I estimated the cost for those habitat modification techniques with the potential for extensive application, i.e., replacement of blue grass on shorelines and fencing. To assess costs relative to budget, the City of Plymouth, a rapidly growing suburb of 57,000 residents located 9 km west of Minneapolis was selected as a study case. Plymouth citizens have complained about goose damage at 19 individual wetlands or lakes, ranging in area from 5 to 432 ha. Aerial photos (Twin Cities Metropolitan Council, 1:9600 scale, flown in 1997) were used to determine the expanse of shoreline that would have to be replanted to non-turf, the length of fence needed to enclose the complaint site wetlands, and extent of goose nest habitat within the wetlands. Existing wooded shorelines were assumed to be sufficiently dense to deter geese, and omitted from the revegetation calculations but not the fencing computations. Cost estimates were attained from local landscaping firms and include materials and installation but not design costs. Two alternative vegetations were included in the costs estimates, tall grass prairie and ground juniper. Tall grass prairie was selected because it is the native plant community most often re-established in the Twin Cities. Except in special cases (see above) it is not known to be used for grazing. Ground juniper, if planted at a minimum spacing of 1 m, would provide near 100% ground cover, and yet, remain low (<1 m) enough to provide human visibility without pruning. Fence height was set at 0.75 m and chain-link material with a pipe top crossbar were specified. This height will thwart flightless goose movement yet permit most humans to step over safely. Contractors projected a 25-year fence longevity if placed in the upland and more frequent replacement if subjected to wave or ice damage, i.e., built below the high water level.
Plymouth goose complaint wetlands have 7 km2 of open grass within 50 m of the shore and a total of 177 km of shoreline. Cost estimate ranged from $0.54/m2 for prairie, $29/m2 for juniper, and $9.84/m for chain-link fencing; the total projected expenditures were $3.7 million, $203 million, and $1.4 million respectively. The 1997 City of Plymouth budget was $15 million with $10,000 allocated to goose management. Clearly, if Plymouth were to opt for the least expensive method, fencing, the city would have to spend 1/25th of total cost every year ($56,000/year) to erect new or replace old fences. Also, the impacts of massive erections of low fences on other species of urban wildlife is unknown and needs study before such a program is undertaken. Expanses of cattail (Typha spp.) ranging from 0.009 to 1.1 km2 were found in 74% of the 19 wetlands, thus, allowances for within-the-enclosure grazing would have to be done in order to avert gosling starvation.
If fencing were used to limit the Twin Cities' brood-rearing carrying capacity to 25,000 geese, 93% of 1,331 km of shoreline currently in mowed grass or pasture would have to be enclosed at a cost of $12.3 million. To replant this length of shoreline with prairie grass would cost $33.9 million and for ground juniper $1.8 billion. Using the population model for the Twin Cites (Cooper and Keefe 1997), 50% of the geese would have to be removed annually to attain population stability at 25,000. Goose removal costs are estimated at $10/bird relocated and $25/bird captured and processed for human consumption (Cooper and Keefe 1997), thus, expenditures from $125,000 to $312,500 per year would be necessary to control the population. Obviously, population management via direct removal is far less costly compared to the least expensive habitat modification.