3.3 Invasive Species: Introduction, Spread, and Impacts
4 min read•july 30, 2024
Invasive species are organisms introduced to new ecosystems, causing harm to the environment, economy, or human health. They spread rapidly, outcompete native species, and disrupt ecosystems. The invasion process involves introduction, establishment, naturalization, and spread, with only a small percentage becoming truly invasive.
These non-native invaders impact biodiversity, alter ecosystems, and cause economic losses in agriculture, forestry, and fisheries. They spread through intentional releases, accidental introductions, and natural dispersal. Human activities, like global trade and habitat changes, accelerate their spread and create new invasion opportunities.
Invasive Species: Definition and Distinction
Defining Invasive, Native, and Non-Native Species
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- Invasive species introduce to ecosystems outside their native range and cause harm to the environment, economy, or human health
- Native species occur naturally in specific ecosystems or regions, evolving there over time
- Non-native (exotic) species introduce to areas outside their native range but may not cause harm or spread rapidly
- Invasive species characteristics include rapid reproduction, high dispersal ability, phenotypic plasticity, and outcompeting native species for resources
Invasion Process and Success Rates
- Invasion process follows sequence: introduction, establishment, naturalization, and invasion (spread)
- Estimated 10% of introduced species successfully establish, smaller percentage become invasive
- "Tens rule" in invasion biology suggests:
- 10% of imported species appear in the wild
- 10% of those establish
- 10% of established species become pests
Impacts of Invasive Species
Ecological Impacts
- results from invasive species outcompeting or preying on native species
- Ecosystem functions alter through disruption of food webs and nutrient cycles
- Extinctions of native species occur through:
- by invasive species
- for resources
- Alteration of habitat structure
- Severe impacts on islands and isolated ecosystems with high endemism levels (Hawaii, Galapagos Islands)
Economic and Human Health Impacts
- Economic costs include damage to:
- Agriculture (crop losses from invasive pests)
- Forestry (destruction of timber resources)
- Fisheries (disruption of native fish populations)
- Control and eradication efforts incur significant expenses
- Annual global economic cost estimates in hundreds of billions of dollars
- Human health effects:
- Invasive species serve as disease vectors (mosquitoes carrying West Nile virus)
- Cause allergic reactions (ragweed pollen)
- Ecosystem services alteration indirectly affects human well-being:
- Water purification disruption (invasive zebra mussels in Great Lakes)
- Pollination changes (displacement of native pollinators)
- Erosion control modification (invasive plants altering soil stability)
Pathways of Invasion
Introduction Methods
- Intentional release for:
- Agriculture ( for erosion control)
- Ornamental purposes ( in ponds)
- Accidental release:
- Pet escapes (Burmese pythons in Florida Everglades)
- Agricultural contaminants (seeds mixed with crop shipments)
- Natural dispersal:
- Wind-carried seeds or spores
- Water-borne organisms
- Animal-mediated transport (birds carrying seeds)
Transportation and Industry Vectors
- Ships transport invasive species through:
- (zebra mussels in the Great Lakes)
- Hull fouling (marine organisms attached to ship hulls)
- Airplanes carry insects and plant materials
- Vehicles spread seeds and small organisms along roads
- Pet trade introduces exotic animals (red-eared slider turtles)
- Horticulture industry spreads invasive plants ()
- Aquaculture operations release non-native fish ( in North American rivers)
Invasion Dynamics
- concept explains invasion success:
- Higher number of individuals introduced increases establishment likelihood
- More frequent introduction events boost invasion chances
- Lag phases occur between introduction and invasion:
- Early detection crucial for effective management
- Rapid response necessary to prevent establishment
- Invasive species traits enhancing spread:
- High reproductive rates (rabbit populations in Australia)
- Generalist habitat requirements (cane toads adapting to various Australian ecosystems)
- Allelopathic capabilities (garlic mustard suppressing native plant growth)
Human Role in Invasion
Globalization and Trade Impacts
- International trade accelerates species introductions worldwide
- Examples of trade-related invasions:
- in North American hardwood forests
- Red imported fire ants spreading through global shipping
- Climate change alters geographic ranges of species:
- Creates new invasion opportunities in previously unsuitable habitats
- Allows tropical species to establish in warming temperate regions
Anthropogenic Environmental Changes
- Habitat fragmentation favors establishment of invasive species over natives:
- Edge effects create disturbed areas for colonization
- Reduced native biodiversity decreases ecosystem resistance
- Land-use changes create novel ecosystems susceptible to invasion:
- Urbanization introduces non-native ornamental plants
- Agricultural expansion creates monocultures vulnerable to pests
- Construction of corridors facilitates invasive species spread:
- Canals connect previously isolated water bodies (Suez Canal allowing Red Sea species into Mediterranean)
- Roads provide pathways for terrestrial species movement
Synergistic Effects and Global Patterns
- Human-mediated introductions lead to biodiversity homogenization:
- Certain invasive species become widespread across continents (water hyacinth in tropical regions worldwide)
- Multiple anthropogenic stressors weaken native ecosystems' invasion resistance:
- Pollution stress on native species
- Overexploitation of natural resources
- Habitat destruction
- Cumulative effects of human activities create global invasion patterns:
- Invasive species hotspots in areas of high human activity
- Similar invasion profiles in regions with comparable climate and trade patterns
Key Terms to Review (25)
Asian Carp: Asian carp refers to a group of invasive fish species, including the Bighead carp, Silver carp, Grass carp, and Black carp, originally introduced to North America in the 1970s for purposes like aquaculture and waterway management. These fish have since escaped into the wild and have proliferated, posing significant ecological threats to native fish populations and aquatic ecosystems due to their rapid reproduction and voracious feeding habits.
Asian Long-Horned Beetle: The Asian long-horned beetle (Anoplophora glabripennis) is a destructive invasive insect native to East Asia that infests and damages hardwood trees, particularly maples. This pest is significant in discussions of invasive species because its introduction to non-native environments can lead to severe ecological and economic impacts, disrupting local ecosystems and threatening biodiversity.
Ballast Water: Ballast water is water carried by ships in their ballast tanks to maintain stability and balance during transit. This water often contains a mix of aquatic organisms, including phytoplankton, zooplankton, and even small fish, which can unintentionally be introduced into new environments when the ship discharges its ballast. As a result, ballast water is a significant vector for the spread of invasive species, which can have profound ecological, economic, and health impacts on the ecosystems they invade.
Biodiversity loss: Biodiversity loss refers to the decline in the variety and variability of life on Earth, which includes the extinction of species, degradation of ecosystems, and reduction of genetic diversity within species. This loss has profound effects on ecosystem structure and function, impacting services like pollination, water purification, and climate regulation. It is driven by factors such as habitat destruction, pollution, overexploitation, and the introduction of invasive species, which can destabilize ecosystems and hinder their ability to provide essential services.
Biological control: Biological control refers to the use of natural predators, parasites, or pathogens to manage pest populations and invasive species, reducing their negative impacts on ecosystems and human activities. This method leverages ecological relationships to suppress harmful species without relying on chemical pesticides, promoting a more sustainable approach to pest management. It connects deeply with the challenges posed by invasive species, offering alternative strategies to mitigate their spread and effects.
Biosecurity measures: Biosecurity measures are practices and policies designed to prevent the introduction and spread of harmful organisms, including invasive species, pathogens, and diseases. These measures are crucial for protecting ecosystems, agriculture, and human health by minimizing the risks associated with biological threats. Effective biosecurity involves monitoring, controlling access to sensitive areas, and implementing quarantine protocols to manage potential invasions and outbreaks.
Burmese Python: The Burmese python is a large non-venomous constrictor snake native to Southeast Asia, recognized for its distinctive patterned skin. In the context of invasive species, this snake has become a significant ecological threat in areas where it has been introduced, notably in the Florida Everglades. Its presence disrupts local ecosystems by preying on a variety of native species and competing for resources, which can lead to population declines and biodiversity loss.
Cane Toad: The cane toad is an invasive amphibian species native to Central and South America that was introduced to Australia in 1935 for biological pest control. This introduction aimed to control agricultural pests, particularly the cane beetle, but instead, the cane toad became a significant ecological threat, impacting native species and ecosystems across Australia.
Citizen Science: Citizen science is the practice of engaging non-professional volunteers in scientific research, allowing them to contribute data collection, analysis, and monitoring efforts. This approach can greatly enhance research capabilities, especially in conservation efforts, as it leverages the power of community involvement to gather large amounts of data and raise awareness about environmental issues.
Competition: Competition is an ecological interaction where two or more species vie for the same resources, such as food, space, or light, which are limited in availability. This interaction can lead to significant changes in population dynamics and community structures, often influencing which species thrive or decline in a given environment. Understanding competition is essential to address the impacts of invasive species on native populations and recognize the role of keystone species in maintaining ecosystem balance.
Ecosystem Disruption: Ecosystem disruption refers to significant alterations in the structure and function of an ecosystem, often resulting from external pressures such as invasive species, pollution, climate change, or habitat destruction. These disruptions can lead to the decline or extinction of native species, changes in community composition, and a loss of ecosystem services. Understanding ecosystem disruption is crucial for conservation efforts, as it highlights the interconnectedness of species and the delicate balance that sustains ecological health.
Emerald Ash Borer: The emerald ash borer (EAB) is a small, metallic green beetle that is native to Asia and has become one of the most destructive invasive species in North America. It primarily targets ash trees, causing significant ecological and economic damage as it tunnels through the tree's bark and disrupts its vascular system, ultimately leading to tree death. The rapid spread of EAB has raised concerns about the loss of ash species and the broader impacts on forest ecosystems and urban areas.
Eradication Programs: Eradication programs are systematic efforts aimed at completely eliminating invasive species from a specific area to restore native ecosystems and prevent further ecological damage. These programs often involve a combination of strategies, such as biological control, chemical treatments, and mechanical removal, targeting species that threaten biodiversity, agriculture, or human health. Successful eradication programs require careful planning, monitoring, and community involvement to ensure that they are effective and sustainable over time.
Invasive Species Legislation: Invasive species legislation refers to laws and regulations aimed at preventing, controlling, and managing the introduction and spread of non-native species that can cause ecological or economic harm. This type of legislation is crucial for protecting native ecosystems, promoting biodiversity, and addressing the impacts of invasive species on agriculture, fisheries, and human health.
Japanese Knotweed: Japanese knotweed is an invasive perennial plant species native to East Asia, known for its rapid growth and ability to thrive in a variety of environments. This plant can outcompete native flora, disrupt ecosystems, and cause significant damage to infrastructure due to its extensive root system. Its resilience and adaptability have made it a notorious invader in many parts of the world, particularly in North America and Europe.
Kudzu: Kudzu is a fast-growing, invasive vine native to Asia that was introduced to the United States in the late 19th century for erosion control and ornamental purposes. It has since become infamous for its aggressive growth habits, which allow it to quickly smother and outcompete native vegetation, resulting in significant ecological and economic impacts. This vine's ability to thrive in various conditions exemplifies the challenges posed by invasive species in ecosystems.
Outreach programs: Outreach programs are initiatives designed to inform and engage the public about specific issues, often focusing on education and conservation efforts. These programs aim to raise awareness, promote community involvement, and drive positive environmental change by connecting scientific knowledge with local communities. Effective outreach can facilitate collaboration between researchers and citizens, ultimately enhancing conservation outcomes.
Pathways of Introduction: Pathways of introduction refer to the various ways in which non-native species enter new ecosystems, often leading to invasive species establishment. Understanding these pathways is crucial because they help identify how and why certain species can thrive in unfamiliar environments, often outcompeting native species and altering ecological balance. By recognizing these pathways, conservationists can better strategize prevention and management efforts to mitigate the impacts of invasive species.
Predation: Predation is the biological interaction where one organism, the predator, hunts and consumes another organism, known as the prey. This relationship plays a critical role in shaping ecosystems by regulating population sizes, influencing community structures, and driving evolutionary adaptations. Through predation, energy flows through food webs and various species interact, establishing complex relationships that maintain ecosystem balance.
Propagule Pressure: Propagule pressure refers to the number of individuals of a species that are introduced to a new area and their likelihood of establishing a viable population. This concept is crucial in understanding how invasive species spread and impact ecosystems, as higher propagule pressure increases the chances of successful establishment and subsequent population growth in non-native environments.
Range Expansion: Range expansion refers to the process by which a species increases its geographical distribution over time, often leading to the colonization of new areas. This phenomenon is particularly relevant in understanding how invasive species spread into new habitats, potentially outcompeting native species and disrupting local ecosystems. As species expand their range, they can alter community dynamics and impact biodiversity in significant ways.
Red Imported Fire Ant: The red imported fire ant (Solenopsis invicta) is an invasive species originally from South America, known for its aggressive behavior and painful sting. This ant has spread rapidly across the southern United States and beyond, causing significant ecological and economic impacts, particularly in areas where it disrupts local ecosystems and agricultural practices.
Red-eared slider turtle: The red-eared slider turtle (Trachemys scripta elegans) is a freshwater turtle species native to the southern United States and northern Mexico, easily identified by the distinctive red stripe behind its eyes. This turtle has become one of the most popular pet turtles globally, leading to its introduction in various ecosystems outside its native range, which raises concerns about its impact as an invasive species. The red-eared slider poses a threat to local biodiversity, as it competes with native turtles for food and habitat, and can carry diseases that may affect indigenous wildlife.
Water Hyacinth: Water hyacinth is an aquatic plant native to the Amazon basin, known for its striking purple flowers and ability to rapidly multiply. It is often regarded as one of the world's most invasive species, causing significant ecological and economic impacts in water bodies where it spreads unchecked. The rapid growth of water hyacinth can disrupt aquatic ecosystems, outcompete native plants, and affect water quality, leading to serious consequences for local wildlife and human activities.
Zebra Mussel: The zebra mussel is a small, freshwater bivalve mollusk native to the Caspian and Black Seas, recognized for its distinctive striped shell. Since its introduction to North America in the 1980s, it has become one of the most notorious invasive species, disrupting local ecosystems, outcompeting native species, and causing significant economic impacts through damage to water infrastructure.