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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Invasive species | 5/9 | https://en.wikipedia.org/wiki/Invasive_species | reference | science, encyclopedia | 2026-05-05T07:18:41.562467+00:00 | kb-cron |
Hybrids resulting from invasive species interbreeding with native species can incorporate their genotypes into the gene pool over time through introgression. Similarly, in some instances a small invading population can threaten much larger native populations. For example, cordgrass (Spartina alterniflora) was introduced in the San Francisco Bay and hybridized with native California cordgrass (Spartina foliosa). The higher pollen count and male fitness of the invading species resulted in introgression that threatened the native populations due to lower pollen counts and lower viability of the native species. Reduction in fitness is not always apparent from morphological observations alone. Some degree of gene flow is normal, and preserves constellations of genes and genotypes. An example of this is the interbreeding of migrating coyotes (Canis latrans) with the critically endangered red wolf (Canis rufus), in areas of eastern North Carolina where the red wolf was reintroduced, reducing wolf numbers.
=== Environmental === In South Africa's Cape Town region, analysis demonstrated that the restoration of priority source water sub-catchments through the removal of thirsty alien plant invasions (such as Australian acacias, pines, eucalyptus, and Australian black wattle) would generate expected annual water gains of 50 billion liters within 5 years compared to the business-as-usual scenario (which is important as Cape Town experiences significant water scarcity). This is the equivalent to one-sixth of the city's current supply needs. These annual gains will double within 30 years. The catchment restoration is significantly more cost-effective then other water augmentation solutions (1/10 the unit cost of alternative options). A water fund has been established, and these exotic species are being eradicated.
=== Human health === Invasive species can affect human health. With the alteration in ecosystem functionality (due to homogenization of biota communities), invasive species have resulted in negative effects on human well-being, which includes reduced resource availability, unrestrained spread of human diseases, recreational and educational activities, and tourism. Alien species have caused diseases including human immunodeficiency virus (HIV), monkey pox, and severe acute respiratory syndrome (SARS). Invasive species and accompanying control efforts can have long term public health implications. For instance, pesticides applied to treat a particular pest species could pollute soil and surface water. Encroachment of humans into previously remote ecosystems has exposed exotic diseases such as HIV to the wider population. Introduced birds (e.g. pigeons), rodents, and insects (e.g. mosquito, flea, louse and tsetse fly pests) can serve as vectors and reservoirs of human afflictions. Throughout recorded history, epidemics of human diseases, such as malaria, yellow fever, typhus, and bubonic plague, spread via these vectors. A recent example of an introduced disease is the spread of the West Nile virus, which killed humans, birds, mammals, and reptiles. The introduced Chinese mitten crabs (Eriocheir sinensis) are carriers of Asian lung fluke. Waterborne disease agents, such as cholera bacteria (Vibrio cholerae), and causative agents of harmful algal blooms are often transported via ballast water.
=== Economic ===
Globally, invasive species management and control are substantial economic burdens, with expenditures reaching approximately $1.4 trillion annually. The economic impact of invasive species alone was estimated to exceed $423 billion annually as of 2019. This cost has exhibited a significant increase, quadrupling every decade since 1970, underscoring the escalating financial implications of these biological invasions. Invasive species contribute to ecological degradation, altering ecosystem functionality and reducing the services ecosystems provide. This necessitates additional expenditures to control the spread of biological invasions, mitigate further impacts, and restore affected ecosystems. For example, the damage caused by 79 invasive species between 1906 and 1991 in the United States has been estimated at US$120 billion. Similarly, in China, invasive species have been reported to reduce the country's gross domestic product (GDP) by 1.36% per year. The management of biological invasions can be costly. In Australia, for instance, the expense to monitor, control, manage, and research invasive weed species is approximately AU$116.4 million per year, with costs directed solely to central and local governments. While, in some cases, invasive species may offer economic benefits—such as the potential for commercial forestry from invasive trees—these benefits are generally overshadowed by the substantial costs associated with biological invasions. In most cases, the economic returns from invasive species are far less than the costs they impose.
==== United States ==== In the Great Lakes region the sea lamprey (Petromyzon marinus) is an invasive species. In its original habitat, it had co-evolved as a parasite that did not kill its host. However, in the Great Lakes region, it acts as a predator and can consume up to 40 pounds of fish in its 12–18 month feeding period. Sea lampreys prey on all types of large fish such as lake trout (Salvelinus namaycush) and salmon. The sea lampreys' destructive effects on large fish negatively affect the fishing industry and have helped cause the collapse of the population of some species. Economic costs from invasive species can be separated into direct costs through production loss in agriculture and forestry, and management costs. Estimated damage and control costs of invasive species in the U.S. amount to more than $138 billion annually. Economic losses can occur through loss of recreational and tourism revenues. When economic costs of invasions are calculated as production loss and management costs, they are low because they do not consider environmental damage; if monetary values were assigned to the extinction of species, loss in biodiversity, and loss of ecosystem services, costs from impacts of invasive species would drastically increase. It is often argued that the key to invasive species management is early detection and rapid response. However, early response only helps when the invasive species is not frequently reintroduced into the managed area, and the cost of response is affordable.