Overall Effect of Cost-Reduction Strategies on Total Management Costs and Cost per Hectare for 1 ha and 10 ha Management Units over 3 Yr and 30 Yr Periods in an Invasive Grass–Dominated Lowland Ecosystem on O'ahu, Hawai'i
Note: Present Value is calculated at a 2% annual discount rate.
a Baseline values calculated in Table 4 are shown in parentheses next to hectare sizes for both the 3 yr and 30 yr time periods.
b Based on interviews with experts, a number of variables were adapted to account for the longer time horizon (30 yr): clearing maintenance frequency (once every other year); and time period and frequency for herbicide application (Supplemental Table S2), clearing and fence maintenance (30 yr) [with the exception of cost-reduction strategy (5)]; replacement period for fencing (20 yr).
c Assumes a labor rate of $25/hr for one person to supervise 10 volunteers during planting, replanting, and watering; assumes planting activities would take 1.5 times longer (i.e., 13 plants/hr/person) when employing volunteer labor versus trained land managers, and watering would be completed at the same speed (132 liters/hr). Although survival can be reduced when employing volunteers, increased mortality beyond the baseline is not accounted for in replanting costs.
d Assumes plant costs are $1/plant, or half the cost assumed under the baseline ($2/plant). See Supplemental Table S8 for propagation labor/equipment cost breakdown per plant.
e Assumes planting speed is 40 plants/hr/person, or twice as fast as the baseline (20 plants/hr/person) through use of improved and more-costly equipment (e.g., $135/Hatfield Transplanter, or equivalent).
f Installation (i.e., labor and materials) of an irrigation system (i.e., getting water infrastructure to the site) at a flat rate of $25,000 and $2,000 ha−1 for installation of a drip system at the site, eliminating labor and equipment for hand watering. Cost of water (municipal) still applies.
g NA, not applicable, goes beyond the 3 yr time frame.
h Assumes maintenance herbicide application and clearing are discontinued after 5 and 10 yr.