Invasive species pose a crucial threat to many native habitats and species in the United States and impose high costs on agriculture, forestry, and recreation. An invasive species refers to an organism that is not native to a specific region and poses significant economic and environmental threats to its new habitat. The term "invasive species" can also refer to feral species or introduced diseases. Some introduced species, such as the dandelion, do not cause significant economic or ecological damage and are not widely considered as invasive. Economic damages from invasive species and control costs are estimated at $120 billion per year. The main geomorphological impacts of invasive plants include bioconstruction and bioprotection. Degrees of ecological impacts by introduced faunas that can potentially compensate for extinct native animals (especially megafauna) and treatments of these animals have long been subjects to discussions most notably mustangs and burros, while contributions by other species to the native ecosystems are also debatable.
Notable invasive species
For a more in-depth example, Zebra mussels (Dreissena polymorpha), like many other invasive species, are not native to the United States and can cause significant damage to ecosystems and severely harm native aquatic wildlife, such as fish and other freshwater shellfish. Zebra mussels (Deissena polymarpha) are a species of shell fish that originated and are native to the Caspian and Black seas of Europe and the western part of Russia. These invasive species of shellfish made their way into the United States and were discovered here in the U.S during the 1980s. Zebra mussels are known for outcompeting native fish species (mainly other shellfish) and can prevent those fish from absorbing nutrients and reproduction. Another problem humans face is (Biofouling), which occurs when mussels attach themselves to surfaces using Byssal threads, protein-based roots. This can damage property by clogging vehicles, pipes, and other systems. Given their appearance, these mussels are depicted as having light brown coloration with black stripes, hence their name, and have a very small, D-shaped shell. They are typically not that big, growing to roughly one-quarter to one and one-half inches in length, possibly two inches. Their size (like other mussel species) is usually dependent on age, and they may also possess stripes that are both yellow and brown.
Economic impact The economic impacts of invasive species can be difficult to estimate, especially when an invasive species does not affect economically important native species. This is partly because of the difficulty in determining the non-use value of native habitats damaged by invasive species and the incomplete knowledge of the effects of all invasive species present in the U.S. Estimates of the damage caused by well-known species can also vary. The Office of Technology Assessment (OTA) has estimated the zebra mussel's economic effects at $300,000 per year, while a United States Army Corps of Engineers study put the figure at $1 billion per year. The United States government spends an estimated $1 billion annually to recover from the invasive Formosan termite, investing $1 billion of this budget in areas surrounding New Orleans, a major port city. Estimates of total yearly costs controlling invasive species range from $1.1 billion to $137 billion per year. In 1993, the OTA estimated that a total of $100 million was invested annually in invasive-species aquatic weed control in the U.S. Introduced rats cause more than $19 billion per year in damages, exotic fish cause up to $5.4 billion annually, and the total costs of introduced weeds are estimated at around $27 billion annually. The total damage to the native bird population from invasive species is approximately $17 billion per year. Approximately $2.1 billion in forest products are lost each year to invasive plant pathogens, and a conservative estimate of the losses to livestock from exotic microbes and parasites was $9 billion per year in 2001.
Government policies and management efforts The federal government has historically promoted the introduction and widespread distribution of species that have become invasive, including multiflora rose, kudzu, and others, for a variety of reasons. Before the 20th century, numerous species were imported and released without government oversight, such as the gypsy moth and house sparrow. Over 50% of the flora recognized as invasive or noxious weeds were deliberately introduced to the United States by either government policy or individuals. Current government policy can be broadly separated into two categories: preventing the entry of a potential invasive species and controlling the spread of species already present. This is carried out by different government agencies, depending on what types of damage a species can cause.
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