Introduced Species: Impacts on Biodiversity

Scientists agree that the following five factors are the major problems contributing to the current loss of biodiversity: Ê habitat destruction Ë introduced species Ì pollution Í overexploitation Î population growth Threats to biodiversity

Terms Y Alien Y Exotic Y Introduced Y Invasive Y Nonnative Y Noxious Y Nuisance Y Indigenous Y Native Bumblebee on flower of introduced thistle

Introduced Species Y Introduced species have been moved from their native habitats to new habitats - usually by humans, accidentally or intentionally. Y Some introduced species become invasive in their new habitats = successfully reproduce and spread; cause economic or environmental harm or harm to human health Herb robert (Geranium robertianum)

Pathways: How are species introduced? Y Intentional introductions for agriculture, horticulture, research, biological control Y Unintentional introductions through contaminated agricultural products, timber, etc. Y Attached to or carried in freight, packing materials, shipping containers, ships, boats, cars, planes and other modes of transport

Biological attributes of invasive species Y This is an area of current research Y Difficult to generalize Y Usually a lag phase before a species becomes invasive - difficult to tell which introduced species will die out and which will become invasive = difficult to decide whether to make the effort to control the species at this point or not Y Pinpointing these attributes would provide a valuable tool for preventing invasions

Theories about why some introduced species succeed: These theories take into account attributes both of the species and the communities being invaded: Ê escape from natural constraints (predators, parasites, etc.) Ë occupation of a niche that was vacant Ì aided by humans, usually through disturbance of the native community

Impacts on Biodiversity Y Invasive species can have a multitude of impacts: l prey on or cause disease of native species l outcompete native species for resources or breeding sites l hybridization with native species l habitat modification (change hydrology, encourage fire, alter nutrient cycles) l agricultural/natural resource losses (pests, diseases)

Impacts on Biodiversity Herb robert (Geranium robertianum) Cichlid fish English ivy (Hedera helix)

Western pond turtle Photo by Kate Slavens Y populations have declined, in large part due to predation by introduced bullfrogs

Economic Impacts of Invasive Species Y Loss of potential economic gain: l crop production l domestic animal and fisheries industries l forest products Y Expense of fighting invasions l preventing invasions (quarantine) l controlling populations of invasive species l eradication

Y In February of 1999, President Clinton signed an executive order which expands and coordinates federal efforts to address the threat of invasive introduced species and to prevent the future introduction of nonnative species. Y The Invasive Species Council, created by the order, has developed a National Management Plan for invasive species. What is being done? Regulating Introductions

Y Invasive species, once established, are very difficult to eradicate  prevention of invasions is key Y International treaty: Agreement on the Application of Sanitary and Phytosanitary Measures (SPS) l WTO members can restrict movement of species that may pose a threat to human, animal or plant life

Y Animal and Plant Health Inspection Service (APHIS) of the Department of Agriculture l attempts to prevent the introduction of nonnative agricultural pests and diseases l focused mainly on protecting agriculture, but also serves to prevent ecosystem damage caused by nonnative species and diseases What is being done? Regulating Introductions

What is being done? Eradication and Control Y Methods of eradication: l chemical l mechanical (including manual) l biological Y Often, eradication efforts are too little, too late Y If eradication fails, then maintenance control is the goal l same methods as for eradication The goal is to maintain or increase native species diversity and to maintain a functional ecosystem that leads to that level of diversity (may have to accept invasives in the mix).

What is being done? Eradication and Control Efforts to eradicate foxes in Western Australia

4Avoid transporting fresh fruits, vegetables, grains or meats across state or country lines What can you do? 4In the garden - choose native plants and pull exotic weeds 4Do not release exotic pets or dump aquariums containing exotic pets or plants 4Volunteer to control invasive species or plant native species in a local natural area 4Be aware of the issues and help to educate others

Not if you can help it!

Produced by Woodland Park Zoo Education Department 2001 Photo credits: All photos by K. Remine/M. White except: Slide 11 - Western pond turtle by Kate Slavens. Used with permission.