Introduced Species Biological invasion occurs when a species

Introduced Species

Biological invasion: • occurs when a species arrives in an area in which it was previously not found

Exotic Species • an organism that has invaded an ecosystem in which it did not evolve • throughout the course of history, human beings have introduced many species to new ecosystems • in some regions a large number of the species present are not indigenous • Examples: – New Zealand: 47% of species have been introduced – Canada: 28% of species have been introduced – Hawaii: 18% of species have been introduced

• not all species that were introduced survived • if 100 new species are placed in a new ecosystem: – 87 will die off – 10 will successfully colonize – 2 -3 will become pests

• species can be introduced: 1. Intentionally: Agriculture Biotechnology Pet trade Ornamental 2. Accidentally: Ship ballast Air travel Escape from agriculture • introduced species have a HUGE impact on the balance of an ecosystem

Epic fail – the cane toad

Ecological Impacts • • • Direct predation Plant pathogens Disease transmission Disruption of food web Loss of biodiversity Extinction

Economic Impacts • • Russian wheat aphid Mediterranean fruit fly Zebra mussel Boll weevil $130 million/year $897 million/year $5 billion/year $50 billion (since 1890's)

• introduction of species to new environments can be prevented in a number of ways 1. Inspections at travel centres 2. Ballast regulations 3. Control of “established exotics” » shooting & trapping » mechanical removal (plants) » Pesticides » biological control

Organic Farming • organic farming involves using agricultural practices that are environmentally friendly • source of nitrates is manure and legumes with nitrogen-fixing bacteria within the roots • crops grown are very diverse and mature at different times of the year • this ensures that different nutrients are released from the different plants on a continual basis – relies on nature to control pests and weeds

• crop diversity reduces the need for pesticides • due to susceptibility of crops to pests, smaller yields are produced resulting in higher prices – many health benefits are realized