Invasive Species and Introduced Diseases Flashcards
(36 cards)
What is an invasive species?
- A non-native species
- Spreads to a degree which can cause damage to the environment, human economy or human health
Examples of invasive species in the UK
- Foxes
- Squirrels
- Red oak
- Walnut
What is the estimated annual cost in the US associated with damage caused by invasive species?
Over $136 billion per year from all invasive organisms
42% of threatened/endangered species in US primarily because of invasive species
What are the impacts of invasive species on ecosystems
- Impacts all aspects of an ecosystem
- Changes biotic/abiotic conditions
- Replaces native species - key to functioning
- Damage to human infrastructure
- Expensive to eradicate
How do species become invasive?
- Travel/ self-introduction
- Human assistance
How do species become invasive through self introduction?
- Reach new areas outside of original range to close neighbouring regions
- Slow process
How do species become invasive through human assistance?
- Human assistance can be accidental or deliberate
- Speeds up process and occurs over long distances
- Movement of waterborne species as water is discharged in other habitats
- Air travel - diverse and isolated ecosystems become connected
Outline deliberate human assistance of invasive species
- Animals and birds for hunting
- Plants for agriculture/forestry
- Domestic animals
- Biological control
- Released pets
Outline accidental human assistance of invasive species
- Transport vehicles
- Unprocessed wood
- Plant nurseries
- Tourists
- Produce shipments
What are the benefits of accidental human assistance?
- Most introduced species do not survive and do not impact ecosystems
What are the benefits of deliberate human assistance?
- Honey bee introduced - able to pollinate, providing a service a native species could not do
Examples of accidental human assistance being disruptive to ecosystems?
- Introduction to cats and rats in NZ
- Small pox and other diseases from Europe to Americas
- Zebra mussels in Great Lakes US, affects water quality
Examples of deliberate human assistance being disruptive to ecosystems?
- US minks in the UK - cause of decline of otters
- Deer in NZ - threat to plants
Why do only some species become invasive?
- Natural predators
- Competitors for food
- Breeding patterns
- Climate tolerances
- Genetic diversity
How to predict which species will be invasive
- Trends:
- High reproductive rates
- Short time to maturity
- Adaptable to diverse environments
- Associated with humans
What controls the success of invasions?
4 main factors:
- Climate and environment
- Propagule pressure (number and frequency of introductions)
- Minimum viable population size
- Lag time (local establishment to exponential growth)
What makes an ecosystem vulnerable to invasion?
- Climatically similar to original habitat
- Early successional (recently distributed)
- Low diversity of native species
- Absence of predators/grazers of invasive species
- Absence of competition/lack of similar species
- Few links on food web
- Human disturbance
How do humans make ecosystems more susceptible to invasion?
- Soil changes (erosion, nutrients)
- Removal of vegetation
- Removal of predators
- Suppression of disturbance regime (fire)
What is the homogenisation of nature?
- Refers to the replacement of local biotas with non-native species, usually introduced by humans
- Ecological specialists are replaced by ecological generalists
What are Browns (1989) rules of invasion? (5)
- Isolated environments - low diversity of native species
- Successful invader are native to continents
- Similarity between source and target areas
- More successful when native do not occupy similar niches
- History of close association with humans
How is the nutrient cycle impacted by invasive species?
- Example - Myrica Faya (fire tree) invasive in Hawaii
- Take Nitrogen out of air and puts into soil
- Native species are slow growing and unable to respond to disturbances
- Ecosystem cycles and dynamics permanently shifted
How are disturbance regimes impacted by invasive species?
- Example - Cheatgrass - introduced 19th century to US through ballast, soil and crop seed
- Thrives in disturbed areas
- Alters fire regime to maintain dominance
What are the ecological impacts of invasive species?
- Invasive species promote homogenisation of the environment
- They reduce local diversity and increase productivity
- Can change ecosystem dynamics and push systems past tipping point - into new normal
Describe the bioerosion/turbation caused by invasive rabbits
- Introduced to Australia in 1859 for sport
- Thrived due to good climate, access to food and no predators
- 70% of land surface covered in rabbits
- Excessive digging and grazing - soil erosion
- Loss of agriculture
- Extinction
- Cost over $200 million AUD/year
