4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Water loss to Tamarisk: – m 3 /ha/yr more than native vegetation

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Water loss to Tamarisk: – m 3 /ha/yr more than native vegetation (willow/poplar) -This amount comparable to TOTAL annual precip ( m 3 /ha/yr) throughout invaded region

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Water loss to Tamarisk: – m 3 /ha/yr more than native vegetation -This amount comparable to TOTAL annual precip ( m 3 /ha/yr) throughout invaded region -Increases water use in several ways: more transpiration, accesses deeper water, creates more areas of dense vegetation, and traps sediment creating banks that it then colonizes (further increasing vegetation along river)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Economic losses related to Consumptive use by municipalities

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Economic losses related to Consumptive use by municipalities Consumptive use for irrigation

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Economic losses related to Consumptive use by municipalities Consumptive use for irrigation Non-consumptive use for hydro power and recreation

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Economic losses related to Consumptive use by municipalities Consumptive use for irrigation Non-consumptive use for hydro power and recreation Additional cost of increased flooding and flood mitigation Impact on threatened species Benefits: reservoirs (reduced sedimentation) habitat for game birds

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – Examined costs in 2 major urban areas: Southern California (Los Angeles south to San Diego) & Central Arizona (Phoenix)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – Metropolitan Water District of S. California plans to line 2 canal systems to conserve water plus build a desalination plant for drainage water from agricultural fields (this would ‘replace’ losses to tamarisk)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – Metropolitan Water District of S. California plans to line 2 canal systems to conserve water plus build a desalination plant for drainage water from agricultural fields Amount of water involved

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – Metropolitan Water District of S. California plans to line 2 canal systems to conserve water plus build a desalination plant for drainage water from agricultural fields Amount of water involved Amount of $$ involved

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – Metropolitan Water District of S. California plans to line 2 canal systems to conserve water plus build a desalination plant for drainage water from agricultural fields Amount of water involved Amount of $$ involved Estimate of cost per a.f. per year = total$ / (a.f. * 55 years)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – total costs $1.2 – 3.2 billion over 55 years ($22-58 million per year)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – $1.2 – 3.2 billion over 55 years (2)Central Arizona – Metropolitan Water District buying farmland and fallowing it at ~$150 per a.f.

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – $1.2 – 3.2 billion over 55 years (2)Central Arizona – Metropolitan Water District buying farmland and fallowing it at ~$150 per a.f. Based on local Tamarix infestations & water use, costs $5-10 million per year

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California – $1.2 – 3.2 billion over 55 years (2)Central Arizona – Metropolitan Water District buying farmland and fallowing it at ~$150 per a.f. Based on local Tamarix infestations & water use, costs $5-10 million per year, or $ million over 55 years

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California –$1.12 – 3.20 billion over 55 years (2)Central Arizona –$0.27 – 0.53 billion over 55 years

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California –$1.12 – 3.20 billion over 55 years (2)Central Arizona –$0.27 – 0.53 billion over 55 years ___________________________ TOTAL$1.4 – 3.7 billion

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses (1)Southern California –$1.12 – 3.20 billion over 55 years (2)Central Arizona –$0.27 – 0.53 billion over 55 years ___________________________ TOTAL$1.4 – 3.7 billion + other metro areas

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses More difficult to estimate because: (1)what crops are planted vary around the area and through time

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses More difficult to estimate because: (1)what crops are planted vary around the area and through time (2)Some crops are cheap (e.g. grains) whereas others are more costly (e.g. melons)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses Low & high estimates of value of irrigation water based on lowest & highest reported values of crops in each region

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses Low & high estimates of irrigation water value Next, 2 estimates of total annual losses: (1)Low estimate based on low irrigation water value and low (1.0 a.f.) Tamarisk water use

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses Low & high estimates of irrigation water value Next, 2 estimates of total annual losses: (1)Low estimate: low irrigation water value and low water use (2)Mean estimate using a 80:20 of Low:High value of irrigation water and mean (1.5 a.f.) Tamarisk water use

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Low & high estimates of irrigation water value Next, 2 estimates of total annual losses: (1)Low estimate: low irrigation water value and low water use (2)Mean estimate using a 80:20 of Low:High value of irrigation water and mean (1.5 a.f.) Tamarisk water use

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power Used values from the literature on how much it would cost to replace the power generated by 4 dams along the Colorado River

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power Cost to replace hydropower along the Colorado River Next, estimated the amount of acreage in Tamarisk upstream from dam and the corresponding amount of water used by Tamarisk

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power Cost to replace hydropower along the Colorado River Amount of water used by Tamarisk upstream from dam Then calculated the economic value of lost hydroelectric power generation

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Cost to replace hydropower along the Colorado River Amount of water used by Tamarisk upstream from dam Economic value of lost hydroelectric power generation

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Cost to replace hydropower along the Colorado River Amount of water used by Tamarisk upstream from dam Economic value of lost hydroelectric power generation Only a part of the hydroelectric power generation in the area

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Recreation Again, limited in data availability

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Recreation Limited data availability Some uses (e.g. fishing) are not an issue until water becomes extremely limited (which is not likely to be due to just Tamarisk)

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Recreation Limited data availability Some uses (e.g. fishing) are not an issue until water becomes extremely limited (which is not likely to be due to just Tamarisk) Rafting and kayaking are more sensitive to flows, and studies are available that have determined the value that boaters are willing to pay for increased flows

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss Municipal uses – $1.4 – 3.7 billion Agricultural uses – $2.1 – 6.7 billion Hydroelectric power – $0.8 – 2.4 billion Recreation 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk stand trap sediments, which leads to a narrowing river channel, and narrowing of the flood plain CHANGES IN RIPARIAN VEGETATION IN THE SOUTHWESTERN UNITED STATES: Floods and Riparian Vegetation on the San Juan River, Southeastern Utah-- USGS

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk narrows river channel and flood plain Narrower channels means channel can hold less water, which means floods at lower volumes of water

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk narrows river channel and flood plain Narrower channels means more frequent floods Plus the dense vegetation backs-up the water, spreading it out over a larger area

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk narrows river channel and flood plain Narrower channels means more frequent floods Dense vegetation means larger floods Thus get more frequent and large floods

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk narrows river channel and flood plain 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Tamarisk narrows river channel and flood plain 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Estimated impact for 3 federally-listed endangered and 1 candidate threatened species

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Estimated impact Used a “Willingness To Pay” (WTP) method to estimate worth of wildlife habitat

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Estimated impact Used a “Willingness To Pay” (WTP) method to estimate worth For willow flycatcher, discounted worth by 50% to account for possibility that people perceive less value in small songbirds than in “charismatic” eagles, cranes, and bighorn sheep

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Estimated impact Used a “Willingness To Pay” (WTP) method to estimate worth Annual cost of $3.7 – 8.7 million

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss 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 Estimated impact Used a “Willingness To Pay” (WTP) method to estimate worth Annual cost of $3.7 – 8.7 million

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss and 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 Tamarisk traps sediments, and hence increases lifetime of resevoirs

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss and 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 – Benefits of $0.07 billion Tamarisk traps sediments, and hence increases lifetime of resevoirs

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #3 – Convert water loss into economic loss and 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 – Benefits of $0.07 billion Dove hunting Doves like Tamarisk thickets Increases value for hunting

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Economic losses and 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 – Benefits of $0.07 billion Dove hunting – Benefits of $0.02 billion Doves like Tamarisk thickets Increases value for hunting

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Add up the total cost 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

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Step #4 – What are the costs to eradicate Tamarisk? Used a 20-year, progressive eradication program

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together Economic losses

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together Economic losses, even when take out the “non-use” values

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together Economic losses, even when take out the “non-use” values, are greater then the costs to eradicate

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together Economic losses greater then the costs to eradicate Thus economically beneficial to eradicate

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together Economic losses greater then the costs to eradicate Thus economically beneficial to eradicate Benefits 2-3 times greater than costs

4)Impacts b)Economic Case study: Tamarix – Will economic benefits justify costs? Put it all together -- Benefits greater than costs even up to 6% discount rate

4)Impacts b)Economic Case study: Klamath weed (Hypericum perforatum) Broad-leaved, perennial herb Introduced to North America from Europe in 1793 Reached California in late 1800’s Jim USDA-NRCS PLANTS Database

4)Impacts b)Economic Case study: Klamath weed (Hypericum perforatum) Broad-leaved, perennial herb Introduced from Europe in 1793; reached California late 1800’s Extremely invasive Toxic to wildlife & livestock ©Norman E. Rees, USDA ARS, Photos: Ian Davidson From northwestweeds.nsw.gov.au

4)Impacts b)Economic 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 rangeland in western North America infested

4)Impacts b)Economic 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

4)Impacts b)Economic 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

4)Impacts b)Economic 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: $750,000 total cost By early 1960’s in California, insects had reduced Klamath weed acreage to <1% of peak acreage

4)Impacts b)Economic 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: $750,000 total cost 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

4)Impacts b)Economic 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: $750,000 total cost 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)

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Aquatic weed Submersed, rooted perennial whose stems branch near water surface and form dense mats. Grows in waters up to 6 m deep, depending on light penetration. Best suited for still waters (lakes, ponds), but does well in rivers and irrigation ditches fwcb.cfans.umn.edu

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Aquatic weed that forms dense, floating mats Native to Europe, Asia, & North Africa Introduced to Chesapeake Bay in 1880’s Today, in 45 of the 48 continental states Colette C. Jacono and M.M. Richerson USGS

4)Impacts b)Economic 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 Fragments float downstream, growing leaves and stems until it settles in and roots Fragments also adhere to boats & trailers, and thus are transported from lake to lake

4)Impacts b)Economic 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 Tahoe Keys Marina since 1960’s Virtually all marinas & shorelines areas around Lake Tahoe are now invaded In 1999, found near Verdi and at Stillwater

4)Impacts b)Economic 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

4)Impacts b)Economic 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

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Used economic values for activities that were developed in other studies and applied them to this case (rather then conduct new and expensive studies) But used local visitation records to calculate the total economic value

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Estimated low & high economic values

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Estimated low & high economic values for only 4 sites on the Tahoe-Truckee-Pyramid watershed

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Low & high economic values for 4 sites on watershed Baseline economic value of 4 areas = $30-45 million per year

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Low & high economic values for 4 sites on watershed Baseline economic value of 4 areas = $30-45 million per year If 100% infestation, lose $30-45 million per year

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Low & high economic values for 4 sites on watershed Baseline economic value of 4 areas = $30-45 million per year If 100% infestation, lose $30-45 million per year If 5% infestation, lose >$1 million per year

4)Impacts b)Economic Case study: Eurasian watermilfoil (Myriophyllum spicatum) From Eiswerth et al. (2000) Weed Technology 14: Economic impacts on recreational activities Used “Benefits Transfer Approach” Low & high economic values for 4 sites on watershed Baseline economic value of 4 areas = $30-45 million per year If 100% infestation, lose $30-45 million per year If 5% infestation, lose >$1 million per year Only part of watershed in economic analysis

4)Impacts b)Economic Other examples include: Fires due to invasive species Loss of property & resources Loss of human life Fire suppression & rehabilitation costs

4)Impacts b)Economic Other examples include: Fires due to invasive species Loss of ecosystem functions Wetland degradation (water purification) Habitat loss and consequences for TES protection & mitigation

4)Impacts b)Economic Other examples include: Fires due to invasive species Loss of ecosystem functions Agricultural losses Weeds in crops Weeds in pastures Weeds that have escaped from crops/pastures