Lecture 9
Overexploitation and Invasive Species
In Georgia, the legend says That you must close your windows At night to keep it out of the house. The glass is tinged with green, even so...
From the poem, "Kudzu," by James Dickey
Valuing Nature and the Early History of the Environmental Movement
I. Overexploitation II. Invasive Species A. Terminology B. Characteristics of Invasive Species C. The Invasion Process D. Examples D. Legislation
1 Overexploitation
The human harvesting of wild plants and animals at rates exceeding the a bility o f the popu la tions o f those spec ies to regenerate.
Overexploitation
2 Overexploitation
Reppported U.S. imports of wildlife py(995)per year (1995)
Overexploitation
Convention in International Trade In Endanggpered Species (1973 ) CITIES • Species threatened with extinction -Trade in specimens of these species is permitted only in exceptional circumstances. • Species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival. • Species that are protected in at least one country, which has asked other CITES Parties for assistance in controlling the trade
3 Overexploitation
Problems with controlling overexploitation: • Oversimplified theory ¾Maximum Sustainable Yield ¾Competition ¾Natural variability and oscillations in populations that mask the effect of overexploitation • Economics • Enforcement Problems
Invasive Species
Native • An indigenous species that occurs wild in a given region Alien • A species that has been introduced to a part of the world to which it is not native • Also referred to as non-native, exotic or simply introduced species Invasive • An alien species that disrupts ecological processes in natural plant and animal communities. Naturalized Species • An alien species that has “naturalized” into the natural plant and animal communities.
4 Invasive Species
Characteristics:
•grow qqikluickly • reproduce abundantly and quickly • have broad habitats • generalist predators (if animals) or pioneer plants (Africanized honey bee) • strong competitors • hig h phenotyp ic plast ic ity
Invasive Species
Pattern of Colonization
Arrival Establishment Population Growth
Integration Spread
Dominance/ Displacement
Disturbance
5 Invasive Species
• Disrupt ecological processes in natural plant & animal communities. • Displace native species leading to their extinction • US: alien species have caused or contributed to the decline of 49% of all species on the threatened or endangered species lists. • Adverse effects on human health • Serious economic & social impacts through reduction of yields in agriculture & fisheries
Invasive Species
Brown tree snake (Boiga irregularis) on Guam
• Extinctions and loss of sppyecies diversity from Guam • Safety and health of Pacific Island residents and tourists • Economic damages from the Brown Treesnake • Impacts on military from the Brown Treesnake
6 Invasive Species
Red Fire Ant (Solenopsis invicta)
http://www.invasivespecies.gov/profiles/bts.shtml
Invasive Species
Yellow Star Thistle (Centaurea stoltiliatis) • Infests 10-15 million acres in California alone (in 56 of the 58 counties), and is still spreading. • Damage from YST in the U.S. is estimated to be many millions of dollars. • Dominates native plants reducing biodiversity and causes rare plant species to go extinct • Significantly depletes soil moisture reserves in grasslands. • Interferes with grazing, lowers yield and forage quality of rangelands, thus increasing the cost of managing livestock.
7 Invasive Species
Legislation : http://www.invasivespeciesinfo.gov/laws/main.shtml
Control : http://www.invasivespeciesinfo.gov/toolkit/control.shtml
8