Tourism's Impact on Reefs

An ecosystem under threat

Coral reefs are under threat, suffering from decline and degradation due to a combination of natural and anthropogenic factors. The scientific community is in agreement about it and the press talks about it. Fifty-eight percent of the world's reefs are potentially threatened by human activity. Overexploitation and coastal development pose the greatest potential threat (WRI, Bryant et al. 1998).

Some of the man-made damage is related to tourism. At the same time, tourism is of great economic importance to countries with significant areas of coral reef, such as the Caribbean states and territories. For some smaller island territories, tourism is the mainstay of the local economy. Because tourism in the Caribbean is dependent almost entirely on coastal resources, most development takes place in the coastal zone and most of the impacts occur in the coastal zone. Impacts from tourism activities include both direct physical impacts (such as diver damage and anchor damage), as well as indirect impacts from resort development and operation, and development of tourism infrastructure in general.

Impacts from tourism can often be reduced by raising awareness and changing behaviour among both tourists and local tourism industry workers.

The tourism-related impacts on coral reefs in the Caribbean are typical of those occurring worldwide. The tourism sector is of major economic importance in the Caribbean region, both for foreign exchange earnings and for employment. Since Caribbean tourism is primarily associated with beaches and the sea, there have been - and continue to be - impacts from tourism on the coastal environment, including the coral reefs.

Tourism has both direct and indirect impacts on coral reefs. Snorkeling, diving and boating can cause direct physical damage to reefs, and fishing and collecting can contribute to over-exploitation of reef species and threaten local survival of endangered species. Indirect impacts relate to the development, construction and operation of tourism infrastructure as a whole (resorts, marinas, ports, airports, etc.).

Direct physical damage from snorkeling and diving has been the subject of extensive study and is well documented. The damage inflicted by divers and snorkelers consists mostly of breaking fragile, branched corals or causing lesions to massive corals. Most divers and snorkelers cause little damage; only a few cause severe or widespread damage. Research indicates that reef degradation and change of reef community structure occurs once a certain level of use by divers and snorkelers is exceeded. As a rule of thumb it is recommended that the level of 5,000 to 6,000 dives per sites per year should not be exceeded. Training and briefing of divers and snorkelers will greatly help to reduce negative impacts.

Physical damage from anchors and especially boat groundings can be severe. Anchor damage is proportional to the size of the boat (i.e. weight of the anchor and length of anchor chain) and is further dependent on the type of coral community. Recovery of coral damage from boat groundings is slow. Anchor damage can be avoided to a large extent by installing permanent moorings, designating anchorages and providing adequate information on anchoring and mooring.

Although fishing has caused declines in reef fish stocks throughout the Caribbean, the direct role of tourism in fishing-related decline is most likely not significant. Indirectly, however, tourism increases the demand for seafood and does have an impact of on reef fish resources. Collecting of marine souvenirs by tourists is probably insignificant but there still is a market for marine curiosities in response to a certain tourist demand. This demand can definitely be decreased by increased awareness.

Tourism-related sources of sewage pollution include resorts and, to a much lesser extent, recreational vessels. There is evidence that a very large percentage of the sewage generated by hotels is discharged in coastal waters without adequate treatment. The main impact of sewage pollution is nutrient enrichment, which favours certain species (algae in particular) at the expense of corals. The impacts of nutrient enrichment from sewage pollution on corals in general have been well studied, but those specifically from sewage pollution from hotels and recreational vessels have not been quantified. The studies indicate that the impact of sewage pollution depends on the level of treatment before discharge and the degree of natural flushing by tides and currents at the point of discharge.

Tourism is not generally a source of petroleum hydrocarbon pollution, other than on a small scale when oil or fuel spills from recreational vessels and marinas occur. The effects of petroleum hydrocarbons on corals has been studied for quite some time, producing evidence that chronic oil pollution is more harmful than a single exposure, and that dispersants and emulsifiers used to combat spills are more toxic to corals than oil alone.

Coastal development and the construction and operation of related tourism infrastructure cause increased runoff and sedimentation. Sedimentation is one of the main reasons for reef degradation. Increased sediment loading of coastal waters increases turbidity, reduces light levels and leads to stress on corals, usually expressed by "bleaching" of corals. Heavy sediment loading may also cause corals to suffocate and die. Other documented impacts of sedimentation on corals include lower growth rates, reduced productivity and reduced recruitment.

Tourism is obviously a source of large amounts of solid waste, the impacts of which depend very much on the method of disposal. If disposed of inappropriately, leaching of toxic substances may harm corals. Of particular concern is the "accidental" waste - plastics in particular - that is blown into the ocean from beaches or vessels and has a detrimental effect on corals and other marine life.

Tourism-related impacts on coral reefs are significant, but they are also compounded by other impacts that are not easily distinguished from those of tourism. This does not mean that we must disregard the impacts of tourism activities. On the contrary, the tourism sector and government agencies involved in tourism development must try to eliminate or reduce those impacts that can be controlled, even if there is no 100% proof that a certain impact is directly related to a tourist activity.

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