Invasive Species
Before we talk about invasive species, we need to first define what a native species is Native species Is an organism (e.g. plant or animal) that occurs naturally in a certain area Because it has evolved in that area over time, it typically has co-evolved with other species that served to keep its population in check through predation, competition, and disease
Non-native species Species that have been introduced or movedby human activities to an area where they do not naturally occur Not all non-native species are harmful Example: Apple trees
When do non-natives become harmful? When they outcompete native species in the natural ecosystems and cause ecological and economical problems Other names for non-natives are Invasive species Introduced species Exotic species Alien species
Common characteristics of Invasive Species 1. Can tolerate a wide range of conditions Ex. European Starling can live in woodlands, open fields, and cities 2. Produces a lot of seeds or eggs Ex. one zebra mussel can release up to 1 million eggs per year
Common characteristics of Invasive Species (continued) 3. Has few natural controls such as predators, disease, or insects Ex. Leafy spurge is inedible to native insects and animals. It also has greatly reduced the plants that native species can eat 4. Disperses itself with ease Ex. Cogongrassintroduced from SE Asia into SE U.S. in the early 1900 s to help with soil erosion. Each plant produces several thousand seeds that can be dispersed up to 15 miles by wind
Common characteristics of Invasive Species (continued) 5. Has long growing season or short generation time Ex. Buckthorn has a much longer growing season than native species which means they can mature faster than native species. 6. New location has climate and environment conditions similar to its native habitat Climate change has created environmental conditions similar to native habitat
Problems that Invasive Species can Cause Degrade and alter habitats Crowd out native species Choke waterways Ruin native fisheries Prevent forest from regenerating Compete with agricultural crops Among many other problems
Invasive species are a worldwide issue (Guam, New Zealand, Hawaii) Once the invasive species have established in a native area, they are nearly impossible to remove Controlling these species is very time consuming and expensive
How did the spreading of invasive Globalization species start? Invention of cars, trains, airplanes, boats Increased the amount of worldwide travel Increased the amount of shipment of goods
Scientists estimate, in the U.S. alone, that there are about 7,000invasive species that have established themselves Species include all types of plants, mammals, birds, amphibians, reptiles, arthropods, and mollusks Caused major environmental damages and economical losses that have totaled about $139 billion per year in agriculture, forestry, and other portions of the U.S. economy
Pathways by which invasive species got to their new locations 1. Intentional introduction for food, medicine, aesthetics, environmental help, etc. People may not have realized that it would be harmful to the native
Examples of intentional introduction Nutria (origin: Argentina) Purpose was to raise them for their fur Introduced in the 1930 but individual quickly escaped By 1955, populations were in the millions Have caused millions of dollars worth of damage to agriculture and have weakened levies Purple Loosestrife Introduced to the NE U.S. in the 1800 s as an ornamental plant and for medicinal purposes Adapts to wetlands and quickly outcompetes native plants and grasses Impacts native waterfowl s habitat
2. Accidental introductions Transport species by barges, boats, footwear, animals, trailers, packing materials, clothing, animals, vehicles, etc.. Ballast water of ships Water that is taken into the ships to help stabilize boats May pump water in at one location and then dump out the water at its destination When unloading the water, it also unloading whatever is in the water Zebra mussels, spiny water fleas
Examples of accidental introductions Brown treesnake In 1952, brown treesnakewas introduced to Guam via cargo on a ship Since there was no predators and there was an abundant source of food, the population of the treesnakereached unprecedented numbers Caused many problems including, power outages, loss of native birds, pets
How to prevent invasive species? Avoid planting non-native plants in gardens Do not buy or release non-native pets Wash all boating gear Do not bring non-native plants, seeds, soils, etc.. from other countries Volunteer to help remove invasive species