Environmental impact of recreational diving


The environmental impact of recreational diving is the effects of diving tourism on the marine environment. Usually these are considered to be adverse effects, and include damage to reef organisms by incompetent and ignorant divers, but there may also be positive effects as the environment is recognised by the local communities to be worth more in good condition than degraded by inappropriate use, which encourages conservation efforts.
During the 20th century recreational scuba diving was considered to have generally low environmental impact, and was consequently one of the activities permitted in most marine protected areas. Since the 1970s diving has changed from an elite activity to a more accessible recreation, marketed to a very wide demographic. To some extent better equipment has been substituted for more rigorous training, and the reduction in perceived risk has shortened minimum training requirements by several training agencies. Training has concentrated on an acceptable risk to the diver, and paid less attention to the environment. The increase in the popularity of diving and in tourist access to sensitive ecological systems has led to the recognition that the activity can have significant environmental consequences.
Scuba diving has grown in popularity during the 21st century, as is shown by the number of certifications issued worldwide, which has increased to about 23 million by 2016 at about one million per year. Scuba diving tourism is a growth industry, and it is necessary to consider environmental sustainability, as the expanding impact of divers can adversely affect the marine environment in several ways, and the impact also depends on the specific environment. Tropical coral reefs are more easily damaged by poor diving skills than some temperate reefs, where the environment is more robust due to rougher sea conditions and fewer fragile, slow-growing organisms. The same pleasant sea conditions that allow development of relatively delicate and highly diverse ecologies also attract the greatest number of tourists, including divers who dive infrequently, exclusively on vacation and never fully develop the skills to dive in an environmentally friendly way. Low impact diving training has been shown to be effective in reducing diver contact.

Types of impact

Research on the effects of divers on tropical coral reefs has shown reduced coral cover on heavily dived sites and a change in coral structure, with more resilient corals becoming dominant and a loss of species diversity over time. These reefs may be less resilient to other stressors like disease outbreaks and severe weather damage.
There is persuasive evidence that reefs can be damaged and the amenity value of dive sites compromised by badly planned or over-intensive tourist use. Marine tourism affects reef communities directly through disturbance such as structural damage to corals, boats grounding on reefs and damage by anchors, and indirectly through alteration of water quality by nutrient enrichment and pollution by toxic substances, waste water and increased turbidity. The level of degradation depends on the intensity, frequency, time and type of use and the specific environment.
Diver impact damage to corals includes skeletal breakage of branching species, tissue abrasion, possibly leading to infection by coral diseases, and an overall reduction of hard coral coverage on reefs. Diving related activities may also reduce the reef's resilience to reef stressors like climate change and bleaching events.
In some frequently dived tropical coral reef sites recreational divers have caused negative ecological impacts by inadvertent impacts with live corals causing physical damage at a rate faster than compensated for by natural recovery. The long term result is reef degradation. One of the common challenges for local policy and management is maximising tourism benefits while also reducing environmental degradation to long-term sustainable levels.
In the soft sediment bottomed "muck diving" environment, it was observed that photography causes greater environmental disturbances than effects caused by diving experience, certification level, gender or age. Divers came into contact with the substrate more often on soft sediment than on coral reefs, but environmental damage was not greater. Divers tend to touch animals more frequently when observing or photographing cryptobenthic fauna, and spent up to five times linger in interactions when using dSLR-cameras. Long-term impacts of this behaviour on cryptobenthic fauna and soft sediment habitats are unknown.
The impacts of photographer behaviour and photographic flashes on a small sample of benthic fish species was investigated. The study showed negligible effects beyond those caused by human presence alone. Flash photography caused no discernible ocular changes in seahorses and feeding success was not affected. Physical handling of animals produced strong stress responses.
Diver impact on subtropical, and particularly temperate reefs is less researched than tropical reefs. The perception is that these reefs are less vulnerable than tropical reefs and the sessile species are less exposed to diver impact. Research in the Mediterranean in Spain indicates that sessile organisms with fragile and brittle calcareous or corneous skeletons are not resilient to frequent disturbances by divers.
Diver contact with the bottom is also prevalent on temperate reefs. One of the main forms mentioned is fin contact with the bottom sediment, raising particulate material into the water column and degrading visibility.
The impact of recreational scuba diving on recreational dive values and the cultural heritage of shipwrecks has been found to comprise four basic types:
Repetitive contact by divers and their equipment on the benthos is the general mechanism of reef degradation by recreational divers. Factors correlating with frequency of reef contact were found to be:
Fin impacts have been identified as contributing the most to damage to reef biota, erect and branching hard corals are the most sensitive taxon to contact damage, and the severity of damage is influenced by habitat complexity. This indicates that better diver trim, buoyancy and finning techniques, situational awareness of position relative to the reef, and awareness of the damage done by contact with corals in habitats where close proximity of fins to sensitive organisms is likely, are priorities for reducing damage. Training in low impact diving skills appears to significantly reduce contact with the benthos in divers of all certification and experience levels. This result can be extrapolated to other diving environments as a method to protect the environment and help to make recreational scuba diving more ecologically sustainable, and may enhance the diving experience.
Several studies have found the main reason for contact by inexperienced divers to be poor buoyancy control.
There appears to be little correlation between site topography and coral damage, but damage is related to coral morphology and structural strength. Most damage is to branching species which are inherently weaker against bending loads.
Studies on recreational divers on tropical coral reefs have shown that the rate of contact between diver and environment varies significantly between divers who are able to maintain neutral buoyancy and those who are deficient in the skill, with divers who do not maintain neutral buoyancy contacting the reef more often. Briefing divers on the effects of contact with the reef reduced contact in divers with good buoyancy skills, but not in divers who lacked those skills. The problem appears to be one of competence. Without the necessary competence, divers are unable to modify their behaviour appropriately, and cannot produce the skills merely by being made aware of their necessity. The solution to reducing reef contact is in requiring the diver to have the skill before allowing them to dive in the environment where it is needed.
There is evidence that the ability of dive guides to positively influence diver behaviour relating to reef contact is less for larger groups of divers, but the implementation of programmes which focus on dive industry operations can contribute to the reduction of anthropogenic reef damage.
Some MPAs in the Mediterranean have prohibited scuba diving completely, or have restricted it to reefs near the boundaries of the MPA. Others have established diving trails which keep divers away from vulnerable areas. Another conservation strategy identified potentially vulnerable species and based the determination of sustainable numbers of visitors on this.
Several studies have found that damage to coral reefs by divers can be minimized by modifying the behavior of those divers.

Strategies for reducing diver impact

training has been shown to be effective in reducing diver contact.
In 1989, Buoyancy Training Systems International, a company based in Seattle, Washington, became the first organization in the world to create an internationally uniform, training and objective underwater test of skill specifically designed to reduce diver impact upon the marine environment. The curriculum and mobile practice venue, now known as the Diamond Reef System, used portable artificial reefs called ‘Diamond Reef Hover Stations' to raise the proficiency and awareness of divers at all stages of diver training including tropical resort acclimation dives. This program remains in use by dive operators world-wide including the U.S. Environmental Protection Agency and Dutch Springs, a commercial underwater recreation area in Bethlehem, Pennsylvania where divers can train and go on recreational dives.
The specific PADI Low Impact Diver training program takes 2 days and appears to be effective for a large range of pre-existing skill and certification levels. Similar training from other providers should have similar results. Many of the skills are included in technical diver training, particularly cave and wreck diving, where they are also important for safety.

Strategies for sustainable use management

Several methodologies have been developed with the intention of minimising the environmental impact of divers on coral reefs