Potential environmental impacts and economic damages of Eurasian watermilfoil (Myriophyllum spicatum) in western Nevada and northeastern California

Eurasian watermilfoil, an aquatic invasive weed, has been identified recent ly at a number of sites in western Nevada and northeastern California, incl uding Lake Tahoe. Because Eurasian watermilfoil is easily spread by fragmen ts, transport on boats and boating equipment plays a key role in contaminat ing new water bodies. This is an important means of the potential spread of this weed throughout key recreational and agricultural areas surrounding L ake Tahoe. Unless the weed is controlled, significant alterations of aquati c ecosystems, with associated degradation of natural resources and economic damages to human uses of those resources, may occur. This research uses th e economic valuation approach known as benefits transfer to estimate the va lue of a portion of the recreational service flows that society currently e njoys in the Truckee River watershed below Lake Tahoe. The lower-bound esti mates of baseline water-based recreation value at a subset of sites in the watershed range from $30 to $45 million/yr. Impacts from the continued spre ad of Eurasian watermilfoil in the watershed could be significant; for exam ple, even a 1% decrease in recreation values would correspond to roughly $5 00,000/yr as a lower bound.