9.3 Invasive species
8 min read•august 21, 2024
Invasive species are reshaping global biogeography, altering ecosystems and species distributions. These organisms impact native biodiversity and ecosystem functioning, often with significant ecological and economic consequences. Understanding invasive species is crucial for predicting and managing changes in world biogeography.
Rapid reproduction, high dispersal ability, and adaptability are key traits of invasive species. They often outcompete natives for resources and can quickly establish in new areas. While not all non-native species become invasive, those that do can dramatically alter ecosystems and pose management challenges.
Definition of invasive species
- Invasive species play a crucial role in shaping global biogeography by altering ecosystems and species distributions
- These organisms significantly impact native biodiversity and ecosystem functioning, often leading to ecological and economic consequences
- Understanding invasive species is essential for predicting and managing changes in world biogeography
Characteristics of invasive species
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- Rapid reproduction and growth allow quick population establishment
- High dispersal ability enables spread to new areas
- Phenotypic plasticity facilitates adaptation to various environments
- Generalist habitat requirements increase survival in different ecosystems
- Ability to outcompete native species for resources (food, space, light)
Native vs non-native species
- Native species evolved in a specific ecosystem over long periods
- Non-native (exotic) species introduced to areas outside their natural range
- Invasive species subset of non-native species causing harm to ecosystems
- Not all non-native species become invasive (approximately 10% do)
- Time since introduction often influences invasive potential (lag phase)
Pathways of introduction
- Invasive species introductions reshape biogeographic patterns globally
- Understanding introduction pathways is crucial for preventing new invasions
- Human activities have dramatically increased the rate of species introductions
Natural dispersal mechanisms
- Wind dispersal carries seeds and small organisms over long distances
- Water currents transport aquatic species across oceans and along rivers
- Animal-mediated dispersal through migration or attachment (burrs, seeds)
- Volcanic activity creates new habitats for colonization (island biogeography)
- Natural range expansion due to changing environmental conditions
Human-mediated introductions
- Intentional introductions for agriculture, horticulture, and pet trade
- Accidental transport through global trade (, shipping containers)
- Tourism and travel facilitate species movement across biogeographic barriers
- Habitat modification creates new niches for non-native species
- Climate change-induced range shifts blur lines between natural and human-mediated introductions
Ecological impacts
- Invasive species significantly alter ecosystem structure and function
- These impacts cascade through food webs and biogeochemical cycles
- Understanding ecological consequences is crucial for predicting biogeographic changes
Biodiversity loss
- Competitive exclusion of native species through resource monopolization
- Predation on native fauna, leading to population declines or extinctions
- Hybridization with closely related native species, diluting genetic diversity
- rendering environments unsuitable for native species
- Disease transmission to native species lacking evolved immunity
Ecosystem disruption
- Alteration of nutrient cycling processes (nitrogen fixation, decomposition)
- Changes in fire regimes, affecting ecosystem structure and succession
- Modification of hydrological cycles through altered transpiration rates
- Soil chemistry changes impacting plant community composition
- Disruption of mutualisms (pollination, seed dispersal) between native species
Trophic cascades
- Top-down effects when invasive predators reduce herbivore populations
- Bottom-up impacts when invasive plants alter resource availability
- Mesopredator release following the introduction of apex predators
- Alterations in energy flow through food webs
- Indirect effects on non-target species through altered interspecific interactions
Economic consequences
- Invasive species have far-reaching economic impacts across various sectors
- These consequences often drive management decisions and policy development
- of invasions influence biogeographic research priorities
Agricultural impacts
- Crop yield reductions due to competition with invasive weeds
- Increased pesticide use to control invasive pests, raising production costs
- Livestock health issues from toxic invasive plants or parasites
- Soil degradation leading to long-term productivity declines
- Market access restrictions due to invasive species quarantine measures
Infrastructure damage
- Structural damage to buildings from invasive termites or plants
- Clogging of waterways and irrigation systems by aquatic invaders
- Road and railway damage from root systems of invasive plants
- Power outages caused by invasive vines on electrical infrastructure
- Increased maintenance costs for public spaces and recreational areas
Management costs
- Surveillance and monitoring programs to detect new invasions
- Research and development of control methods (biological, chemical, mechanical)
- Implementation of eradication or containment strategies
- Public education and outreach campaigns on invasive species
- Economic losses from reduced ecosystem services provided by native species
Biological factors in invasion success
- Certain biological traits increase the likelihood of successful invasions
- Understanding these factors helps predict potential invaders and vulnerable ecosystems
- Biological adaptations of invasive species often challenge traditional biogeographic patterns
Rapid adaptation
- Genetic bottlenecks leading to rapid evolution in new environments
- Epigenetic changes allowing quick responses to novel conditions
- Hybridization between closely related species creating more robust genotypes
- Phenotypic plasticity enabling survival in diverse habitats
- Selection for traits that promote invasiveness (e.g., increased dispersal ability)
Lack of natural predators
- Enemy release hypothesis explains increased fitness in new environments
- Absence of co-evolved parasites and pathogens reduces population regulation
- Altered allocation of resources from defense to growth and reproduction
- Naive prey species lacking appropriate anti-predator behaviors
- Potential for invasive species to develop novel defenses over time
Competitive advantages
- Superior resource acquisition strategies (e.g., allelopathy in plants)
- Higher reproductive rates allowing rapid population growth
- Broader environmental tolerances compared to native species
- Ability to modify habitats to their advantage (ecosystem engineers)
- Exploitation of empty niches in recipient ecosystems
Geographic patterns of invasion
- Invasive species distributions reveal global patterns of biotic exchange
- These patterns inform our understanding of modern biogeography
- Identifying invasion hotspots helps prioritize conservation efforts
Global hotspots of invasion
- Mediterranean-type ecosystems highly susceptible to plant invasions
- Temperate grasslands vulnerable to both plant and animal invaders
- Tropical islands experiencing high rates of species introductions
- Coastal marine ecosystems impacted by shipping-related invasions
- Urban areas serving as entry points and habitats for many invasive species
Island vs continental invasions
- Islands more vulnerable due to isolated evolutionary history
- Higher endemism on islands increases risk of extinction from invaders
- Continental ecosystems often more resistant due to higher native diversity
- Differences in invasion success related to island size and isolation
- Human-mediated introductions blurring distinctions between island and continental invasion patterns
Case studies of invasive species
- Examining specific invasions provides insights into biogeographic processes
- Case studies illustrate the diverse impacts of invasive species across ecosystems
- These examples highlight the complexity of managing biological invasions
Terrestrial plant invaders
- (Pueraria montana) rapid spread across southeastern United States
- Australian Acacia species altering fire regimes in South African fynbos
- Japanese knotweed (Fallopia japonica) damaging infrastructure in Europe
- Garlic mustard (Alliaria petiolata) disrupting forest understory communities
- Cheatgrass (Bromus tectorum) transforming western North American rangelands
Aquatic invasive species
- Zebra mussels (Dreissena polymorpha) altering Great Lakes ecosystems
- Water hyacinth (Eichhornia crassipes) clogging waterways in tropical regions
- Lionfish (Pterois volitans) impacting Caribbean coral reef fish communities
- species threatening North American river systems
- Caulerpa taxifolia altering Mediterranean Sea benthic habitats
Invasive animals
- Cane toads (Rhinella marina) poisoning native predators in Australia
- European rabbits (Oryctolagus cuniculus) degrading Australian rangelands
- Brown tree snakes (Boiga irregularis) decimating Guam's bird populations
- Feral pigs (Sus scrofa) damaging ecosystems worldwide
- Argentine ants (Linepithema humile) displacing native ant species globally
Management and control strategies
- Effective management is crucial for mitigating invasive species impacts
- Strategies vary depending on invasion stage and ecosystem characteristics
- Management approaches influence the future biogeography of invaded regions
Prevention methods
- Risk assessment protocols to identify potential invasive species
- Strict quarantine measures at ports of entry (airports, seaports)
- Public education programs to reduce intentional introductions
- Development of invasion-resistant crop varieties
- Implementation of ballast water treatment technologies for ships
Eradication techniques
- methods (herbicides, pesticides) for localized invasions
- Mechanical removal of invasive plants or animals
- using carefully selected natural enemies
- Genetic techniques (sterile male release, gene drive) for insect pests
- Integrated management combining multiple eradication approaches
Containment approaches
- Establishment of buffer zones to limit spread
- Use of physical barriers (fences, nets) to restrict movement
- Implementation of early detection and rapid response systems
- Habitat manipulation to favor native species over invaders
- Controlled burning to manage fire-adapted invasive plants
Policy and legislation
- Policy frameworks shape the global response to invasive species
- Legislation at various levels influences management and prevention efforts
- International cooperation is essential for addressing transboundary invasions
International agreements
- Convention on Biological Diversity addresses invasive species globally
- International Plant Protection Convention focuses on plant health and trade
- Ballast Water Management Convention targets marine invasions
- Cartagena Protocol regulates movement of living modified organisms
- Regional cooperation initiatives (e.g., European Strategy on Invasive Alien Species)
National invasive species programs
- Executive Order 13112 establishes U.S.
- Australia's Weeds of National Significance program prioritizes management
- New Zealand's Biosecurity Act provides comprehensive invasion management framework
- South Africa's Working for Water program combines invasive control with job creation
- European Union Regulation 1143/2014 on Invasive Alien Species
Climate change and invasive species
- Climate change alters the dynamics of species invasions globally
- Shifting climatic zones create new opportunities for invasive species
- Understanding these interactions is crucial for predicting future biogeographic patterns
Range expansion predictions
- Poleward shifts in species distributions opening new invasion pathways
- Altitudinal range expansions in mountainous regions
- Changes in ocean currents affecting dispersal of marine invaders
- Increased frequency of extreme weather events facilitating long-distance dispersal
- Modeling approaches (species distribution models) to forecast future invasions
Altered invasion dynamics
- Changes in competitive relationships between native and invasive species
- Shifts in phenology affecting plant-pollinator interactions
- Increased stress on native ecosystems reducing resistance to invasion
- Altered fire regimes favoring fire-adapted invasive species
- Changes in host-parasite relationships affecting invasive species success
Positive impacts of invasive species
- While often harmful, some invasive species can have beneficial effects
- These positive impacts complicate management decisions and public perception
- Understanding potential benefits is important for comprehensive invasion biology
Ecosystem services
- Habitat provision for native species in degraded environments
- Soil stabilization and erosion control by invasive plants
- Carbon sequestration by fast-growing invasive trees
- Pollination services provided by introduced insects
- Bioremediation of contaminated sites by certain invasive plants
Economic benefits
- Commercial value of some invasive species (timber, food, ornamental)
- Job creation through
- Ecotourism opportunities centered around charismatic invasive species
- Utilization of invasive biomass for biofuel production
- Development of novel products or medicines from invasive organisms
Future challenges in invasion biology
- Ongoing globalization and environmental change present new invasion risks
- Emerging technologies offer both challenges and opportunities for management
- Addressing these challenges is crucial for predicting and shaping future biogeography
Emerging invasive threats
- Climate change creating novel invasive species assemblages
- Increased risk from Arctic invasions due to melting sea ice
- Potential for invasive microorganisms to disrupt ecosystem processes
- Threats from novel genetically modified organisms escaping containment
- Invasive species benefiting from increased atmospheric nitrogen deposition
Novel ecosystems
- Formation of new ecological communities with no historical analogues
- Challenges in defining management goals for hybrid ecosystems
- Potential for increased ecosystem resilience through diverse species assemblages
- Ethical considerations in managing novel ecosystems
- Need for adaptive management approaches in rapidly changing environments
Key Terms to Review (18)
Asian Carp: Asian carp refers to a group of invasive fish species originally from Asia, including species like the bighead carp, silver carp, and black carp. These fish were introduced to the United States in the 1970s for aquaculture and waterway management but have since spread rapidly, causing significant ecological and economic impacts in North American waterways.
Ballast water: Ballast water is water taken on board ships to provide stability and balance during transit. While it serves a crucial role in maritime operations, this water often contains a variety of aquatic organisms, including invasive species, that can be discharged into new environments, leading to ecological disruptions and economic impacts.
Biodiversity loss: Biodiversity loss refers to the decline in the variety and variability of life forms within a given ecosystem or the entire planet. This loss can occur through various mechanisms, including habitat destruction, climate change, and species extinction, which can significantly impact ecological balance and resilience. The interconnectedness of species means that biodiversity loss can lead to shifts in ecosystem functions, disruptions in food webs, and an overall reduction in ecosystem services that are vital for human well-being.
Biological control: Biological control refers to the method of managing pest populations by using natural predators, parasites, or pathogens. This technique aims to reduce the reliance on chemical pesticides and promote ecological balance, especially in the context of invasive species, which can disrupt local ecosystems. By introducing or enhancing the effectiveness of these natural enemies, biological control can help restore native biodiversity and minimize the negative impacts of invasive organisms.
Burmese Python: The Burmese python is a large non-venomous snake native to Southeast Asia, known for its impressive size and distinctive patterns. As an invasive species in the Florida Everglades, it poses significant ecological threats by preying on native wildlife and competing with local species for resources. The expansion of the Burmese python population in non-native areas showcases the challenges posed by invasive species in disrupting local ecosystems.
Chemical control: Chemical control refers to the use of pesticides or herbicides to manage and suppress invasive species in an ecosystem. This approach is often employed when biological or mechanical methods are insufficient, and it can effectively reduce populations of harmful species, protecting native flora and fauna. However, chemical control must be applied carefully to minimize negative impacts on the environment and non-target organisms.
Economic costs: Economic costs refer to the total expenses associated with a specific action or event, including both explicit costs (actual cash outflows) and implicit costs (the opportunity costs of foregone alternatives). These costs play a significant role in assessing the impact of various factors, particularly when evaluating the effects of invasive species on ecosystems and economies. Understanding economic costs is essential for making informed decisions about management strategies and resource allocation.
Ecosystem disruption: Ecosystem disruption refers to significant changes or disturbances in the structure and function of an ecosystem, often caused by external factors such as invasive species, climate change, pollution, or human activities. These disruptions can lead to loss of biodiversity, altered habitat conditions, and changes in species interactions, ultimately affecting the health and resilience of the ecosystem.
Habitat alteration: Habitat alteration refers to the change or modification of natural environments, often due to human activities, which can significantly impact the flora and fauna that inhabit these areas. This process can lead to the destruction or fragmentation of ecosystems, making it challenging for species to survive and thrive. Invasive species often contribute to habitat alteration by outcompeting native species and changing the structure of the environment, further exacerbating the effects on biodiversity.
Horticultural Trade: Horticultural trade refers to the commercial exchange of plants, flowers, fruits, vegetables, and other related products cultivated through gardening and farming practices. This trade plays a significant role in agriculture and can impact local economies, biodiversity, and ecosystems, especially when non-native species are introduced into new environments.
Invasive Species Act: The Invasive Species Act is a piece of legislation aimed at preventing, managing, and controlling the introduction and spread of invasive species that threaten ecosystems, agriculture, and human health. This act is critical in setting regulations for monitoring and managing species that can disrupt native biodiversity and the balance of ecosystems.
Invasive species management programs: Invasive species management programs are structured efforts aimed at controlling or eradicating non-native species that disrupt local ecosystems, harm biodiversity, and negatively impact human activities. These programs involve various strategies, such as monitoring populations, physical removal, chemical treatments, and public education to mitigate the adverse effects of invasive species on native habitats and species.
Kudzu: Kudzu is a fast-growing vine native to Asia, specifically Japan and Southeast China, that was introduced to the southeastern United States in the late 19th century for erosion control and ornamental purposes. It has since become an invasive species, spreading rapidly and outcompeting native plants, disrupting local ecosystems, and causing significant economic and environmental issues in the region.
National Invasive Species Council: The National Invasive Species Council (NISC) is a U.S. government body established to address the growing threat of invasive species, which can disrupt ecosystems, harm native species, and cause significant economic losses. By coordinating efforts among federal, state, tribal, and local governments, NISC aims to enhance the nation's ability to prevent, control, and manage invasive species across different habitats and regions.
Niche Theory: Niche theory explains how different species interact with their environment and each other, focusing on the roles they play within an ecosystem. It emphasizes the idea that every species has a specific niche, which includes its habitat, resource use, and interactions with other species. Understanding niche theory helps in grasping how species coexist, compete, and how invasive species can disrupt these dynamics.
Predation pressure: Predation pressure refers to the impact that predation has on the population dynamics and behaviors of prey species within an ecosystem. It encompasses both the direct effects of predators on prey populations, such as mortality rates, and the indirect effects, including changes in prey behavior, reproduction, and distribution in response to the presence of predators. This term is particularly relevant when considering how invasive species can disrupt existing predator-prey relationships and alter ecological balances.
Theory of island biogeography: The theory of island biogeography explains how the size and distance of islands from the mainland influence the diversity of species found on those islands. It highlights the balance between immigration and extinction rates, where larger islands closer to the mainland tend to support more species due to greater habitat variety and increased opportunities for species to migrate.
Zebra mussels in the Great Lakes: Zebra mussels are small, invasive freshwater bivalves native to the Caspian Sea, which have dramatically altered the ecosystem of the Great Lakes since their introduction in the 1980s. These mussels are known for their rapid reproduction and ability to attach to various surfaces, leading to significant ecological and economic impacts, including competition with native species and costly damage to infrastructure.