25 - Invasive species RNR 2031

Invasive Species

Invasive species

  • Invasive species – non-native, undesirable, rapidly expanding plants, animals, and pathogens

  • Damage and control costs in the United States approach $150 billion annually

  • With modern globalization, invasive species can be transported anywhere in the world overnight

Characteristics of invasive species

  • Fill an empty niche

  • Few or no natural predators

  • Rapid reproduction

  • Capacity to outcompete native species through aggression or sheer numbers

  • High dispersal ability (innate or human-assisted)

Intentional introductions

  • Humans have intentionally been moving species around since domestication (9000 BC)

  • Primarily for food (early times)

  • Later for work/utility, companionship, economic value, aesthetics, and biological control

Cane toad introductions

  • Native to Central and South America

  • Can grow to 15” in size and weigh 6 lbs

  • Toxic skin; tadpoles are highly toxic when ingested by predators

  • First introduced to Puerto Rico in the 1930s to help control beetles that were ravaging sugarcane plantations

  • Hailed as a miraculous means of biological control!

Australia

  • Introduced sugar cane in the late 1800s as a cash crop

  • Increasing crop damage caused by the native Grey-backed Cane Beetle and Frenchi Beetle

  • Released 102 cane toads in northeastern Australia in 1935

  • By early 2000s they spread throughout northern Australia

Ecological impacts

  • Lack predators that can deal with the poisonous toad; Evolution!

  • Massive declines in native species such as the northern quoll, freshwater crocodile, and Argus monitor

Social and economic impacts

  • Toxicity to pets, children

  • Public nuisance

  • Difficult to quantify economic impacts, as they don't control the beetles and potentially increase disease in cattle

  • There appears to be no effective solution to this problem

Nutria

  • Native to South America

  • Phenomenal reproductive capabilities

    • Mature at 6 months

    • Can produce a litter of up to 13, three times a year

    • At any given time, 65% of females are pregnant

  • Consume 25% of their body weight daily, eating both above- and belowground biomass of aquatic vegetation

Nutria invasion

  • Introduced to Louisiana in the 1930s for their value as a furbearer

  • Widely advertised that one could "retire on half an acre" by raising nutria

  • Many nutria were turned loose when people realized they weren't profitable, and the rest escaped during a hurricane

Nutria control

  • Herbivory damage to LA wetlands totaled >100,000 acres in 1998

  • Well-funded bounty program established

    • reducing damage to 8,000 acres during the 2020-2021 season

    • $4 (now $6) per nutria tail

  • Attempts to create a market for nutria meat, such as Marsh Dog biscuits made from nutria

European Starling

  • Native to temperate Europe and western Asia

  • 60 birds released into Central Park by Eugene Schieffelin, head of the American Acclimatization Society

  • Goal was to introduce foreign varieties of the animal and vegetable kingdom as may be useful or interesting, with a special focus on introducing every bird mentioned in Shakespearean writing

Starlings today

  • More than 200 million throughout North America

  • Vicious competitors for nest cavities, outcompeting swallows, bluebirds, etc.

Accidental introductions

  • Boats, rafts, trains, ballast tanks, passenger planes, cargo planes, military transports, automobiles, hiking boots, livewells, backpacks, bait buckets, firewood, produce, propellers, other animals, flowers

Brown Tree Snake

  • Native to Australia, New Guinea, and adjacent islands

  • Arrived in Guam as a stowaway in military cargo or landing gear in the late 1940s

Consequences

  • Loss of avian and reptile species on Guam, trophic cascades

    • A lot of avian extinctions and as a result a lot of native plant species were not dispersed causing many species to be eliminated

  • With no natural predators and an abundant naïve prey base, snake numbers grew to over 2 million from 1940s - 1970s

  • Problems with snakes shorting out power lines

  • Concern about venomous bites to children

Controlling The Brown Tree Snake

  • Barriers, trapping, chemical, biological

Zebra mussels

  • Native to Russia

  • Escaped from a ballast tank into the Great Lakes in 1985

  • Spread through river connections, fishing boats

Negative impacts

  • Serious economic consequences - foul marine equipment and pipelines, densities as high as 750,000 mussels/m²

  • Overwhelm other benthic species

  • Alter water clarity and ecosystem ecology

  • Concentrate toxins; bioaccumulation in predators

Spongy moths (formerly Gypsy moths)

  • Native to Europe

  • Imported by Etienne Trouvelot to interbreed with silkworms

  • Escaped and dispersed rapidly through wind and campers bringing firewood containing eggs

Consequences

  • Responsible for defoliating more than 80 million acres since 1970

  • Economic impacts on valuable trees ($ billons)

  • Ecological impacts on forest-dependent species, especially birds

Control options for spongy moths

  • Extensive monitoring

  • Pheromone flakes to prevent males from finding females ($14/acre)

  • Viral insecticides specific to spongy moth caterpillars ($25/acre)

  • Bacterial insect - only when outbreaks are severe; indiscriminat poison ($25/acre)