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 billion Limited data availability Some uses are not valuable, but rafting and kayaking are valuable For 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 billion Tamarisk stand trap sediments, which leads to a narrowing river channel, and narrowing of the flood plain Narrower channels means channel can hold less water, which means floods at lower volumes of water Plus the dense vegetation backs-up the water, spreading it out over a larger area Thus get more frequent and large floods Used Army Corps of Engineer’s conservative estimates of extra flood damage due to Tamarisk of $52 million per year times 55 years 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 billion Tamarisk traps sediments, and hence increases lifetime of reservoirs Dove hunting – Benefits of $0.02 billion Doves like Tamarisk thickets Increases 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 introduced 1950: root feeder introduced Total Cost: $750,000 By early 1960’s in California, insects had reduced Klamath weed acreage to <1% of peak acreage Annual benefits $3,500,000 per year in California Total Benefits (1965 – 2005): $140 million Benefit : Cost ratio = 187 : 1 (not adjusted for inflation)

Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: 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 pipes Non-use value: degradation of Lake Tahoe Study only focused on recreational uses Low & high economic values for 4 sites in Lake Tahoe – Truckee – Pyramid watershed If 100% infestation, lose $30-45 million per year If 5% infestation, lose >$1 million per year

South African fynbos Eucalypts, 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