Invasive species threaten native plants and native plant communities. After habitat destruction, invasive species are the single largest cause of native plant extinction. The rate at which new, potentially invasive, species are being introduced is increasing.
What is an Invasive Species? An "invasive species" is defined as a species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112).
What is an Invasive Species? Sometimes you will see invasive species referred to as exotic, alien, or non- indigenous species. The problem with these names is that they only refer to the non-native part of the definition above.
What is an Invasive Species? Many exotic or alien species do not cause harm to our economy, our environment, or our health. In fact, the vast majority of "introduced" species do not survive and only about 15% of those that do go on to become "invasive" or harmful.
What is an Invasive Species? An invasive species grows/reproduces and spreads rapidly, establishes over large areas, and persists. Species that become invasive succeed due to favorable environmental conditions and lack of natural predators, competitors and diseases that normally regulate their populations.
What is an Introduction? When a species ends up in a new ecosystem, it is considered "introduced." Species do naturally change their ranges slowly over time, but it is not these "natural" events that we are concerned with. Most of the introductions that result in invasive species are human caused.
What is an Introduction? In some cases, we deliberately introduce species. Examples of this include garden ornamentals, range forage plants for cattle, animals and insects used to control other organisms (particularly in agriculture), and plants used for erosion control and habitat enhancement for wildlife.
What is an Introduction? Other species are introduced accidentally on imported nursery stock, fruits, and vegetables, in ship ballast waters, on vehicles, in packing materials and shipping containers, through human-built canals, and from human travel.
Ailanthus altissima (P. Mill.) Swingle Tree-of-heaven was first introduced to America by a gardener in Philadelphia, PA, in 1784, and By 1840 was commonly available from nurseries.
Ailanthus altissima (P. Mill.) Swingle The species was also brought into California mainly by the Chinese who came to California during the goldrush in the mid- 1800s. Today it is frequently found in abandoned mining sites there. The history of ailanthus in China is as old as the written language of the country.
Arundo donax L. Introduced from western Asia, northern Africa, and southern Europe in the early 1800s. Giant reed was probably first introduced into the United States at Los Angeles, California in the early 1800's.
Arundo donax L. Since then, it has become widely dispersed into all of the subtropical and warm temperate areas of the world, mostly through intentional human introductions.
Arundo donax L. Today, giant reed is widely planted throughout the warmer areas of the United States as an ornamental and in the Southwest, where it is used along ditches for erosion control.
Arundo donax L. Giant reed chokes riversides and stream channels, crowds out native plants, interferes with flood control, increases fire potential, and reduces habitat for wildlife, including the Least Bell's vireo, a federally endangered bird.
Arundo donax L. The long, fibrous, interconnecting root mats of giant reed form a framework for debris dams behind bridges, culverts, and other structures that lead to damage. It ignites easily and can create intense fires.
Eichornia crassipes (Mart.) Solms Water hyacinth is thought to be native to the Amazon River basin of South America. It was introduced to the United States in 1884 at the Cotton States Exposition in New Orleans, Louisiana.
Eichornia crassipes (Mart.) Solms It spread across the southeastern U. S. and was identified in Florida in 1895. It was reported to be in California in 1904.
Eichornia crassipes (Mart.) Solms Alters native vegetation and fish communities by lowering light penetration and dissolved oxygen levels. Impedes boat traffic on rivers and waterways and clogs irrigation canals and intake pumps.
Hydrilla verticillata (L.f.) Royle Hydrilla was first introduced into North America in the mid to late fifties by the aquarium trade. California officials have also traced hydrilla infestations to shipments of mail order waterlilies.
Hydrilla verticillata (L.f.) Royle Once introduced and established, hydrilla is easily spread through boating and fishing activities and by waterfowl. Hydrilla tubers are readily consumed and regurgitated tubers have been shown to be viable.
Hydrilla verticillata (L.f.) Royle Dense underwater stands of hydrilla raise water pH and temperature, and lower dissolved oxygen. While the number of fish is often increased, large fish become more rare.
Hydrilla verticillata (L.f.) Royle Promotes mosquito habitat. Potentially affects power generation by clogging dams.
Lythrum salicaria L. The first North American record of purple loosestrife was in wet Canadian meadows and in New England, as recorded in Pursh’s Flora Americae Septentrionalis, in 1814. It was first recorded as a problem weed in Quebec in the 1930’s.
Lythrum salicaria L. By 1942, a pasture that at one time supported 800 head of cattle was declared useless.
Lythrum salicaria L. Purple loosestrife adapts readily to natural and disturbed wetlands. As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife.
Lythrum salicaria L. The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species, including some federally endangered orchids, and reduce habitat for waterfowl.
Information Resources http://www.texasinvasives.org http://bc4weeds.tamu.edu/weeds/index.html http://www.tapms.org/ http://www.agr.state.tx.us http://www.tpwd.state.tx.us/http://www.tpwd.state.tx.us/