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Invasive species

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**1. Definition and Classification of Invasive Species:**
Invasive species are non-native species that harm their new environment.
– Definitions of ‘invasive’ vary and can include native species harmful in human habitats.
– Colautti and MacIsaac proposed a new nomenclature system based on biogeography.
– The lack of standard terminology in invasion biology has led to varied definitions.
– The USDA’s definition of invasive species is narrow and harm-focused.

**2. Causes and Mechanisms of Invasive Species Introduction:**
– Human activities like shipping create opportunities for species establishment.
– Stable ecosystems can be disrupted by invasive species.
– Changes in ecosystems can create new niches for invasive species.
– Resource availability determines the impact of additional species in ecosystems.
– Island ecosystems may be more prone to invasion due to fewer competitors.

**3. Examples and Impact of Invasive Species:**
– The brown tree snake devastated native bird populations on Guam.
– Logging has allowed non-native species to invade ecosystems.
– Water hyacinth limits light penetration in water bodies.
– Japanese knotweed and cats are considered invasive species.
Invasive species have specific traits allowing them to outcompete natives.

**4. Vectors and Spread of Invasive Species:**
– Human activity is a major vector for non-native species.
– Invasive propagules’ arrival depends on the invasibility of the site.
– Ballast water transport introduces thousands of species daily, some harmful.
– Climate change impacts ocean temperature, leading to range shifts and new species interactions.
– Economics play a role in the intentional introduction of exotic species.

**5. Impacts of Invasive Species:**
Invasive species can alter ecosystem functions like fire regimes and nutrient cycling.
– Inadequately regulated fresh water systems are particularly vulnerable to invasive species.
Invasive species can adversely affect ecosystems, causing ecological, environmental, or economic damage.
Invasive species can reduce agricultural yields and disrupt outdoor recreation activities.
– Globally, $1.4 trillion is spent annually on managing invasive species.

Invasive species (Wikipedia)

An invasive species is an introduced species to an environment that becomes overpopulated and harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native species that become harmful to their native environment after human alterations to its food web. Since the 20th century, invasive species have become a serious economic, social, and environmental threat worldwide.

North American beaver dam in Tierra del Fuego
Kudzu, Atlanta
Canada goldenrod as a roadside weed in Poland
Vinca in a garden

Invasion of long-established ecosystems by organisms is a natural phenomenon, but human-facilitated introductions have greatly increased the rate, scale, and geographic range of invasion. For millennia, humans have served as both accidental and deliberate dispersal agents, beginning with their earliest migrations, accelerating in the Age of Discovery, and accelerating again with international trade. Invasive plant species include the kudzu vine, Japanese knotweed, and yellow starthistle. Invasive animals include European rabbits, domestic cats, and carp.

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