Invasive species: challenges and solutions
Rachel Lange
Invasive species• Non-indigenous plants or animals that adversely affect
the habitats in which they establish
• Introduced accidentally or intentionally– Horticulture
– “Stowaways” of land, air and water transport
– Failed resource management efforts
– Food production
– Recreational opportunities
– Nostalgia
Costs of invasives
• Ecological– “Competitive release” in their
new environment– Compete with natives for
resources– Spread through and dominate
the landscape, reducing biodiversity
• Trickle-down effects through food web
• Aesthetic
• Economic– 2010:
• U.S. $138 billion
– 2006• Global $1.4 trillion
Invaders of local importance
Salt cedar (Tamarix spp.)• Native to Eurasia
• Introduced mid 1800’s– Ornamental, windbreaks, erosion control
– Invaded 2 million + acres
– Waterways
Why so invasive?
• Prolific seed production– Small seeds easily
transported
• Vegetative spread – Roots
• Allelopathy– Salts inhibit growth of
other plants
• Hardy
• Lack of coevolved predators and disease
• Deliberate introductions
Problems• Diverts water away from native ecosystem and
human use– Mature tree consumes 200 gallons/day
– Stand removes 3-4 feet from water table/year
– Utilizes more water than displaced native vegetation (4000m3/ha per year more!)
• Increased soil salinity
• Poor quality habitat
Problems, cont.• Increased fire risk• Costs of tree control, land clearing and
restoration– $100 (aerial)- $771 (stump treatment) per acre
• $150-$300 per acre backpack sprayer
– Texas High Plains $72 million estimated irrigation losses in 1998
• Diminished recreational value– Water sports, fishing, camping, hiking, bird
watching……even ORV’s
Control methods
• Herbicide– Aerial application
– Ground application
• Mechanical
• Fire
• Biological
Biological control
• Utilizing coevolved predators, parasitoids, or pathogens found in the invasive species’ native range as a management method– Must be extremely host specific
– Rigorously tested
– Continued monitoring post-release
• Technique has experienced vast improvement
Salt cedar leaf beetle (Diorhabda spp.)
• Chrysomelid beetle chosen as best biocontrol agent for salt cedar– USDA
– USFWS
• Highly specific
• All life stages feed on salt
cedar– 90-100% defoliation observed in native range
– Repeat attacks can prevent regrowth of trees
Benefits of Diorhabda establishment
• Low costs
• Once established– Self-sustaining
– Dispersal and colonization • Remote / inaccessible locations
– Self-regulating
• Limits need for herbicide
• Better resources for natives
Locally• Establishment has been problematic
– Climate and photoperiod
– Multiple species of Diorhabda
– Number needed for successful establishment after release?
• 2004: Began introductions to Lake Meredith/Plum Creek and Borger, TX– Uzbekistan, Posidi (Greece), Crete, Fukang (China)
– No sustained populations
• Success elsewhere in US
Challenges
• Red tape
• Education of concerned parties– Environmental
– Agriculture/Horticulture
– Individual citizens
• Revegetation/Restoration
What can you do?
• Don’t facilitate spread– Clean boats, trailers and
vehicles
– Clean clothing, shoes and gear
– Inspect pets
– Avoid transport of wood, sod, soil or hay from one area to another
– Don’t release bait
– Don’t release pets
• Investigate and be informed– “if you don’t know it,
don’t grow it”• Go native
– Buy from reputable sources
• Gardens
• Exotic pets
• Abide by regulations and laws
• Share your knowledge
Resources