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</p></li></ul></li><li><p>Attempts to create a market for nutria meat, such as Marsh Dog biscuits made from nutria</p></li></ul><h3 collapsed="false">European Starling</h3><ul><li><p>Native to temperate Europe and western Asia</p></li><li><p>60 birds released into Central Park by Eugene Schieffelin, head of the American Acclimatization Society</p></li><li><p>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</p></li></ul><h4 collapsed="false">Starlings today</h4><ul><li><p>More than 200 million throughout North America</p></li><li><p>Vicious competitors for nest cavities, outcompeting swallows, bluebirds, etc.</p></li></ul><h3 collapsed="false">Accidental introductions</h3><ul><li><p>Boats, rafts, trains, ballast tanks, passenger planes, cargo planes, military transports, automobiles, hiking boots, livewells, backpacks, bait buckets, firewood, produce, propellers, other animals, flowers</p></li></ul><h3 collapsed="false">Brown Tree Snake</h3><ul><li><p>Native to Australia, New Guinea, and adjacent islands</p></li><li><p>Arrived in Guam as a stowaway in military cargo or landing gear in the late 1940s</p></li></ul><h4 collapsed="false">Consequences</h4><ul><li><p>Loss of avian and reptile species on Guam, trophic cascades</p><ul><li><p>A lot of avian extinctions and as a result a lot of native plant species were not dispersed causing many species to be eliminated</p></li></ul></li><li><p>With no natural predators and an abundant naïve prey base, snake numbers grew to over 2 million from 1940s - 1970s</p></li><li><p>Problems with snakes shorting out power lines</p></li><li><p>Concern about venomous bites to children </p></li></ul><h4 collapsed="false">Controlling The Brown Tree Snake</h4><ul><li><p>Barriers, trapping, chemical, biological</p></li></ul><h3 collapsed="false">Zebra mussels</h3><ul><li><p>Native to Russia</p></li><li><p>Escaped from a ballast tank into the Great Lakes in 1985</p></li><li><p>Spread through river connections, fishing boats</p></li></ul><h4 collapsed="false">Negative impacts</h4><ul><li><p>Serious economic consequences - foul marine equipment and pipelines, densities as high as 750,000 mussels/m²</p></li><li><p>Overwhelm other benthic species</p></li><li><p>Alter water clarity and ecosystem ecology</p></li><li><p>Concentrate toxins; bioaccumulation in predators</p></li></ul><h3 collapsed="false">Spongy moths (formerly Gypsy moths)</h3><ul><li><p>Native to Europe</p></li><li><p>Imported by Etienne Trouvelot to interbreed with silkworms</p></li><li><p>Escaped and dispersed rapidly through wind and campers bringing firewood containing eggs</p></li></ul><h4 collapsed="false">Consequences</h4><ul><li><p>Responsible for defoliating more than 80 million acres since 1970</p></li><li><p>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)