Biodiversity loss: Introduced species can outcompete native species for resources such as food and habitat, leading to population decline and potential extinction. For example, the introduction of the European rabbit in the late 18th century has significantly impacted Australia's native plant communities due to its voracious appetite.
Habitat modification and degradation: Many introduced species have different ecological roles than native species, which can disrupt ecosystem processes. For instance, feral pigs alter the soil structure through digging, affecting vegetation growth and water retention. Additionally, invasive plants might replace native vegetation, altering habitats crucial for native wildlife.
Disease transmission: Introduced species can carry and transmit diseases and parasites that are harmful to native species. For example, the introduction of the cane toad in the 1930s led to the decline of native frog species due to a fungal disease carried by the toad.
Predation and competition: Introduced predators can severely impact native species. The introduction of feral cats, foxes, and dogs has had devastating effects on native Australian mammals, birds, and reptiles. Introduced herbivores can also outcompete native herbivores for food resources.
Hybridization and genetic introgression: In some cases, introduced species can interbreed with native species, leading to hybridization and dilution of the genetic integrity of the native species. This can disrupt reproductive patterns and affect the long-term survival of native populations.
Economic and social impacts: The presence of introduced species can have financial implications for industries like agriculture, fisheries, and tourism. Invasive species can cause substantial damage to crops, livestock, and infrastructure. Additionally, they can impact human health and safety, as well as have negative effects on cultural and recreational activities.
The impacts of introduced species can be complex and far-reaching, affecting entire ecosystems and ecological balances. Managing introduced species is a significant challenge, requiring concerted efforts from governments, scientific institutions, environmental organizations, and the public to mitigate their negative effects.