of invasive species. Annual review of ecology and systematics, 32(1), 305-332.