Knapp, J.J.; P.T. Schuyler, K.N. Walker, N.L. Macdonald,Island and invasives: S.A. Morrison. Benefieradication ts of supporting andinvasive management plant and animal eradication projects with helicopters
Benefits of supporting invasive plant and animal eradication projects with helicopters
J. J. Knapp 1, P. T. Schuyler 2, K. N. Walker 1, N. L. Macdonald 1, and S. A. Morrison 3 1Native Range, Inc., 1746-FS. Victoria Avenue, #378, Ventura, California, 93003, USA.
INTRODUCTION Invasive alien species pose a signifi cant and increasing relatively few visitors. Santa Cruz is within the Channel threat to native biota and unique ecosystems of islands Islands National Park (CINP) which owns 24% of the worldwide. Because conservation funding is limited, an island; the remaining 76% is owned and managed by The imperative for managers is to ensure that threats posed by Nature Conservancy (TNC), a non-profi t conservation invasive species are resolved as effi ciently and effectively organisation. Other than a few management staff, there are as possible. Eradication of pest taxa often can be a cost- no permanent residents on Santa Cruz, although the public effective strategy relative to alternatives such as perpetual does have limited hiking and camping opportunities. control. But eradications require managers to meet a number Below, we highlight the similarities and differences of criteria. They must be able to: 1) detect all individuals, between the pest eradication programmes on the two 2) remove all individuals, 3) outpace reproduction, and islands. We do so in the context of the aforementioned 4) commit adequate resources to ensure completion four eradication criteria, and discuss how the systematic (Bomford and O’Brian 1995). If these criteria cannot be use of a small helicopter can help managers meet those met, a project risks failure. Fortunately, managers today criteria. In contrasting the two projects it is important to can review decades of eradication projects. By analysing note the relationship between the two islands. Channel numerous taxa in a variety of island conditions, it is possible Islands land managers regularly share lessons learned from to identify methods that might reduce the risks inherent conservation activities on other islands. The Santa Cruz in eradication efforts, and complete the eradication with feral pig and IAP programmes were thus able to benefi t greatest effi ciency. from the prior experience of the Catalina programmes. The In this paper, we compare and contrast the cost and risks Catalina programmes were infl uenced by invasive species of using aerial-based eradication methods versus more management programmes on other Channel Islands, such traditional, ground-based methods. We do so by examining as feral sheep ( Ovis aries ) and feral goat ( Capra hircus ) eradication efforts focused on the invasive feral pig ( Sus eradications on Santa Cruz and San Clemente islands, scrofa ) and a suite of invasive alien plant (IAP) species on respectively. two of the eight Channel Islands off the coast of southern California, USA (Fig. 1). Santa Cruz Island (Santa Cruz), at 249 km 2 is the largest of the Channel Islands; Santa Catalina Island (Catalina), at 194 km 2, is third largest. Both islands have a Mediterranean-type climate, support similar vegetation communities, and exhibit generally similar topographical relief, although Santa Cruz is more diverse due to its larger size and higher elevation (Schoenherr et al . 1999). Since the 1800s, each island has experienced a history of intensive livestock grazing that has signifi cantly altered the native ecosystems. Neither island has any native ungulates (Schoenherr et al . 1999). Although both islands share many of the same native and alien taxa, there are important differences. Since 1972, the Catalina Island Conservancy (CIC), a non-profi t conservation organisation, has managed 88% of Catalina Island. The remaining 12% is owned by a variety of private land owners. Catalina is the only Channel Island that has an incorporated city (Avalon), with a resident population of approximately 4000 that swells to over 15,000 in the summer months. This has undoubtedly represented a signifi cant challenge to conducting eradications. In addition, the island receives nearly 1.2 million visitors annually (Ann Muscat, CIC President pers. comm.). In Fig. 1 Santa Catalina and Santa Cruz Islands in the contrast, all of Santa Cruz is protected, and the island has Southern California Bight.
Pages 188-191 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011. Island invasives: eradication and management. IUCN,188 Gland, Switzerland. Knapp et al .: Benefits of aerial methods in eradication
Table 1 Comparison of feral pig eradication programmes. Data from Macdonald and Walker (2008), Morrison (2007), and Schuyler et al. (2002). Island area Hunting duration Animals Contractor Expense Project Island (hectares) (years) dispatched (U.S. dollars)* Completed Catalina 19,400 10.0 11,855 $3.2 million No Santa Cruz 24,000 1.1 5036 $3.9 million Yes *See Morrison 2007 for calculations. Fencing costs not included. Adjusted for inflation to 2005 value.
FERAL PIG PROGRAMMES of educating pigs to removal methods. This in turn reduced the rate of population replacement and the total number of The attempted eradication of feral pig populations pigs ultimately dispatched (Table 1). A light piston engine on Catalina Island evolved from a control programme three-person, helicopter (Schweizer 300C) was used to that began in 1990 (Schuyler et al . 2002a). Financial support the full array of activities throughout the project: constraints, and uncertainty of some CIC board members from aerial shooting to deploying bait and checking traps, that eradication was achievable, helped to establish control from transporting hunters and dogs to tracking Judas pigs rather than eradication as the initial goal (Schuyler et al . and monitoring (Macdonald and Walker 2008). 2002a). Methods and strategies were refi ned and adapted as the control programme was underway. Throughout the effort, ground hunting with and without dogs, spotlighting, INVASIVE ALIEN PLANT ERADICATION and trapping were used; helicopters were occasionally used PROGRAMMES to deploy equipment. A helicopter was used as a platform In 2003, following the near eradication of feral pigs for an aerial shooter only occasionally in the early phases of from Catalina, a ground-based island-wide survey for 72 the project and was later abandoned due to public pressure invasive alien plant (IAP) species was commissioned by (Schuyler et al . 2002a). In 1998 the objective was changed the CIC. The survey revealed that several species were to eradication, in part because it had become increasingly ideal candidates for eradication based on their limited apparent that sustained control would not accomplish the abundance and distribution (Knapp in press). In 2004, the desired conservation goal (Schuyler et al . 2002a). Fencing CIC developed a programme to eliminate 25 species of was then erected to subdivide the island and create hunting IAPs from either the CIC property or throughout the island zones. Throughout the programme, if hunters encountered while the infestations were relatively manageable (Knapp multiple pigs they would attempt to dispatch them, even if in press). Similarly, in 2007, following the successful some were likely to escape (Kevin Ryan and Mark Szydlo, completion of the Santa Cruz feral pig eradication Catalina hunters pers. comm.). As is discussed below, this programme, TNC conducted an island-wide IAP survey approach was not used on Santa Cruz. for 55 species of IAPs (McKnight et al . 2007) and selected In contrast to Catalina, on Santa Cruz Island, eradication 18 species for eradication following the same criteria used of pigs was the goal of TNC and CINP from the outset on Catalina (Knapp et al . 2007). The IAP survey on Santa (Morrison 2007). Prior to the beginning of the eradication Cruz was conducted 95% via helicopter and 5% on foot, effort, fenced zones were established across the island. The and covered the entire island (Knapp et al . 2009); this is in project was planned and implemented to ensure that the pig contrast to Catalina, which was surveyed on foot and only populations would remain naive to removal methods as the covered a portion of the island. More infestations were eradication progressed (Morrison et al . 2007). Trapping mapped on Catalina than Santa Cruz (Table 2). However was employed fi rst, followed by aerial hunting, and only the species targeted on Santa Cruz had limited distributions, then would Judas pigs and teams of ground hunters with whereas on Catalina some widely established species were dogs mobilise. By reducing the pig population, the number also surveyed (Knapp 2004; Knapp et al . 2009). of pigs encountered by ground hunters was reduced and On both islands, surveyors collected the same data on that increased the likelihood of successful dispatch due to population attributes and delineated infestations in a similar dogs being able to focus on one or two pigs versus many way (Knapp 2004; Knapp et al . 2009). Both programmes (Macdonald and Walker 2008). utilised a similar prioritisation scheme to rank species for An essential ethic of the hunters on Santa Cruz, whether management action (Knapp 2004; Knapp et al . 2007), and based on the ground or in the air, was to only attempt to both programmes had a common objective for treatment: dispatch a pig if: 1) there was very high likelihood of a control each species to zero density (no above-ground successful shot, 2) it would be similarly possible to dispatch plants remaining), until the soil seed banks are exhausted any other pigs in the vicinity, and 3) it was safe for hunters (Knapp et al . 2007; Knapp in press). Currently, both to do so (Morrison et al . 2007; Macdonald and Walker programmes are monitoring seed banks for germination. 2008). The skill and discipline required to adhere to this Both control programmes utilised the same herbicides and ethic had the additional benefi t of reducing the likelihood used similar application rates and methods (Knapp et al . of injury and escape, which increased the humaneness 2007; Knapp in press). of the programme (Cowan and Warburton 2011). It was The two efforts differed signifi cantly in: 1) how the also instrumental in reducing the duration of the project surveys were conducted, and 2) how populations were through decreased access time, and overcame the chances accessed for treatment. Catalina’s ground-based survey
Table 2 Comparison of invasive alien plant detection projects. Data from Knapp et al . (2009) and Knapp et al . in press). Duration Populations Transects Expense Island (months) Mapped Surveyed (km) Species (U.S. dollars) Catalina 12 32,708 966 72 $35,000* Santa Cruz 3 5020 4023 55 $161,000 *Survey conducted by a Master’s student (Knapp in press).
189 Island invasives: eradication and management was conducted primarily by a single graduate student with reproduction of the target population. Ground-based access limited aid from volunteers surveying roads, coastline, major and detection methods can be restricted by road conditions, drainages and ridgelines, and scanning the corresponding moving populations, and other limitations (Table 2). slopes for infestations (Knapp 2004). The survey on Santa Cruz primarily used a Schweizer 300C helicopter fl ying 4 Ability to commit to completion within metres of the ground or vegetation; ground survey Land managers often struggle to maintain the resources teams were used only to scan for infestations along roads for a consistent level of staffi ng, equipment, and funding. and highly disturbed sites or sites heavily infested by Eradication projects can also be delayed due to political multiple IAP species (Knapp et al . 2009). Since the entire and social pressure (Temple 1990), which can jeopardise island was surveyed, the Santa Cruz mapping project more progress made towards completing the eradication closely resembles a census rather than a survey. (Morrison et al . 2011). For example, animal rights activists Although both IAP control programmes used similar attempted to halt the feral pig eradication on Santa Cruz treatment protocols on the infestations, they varied Island through multiple legal actions, and forced the CIC to signifi cantly in how the infestations were accessed. All adopt more costly removal methods during the last months Catalina infestations were accessed on foot by two-person of the goat eradication programme (Schuyler et al . 2002b). teams. Many infestations took less than an hour to treat, but Rapid completion of the project reduced the exposure of took nearly the whole day to get to (Knapp, unpublished the project to such potential disruption, and so was an data). In contrast, on Santa Cruz, applicators were deployed important means of reducing the risk of failure. individually by either a Schweizer 300C or 333 turbine Indirect Expenses of a Longer Project engine helicopter to their respective infestations, treating 12 populations on average per day. By eliminating the The costs of ineffi ciencies in eradication programmes fatigue associated with accessing infestations or carrying are many and varied: 1) the physical and emotional well- heavy equipment, applicators had more time and energy being of personnel; 2) impacts to habitat due to “bush to scout the surrounding infestation for outlier plants on whacking” (including dispersal of invasive taxa, soil foot once on the ground, and continued to survey from the disturbance, vegetation damage, and wildlife disturbance); helicopter for additional infestations while en route. 3) prolonged input of pesticides into the environment; 4) indirect monetary costs associated with managing and DISCUSSION housing contractors; 5) expended political capital with regulatory agencies, funders, local community members Eradication Criteria and supporters stemming from disagreement with the Each of the following four eradication criteria (Bomford projects objective, lawsuits, and negative press; and 6) and O’Brian 1995) is dependent on the other three, and the opportunity costs of sustaining focus on one project at inability to meet any one will adversely affect the overall the expense of other priorities. These expenses are rarely effort. (if ever) tracked, but are considerable and can have long- lasting repercussions. 1 Ability to detect all individuals Personnel that see progress being made, and are not Populations at very low abundance can be exceedingly fatigued, have a better chance of detecting and responding diffi cult to detect. Flown at low altitude, helicopters can to an eradication target, and bringing an eradication cover large areas quickly while providing surveyors with programme to completion. In contrast, the health, stamina, an exceptional platform from which to detect eradication and morale of project personnel can suffer as a project wears targets (McCormick 1999; Welch et al . 1999). Many on – with risk of injury increasing in a negative feedback vegetation and topographical features can be scanned cycle. Retention of personnel becomes much more diffi cult with ease from a helicopter. Surveying the same features when eradication objectives are not reached quickly. The from the ground can often be labour intensive, hazardous emotional toll of an eradication attempt can be tremendous. (sometimes impossible), and cost-prohibitive. For example, a Catalina pig hunter expressed how he felt 2 Ability to remove all individuals traumatised by four years of dispatching animals with no end in sight (Anonymous pers. comm.). The speed and manoeuvrability of the helicopter increases the ability of the hunter to dispatch groups of The CIC lost several of its local volunteers who animals while ensuring that there is a high probability disagreed with pig eradication; some became vocal that no individuals will escape to become educated to opponents of the project in the local community. Even eradication methods (Morrison et al . 2007). Hunters on CIC personnel not involved with the pig eradication were Santa Cruz avoided attempting to dispatch pigs if they regularly accosted outside of the workplace by members were not confi dent that they could dispatch all the animals of the local community. A divide developed within the in the group. Keeping the remaining feral pig population organisation between staff that supported the project and naive to hunters and helicopters was the key factor of the those that did not, and this disagreement overshadowed success of the Santa Cruz pig eradication (Macdonald and daily operations. A shorter programme may not have Walker 2008) and may be the main factor why Catalina is swayed opposition against the eradication, but a protracted still not free of pigs (Morrison 2007) (Table 1). programme kept it at the forefront. Incipient IAP infestations are relatively small and quick Helicopter Use to remove, but access time can be considerable (Table 2). It may seem obvious that the use of a helicopter to For example, a single Cortaderia selloana (pampas grass) eradicate invasive taxa will help meet eradication criteria plant can be treated with herbicide in approximately fi ve and speed up eradication projects. Helicopters are not a minutes; but remote infestations may take hours to access new tool to conservation (McCormick 1999; Schuyler et on foot. In addition to reducing access time, the helicopter al . 2002a). Why, then, would managers opt not to utilise provides a vantage for another rapid survey of the area helicopters in their projects? Helicopters are not free from surrounding the infestation. stereotypes, including that they are dangerous and costly. 3 Ability to outpace reproduction Regardless of whether the result was the same, a helicopter The mobility and speed of a helicopter reduces access accident would likely be more spectacular than an accident time, which enables the eradication team to outpace the on foot or by an automobile, and for this reason helicopters
190 Knapp et al .: Benefits of aerial methods in eradication
Table 3 Comparison of invasive alien plant eradication programmes. Data from Knapp (2009) and Knapp (in press). Injuries treated in Populations Area treated Treatment Expense Island hospital* targeted (hectares) months Species (U.S. $) Catalina 7 404 11 24 25 $1,000,063 Santa Cruz 0 421 7 7 18 $520,000 * Knapp, unpublished records. may seem more dangerous. This is not to suggest that Knapp, J. J.; Cory, C.; Chaney, S.; Wolstenholme, R. and Cohen, B. 2007. danger is not associated with helicopter fl ying at low Santa Cruz Island weed management strategy. Unpublished report prepared for The Nature Conservancy, Santa Cruz Island Preserve and altitude in rugged terrain, but risks associated with ground- Channel Islands National Park, Ventura, California. 146 pp. based activities are often overlooked. And although land Knapp, J. J. 2009. Native Range, Incorporated, weed treatment fi nal managers may be at fi rst daunted by a helicopter’s hourly project report, 2008 and 2009. Unpublished report prepared for The rate, considerable saving can accrue by the reduction in Nature Conservancy’s Santa Cruz Island Preserve, California, Ventura, access time afforded by helicopter use (Table 3). California. 76 pp. Aerial shooting of vertebrates can also be perceived as Knapp, J.J.; Cory, C.; Walker, K. and Wolstenholme, R. 2009. Santa inhumane. Yet, due to the speed and manoeuvrability of a Cruz Island invasive plant species map. In: C. C. Damiani and D. K. helicopter it is arguably more humane for an expert aerial Garcelon (eds.). Proceedings of the 7 th California Islands Symposium, shooter to dispatch an animal than it is from the ground. pp. 245-252. Oxnard, California. Like all tools, there are various helicopter models that Knapp, J. In press. Catalina Island’s invasive plant management program, are more suitable to this task than others. The Schweizer with an emphasis on invasion and protection of oak ecosystems. In: D.A. Knapp (ed.). Oak ecosystem restoration on Catalina Island, California . 300C and 333 helicopters, fl own on Santa Cruz, each have Catalina Island Conservancy, Avalon, CA. attributes which made them ideal choices for the work Macdonald, N. and Walker, K. 2008. A new approach for ungulate described here. The biggest advantage of these machines eradication: A case study for success . Internal Report prepared by was their reliability and cost-effectiveness to operate, Prohunt, Inc. Ventura, California. 60 pp. which enabled them to be fl own when they were needed McCormick, C.M. 1999. Mapping exotic vegetation in the Everglades (Macdonald and Walker 2008). from large-scale aerial photography. Photogrammetric Engineering and A tool is only as effective as its user. Pilots operating a Remote Sensing 65(2): 179-184. helicopter must be experienced and able to safely deploy McKnight, S.; Walker, K. and MacDonald, N. 2007. Final invasive weed eradication personnel and their equipment in rugged terrain, survey report to the Nature Conservancy’s Santa Cruz Island Preserve . often under high wind or other adverse weather conditions. Unpublished report prepared for The Nature Conservancy, Ventura, A pilot working on an eradication project must also be able California. 22 pp. to detect the target of the eradication effort. In the case of Morrison, S.A. 2007. Reducing risk and enhancing effi ciency in non- supporting projects focused on large vertebrates, the pilot native vertebrate removal efforts on islands: A 25 year multi-taxa ideally is also a skilled hunter, with an understanding not retrospective from Santa Cruz Island, California. In: Witmer, G.W.; Pitt, W.C. and Fagerstone, K.A. (eds.). Managing Vertebrate Invasive only of the behaviour of the target but also the requirements Species: Proceedings of an International Symposium , pp. 398-407. of the shooter, so as to be able to position the helicopter USDA/APHIS/WS, National Wildlife Research Center, Fort Collins, optimally. CO. Morrison, S.A.; Faulkner, K.R.; Vermeer, L.A.; Lozier, L. and Shaw, M.R. CONCLUSION 2011. The essential non-science of eradication: Creating conditions for success. In: Veitch, C.R.; Clout, M.N. and Towns, D.R. (eds.). Island By planning helicopter support as an integral component invasives: eradication and management , pp. 461-466. IUCN, Gland, of an eradication strategy, land managers can increase the Switzerland. likelihood of the project success. The right helicopter Morrison, S.A.; Macdonald, N.; Walker, K.; Lozier, L. and Shaw, M. R. piloted by an experienced pilot can be a safe, humane, 2007. Facing the dilemma at eradication’s end: Uncertainty of absence and cost-effective means to eradicate myriad pest taxa. and the Lazarus effect. Frontiers in Ecology and the Environment 5: Regardless of the eradication task, enhancing detection and 271-276. reducing access time is vital to achieve an eradication goal, Schoenherr, A.A.; Feldmeth, C.R. and Emerson, M.J. 1999. Natural thus freeing land managers to direct limited funds to other history of the islands of California. University of California Press, conservation priorities. Berkeley, California. 491 pp. Schuyler, P. T.; Garcelon, D. K. and Escover, S. 2002a. Eradication of feral pigs ( Sus scrofa ) on Santa Catalina Island, California, USA. In: ACKNOWLEDGEMENTS C.R. Veitch and M.N. Clout (eds.). Turning the tide: the eradication of invasive species , pp. 274-286. IUCN SSC Invasive Species Specialist We thank Darcee Guttilla and Denise Knapp for Group. IUCN, Gland, Switzerland and Cambridge, UK. improving this manuscript through their review. We also thank the Catalina Island Conservancy, Channel Islands Schuyler, P. T.; Garcelon, D. and Escover, S. 2002b. Control of feral goats ( Capra hircus ) on Santa Catalina Island, California, USA. In: National Park, and The Nature Conservancy for the C.R. Veitch and M.N. Clout (eds.). Turning the tide: the eradication of investment in these conservation management actions. invasive species, pp. 412 – 413. IUCN SSC Invasive Species Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. REFERENCES Temple. S. A. 1990. The nasty necessity: Eradicating exotics. Conservation Biology 4(2) : 113-115. Bomford, M. and O’Brian, P. 1995. Eradication or control for vertebrate pests? Wildlife Society Bulletin 23 : 249-255. Welch, R.; Madden, M. and Doren, R. 1999. Mapping the Everglades. Photogrammetric Engineering and Remote Sensing 65(2) : 163-170. Cowan, P. and Warburton, B. 2011. Ethical issues in island pest eradication. In: Veitch, C.R.; Clout, M.N. and Towns, D.R. (eds.). Island invasives: eradication and management , pp. 418-421. IUCN, Gland, Switzerland. Knapp, J.J. 2004. Invasive plant ranking plan for the Catalina Island Conservancy. Unpublished report prepared for the Catalina Island Conservancy, Avalon, California. 150 pp.
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