Invasive Species

Invasive Species

The world consists of a large finite number of ecosystems that coexist, but often face trouble when their distinct habitats are altered in the slightest. Often times the cause of this problem is the introduction of invasive species that grow quickly and manifest themselves in the ecosystem. Invasive species are flora or fauna that are non-native to an environment, and/or alter habitats by changing the natural controls of that distinct ecosystem (US Department of Agriculture).

These species are organisms that have the ability to adapt easily to new environments and often reproduce at high rates, allowing them to establish themselves in an ecosystem in large quantities in a short period of time. In the new environment, the invasive species often does not have a natural predator to stabilize its population, so it expands without limit. With its overwhelming numbers, the species can out-compete native species for nutrients, and cause extinctions. These extinctions cause further repercussions in the food chain that disrupt the whole ecosystem (Convention of Biological Diversity).

Map of the spread of the beaver population in Argentina
Figure 1: From a starting population of only fifty beavers introduced in 1946, the Canadian beaver has greatly altered the environment of Tierra Del Fuego.
(Source: Christina Baird/NPR, 2011)

Invasive species are located on all corners of the globe. One notable invasive species is the North American beaver, which has wreaked havoc on the southern-most tip of South America's Tierra del Fuego. When inhabiting an environment, beavers first build dams and underwater canals. This causes water levels to rise, and new vegetation grows in the sediment on the newly raised coastal line (National Park System). In 1946, the Argentinian government imported fifty beavers form Canada in an effort to expand on the South American fur trading economy. However, the idea never became economically efficient, so the plan came to a halt, and the beavers were left to live in the Argentinian forests. In this new environment there were no predatory controls on the beaver population, whereas in Canada, the beavers had major predators such as bears and wolves that kept their population numbers in check. The most recent report, from June 2011, claims that there are now over 200,000 beavers living in Argentine national forests, and that the beavers have settled in and threatened sixteen million hectares of forests. The beavers change the Argentine ecosystems by gnawing down trees for their homes, creating higher water levels that affect the relative abundance levels of the plant communities in the area. This change in the ecosystem forces the Argentine government to take action.

Invasive species often affect tourist areas. Many common tourist destinations are nestled in the world's wilderness, and the surrounding areas often lack enforced resource legislation (Convention of Biological Diversity). Due to this, many surrounding areas are often affected by invasive species, leading to a lack of species abundance or a loss of rare endemic wildlife because of change in water quality or local resources. An example of this occured in the Florida Everglades, where the Melaleuca quinquenervia, also known as the Paper Bark Tea Tree, now lives. This tree is known for taking over ecosystems, most commonly sawgrass marshes, and turning them into swamps. During this process, the medium sized tree acts as a noxious weed, modifying the water quality, altering the soil resources, increasing the risk of fire in that area, and decreasing the valued pricing estimate of the land. Additionally, the plant is often resistant to environmental changes: it resists floods and droughts and disperses seeds efficiently when fires arise. Thus, it can grow constantly in most situations.

A major problem associated with invasive species is the cost of remediation and arguments over who should fund it. In Argentina, because the beavers reside in remote and rugged areas the cost of eradicating the species is extremely high (Tierra del Fuego). In the Florida Everglades, the problem is focused on who will fund the effort. Local honey growers lose the most – the Paper Bark Tea Tree it makes the environment incapable of fostering honey-making bees. Removing the tree from the Everglades would cost the honey growers 15 million USD, but the benefits are not limited the honey growers. The estimated financial gain for the tourist industry is 168 million USD, making the removal of the Paper Back Tea Tree extremely profitable. The problem arises from the fact that the group fronting the costs will not reap most of the benefits from their project, so it seems inefficient for them to take action (United States Department of Agriculture, Center for Aquatic and Invasive Plants-University of Florida, Smithsonian Marine Station).

Despite the negative aspects mentioned above, not all invasive species damage ecosystems, if controlled properly; some are useful tools for fixing problems associated in varying locations. An example of this is the water hyacinth, which was introduced in China during the 1950's through to the 1970's. The flowers of this plant are prized for their ornamental value, and they are cheap way to feed cattle. They also help decrease water pollution because, due to their rapid growth, they tend to reduce the concentration of heavy metals in the water. However, they do have the potential to cause some problems. They grow rapidly, and if left uncared for, they can overtake lakes and ponds entirely, blocking sunlight from entering the water and stopping aquatic plants, protists, and bacteria from photosynthesizing. This in turn deprives the water of oxygen, effectively strangling the wildlife of the area. Despite this, the benefits of using water hyacinths, on a global note, total 3.8 million USD, whereas the costs associated are $.28 million, so the benefits far outweigh the costs (Center for Aquatic and Invasive Plants-University of Florida, Department of Ecology-State of Washington)

On the whole, the problem of invasive species is one that affects the entire world. Most of the time, invasive species negatively affect biodiversity, which reduces tourism by deterring people from visiting marred and altered environments. For example, per annum the US spends 7% of its total GDP, 136 billion USD, to control invasive species, and remove wild and rapidly growing species around the country (CIA Factbook). This problem does not only affect the US, so the cost that the world must pay is far greater. Invasive species can be beneficial, but only under strict control. If the species gets out of hand, it can leave lasting effects on their non-native environments with tremendous repercussions.