228.22

Municipal uses – Examined costs in 2 major urban areas: Southern California (Los Angeles south to San Diego) & Central Arizona (Phoenix)

Recreation – $0.03 – 0.13 billionLimited data availabilitySome uses are not valuable, but rafting and kayaking are valuableFor Green River and Colorado River above Lake Mead, value of

lost water for boating estimated at $0.5 – 2.3 million per year

Underestimates total value because only considers part of system

Flood control – $2.9 billionTamarisk stand trap sediments, which leads to a narrowing river

channel, and narrowing of the flood plainNarrower channels means channel can hold less water, which

means floods at lower volumes of waterPlus the dense vegetation backs-up the water , spreading it out

over a larger areaThus get more frequent and large floodsUsed Army Corps of Engineer’s conservative estimates of extra

flood damage due to Tamarisk of $52 million per year times 55 years

1953

1998

CHANGES IN RIPARIAN VEGETATION IN THE SOUTHWESTERN UNITED STATES: Floods and Riparian Vegetation on the San Juan River, Southeastern Utah-- USGS

Sedimentation – Benefits of $0.07 billionTamarisk traps sediments, and hence increases lifetime of

reservoirs

Dove hunting – Benefits of $0.02 billionDoves like Tamarisk thicketsIncreases value for hunting

Add up the total losses & benefits• Municipal uses $1.4 – 3.7 billion• Agricultural uses $2.1 – 6.7 billion• Hydroelectric power $0.8 – 2.4 billion• Recreation $0.03 – 0.13 billion• Flood control $2.9 billion• Wildlife $0.09 – 0.37 billion• Sedimentation - $0.07 billion• Dove hunting - $0.02 billion

________________TOTAL $7.3 – 16.1 billion loss

Case study: Klamath weed (Hypericum perforatum)• Broad-leaved, perennial herb• Introduced from Europe in 1793; reached California

late 1800’s• Extremely invasive; toxic• By early 1940’s: 5 million acres of infested rangeland• Biological control in California

1945/1946: 2 leaf feeders introduced1950: root feeder introducedTotal Cost: $750,000

• By early 1960’s in California, insects had reduced Klamath weed acreage to <1% of peak acreage

• Annual benefits estimated @ $3,500,000 per year in CaliforniaTotal Benefits (1965 – 2005): $140 millionBenefit : Cost ratio = 187 : 1 (not adjusted for

inflation)

Case study: Eurasian watermilfoil (Myriophyllum spicatum)From Eiswerth et al. (2000) Weed Technology 14:511-518• Aquatic weed that forms dense, floating mats• Introduced to Chesapeake Bay in 1880’s; now widespread throughout US• Spreads primarily by plant fragments• Population reported at Lake Tahoe since 1960’s• Economic impacts include

↓ recreational activities (fishing, boating, swimming, etc.)Clog irrigation canals, gates, etc.↓hydroelectric generation by clogging intake pipesNon-use value: degradation of Lake Tahoe

Study only focused on recreational uses• Low & high economic values for 4 sites in

Lake Tahoe – Truckee – Pyramid watershedIf 100% infestation, lose $30-45 million per yearIf 5% infestation, lose >$1 million per year

South African fynbosEucalypts, pines, Acacias, and other species have invaded the

fynbos of South Africa’s Cape Province

Neotropical shrub Lantana camara is invading east Africa

Parthinium weed (Parthenium hysterophorus) in Pakistan and Australia