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