تجزیه و تحلیل اقتصادی حذف روش های شکار کننده برای حفاظت از لانه لاک پشت دریایی در پناهگاه ملی حیات وحش ساند هوب i

Hobe Sound National Wildlife Refuge (HSNWR) on Florida's east coast provides undisturbed nesting habitat for three species of threatened or endangered marine turtles. Predation by raccoons and armadillos poses the greatest risk to turtle nests, and predator control has been identified as the most important management tool for enhancing nesting productivity. Recently, estimates of the number of nests that would have been lost in the 2000 nesting and incubation season were made using the results from four control approaches. These approaches were, in order of descending complexity: (1) refuge control enhanced by a one person-month contract with federal control specialists, with that control optimized using a passive tracking methodology for monitoring predators; (2) refuge control enhanced by a one person-month contract with federal control specialists, without predator monitoring; (3) refuge control, but no contract with specialists; (4) no control. In that analysis, approach 1 resulted in the fewest turtles lost to predation. In this paper, we perform a benefit–cost analysis to determine if operational efficacy translates into economic efficiency. Approach 1 had by far the best benefit–cost ratio for loggerhead turtles, but approach 2 was best for Atlantic green and leatherback turtles. However, almost 90% of the turtles nesting at HSNWR are loggerhead, and this area is vital to loggerhead survival. Thus, approach 1 also had by far the best benefit–cost ratio over all turtle species, saving approximately $1.7 million over approach 2, $2.6 million over approach 3 and $8.4 million over approach 4. Given these results, one must ask how can we afford not to control predators, and furthermore, how can we not afford to take the minimal extra steps to maximize control efficacy.

The fundamental focus of the Hobe Sound National Wildlife Refuge (HSNWR) on the east coast of Florida is to offer undeveloped and protected beach habitat for nesting by loggerhead (Caretta caretta), leatherback (Dermochelys coricea), and green (Chelonia mydas) marine turtles ( U.S. Fish and Wildlife Service, 1996), each of which is threatened or endangered ( U.S. Fish and Wildlife Service, 1994). Prior to controlling raccoons (Procyon lotor) on the refuge, as many as 95% of turtle nests were destroyed annually ( Bain et al., 1997). Beginning in 1988, armadillos (Dasypusnovemcinctus) became noticeable as another primary predator of turtle nests at HSNWR ( Drennen et al., 1989). Their level of predation has since risen to a similar level as that from raccoons ( Bain et al., 1997). Predator removal has been carried out by refuge personnel since 1972 and has been identified as the most important management approach at the refuge ( Bain et al., 1997). The refuge in recent years has sought to improve efficacy of predator control by contracting with specialists to provide additional control of turtle nest predators. Beginning in 1999, the refuge has contracted with USDA Wildlife Services to carry out approximately one person-month of control. In 2000, the efficiency of this one person-month control budget was improved by using a passive tracking index to: (1) optimize the timing and strategy for application of control; (2) minimize labor by identifying areas where control would have maximal effect; (3) examine beach invasion patterns of predators; (4) assess control efficacy; (5) provide anticipatory information for future turtle nesting seasons; and (6) serve as a detection method for invasion by additional species known to depredate turtle nests (Engeman et al., 2001, in review). In a recent evaluation of control strategies at the refuge, this approach of concomitant predator monitoring in support of a contract with control specialists produced the highest efficacy in terms of reduced predation rates and estimated numbers of hatchlings produced (Engeman et al., 2001, accepted). However, operational efficacy does not guarantee economic efficiency. Therefore, we carried out an economic analysis of four control approaches that have been applied at the refuge.

The results of this economic decision analysis demonstrate that, from HSNWR's perspective, a control contract and monitoring approach (approach 1) is a more cost-beneficial predation management technique with the potential to save HSNWR an average of almost $1.3 million annually in comparison to other approaches. Benefits would most likely continue to accrue for each year thereafter; however, the model used does not predict benefits beyond the short-term horizon. From an ecological standpoint, HSNWR is located in one of most important marine turtle nesting areas in Florida (Meylan et al., 1995). The southeastern U.S. nesting concentration of loggerhead turtles is the second largest in the world. From a global perspective, this nesting aggregation is crucial to survival of loggerhead turtles because the world's largest concentration is in a Middle-Eastern region vulnerable to war, political upheaval and turmoil, and severe oil spills (Meylan et al., 1995). While the Atlantic green and leatherback turtles comprise only small proportions of the nesting concentrations at HSNWR, their populations are considered at greater risk (endangered) than the loggerhead's, and production at even small nesting sites is important. Therefore, minimization of the single greatest annual threat to the turtle nests, predation, is of great importance to the conservation of these species. Given the benefit-cost performance of any of the control efforts over no control, we have to ask ourselves how can we not afford to protect the turtle nests from predators. Moreover, given the benefit-cost performance of the monitoring plus control contract with specialists approach relative to the other tested control approaches, we must ask how can we not afford to take the minimal extra steps to maximize the beneficial impact from control.