Human activities have interfered with the distribution ranges and dispersal barriers of many species for hundreds of years. Common methods of accidental dispersal include the use of contaminated equipment and the release of exotic pets (Hardion et al., 2014). The introduction of a species may also be deliberate, such as the relocation of species into a novel area for gardening, construction, erosion control, or food production (Hardion et al., 2014). Anthropogenically introduced species may threaten local ecosystem biodiversity by outcompeting native species for resources (Hardion et al., 2014). Therefore, the introduction of non-native species, which are key drivers of human-induced environmental change globally (Vitousek et al., 1997), alter the evolutionary trajectory of native species. This is accomplished by means of competitive exclusion, niche displacement, hybridization, predation, and ultimately, extinction (Shea, 2002). Species categorized as either threatened or endangered are particularly vulnerable to extinction (Wilcove et al., 1998). The resulting loss of native species constitutes an irreversible removal of evolutionary potential (Mooney et al., 2001), as well as a critical cause of ecosystem degradation.
The negative impact of invasive species on ecosystem health extend to a multitude of ecosystem goods such as agricultural products and fisheries. They also hinder ecological services that are typically provided by native species, such as clean drinking water and climate stabilization. This poses a threat because ecosystem goods and services are fundamental to human well-being (Daily et al., 1997). Translating this impact into a monetary value is often challenging. The lack of a concrete and precise economic impact assessment allow the burdens imposed by invasive species to be overlooked. This results in an “invisible tax” on ecosystem services that is rarely considered during decision making (Pejchar and Mooney, 2009).
Furthermore, invasive species have a direct impact on human and animal health (e.g., via toxins, thorns, and allergenic pollen). For example, mosquitoes, which are common vectors for disease, are capable of altering the transmission cycle of pathogens (Juliano and Lunibos, 2005). The introduction of new species of mosquitoes into novel areas has been facilitated by worldwide ship transport (Lunibos, 2002).
Given the broad and substantial burden of invasive species, urgency is required to control and limit their harmful impacts. Such a feat would necessitate specific knowledge regarding their biology, ecology, and geographic origin (Hardion et al., 2014). In the following review, we conducted a thorough assessment of five key invasive species in the County of Los Angeles, providing information on their origins, current distribution, ecological and health impacts, economic costs, as well as ideal management guidelines founded in scientific research.