Recreational scuba-diving and carrying capacity in marine protected areas

ELSEVIER

Ocean & Coastal Management, Vol. 26, No. 1, pp. 19-40, 1995 Copyright C) 1995 Elsevier Science Ltd Printed in Northern Ireland. All rights reserved 0964-5691/95 $9.50 + 0.00 0964-$691(95)00004-6

Recreational scuba-diving and carrying capacity in marine protected areas Derrin Davis a & Clem Tisdell b °Centre for Coastal Management, Southern Cross University, Lismore 2480, Australia bDepartment of Economics, The University of Queensland, Brisbane 4072, Australia (Received 29 July 1994; revised 3 January 1995; accepted 30 January 1995)

ABSTRACT Marine protected areas (MPAs) are declared principally to protect biological and environmental values in areas where such values are special. The declaration o f MPAs is well accepted and widely used in a number of countries. Many recreation pursuits rely heavily upon marine resources, and marine-based tourism is growing at a significant rate. Scuba-diving is one recreational pursuit which is experiencing greater participation rates. Consequently, conflicts between recreation and conservation may occur in multi-use MPAs, with scuba-divers impacting the natural environment on which the sport relies. Heavy usage by scuba divers also reduces amenity values in MPAs. The evidence is that critical social and biological thresholds exist. Above these thresholds amenity values are reduced severely, while biological impacts may also become significant. The interrelationships between amenity and biological values are worthy o f further research to identify biological and social carrying capacities in MPAs and, subsequently, to formulate suitable management responses to reduced MPA values.

INTRODUCTION Recreational scuba-diving is a rapidly-growing component of the international tourism industry, and is a particularly popular activity in countries such as Australia, the US and, increasingly, Japan. It is, consequently, an activity which is making increasing demands on marine resources. Continued growth in this component of the tourism industry may conflict with the ecological values which form the basis of 19

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marine protected area (MPA) status, may lead to accelerated environmental degradation in marine areas, and is likely to reduce amenity values in those areas. The importance of MPAs and the impact of activities such as scuba-diving on MPAs is reviewed below, along with consideration of the economic values of those areas. A review of the limited evidence available suggests that it is amenity values rather than biological values which may be most heavily impacted by excessive use of MPAs by recreational users such as scuba-divers. Amenity values are those values which arise from the recreational opportunities provided in MPAs, and relate to the satisfaction gained by recreational users of various MPAs. 1 Biological values are often described in terms of the maintenance of ecological functions and biological diversity--if indeed the two are separable--and usually relate to the maintenance of essential ecological processes and life-support systems. 2-4 The conservation of representative habitats and the habitats of rare and vulnerable species are also considered to give rise to important, specific biological values in MPAs. 3--6 However, further research is needed into aspects such as the ecological damage caused by such users as divers, and into concepts of carrying capacity and thresholds. Additionally, research is needed into the economic aspects of the scuba-diving industry in countries such as Australia, particularly into those factors influencing demand for dive sites. The ultimate aim of such research activities will be to develop appropriate management strategies for the dive industry in marine protected areas. W H Y H A V E MARINE PROTECTED AREAS? WHAT IS THEIR SIGNIFICANCE FOR SCUBA DIVING? The case for establishing marine parks and reserves rests on three main bases, according to Ivanovici.7 First, the concept of these parks and reserves is seen as a logical development from the terrestrial park movement. The concept has, at least partly, sprung from an awareness of 'the beauty and scientific interest of the world of nature beneath the sea, coupled with the increasing evidence of the vulnerability of this world to damage and alteration by man' (Ref. 7, p. 427; emphasis added). Second, the fact that there is a high and increasing level of interest in water-based recreation adds to the relevance of MPAs. Increasing use of marine areas, such as the Great Barrier Reef in Australia, near-shore areas in the Caribbean and Florida and, increasingly, in Pacific island nations such as the Republic of Palau by

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international tourists, strengthens this rationale. Third, there is great biological diversity in certain marine and estuarine waters, particularly in tropical and sub-tropical zones, which has attracted scientific interest and means they are an important resource for activities such as commercial fishing. This is particularly true of near-shore areas such as wetlands and mangroves, as well as in coral reef areas which are typified by high species diversity. Conversely, deep off-shore pelagic waters typically feature relatively low biological diversity. Additionally, welfare economics and market failure arguments support government establishment of MPAs3 The potential environmental impacts from activities like scuba-diving arise due to market failure. Distorted markets occur in natural areas where prices do not reflect the true value of the good in question. Many of the benefits of protected areas (including MPAs), such as ecological, biological or aesthetic value, are subject to market imperfections. 9 Because there is no 'environmental price' to be paid by consumers who reap the benefits of, say, a pristine coral reef, then the reef is made available at an inefficiently cheap price and may, subsequently, be overused and degraded. One reason for this is that many MPA benefits are difficult to measure and express in monetary terms) ° Additionally, overuse is possible because of the open access nature of most marine resources, including those found in MPAs. Open access resources are those which are owned by nobody, and from which it is difficult to exclude users. 11 Open access also involves questions of excludability, rivalry and congestibility and these are discussed in a later section on factors influencing the demand for using dive sites. It should also be noted that when open access is the case, then individual users of the site (in this case individual divers) have no incentive to conserve it. In other words, they do not take account of user costs. There is always a risk that if an individual diver takes care then others will not. This supports the adage that the property of all becomes the responsibility of none. Tisdell, 12 in discussing tourism development in natural areas, concluded that the aim should be for an optimal mixture of assets and their use. The existence of market failure implies that leaving 'the outcome to chance or naked individual self-interest' (Ref. 12, p. 185) will lead to excessive use of resources such as popular dive sites. The public good nature of marine areas means that it is unlikely that free market mechanisms will result in an efficient or equitable level of protection of those areas. That is, public intervention through the establishment of protected area status is needed to protect and maintain biological values, and to keep future human use options open.

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MPAs are generally thought to be relevant for conservation, preservation, scientific, recreational and educational purposes. They may also be important in relation to commercial production, for example as breeding grounds in various fisheries. This variety of purposes means that there are, as shown in Table 1, many different types of MPAs which can serve a variety of functions, ranging from strict preservation to m a n a g e d use. In this context the International U n i o n for the Conservation of Nature and Natural Resources (IUCN), now r e n a m e d the World Conservation Union, provides a listing of eight classifications of marine park and protected areas, from strict nature reserves to multiple use management areas. 13 A useful categorisation of the numerous and often interrelated values of MPAs has been provided by the Western Australian D e p a r t m e n t of Conservation and Land Management. TM This categorisation is focused on the values which arise from MPAs, and consists of the six broad categories shown in Table 1. References in which the various values are discussed are listed in the Table. While the values of MPAs shown in Table 1 have been recognised, the question arises as to the potential conflicts which may occur between them, particularly between conservation values and use values in MPAs. This may translate into consideration of whether or not TABLE 1

Values and purposes of marine protected areas Value category

Main purpose

Conservation values Maintenanceof ecological functions and biological diversity; conservation of representative habitats and habitats of rare and endangered species Recreation values Recreational opportunities; e.g. for scubadiving Commercial values Conservation of areas of significanceto economically important species; sustainable use of species and ecosystems Education values Understanding of natural systems and human impacts on them; interpretation for the purposes of tourism Historic values Protection of archaeological, historical and cultural sites Research values Provisionof baseline data; monitoring human and other impacts

References

2, 3, 4, 5

1 2, 3, 14 3, 4, 17 3, 4, 14 17

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MPAs are able to be managed in a sustainable fashion when a range of uses is being pursued. The Australian House of Representatives Standing Committee on Environment, Recreation and the Arts, in a report on the role of protected areas for the maintenance of biodiversity, was concerned to ' . . . manage the overall impacts of human use on protected areas; and restore habitats and ameliorate existing impacts such that nature conservation values are maintained and enhanced' (Ref. 15, p. 79). Similarly, the chairman of Australia's Great Barrier Reef Marine Park Authority ( G B R M P A ) - - t h e agency which manages the world's largest MPA--emphasised managing the reef for ecological sustainability (Kelleher, in Tisdell & BroadusS). Overcoming the likely conflicts between use values and conservation values revolves around managing human usage and impacts on resources in MPAs. But the question is how? The simple solution is to keep user numbers below the biological carrying capacity of the area in question, but as discussed in a later section, defining the carrying capacity is difficult. Distributing users optimally throughout an MPA, by a combination of economic instruments, including user-pays and the establishment of property rights to individual sites, and the regulation of human activities may be an appropriate policy response. 16 At this point, and based on the foregoing discussion, it is worth reflecting on what is meant by the term 'conservation', for that will surely determine the stance to be taken in terms of managing protected areas. Hundloe is noted that conservation has been defined as 'wise use over the long term' but then posed two questions: (a) what does wise use mean?; and (b), wise use according to whom? Hundloe concluded that wise use is synonymous with increasing the welfare of society as determined by the 'market place' of value systems, attitudes and revealed preferences. Hundloe's conclusion would, however, be too anthropocentric for many, as it does not clearly focus on the salvation of natural areas, nor sufficiently provide for ethical considerations (Doelman, as quoted by TisdeU19). It also does not take sufficient account of the existence of market failure in marine areas which are freely accessible to a range of users. A significant use of MPAs is as an asset to support tourism, much of which is marine-based. To some extent, the tourist-support function of MPAs is implicit in Table 1, but it is important to state it specifically. In many countries, including Australia, scuba-diving is an important part of the marine-based tourism industry and relies heavily on the use of MPAs such as the Great Barrier Reef Marine Park (GBRMP), the largest marine protected area in the world. Environmental damage to such areas by tourists, including scuba

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divers, is a concern,~-" and parallels concerns for similar damage in terrestrial areas. 23 In summary, diverse benefits are associated with MPAs, including those from recreation and tourism. In many cases the existence of protected areas increases visitor satisfaction. Dixon and Sherman noted that such areas, by protecting an ecosystem, provide the goods and services that attract tourists. They go on to say that this conclusion is 'more true for special interest tourism...' (Ref. 9; p. 178). One significant class of special interest tourism in MPAs is that of scubadiving.

SCUBA DIVING AND MPAs Recreational scuba-diving is an important and growing industry in many countries, and notably in Australia, the US and Japan. Tabata 24 and Dignamz~ concluded that scuba-diving is one of the fastest growing sports in the world, with dive travel being an important part of the industry. The Professional Association of Dive Instructors (PADI) reports increasing numbers of scuba certifications in countries such as the US, Australia and Japan. z6 Divers from these countries also constitute the bulk of the dive travellers to international destinations. The US, Australia and Japan also have the largest numbers of PADI-certified divers in the world. The number of new PADI certifications in the US in 1989 was 422 000, while in 1988 some 39 000 were certified in Australia and 33 000 in Japan. Examination of the data provided by PADI gives some indication of the growth in certified diver numbers, yet these data provide only a partial guide to overall diver numbers and dive activity. There are three main reasons for this. First, there are a number of organisations which provide diver certification. For example, in Australia this certification is provided by PADI, the National Association of Underwater Instructors (NAUI), the National Association of Scuba Diving Schools (NASDS) and Scuba Schools International (SSI). The figures quoted above refer only to PADI certification numbers. Esguerra et al., 27 in the first national survey of scuba diving in Australia, estimated that 50 550 new divers were certified at the open water level in 1988. Dive Australia, the industry's umbrella organisation, says that around 100 000 people now learn to dive each year in Australia (Cummins, pers. comm.). Second, so-called 'resort dives' constitute an important and growing component of the recreational diving industry. Wilks2s explained that these are non-certification 'courses' designed to provide tourists with a

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carefully supervised introduction to diving. However, because there is no registration or certification of participants the numbers of people undertaking such dives are not readily available. (Wilks attempted to estimate the number of resort dives in the Australian state of Queensland and suggested a 'conservative' number of 85000 each year.) The changing demographic structure of tourism may add to the difficulties in estimating resort dive numbers. For example, in Australia, Japanese tourists are expected to increase in number from 529 000 in 1991 to an estimated 1.8 million in 2000 (Australian Tourist Commission, as quoted by Daly and Stimsonag). Japanese tourists comprise a significant proportion of resort divers, meaning there is considerable potential for increased numbers to participate in this activity. Third, and possibly most relevant, is the fact that scuba certifications do not expire. Once a diver has completed their 'C-Card' (the entry level qualification) they may or may not remain an active diver. There is also no requirement for divers to upgrade their skills beyond the initial level of qualification. A fourth reason why examination of new diver certifications may give an incomplete picture of the level of activity and potential impacts of recreational scuba-diving in some MPAs, is the use of 'live-aboard' vessels and faster boats. For example, the growing number of liveaboard dive vessels in Australia's Great Barrier means that divers can go to sea for a week or more and dive in previously untouched areas. Concomitantly, high speed vessels mean that ever-larger numbers of divers can gain access to popular dive sites, thereby increasing localised impacts. Wilks z8 asserted that there are no reliable estimates of active divers in Australia, yet pointed out that such estimates are of importance to two broad interest groups--those interested in the size of a potential customer market for diving, dive tourism and dive equipment; and those interested in the safety aspects of scuba diving. However, a third group not referred to by Wilks is also interested in how many active divers there are. This group may be categorised as resource managers responsible for MPAs. Thomas 3° undertook a survey of dive operators who conduct business in the GBRMP. This survey, which is presently being redone, was undertaken under the auspices of the G B R M P A which has indicated considerable interest in the activities of dive operators in the Park. Wilks 2a'31 attempted to estimate the numbers of divers in Queensland. Wilks' focus on Queensland was because 'it is rated the most popular Australian state as a diving destination (largely because of the Great Barrier Reef) and, also, about half of the country's new divers are

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certified there' (Ref. 28, p. 84). Wilks estimated that, during 1991, the 'known' number of actual dives in Queensland waters exceeded 800 000. By adding in the 'unknown' numbers of certified divers who have little or no contact with commercial facilities, along with the introductory dives in swimming pools, Wilks concluded that the final number 'is probably closer to one million recreational dives made in Queensland each year' (Ref. 28, p. 14). Other estimates for Queensland include that provided by the Queensland Dive Industry Tourism Association who reported 884 000 recreational dives from July 1989 to June 1990 (DITA, as quoted by Wilks28). Telford 32 noted that industry sources suggest a 'conservative number' of 500 000 dives each year in the Cairns area alone. In terms of potential environmental impacts and the needs of MPA managers everywhere, this last figure is of special importance. The concentration of divers in particular locations may place those locations under high levels of stress. It may also impact on the wilderness experience which is often associated with scuba diving. Two Australian studies serve to emphasise this localised impact of heavy diver usage. The first, under the auspices of the Queensland Department of Environment and Heritage, 33 was focused on the 'Cod Hole', a dive site in far north Queensland famous for tame, giant Potato Cod. Concern about heavy usage by divers resulted in the production of an educational video, along with the adoption of self-regulation by dive tourism operators (The Ribbon Reefs Operators Association). The second study was focused on the dive tourism industry at Byron Bay in northern New South Wales. 34 The industry at Byron Bay is dependent on the Julian Rocks Aquatic Reserve, a small marine protected area of 80 ha which is located 3 km off-shore from Byron Bay township. It was estimated that more than 43 000 individual dives are undertaken in limited parts of the Reserve each year and that the current use level constitutes 'the greatest potential threat to the future sustainability of the industry' (Ref. 34, p. iii) due to damage inflicted by divers. Again, heavy usage of one particular dive site is emphasised in this study. An examination of the information presented above indicates the considerable uncertainty about the extent of diver activity in Australia. However, while the estimates of diver numbers vary, certain aspects of diving and the dive industry seem clear. The number of divers, both certified and engaged in resort dives, is increasing. The increase involves both Australian and overseas divers, with the projected growth in international visitor arrivals being particularly relevant. Additionally, recreational diving, particularly in Queensland, is now being heavily promoted with the release, in July 1993, of an attractive and highly

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professional 'Dive Queensland' brochure. Consequently, the numbers of divers and of individual dives are likely to continue to increase in areas such as the GBRMP. An important associated consideration for which few data are available relates to the 'mix' of divers who use certain areas. In terms of environmental damage, better trained and more experienced divers who can control their buoyancy will have a lesser impact than will learner, resort and other inexperienced divers. This is because most experienced divers become adept at achieving 'neutral buoyancy', and avoid uncontrolled contact with fragile corals and other organisms. Conversely, inexperienced divers are more likely to crash into these organisms, and to kick them in an uncontrolled manner with their fins. If then, for example, the number of resort dives is proportionally increasing, this may imply greater environmental damage. Tabata 24 concluded that the diverse interests and skill levels of divers presents a major challenge to resource managers in accommodating their varied recreational needs in underwater environments. It is also clear that the dive industry relies, to a considerable extent, on the use of MPAs for its operations. This is, of course, not surprising. Areas with special values are more likely to be given protected area status. These special values, such as attractive underwater flora and fauna and geological formations, are also the reason that such areas attract divers. It is problematic as to whether the granting of protected area status makes these areas more well-known and, consequently, more heavily used for recreational pursuits (sometimes referred to as 'loving an area to death'). Related to the issues raised above is increasing concern about the possible d a m a g e within MPAs as a result of increasing recreational uses such as scuba-diving. Kenchington 35 noted that the development of more reliable diving equipment and improved underwater cameras have brought a new perspective to areas such as the Great Barrier Reef. Kenchington concluded that: 'The variety of form and colour of the fish and the intricacy and delicacy of the corals made the coral reefs generally, and the Great Barrier Reef in particular, striking examples of beautiful and fascinating natural environments vulnerable to misuse and abuse by humans' (Ref. 35, p. 119). It might be observed (and this relates back to the earlier section on the values of MPAs) that different individuals often have different perspectives on marine conservation. These perspectives, as pointed out by Kenchington, depend upon personal judgements regarding the amenity value of the marine environment. Kenchington recognised a 'more

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recent' utilitarian approach that places value on natural areas for recreation, tourism and education. These values may, in many instances, be in conflict with other conservation needs, particularly biological values. Two important questions are raised by the above. First, what are the factors which most influence the demand for dive sites, and second, do divers have severe environmental impacts on popular dive sites? The limited international evidence on these questions is reviewed in the following sections of this paper.

FACTORS INFLUENCING D E M A N D FOR D I V E SITES An assessment of the demand for use of recreational dive sites requires a focus on two questions: (i) why do people participate in recreational scuba diving; and (ii) what factors are important in the choice of a dive site? The literature relating to the first issue appears to be virtually non-existent, while that in relation to the second question is, at best, extremely limited. While further research is needed to gather information on the factors influencing demand to go scuba-diving, the reasons people participate in recreational scuba-diving appear to include the following: (i) a desire for a 'wilderness experience;' (ii) a general interest in marine ecology; (iii) the fact that the sport is seen as 'different' and perhaps 'special' (image); (iv) an interest in particular underwater features (e.g., geological formations, shipwrecks) or marine life (e.g., sharks, other individual fish species, corals); (v) pursuit of hobbies such as underwater photography; (vi) simply to experience the activity (mainly through resort dives); and (vii) it may also be regarded as an adventure with some risk. Hundloe 36 suggested that the marine environment is correctly entitled the 'last frontier' and that, therefore, the wilderness experience to be gained from scuba diving is normally the most significant explanation of demand for the sport and for individual dive sites. The benefits to be appropriated from such a wilderness experience are affected by the extent of 'competitiveness' in use of the resource in question. This

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concept is often discussed by economists in terms of rivalry and excludability. 9 Nonrivalry occurs when one person's consumption does not affect the total amount available to anyone else. That is, the total amount of a good available can be enjoyed by anyone without diminishing the supply of that good. Scuba-diving sites might be expected to meet a criterion of nonrivalry. However, Dixon and Sherman 9 made the point that some goods, and particularly recreational goods, are in fact 'congestible'. That is, some goods are nonrival up to a certain level of usage; beyond that level rivalry will set in. This appears to be the case for scuba-divers, particularly with the concentration of activity in accessible and popular locations. Hundloe stressed this point in the following way: 'It is surely not possible for the ever increasing number of nature seekers to venture into the remaining wildernesses or near natural areas without changing the nature of the satisfaction sought. Disregarding ecological impacts (which, presumably, could be controlled by regulating visitor numbers), there is a very real loss of satisfaction to some visitors if they are but some of a multitude that have visited the area' (Ref. 36, p. 175). While Hundloe was generalising across all marine park users, it is clear that his comments could apply specifically to divers. The suggestion about regulating visitor numbers relates to excludability--is it feasible to exclude anyone from consuming the good (in this case diver amenity)? A nonexcludable good is one where the cost of excluding consumers is greater than the benefit received.9 In relation to scubadiving in MPAs a degree of nonexcludability does exist. It is very difficult, except in areas where all public use is disallowed (as in the Scientific Research and Preservation Zones of the GBRMP), to exclude private divers. Nevertheless, commercial dive tour operators can be regulated through such means as permit systems. The desire for a wilderness experience, along with the other reasons postulated as to why people dive, relates to the second question raised concerning the factors influencing choice of dive sites by divers. Dixon and Sherman 9 described the results of a survey of divers by a leading US sport diving magazine (Skin Diver), which reported that the most important criterion for selection of a destination by divers was the 'quality' of the diving at a site. Dixon and Sherman concluded that divers 'are willing to pay a premium for environmental quality and good diving (clear water, healthy reefs, abundant fish life)' (Ref. 9, p. 182). Tabata 24.26 reported similar findings from certain other studies, with

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clear water and abundance and diversity of marine life being important to the choice of dive site. Natural geological formations and, significantly, safe and easy access also figured prominently in findings reported by Tabata. Additionally, access in relation to the other attractions of an area is likely to be important. On the Australian east coast, for example, Julian Rocks Aquatic Reserve is nearby to Byron Bay, while the Solitary Islands Marine Reserve is close to Coifs Harbour. Both Byron Bay and Coifs Harbour are very popular tourist destinations and many holiday-makers participate in scuba-diving as an 'add-on' to their vacation. The same would be true for the Cairns section of the GBRMP, along with locations in the Caribbean and other areas. The availability of commercial dive services in these locations complements the accessibility of the various dive sites in the adjacent MPAs. Conversely, some locations, such as Chuuk Lagoon and Palau (both in Micronesia) have tourist industries based almost entirely on diving attractions. Access was also identified as being a critical determinant of the use of m a r i n e a r e a s . 37 'The intensity of use of a reef is inversely proportional to its distance from the nearest harbour, boat ramp or anchorage' (Ref. 37, p. 154). Consequently, sites which are most accessible are more likely to 'show symptoms of user-related damage such as anchor or diver damage and for which restricted access is less likely to be popularly acceptable' (Ref. 37, p. 154). Better understanding of why people dive and of the choice of dive site will help provide resource managers with valuable information concerning the needs of MPA management. It may also allow these managers to develop new diving sites and distribute diving to more areas. Tabata, 26 while noting the importance of clear water, abundant marine life or other attractions such as wrecks, also argued that a popular dive site requires neither pristine conditions nor biological diversity. He further suggested that the promotion of less-sensitive dive sites, or even creating artificial attractions, could reduce the environmental impact of recreational diving. This raises the issue of environmental damage caused in MPAs by recreational users such as divers. Concern about such impacts has been raised by a number of authors including Hundloe,a6 Kenchington,a5,37 Phillips, 34 Hawkins and Roberts, 3s,39Dixon et a l : ° and Geen and Lal. 41 Kenchington35 noted that the conservation of marine environments is a matter of managing human uses and impacts. Human impacts may arise through alterations to the 'pre-existing natural system by removing biological or physical resources or by introducing physical, chemical or biological factors that distort processes that maintain the system' (Ref.

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35, p. 40). Furthermore, the amenity values associated with the use of MPAs may be reduced if human impacts are substantial.

IMPACTS OF SCUBA DIVERS IN MPAs MPAs are established to protect endangered marine ecosystems and the biodiversity they support: ° Such areas are also likely to contain valuable (consumptive) economic resources, meaning that there may be conflicts in use and, subsequently, trade-offs between protection and (consumptive) economic use. Unfortunately, there have been few studies of the impacts of activities such as scuba-diving in MPAs. The findings of certain studies which have been undertaken are reported below. Tilmant and Schma142 undertook a three year study of coral reef damage on recreationally used reefs in Florida. They were interested in the levels of activities which could be allowed without significantly altering coral communities, what area of coral is needed to ensure maintenance of species numbers and genetic variability, and what programs could be put in place to monitor impacts. The main recreational activities in the area studied were snorkelling and spearfishing. The results of the Tilmant and Schmal study may be summarised as: (i) natural wave action and substrate erosion accounted for the vast majority of coral damage encountered; (ii) levels of damage due to human use were increasing but not to a level which masked natural damage; (iii) boat groundings were a serious problem; and (iv) higher rates of use by humans would lead to a greater incidence of coral damage. A study of the effects of trampling on the Great Barrier Reef was undertaken by Liddle and Kay, 43 with the focus being on the resistance, survival and recovery of four common coral species. Not surprisingly the results varied across the species. While it is difficult to generalise Liddle and Kay's results it appears that some concern arises that damage will be cumulative and will, therefore, increase with increasing human use. Conversely, survival rates for damaged corals were very high (at or near 100% under the conditions examined), as were the recovery (regrowth) rates for the species studied. In a later paper Liddle and Kay ~ indicated that the initial phases of trampling caused the most damaging impacts. The more vulnerable

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corals, such as the branching types, were broken first but then additional damage accumulated less rapidly. This result is basically in accordance with that of Hawkins and Roberts 3s reported below. One of the few studies specifically focused on the impact of scuba-diving on the underwater environment was that of Hawkins and Roberts. 3s While Ward 45 raised the spectre of excessive diving pressure degrading reefs, Hawkins and Roberts noted that the direct impact of divers on reefs has received very little investigation. Drawing on the work of Rogers (as quoted by Hawkins and Roberts38), they stated that divers may damage reefs in a number of ways, and that 'This is usually accidental and can result from kicking ('finning'), trampling, holding, kneeling or standing on benthic organisms. Resuspension of sediment may also stress organisms' (Ref. 38, p. 171). Hawkins and Roberts undertook comparisons of the impacts on benthic communities in heavily dived and lightly dived sites near Sharm-el-Sheikh, a popular resort in Egypt. Sampling was undertaken at depths of 10-15m where there was very little wave action and, consequently, such natural impacts were considered to be minimal. Hawkins and Roberts found that there were significant differences in the levels of damage between dived and undived areas, yet added the caveat that absolute levels were relatively low. There were more damaged coral colonies, loose fragments of live coral, reattached coral fragments and partially dead and abraded corals in the heavily dived areas. Subsequently, three main conclusions were documented by Hawkins and Roberts: (i) the differences between heavily and lightly dived areas may be relatively unimportant biologically 'but aesthetically were striking' (Ref. 38, p. 178). Heavily dived sites look much more degraded and so are less attractive to divers. Therefore, 'management of reefs for the purposes of recreational diving may require stricter controls than management based on biological criteria alone' (Ref. 38, p. 178); (ii) levels of damage appear to stabilise at a certain level, but the conversion from pristine to 'diver-damaged' reef can occur very quickly where dive tourism develops without regulation; but (iii) the authors were unable to say whether additional diving pressure could be accommodated (i.e. stress thresholds are unknown). Nor could they say whether or not the diver-induced damage left reefs more susceptible to other forms of stress such as disease or extreme temperature changes. Dixon

et al. 4°

reported on a study of diving at certain sites in Bonaire

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Marine Park (BMP) in the Netherlands Antilles. Ecological sustainability was assessed in two ways in this study. First, divers were surveyed and asked to rate factors such as the condition of the reefs, fish life, visibility and species abundance. They were asked also to compare diving in BMP with certain other sites, and to compare conditions, coral cover, fish life and so on between the present and 'several years ago'. The results of the diver survey were, generally, that some changes had occurred. However, the authors raised concerns about the ability of untrained observers to document ecological change, and urged cautious interpretation of the results of the survey. Second, a photo-analysis of experimental and control sites was undertaken, with prepared quadrats analysed for percentage coral cover, species diversity and species richness. The photo-analysis was commenced at moorings (where available) and extended to quadrats up to 108 m from the moorings. Linear assessments of diver impacts were undertaken up to 300 m from moorings. As expected, coral cover and diversity both decreased in the immediate surroundings of the moorings, and there was a decreasing gradient with increasing distance from the moorings. Conversely, in comparing heavily dived and control sites it was found that diversity increased in the heavily dived areas. The authors concluded that these data 'confirm... that a higher species diversity is maintained at intermediate levels of physical stress or disturbance' (Ref. 40, p. 120). Finally, Dixon et al. found that the linear extent of diver impact was more than 100 m but less than 260 m from moorings. In a study which complemented that reported in 1992,38 Hawkins and Roberts 39 examined the effects of trampling on reef flat communities. The results were broadly similar to those found in the previous study. Amongst the main findings was that trampling appeared not to affect the diversity of coral species but seemed to alter coral population structure on the reef flat. Notably, coral colonies were smaller on average in trampled areas, and there were fewer coral colonies and lower hard coral cover in those areas. However, coral species composition and the relative abundances of different coral growth forms did not seem to be affected by trampling. In their conclusions, Hawkins and Roberts again raised the spectre of reduced amenity values: 'In addition to the deleterious biological effects.., trampling reduced the aesthetic appeal of the reef-flat for the many snorkellers who use it. Trampled areas support less attractive coral communities than untrampled areas, appearing rather barren by comparison' (Ref. 39, p. 30).

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Reference to the foregoing discussion indicates that there is considerable uncertainty surrounding concerns about biological damage and reduced biological diversity resulting from scuba-diving activities in MPAs. Longer term monitoring studies will be needed to ascertain such biological impacts of scuba-diving. There is, however, a clear concern about reduced amenity values associated with increased numbers of scuba divers. 34'a~° In relation to amenity values, Dixon et al. posed the 'difficult question' of 'What is acceptable in terms of diver-induced damage and what isn't?' (Ref. 40, p. 120). Based on their diver interviews and photo-analysis they concluded that diver impacts at certain locations in BMP were already beyond an acceptable level; that is, visitation at those sites had exceeded the carrying capacity. Dixon et al. attempted to estimate the carrying capacity for diving in BMP, settling on a figure of 190000-200000 individual dives per year. On the way to this estimate they raised an important point which is that up to a certain level of activity, diver-induced impacts appear to be minor, but that beyond some threshold (or 'critical level') those impacts quickly become significant. The management challenge is to identify critical levels and attempt to restrict dives to a number below the threshold. Phillips, in her study of the Julian Rocks Aquatic Reserve, also raised the idea of carrying capacity, and commented that 'possibly the main threat to the long-term sustainability of both the Aquatic Reserve and the diving industry is the extent of the use of the more popular dive sites' (Ref. 34, p. 76). Phillips contended that, at least during peak periods, the carrying capacity of the Reserve's dive sites was being exceeded. The carrying capacity concept used by Phillips implies both biological and human aspects in that she used a definition of carrying capacity based on 'the level of u s e . . , which a natural resource can sustain without an unacceptable degree of deterioration of the character and quality of the resource or the use of that resource' (Prosser, as quoted by Phillips). Phillips referred also to divers being discouraged from visiting the area due to the sense of overcrowding or congestion which may be experienced. Similar concerns have been raised in newly popular dive sites such as 'Blue Corner' in the Republic of Palau (Sam Scott, pers. comm.). In summary, there is little evidence that severe biological degradation or loss of biological diversity results from recreational scuba-diving in MPAs. The caveat which applies to this coaclusion is that no long-term monitoring studies have been undertaken of diver-induced impacts, even in very heavily dived areas. However, concerns do arise about critical threshold levels of use at particular dive sites. Beyond such

Recreational scuba-diving and carrying capacity in M P A s

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thresholds biological impacts might be severe and, ultimately, irreversible:° Additionally, significant amenity value losses from both diver-induced damage (reducing aesthetic quality) and overcrowding (reducing wilderness and other experiences) may occur at some threshold level of use of a dive site. The analysis of critical threshold stress levels and, subsequently, the identification of carrying capacities, is considered to be an important component of the development of appropriate management strategies in MPAs. 4°

CRITICAL THRESHOLDS: BIOLOGICAL DAMAGE, CROWDING AND CARRYINC CAPACITY Dixon et al. 4° presented a simple conceptual model of the relationship between diver density (as measured by the number of individual dives) and threshold stress level, with the main purpose of indicating whether or not the threshold can be changed through, for example, diver education. A slightly simplified version of Dixon et al.'s model is shown in Fig. 1, where the line OD is a 'damage function' which shows diver impact. Level A represents the threshold stress level where pressure on the ecosystem becomes noticeable. Point E is the number of dives [M] where the threshold level is reached. Dixon et al. estimated this number to be 190000-200000 dives per year. Dixon and his colleagues then argued that the threshold stress level may be increased through better marine park management, while the damage function OD may be

Damageor StressLevel ThreshOldlevel ~Sh~$S

~

D

y 0

M

Numberof Dives

Fig. 1. Thresholdstress leveland diver numbers (after Dixon et al.4°).

36

D. Davis, C. Tisdell

rotated to the right by diver education. The net result will be to increase the carrying capacity of the marine park, perhaps to 300 000 dives or even more each year. The Dixon et al. diagram is a useful step in developing a model of the relationship between diver impact, ecology and the economics of dive site exploitation. However, there are still many issues to be resolved, as will be apparent from the foregoing discussion. For example, the damage function is most likely not linear. Also, how is damage to be objectively measured by a single variable, particularly as it is likely to consist of multiple attributes? Furthermore, objective measures of damage may differ from perceptions of individuals or subjective measures as is implicit in the analysis of Dixon et al. Again, the threshold value suggested by Dixon et al. is not easy to identify. It is said to be the level at which damage becomes 'noticeable' to divers. Presumably this is the level at which it becomes so noticeable to divers that the demand of each diver to dive at a site falls away sharply with any further damage at this site. So the threshold stress level seems to be designed from a management point of view to provide an indicator of the carrying capacity as a function of the number of divers at a site. Note that this capacity as a function of the number of divers need not be fixed. It might be increased as a result of better education of divers, better management of areas to be used or by only allowing more experienced divers to dive at a site. The effect of this in terms of Fig. 1 would be to rotate or shift the line O E D to the right. Consequently, the carrying capacity at a site in terms of the number of dives increases. There is also the question of whether thresholds are determined by the state of the natural environment or by the degree of avoidance of congestion at a site, or by both. There may be more than one sort of threshold or environmental limit. In any case, it appears that both social and biological thresholds (the former being influenced by crowding) are important and interrelated factors to consider in managing MPAs to meet conservation and recreation needs. Unfortunately, like carrying capacity, critical thresholds are difficult to define, and mean different things to different people and in different settings. Attempts to separately identify social and biological thresholds may, ultimately, lead to more accurate definition of carrying capacities and to reduced conflicts between conservation and recreation as management agencies seek ways to reduce the impacts of user groups such as scuba-divers. Such a conclusion applies also in terrestrial settings such as in national parks.

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CONCLUSIONS Over-crowding at dive sites may lead to excessive deterioration of those sites. Congestion may have two, interrelated impacts. First, it may reduce the amenity value of a dive site. And second, a high level of use may reduce the ecological functions and values at particular dive sites. The interdependence between special interest tourism, such as scuba-diving, and the environment is important but poorly understood. Loss of amenity values and biological degradation may be the results of excessive scuba-diving pressures, with critical threshold points resulting from cumulative damage at dive sites. Rapidly increasing use of MPAs by divers and other tourists may lead to significant amenity and biological losses in the medium-term future. Consequently, there is a need to design and implement management strategies which will ensure sustainable use of underwater resources. Scuba-diving is a rapidly growing and important industry which relies on a quality natural environment. Unfettered growth in the industry could degrade many of the resources on which it relies. More information on the ecological impacts of heavy diver usage at certain sites is needed, requiring long-term monitoring studies. Concomitantly, the economic aspects of scuba-diving require study in an effort to identify potential trade-offs between environmental damage and economic benefits. The difficult task of estimating demand curves for dive consumers will be an important aspect of this work. Ultimately, the challenge is to identify both social and biological thresholds and, subsequently, social and biological carrying capacities, as well as to design and implement management strategies to reduce conflicts between recreation and conservation.

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4. Lucas, P. H. C., Protected Landscapes--A Guide for Policy-Makers and Planners. Chapman and Hall, London, 1992. 5. Clayton, D., Solitary Islands Marine Reserve--A Guide to Recreational and Commercial use of the Marine Reserve. NSW Department of Agriculture and Fisheries, Sydney, Australia, 1991. 6. Queensland Government, Green Paper--Coastal Protection Strategy. Government Printer, Brisbane, 1991. 7. Ivanovici, A. M. (ed.), Inventory o f Declared Marine and Estuarine Protected Areas, Vols I & II. Special Publication 12, Australian National Parks and Wildlife Service, Canberra, 1984. 8. Tisdell, C. & Broadus, J. M., Policy issues related to the establishment and management of marine reserves. Coastal Management, 17 (1989), 37-53. 9. Dixon, J. A. & Sherman, P. B., Economics of Protected Areas: A New Look at Benefits and Costs. Earthscan Publications, London, 1990. 10. Dixon, J. A., Economic benefits of marine protected areas. Oceanus, 36(3) (1993) 35-40. 11. Pearce, D. W. & Turner, R. K., Economics of Natural Resources and the Environment. Harvester Wheatsheaf, UK, 1990. 12. Tisdell, C., Economics of Environmental Conservation: Economics for Environmental and Ecological Management. Developments in Environmental Economics, Vol. 1. Elsevier, Amsterdam, 1991. 13. IUCN, Review of the Protected Areas System in Oceania. IUCN, Commission on National Parks and Protected Areas, Gland, Switzerland, 1986. 14. Western Australian Department of Conservation and Land Management (WACALM), Ningaloo Marine Park: Management Plan 1989-1999. CALM, Perth, Australia, 1989. 15. Australian House of Representatives Standing Committee on Environment, Recreation and the Arts, Biodiversity: The Role of Protected Areas. Australian Government Publishing Service, Canberra, 1993. 16. Davis, D. C. & Tisdell, C., Economic Management of Recreational Scuba Diving and the Environment. Faculty of Resource Science and Management, Southern Cross University, Mimeo, 1994. 17. Lassig, B. R. & Kelleher, G., Crown of thorns starfish on the Great Barrier Reef. In Environmental Research in Australia--Case Studies. Australian Science and Technology Council, Australian Government Publishing Service, Canberra, 1991. 18. Hundloe, T. J., Measuring the value of the Great Barrier Reef. Australian National Parks and Recreation, 26(3) (1990) 11-15. 19. Tisdell, C., Economics of wilderness. Proc. of the Symp. on Wilderness Management in Australia. Canberra College of Advanced Education, 1980. 20. Australia: Review Committee on Marine Industries, Science and Technology, Oceans o f Wealth? A report by the Review Committee on Marine Industries, Science and Technology, AGPS, Canberra, 1989. 21. Ecologically Sustainable Development Working Groups, Final Report-Executive Summaries. Australian Government Publishing Service, Canberra, 1991. 22. Ecologically Sustainable Development Working Groups, Draft Report-Tourism. Australian Government Publishing Service, Canberra, 1991.

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23. Davis, D. C. & Weiler, B., Kakadu National Park---conflicts in a world heritage area. Tourism Management, 13(3) (1992) 313-20. 24. Tabata, R. S., Scuba-diving holidays. In Special Interest Tourism (ed. B. Weiler & C. M. Hall). Belhaven Press, NY, 1992. 25. Dignam, D., Scuba gaining among mainstream travellers. Tour and Travel News, 26 March (1990). 26. Tabata, R. S., Dive travel--a case study in educational tourism: policy implications for resource management and tourism development. Paper presented at The Global Classroom Syrup. Christchurch, New Zealand, 19-22 August 1990. 27. Esguerra, R., Ashbolt, L. & Callenbach, P., Report on a Study of the Australian Diving Industry. Diving Industry and Travel Association of Australia, Lindfield, New South Wales, 1989. 28. Wilks, J., Calculating diver numbers: critical information for scuba safety and marketing programs. SPUMS J., 23(1) (1993) 11-14. 29. Daly, M. T. & Stimson, R. J., Policy implications of the tourism boom in Australia. Paper presented at The Nat. Conf. on Tourism Research. Sydney University, 19 March 1993. 30. Thomas, C. Clark, Dive Tourism in the Great Barrier Reef Region. Study report for the Great Barrier Reef Marine Park Authority, Townsville, Queensland, Australia, 1992. 31. Wilks, J., A profile of NAUI divers in Queensland, Australia. Sources, July/August (1991) 84-7. 32. Telford, H., Project SAFER divers: provisional report. NAUI News Australia, 10(6) (1990) 5-8. 33. Queensland Department of Environment and Heritage. The Cod Hole (1992) (video). 34. Phillips, S., The Dive Tourism Industry of Byron Bay: A Management Strategy for the Future. Unpublished Integrated Project dissertation, Faculty of Resource Science and Management, University of New England--Northern Rivers, Australia, 1992. 35. Kenchington, R. A., Managing Marine Environments. Taylor and Francis, NY, 1990. 36. Hundloe, T. J., Parks in the marine environment. In The Value of National Parks to the Community: Values and Ways of Improving the Contribution of Australian National Parks to the Community (ed. J. Messer & G. Mosley). Australian Conservation Foundation Inc., Melbourne, 1979. 37. Kenchington, R. A., The concept of marine parks and its implementation. In The Capricornia Section of the Great Barrier Reef: Past, Present and Future (ed. W. T. Ward & P. Saenger). Royal Society of Queensland and the Australian Coral Reef Society, Brisbane, 1984, pp. 153-8. 38. Hawkins, J. P. & Roberts, C. M., Effects of recreational scuba-diving on fore-reef slope communities of coral reefs. Biological Conservation, 62 (1992) 171-8. 39. Hawkins, J. P. & Roberts, C. M., Effects of recreational scuba diving on coral reefs: trampling on reef-flat communities. J. Appl. Ecology, 30 (1993) 25-30. 40. Dixon, J. A., Scura, L. F. & van't Hof, T., Meeting ecological and

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