6.8 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Invasive species | 6/9 | https://en.wikipedia.org/wiki/Invasive_species | reference | science, encyclopedia | 2026-05-05T07:18:41.562467+00:00 | kb-cron |
Weeds reduce yield in agriculture. Many weeds are accidental introductions that accompany imports of commercial seeds and plants. Introduced weeds in pastures compete with native forage plants, threaten young cattle (e.g., leafy spurge, Euphorbia virgata) or are unpalatable because of thorns and spines (e.g., yellow starthistle, Centaurea solstitialis). Forage loss from invasive weeds on pastures amounts to nearly US$1 billion in the U.S. A decline in pollinator services and loss of fruit production has been caused by honey bees (Apis mellifera) infected by the invasive varroa mite (Varroa destructor). Introduced rats (Rattus rattus and R. norvegicus) have become serious pests on farms, destroying stored grains. The introduction of leaf miner flies (Agromyzidae), including the American serpentine leaf miner (Liriomyza trifolii), to California has caused losses in California's floriculture industry, as the larvae of these invasive species feed on ornamental plants. Invasive plant pathogens and insect vectors for plant diseases can suppress agricultural yields and harm nursery stock. Citrus greening is a bacterial disease vectored by the invasive Asian citrus psyllid (Diaphorina citri). As a result, citrus is under quarantine and highly regulated in areas where the psyllid has been found. Invasive species can impact outdoor recreation, such as fishing, hunting, hiking, wildlife viewing, and water-based activities. They can damage environmental services including water quality, plant and animal diversity, and species abundance, though the extent of this is under-researched. Eurasian watermilfoil (Myriophyllum spicatum) in parts of the US, fills lakes with plants, complicating fishing and boating. The loud call of the introduced common coqui (Eleutherodactylus coqui) depresses real estate values in affected neighborhoods of Hawaii. The large webs of the orb-weaving spider (Zygiella x-notata), invasive in California, disrupts garden work.
==== Europe ==== The overall economic cost of invasive alien species in Europe between 1960 and 2020 has been estimated at around US$140 billion (including potential costs that may or may not have actually materialized) or US$78 billion (only including observed costs known to have materialized). These estimates are very conservative. Models based on these data suggest a true annual cost of around US$140 billion in 2020. Italy is one of the most invaded countries in Europe, with an estimate of more than 3,000 alien species. The impacts of invasive alien species on the economy has been wide-ranging, from management costs, to loss of crops, to infrastructure damage. The overall economic cost of invasions to Italy between 1990 and 2020 was estimated at US$819.76 million (EUR€704.78 million). However, only 15 recorded species have more reliably estimated costs, hence the actual cost may be much larger than the aforementioned sum. France has an estimated minimum of 2,750 introduced and invasive alien species. Renault et al. (2021) obtained 1,583 cost records for 98 invasive alien species and found that they caused a conservative total cost between US$1.2 billion and 11.5 billion over the period 1993–2018. This study extrapolated costs for species invading France, but for which costs were reported only in other countries but not in France, which yielded an additional cost ranging from US$151 million to $3.03 billion. Damage costs were nearly eight times higher than management expenditure. Insects, and in particular the Asian tiger mosquito (Aedes albopictus) and the yellow fever mosquito (A. aegypti), created the highest economic costs, followed by non-graminoid terrestrial flowering and aquatic plants (Ambrosia artemisiifolia, Ludwigia sp. and Lagarosiphon major). Over 90% of alien species currently recorded in France had no costs reported in the literature, resulting in high biases in taxonomic, regional and activity sector coverages. However, the lack of reports does not mean there are no negative consequences or costs.
== Favorable effects ==
The consensus of the scientific community is that the effects of invasive species on biodiversity are primarily negative, despite the potential for some favorable impacts. The entomologist Chris D. Thomas argues that most introduced species are neutral or beneficial with respect to other species but this is a minority opinion. Some invasive species can provide a suitable habitat or food source for other organisms. In areas where a native has become extinct or reached a point that it cannot be restored, non-native species can fill their role despite having negative impacts elsewhere. For instance, in the US, the endangered southwestern willow flycatcher (Empidonax traillii) mainly nests in the non-native tamarisk. The introduced mesquite (Neltuma juliflora) is an aggressive invasive species in India, but is the preferred nesting site of native waterbirds in small cities like Udaipur in Rajasthan. Similarly, Ridgway's rail (Rallus obsoletus) has adapted to the invasive hybrid of Spartina alterniflora and Spartina foliosa, which offers better cover and nesting habitat. In Australia, saltwater crocodiles (Crocodylus porosus), which had become endangered, have recovered by feeding on introduced feral pigs (Sus domesticus). Non-native species can provide ecosystem services, functioning as biocontrol agents to limit the effects of invasive agricultural pests. Some species have invaded an area so long ago that they are considered to have naturalised there. In the US, the endangered Taylor's checkerspot butterfly (Euphydryas editha taylori) has come to rely on invasive ribwort plantain (Plantago lanceolata) as the food plant for its caterpillars. Some invasions offer potential commercial benefits. For instance, silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) can be harvested for human food and exported to markets already familiar with the product, or processed into pet foods or mink feed. Water hyacinth (Pontederia crassipes) can be turned into fuel by methane digesters, and other invasive plants can be harvested and utilized as a source of bioenergy.
== Control, eradication, and study == Humans are versatile enough to remediate adverse effects of species invasions. The public is motivated by invasive species that impact their local area. The control of alien species populations is important in the conservation of biodiversity in natural ecosystem. Previous studies and control programs that target invasives are the most effective during the earlier phases of invasion, such as eliminating founder population quickly before the introduced species can spread. One of the most promising methods for controlling alien species is genetic.