Marine life, archaeological sites, site management and environmental policies
Underwater cultural heritage sites tend to automatically develop into a sensitive ecological niche, within the wider area. Many algae and sessile animals need hard substrate to hold onto. They will colonize ‘foreign bodies’ and foreign materials extensively, including artefacts. In turn, this plant and animal cover will attract sedentary fish and predators that stand higher in the food chain. Isolated spots of foreign materials at the bottom surface therefore automatically tend to create a rich biotope. It is also for this reason that many initiatives around the world seek to intensify bio-production by creating artificial reefs. Car tyres have been dumped for the purpose and worn out ship’s hulks have been scuttled. Sometimes such efforts have been integrated with the creation of an underwater park for recreational divers; sometimes the purpose is purely ecological, although mostly with the expectation of economic spin-off for fisheries.
The described process does not apply for sites that are deeply buried, but it does for sites that occur at the bottom surface of a body of water. Their specific ecological qualities derive from the fact that their substance is alien to the environment. This brings positive effects in that it allows for colonising by other species and creating biotopes that allow more biodiversity. This may be considered of great significance for conservation of nature in a wider area. As in many ‘life cycles’, these positive effects may be of a temporary nature. Wooden structures, for instance, are attacked by animals and wood-eating micro-organisms. Mechanical resistance decreases and eventually the structures collapse. Although the biotopical advantages may disappear when what finally remains is covered in sand and silt, such processes are not in themselves negative for the environment. This may be different with the degradation of other materials that may have a negative impact on the environment.
Heritage with a negative impact on the environment
- Archaeological objects are alien to the natural environment.
- Archaeological sites are often special biotopes.
- Environmentally suspect substances may present a hazard, but can also be important for research.
Stones and ceramics are relatively inert and harmless, but other materials are not. Metal ships from the last century have formed wreck sites of huge size.
Iron or steel is their main component and in the long run that is not resistant to (sea) water. Depending on their specific character, such wrecks will tend to continuously produce iron oxides. This is not generally considered a menace for the environment. Heavy metals and alloys that are also present are another matter. Sometimes their corrosion will come to a balanced standstill when a protective layer has formed. But if several metals are present, electrolytic processes will continue to produce materials in solution that are called minerals if they have a positive effect on bio production, and contaminants if their effect is assessed negatively.
For the sake of cultural heritage protection, sacrificial anodes have occasionally been mounted to stop corrosion processes. In such cases, the argument for cultural significance had better be very strong, because environmentally speaking, it is just replacing one contaminant with another. Management strategies that isolate archaeological materials from the environment by covering or packing them will not suffer from such critique, but will on the other hand allow for a lesser experience during recreational visits.
Many wrecks are likely to induce oil spills that are certainly hazardous. But due to gradual corrosion of tanks such a spill may also occur after many years. The wreck in question may however still be considered significant heritage. An example of a high-risk wreck is the USS Neosho, which lies off the Great Barrier Reef, off Australia, and still holds four million gallons of fuel oil.
Toxic or explosive content
An even more problematic issue is formed by the presence of containers with toxic or explosive content. It is obvious that such substances have been transported in ever greater quantities since early times and at least since the industrial revolution. Unfortunately, they have also been lost at sea. Even worse, they have even been dumped in great quantities in the context of armed conflict or clearance actions that followed. Such objects evidently pose a serious problem, the more so since they are encountered by fishermen and recreationists. They may be intertwined with other objects or may be part of an unfortunate, but often important cultural heritage. In any case, they do not contribute to a pleasant experience when encountered in isolation or as part of a heritage site. They are environmentally dangerous if touched or unstable. Archaeologists that are charged with heritage assessment and the preparation of heritage decisions are constantly reminded of this, both in relation to impact studies, to inventory and to regular management.
Cargoes of ingots, raw materials and chemical ingredients
Nevertheless, heavy metals and toxic substances are not just characteristic of relatively modern wrecks. Cargoes of ingots, raw materials and chemical ingredients are as old as seafaring itself. Such cargoes would have been processed had they arrived at their final destination. It is for this reason that they offer exceptional opportunities for research. There is no other source that allows for any quantitative analysis of these materials, and consequently, some such cargo deposits are considered to be among the most significant underwater cultural heritage that we know of. Such sites should therefore be managed and addressed in conformity with environmental policies, but also with due respect to the concerned heritage.
Archaeological interventions and the environment
Site formation processes are such that over time a site achieves a state of relative stability and equilibrium. More often than not, this stabilization process is interrupted by the event that leads to its discovery. That applies both to the physical and chemical condition of the artefacts it contains and to the resilience of the local ecosystem. The ecosystem derives its strength from the presence of its flora and fauna. Removing growth may disrupt this fragile balance. For proper assessment of the archaeological significance, this may nevertheless be necessary. Stabilization and consolidation measures will equally impact both the seabed and marine life. For excavations, this is even more evident.
Balancing the operation
The environmental policy that is put in place to ensure that the seabed and marine life are not unduly disturbed, should balance the scale of the operation with the resilience of the ecosystem in question. Generally, this can easily be done. Archaeological interventions are small scale as compared to many of the impacts an ecosystem stands to survive. They may also be small scale as compared to the spatial extent of the specific biotope. On the other hand, there may be situations in which the ecosystem is already under great stress, and in which it should not be disturbed during critical phases of breeding or blooming. Such seasonal phases can easily be avoided to diminish negative impact. This example shows that in integrating an environmental policy in the project design for an archaeological intervention, local environmental and ecological knowledge is essential.
Responsibility and compliance with the law
Other aspects of the policy are general. One should act in compliance with the laws and rules governing environmental issues of the location, and one should handle equipment, engines and fuel as well as food, garbage and the like in the same responsible way as one would do at home. No litter or waste should be discarded from vessels into the sea, including cigarettes, tissues and paper towels, bottles, cans and batteries. Ashtrays and rubbish bins must be provided on board for sorting waste. This also applies to biodegradable waste, especially leftover food. Animals must not be fed either directly or indirectly. Waste collection, management and disposal are compulsory.
Such rules and policies apply for the whole duration of the project. They will not extend beyond the scope of the project design.
A different situation occurs if the intervention aims to facilitate access to the site. Impact is then not only a one-off, from which site and ecosystem can recover, but it will be sustained over longer periods of time. The project therefore needs to take the consequences of an intensified human presence into consideration. Integrated site management addresses whether the ecosystem can bear this.
The human factor
In all cases, the human factor is the key. If one behaves responsibly, impacts are significantly reduced. In contrast, if this aspect is neglected, the impact can be considerable. Underwater archaeologists must be responsible diver-scientists who respect the environment in which they operate. Site workers must be aware of any specific or fragile areas and these should, if necessary, be clearly indicated. If operations include many people, the environmental policy should formulate clear directives to which all the team members must subscribe. This can include, for example, the commitment not to waste fresh water, which is a major issue in many places, including areas of scarcity. Water should be used sparingly and wisely. Rinsing sieves and cleaning objects can use huge amounts. Recycling and treatment of waste water should be considered before the water is released into the environment. Likewise, domestic use of water for individual needs such as washing and the toilet must be kept in check. Boats and equipment should be rinsed with water management in mind.
Site management and the environment
Long-term management of an archaeological site should take account of environmental issues, at least as much as a single intervention would. Human presence will be a key factor in sustainable development and protection. This is true both for the cultural heritage at the underwater site and for the ecosystem. The protection of fauna and flora and their environment is necessary, as they are important to human life. Protection means in this regard protecting habitats and interchanges rather than preserving the life of every entity.
- Visitor impact
The degree of attention paid to environmental issues in a site management plan depends on the stability of the situation and on the number of expected visitors. Visitors should leave no trace of their presence, neither in the short- nor long-term. This certainly also applies to diving, during which nothing should be broken, overturned or uncovered, either voluntarily or involuntarily. Accordingly, certain forms of behaviour such as scraping the bottom with a control valve or monitoring instrument, giving blows with swim fins, bumping or colliding with obstacles etc. are not admissible. Similarly, trampling should be avoided, particularly in areas with coral, grasses and algae. Stones must not be turned over. Finally, the divers, including scientist-divers, must collect all waste they come across while diving. On-site facilities must be proportional to the number of visitors. This is in no way different to the management of sites on land.
- Boat and vehicle use
Site installations and the boats used should not cause the erosion or degradation of beaches, shorelines, wharves or working areas. The site, its accessibility and its enjoyment must not be detrimental to the immediate environment. Vehicles’ use should also not contribute to weakening the substrate, as for instance with regards to coral, cliffs, and slopes. These are, of course, aspects that need to be integrated in the management plan. Other users in the area must not be exposed to any danger incurred from vehicles. The site can be provided with marked access routes avoiding particularly sensitive areas. These can be explicitly signposted to avoid degradation. It is advisable to involve marine biologists in the management process in order to conduct diagnostic assessments and monitoring.
Boats, working and surface platforms must have fixed moorings, so that regular recasting of anchors is avoided. Even in sandy areas anchors have quite considerable impact, whereas mooring in sea grass or seaweed beds may destroy these. Of course one would not want to cast anchors on archaeological remains.
- Introduction of species
In some areas, particular care must be taken to avoid the introduction or spread of invasive species. The seaweed Caulerpa taxifolia, though beautiful, is considered a disaster outside its original habitat. The same is true for several bivalve species, crustaceans and fish. Although ensuing ecological problems may be extensive, and although they are important in marine environmental policies that deal with the movement of ships and their operators, they are not typical for the management of archaeological sites. Let us not – although we could – count the visiting humans under this kind of invasive species. Public enjoyment is after all an important reason to devise a site management plan in the first place.
- Visitor impact