CASE STUDY: SEA GRASS (POSIDONIA OCEANICA) STAKEHOLDER AWARENESS AND CONFLICTS IN MALLORCA
AQA A Level Geography
3.1.3 Coastal systems and landscapes
188.8.131.52 Coasts as natural systems
184.108.40.206 Systems and process
220.127.116.11 Coastal landscape development
18.104.22.168 Coastal management
22.214.171.124 Quantitative and qualitative skills
126.96.36.199 Case studies
Cambridge International A Level Geography
3.3 Paper 3 Advanced Physical Geography Options
8. Coastal environments
8.1 Coastal processes
8.2 Characteristics and formation of coastal landforms
8.4 Sustainable management of coasts
EDUQAS A Level Geography
Section A – Changing Landscapes
1.1: Coastal landscapes
IB Diploma Geography
Option B: Oceans and coastal margins
3. Managing coastal margins
OCR A Level Geography
Topic 1.1 – Landscape systems
1.1.1 Option A – Coastal landscapes
1. How can coastal landscapes be viewed as systems?
2. How are coastal landforms developed?
3. How do coastal landforms evolve over time as climate changes?
4. How does human activity cause change within coastal landscape systems?
Pearson Edexcel A Level Geography
Topic 2: Landscape Systems, Processes and Change
Option 2B: Coastal Landscapes and Change
E.Q. 1: Why are coastal landscapes different and what processes cause these differences?
E.Q. 2: How do characteristic coastal landforms contribute to coastal landscapes?
E.Q. 3: How do coastal erosion and sea level change alter the physical characteristics of coastlines and increase risks?
E.Q. 4: How can coastlines be managed to meet the needs of all players?
The study is always tailored to the particular requirements of individual schools and colleges.
2. Subject overview
Prior to the advent of mass tourism in Mallorca, coastal processes and systems were largely unaffected by human interference. For example, coasts were afforded natural protection by dead seagrass leaves and water transparency was aided by seagrass meadow sediment retention. However, since the 1970s, the impact of human activity has been substantial. It is estimated that 46% of underwater seagrass meadows in Mallorca have been affected and there has also been increased beach erosion. This study looks at: the causes of the decline; the current situation; the level of awareness among the stakeholders and the conflicts between them; and the possibility of implementing sustainable coastal management policies.
3. Key information
Posidonia oceanica: the name
Sea grass (also known as Neptune Grass or Mediterranean Tapeweed) is referred to in Mallorca as alga (seaweed) or by its Latin name – Posidonia oceanica. Posidonia refers to Poseidon, the Greek god of the sea, whereas oceanica refers to its wide distribution.
It is a plant which grows in dense meadows on the sandy sea beds of the Mediterranean. It is found at depths of between one and forty metres depending on water clarity. The bright green leaves are ribbon-like and grow in tufts of six or seven leaves up to one metre in length. Subsurface roots and plant stems (rhizomes) grow to a length of up to 150 cm and anchor the plant to the seabed. Rhizomes also grow on the surface of the seabed. The surface and subsurface rhizomes combine to form a reef like structure (matte) comprising a dense network of roots and decomposing stems as well as the active parts of the plant.
The species is endemic to the Mediterranean. It occupies an area of about 38,000 square kilometres, about 3% of the Mediterranean basin. The presence of Posidonia can be detected by piles of decomposing leaves on beaches.
The transparent waters and the sandy sea beds around the coast of Mallorca provide ideal conditions for the growth of submerged seagrass meadows. Mallorca is the largest island in the Balearic Islands archipelago, located in the western Mediterranean, with 555 km of coastline.
In 2006, a huge Posidonia meadow was discovered south of the island of Ibiza. At 8 kilometres across, and estimated at around 100,000 years old, it may be one of the largest and oldest clonal colonies on Earth.
Why are the Posidonia meadows such an important ecosystem?
- In daylight, Posidonia meadows oxygenate coastal waters.
- Due to the slow decomposition of roots and rhizomes, the reef structure or matte acts as a long-term carbon sink. Per hectare, a Posidonia meadow holds twice as much carbon dioxide as a rain forest.
- The matte helps to protect the integrity of the seabed through compaction and prevents coastal currents transporting excessive amounts of sediment. (This results in Posidonia being referred to as an ecosystem engineer as it, in part, creates its own habitat.)
- They provide a habitat, a breeding ground and food for many types of fish and invertebrates.
- The leaf canopy retains floating sediment particles thus enhancing the transparency of the water above.
- When waves pass over the meadows, some of the wave energy is absorbed thus lessening the impact of waves on the beach and reducing the amount of coastal erosion.
- A moderately wide (1 km) belt of Posidonia meadow can generate more than 125 kg of dry seagrass material (litter) per metre of coastline each year, mostly during the autumn. The accumulation of this material that is washed up on beaches forms natural sea defences. These natural cushions or buffers, up to 4m high, are able to absorb wave energy due to their elasticity and porosity. As a result, beach erosion is limited, particularly during winter storms.
- Posidonia meadows are excellent indicators of environmental quality as they can only grow in clean unpolluted waters. In addition, radioactive and synthetic chemicals and heavy metals are concentrated in their rhizomes. As a result, there is a record of the level of these persistent contaminants.
What is the current situation with regard to the decline of the Posidonia meadows?
It is estimated that 46% of the underwater meadows in the Mediterranean have experienced some reduction in range, density and/or coverage, and 20% have severely regressed since the 1970s. It has been calculated that Posidonia meadows in Spain are disappearing at a rate of 5% per year. This is more than double the global rate of decline in seagrass ecosystems. The seriousness of the situation is compounded by the fact that the species grows extremely slowly (1-6 cm per year). Such losses are virtually irreversible.
What are the causes of the decline?
- Eutrophication: an ecosystem’s response to the addition of nutrients is called eutrophication. The addition of artificial nutrients (e.g. detergents, fertilizers, sewage) to coastal waters has led to an abnormal growth of epiphytic algae which hinders photosynthesis.
- Dredging: coastal dredging takes place as part of the construction process for ports, piers and breakwaters. Dredging can leave Posidonia roots and rhizomes exposed thus making their removal by wave action more likely. After dredging, the extracted material is then taken to a different area for dumping and this can result in Posidonia plants being buried in sand and mud (siltation).
- Construction: the Posidonia ecosystem is very sensitive to changes in the input and output of sediment. The construction of roads, houses and hotels in coastal areas along with the altering of natural river courses sharply reduces sediment input to submersed coastal habitats. Meadow erosion can be the result. The construction of sewage outfall pipes has led to increased water turbidity in the area where the sewage enters the water. This hinders photosynthesis.
- Anchoring: in permanent anchorage sites, anchor chains being repeatedly dragged through the Posidonia meadows have stripped leaves and even cleared sections of sea bed. In non-permanent anchorage sites, the dropping and raising of anchors has ripped out Posidonia leaves and rhizomes.
- Propeller action: when motor boats drive over Posidonia meadows in shallow waters, the propeller blades sometimes sever leaves or tear out Posidonia thickets.
- Pollution: Posidonia is very sensitive to pollutants. Oil, detergents, paints, and solid waste from motor boats have all been detected and have damaged the species.
- Trawling: trawler fishing in areas where there are Posidonia meadows is both illegal and damaging. Trawling results in plants and thickets being pulled up leaving clearings in the Posidonia meadows. It also increases water turbidity as it stirs up sediments which decreases the amount of light reaching the plants
- Competition from invasive species: more recently, it has been claimed that the meadows have been threatened by competition from two non-native, fast growing tropical algae. Caulerpa taxifolia and caulerpa racemosa were both accidentally introduced into the Mediterranean. However, there is an ongoing scientific debate as to whether these algae are harmful or beneficial to Posidonia.
- Water desalination plants: Posidonia is very sensitive to increases in salinity levels. These occur in the vicinity of water desalination facilities and result in the death of sections of meadow. Pipelines that transport the brine to be released in offshore areas could be seen as preferable in the long term. However, pipeline construction causes the destruction of large areas of meadows in the short term.
Beach cleaning and beach replenishment: piles of dead Posidonia leaves on beaches form natural buffers to protect beaches against erosion. However, they are viewed as unsightly and smelly by hoteliers, sunbed rental companies, beach bar and restaurant owners. Current thinking is that beaches covered with Posidonia will not be attractive to tourists. As a result, before the summer tourist season, bulldozers are used to remove all traces of Posidonia. Ironically, in the winter, due to the lack of protection afforded to the beaches by the leaves, much of the sand is removed by storm wave action and run off from seasonal rivers. This means that prior to the arrival of new tourists around Easter, beach replenishment is necessary. Sand is either purchased and transported from inland quarries, or dredged from the sea bed. Neither are cheap options. The sand is then dumped onto the beaches in order to cover rocks and pebbles and to increase beach width. This process is also known as beach nourishment.
Fertilizer use: although illegal, there is anecdotal evidence that some hoteliers who have cleared beaches in front of their hotels, have then sold the Posidonia to local farmers for use as fertilizer.
What is being done?
In 1999, the Posidonia oceanica meadows in Ibiza and Formentera were declared a UNESCO World Heritage Site. Under the European Commission Habitats Directive (Dir 92/43/CEE) the Posidonia oceanica meadows are identified as a priority habitat type for conservation.
There is an annual Posidonia festival in the village of Deià located on the north western coast of Mallorca. It aims to increase awareness of practices that promote the protection of Posidonia and the natural environment.
The http://www.balearslifeposidonia.eu/index.php?register_vars[lang]=en is a website for the Balearic Islands which enables boat users to reserve buoys in designated anchorage sites from June to September.
On 14 August 2016, the newspaper Diario de Mallorca, reported that the Balearic Island government recognised that the processing of fines for anchoring in Posidonia meadows was taking far too long.
In May 2017, the Balearic Islands regional government published a draft law related to the protection of Posidonia. Anchoring will only be allowed in sea grass areas if undertaken with ecological buoys. These are designed to prevent the damage that traditional anchors cause to Posidonia meadows. In addition, the law also addresses the removal of dead Posidonia leaves from beaches using bulldozers. This will not be permitted on beaches classified as ‘natural’ (i.e. with very little or no urban development). However, it will still be permitted on beaches classified as ‘urban’. Heavy fines will be imposed on anyone not complying with the new legislation.
For a small Mediterranean island whose economy relies heavily on beach tourism, the preservation of a plant that provides natural protection against the erosion of beaches should be a high priority.
The study includes visits to different sites. Each site focuses on a different aspect in order to obtain an overview of the subject.
- to survey an unreconstructed beach landscape that includes Posidonia litter (dead leaves); to consider the threats to Posidonia and the possible consequences if these are not addressed.
- to investigate the impact of human intervention in a natural ecosystem;
- to investigate the level of awareness of the issues surrounding Posidonia within different stakeholder groups; to survey a reconstructed beach landscape that includes Posidonia litter.
Both qualitative and quantitative primary data can be collected by students. Qualitative techniques can include interviews, questionnaires and observations. Quantitative techniques can include the measurement of Posidonia cover on different beaches.
Qualitative and quantitative secondary data can be requested. This includes: transcripts of interviews with members of different stakeholder groups; photos, maps and newspaper reports; and data related to tourism, demographics and employment.
Students will be assisted in designing a study that allows data to be collected in order to investigate and answer a research question. Possible research questions are:
- Why are the Posidonia meadows so important to Mallorca?
- What are the main threats to Posidonia meadows in Mallorca?
- What solutions have been found to counter these threats?
- Have solutions had a positive impact?
- What are the possible consequences if these threats remain unresolved?
- Has there been an impact on the tourist industry?
- How can this impact be measured?
- Are tourists aware of the issues surrounding Posidonia?
- If so, are they concerned?
- Is the Mallorcan government addressing the issue of the decline in Posidonia meadows?
- Has there been any conflict between the different stakeholder groups?
- How aware are the different stakeholder groups of different view points?
- Can the impact of clearing Posidonia from beaches be measured? If so, how?
Field study sites
1. Around Port Vell near Cala Bona
Objectives: To survey an unreconstructed beach landscape that includes Posidonia leaves; to consider the threats to Posidonia and the possible consequences if these are not addressed.
Methodology (primary data collection): Qualitative: interviews, observations and photpography; quantitative: beach transects to measure the presence of Posidonia, beach width and beach gradient.
Background information: This is one of the areas in Mallorca where a lack of industrialised tourism means that Posidonia is not removed from the beaches. However, the ‘unspoilt’ nature of these beaches means that they are attractive to boat owners who anchor close to shore as well as to property speculators.
Conflict: It is alleged that boat owners who anchor their craft near this coastline are damaging the Posidonia meadows. At a micro level, owners of the beach front houses are reliant on Posidonia to provide protection for the beach and reduce erosion. At a macro level, the cumulative effect of all actions that result in a decrease in Posidonia will be damaging to the whole Mediterranean area. Stakeholder groups include: the European Commission Directorate-General for the Environment, the Balearic Islands government, the Mallorcan government, Mallorcan government agencies, town councils, NGOs, the fishing industry, the yachting industry, the construction industry, quarry owners, hotel owners, local business people, tourists and local residents.
2. Cala Bona
Objective: To investigate the impact of human intervention in a natural ecosystem.
Methodology (primary data collection): Qualitative: interviews, observations and photography.
Background information: The main economic activities of this area are related to tourism. The majority of local residents are employed by the tourism industry. Beaches are cleared of Posidonia during the tourist season as it is viewed as undesirable. Natural protection was initially replaced with hard engineering schemes in order to try to attempt to protect the beaches from erosion from September to May. These included piers, breakwaters and sea walls. More recently, soft engineering schemes such as beach replenishment have been implemented. However, it is debatable if beach replenishment is really undertaken in order to prevent erosion. Making beaches attractive to tourists safeguards income for many local businesses.
Conflict: The development of conflict between stakeholder groups is related to the reliance of the tourist industry on an altered touristed beach landscape in defiance of environmental well being.
Summer: Posidonia clearance from beaches plus beach replenishment
Summer: mass tourism
Autumn: beach erosion due to storm rainfall and higher tides
Winter: beach erosion due to storm waves
Spring: beach erosion due to higher rainfall and higher tides
Summer: Posidonia clearance from beaches plus beach replenishment
Regional stakeholder groups include: Mallorcan government agencies, the town councils, NGOs, the construction industry, quarry owners, hotel owners, local business people, tourists and local residents.
3. Cala Millor
Objectives: To investigate the level of awareness of the issues surrounding Posidonia within different stakeholder groups; to survey an reconstructed beach landscape that includes Posidonia leaves.
Methodology (primary data collection): Qualitative: interviews, questionnaires, observations and photography. Quantitative: questionnaires, beach transects to measure the presence of Posidonia, beach width and beach gradient.
Background information: The main economic activities of this area are related to tourism. The majority of local residents are employed by the tourism industry. As in Cala Bona, beaches are cleared of Posidonia for the summer tourist season.
Conflict: Again, the development of conflict between stakeholder groups is related to the reliance of the tourist industry on an altered, touristed beach landscape in defiance of environmental well being. Regional stakeholder groups include: Mallorcan government agencies, the town council, NGOs, the construction industry, quarry owners, hotel owners, local business people, tourists and local residents.