Coastal Ecosystems, Conflicts and Management
Coastal Dunes
Dunes develop along coasts with a constant supply of sand. These tend to be at coasts with a dominant constructive wave pattern that supplies material through the swash. A large tidal range allows for a large beach to develop and dry out so that sand can be moved by the wind and allowed to build up at the back of the shore. Sand accumulates at the backshore where seaweed and drfit wood traps it. Over time the area becomes colonised by salt resistent plants like sea couch grass. Later marram grass stabilizes the dunes. This vegetation stabilises the dunes and allows further vegetation to colonise it. As you move landward away from the sea, dunes grow in size and maturity and the density of vegetation and biodiversiy increases. The diagram below shows the text book dune cross profile and plant succession.
Salt Marshes
Salt marshes develop mainly in temperate climates along coasts that have remained relatively unregulated by human management. They form in low energy zones where sediment has been deposited and salt resistent vegetation has colonised. Typically they form at estuaries and behind spits. They are frequently inundated by salt water from the sea and may also have a supply of freshwater from a near by river. The mix of salt water and freshwater is called bracken water. Saltmarshes are dynamic environments and in constant change. Creeks, streams and lagoons form between sand bars which constantly change location. The salt marsh is characterised by dense salt resistent plants and high biodiversity that supports an enormous variety of marine life and wading birds.
Mangroves
Mangroves develop in tropical climate regions with average temperatures above 20°C. They form at coasts that have a good sediment supply and extensive tidal ranges. Typically mangroves are found on sheltered muddy shores where the land is encroaching on the sea but they also grow on coral reefs and on sandy shores. Mangrove forests and swamps produce a dense low lying forest canopy that has adapted to thrive in salty waters and remain in waterlogged environments. They grow both within the salt water and extend inland where they can reach heights in excess of 30 meters. There are different plants within the cross profile of the mangrove forest. The Red Mangroves have especially adapted to waterlogging and salt water as they grow on a dense root structure called prop roots and stilt roots and excrete salt from filters in their roots as well as store salt in older leaves and thick bark. Their roots also have lenticles for capturing air during low tide.
Biodiversity
- Mangroves can be nearly as productive as tropical rainforests
- The mud is a critical role as a nursery for the sea’s fish, shrimp larvae, crabs and crustacea
- Mangrove mud is loaded with billions of bacteria. This is a great indication of the incredibly high productivity
- It support over 250 different bird species and many large mamals, including the Royal Bengali Tiger
Coral Reefs
Coral reefs usually form in shallow tropical waters. There are 4 types of coral reefs. These include Fringe Reefs, Barrier Reefs, Patch Reefs and an Attol. Reefs need shallow water as this provides the sunlight needed for the photosynthesis. Firstly Fringe Reefs develop around small islands that are often volcanic in their form. Later larger reefs encircle the island and build up height through the laying down of calcium carbonate. These large Barrier Reefs have a crest that marks the highest point and either side a back reef and forereef. As the forereef slopes seaward it often has a characteristic steep drop off where deeper water reefs develop. In the lagoon zone between the island and the Barrier Reef smaller Patch Reefs grow and the entire network of reefs may become an Atoll if the original volcanic island becomes sufficiently weathered and eroded or simply sinks in the mantle due to its weight. Plants and algae convert sunlight into chemical energy through photsynthesis and provide oxygen and sugar for other organisms to grow. These organisms live in polyps. As the organisms grow they secrete calcium carbonate. At night the polyps extend their tenticles and feed on plancten. The entire ecosystem supports a vast quantlty of marine life.
Biodiversity
Coral reefs are the most productive of all ecosystems and support when in a healthy state an abundance of marine life. They produce over 2500 tones of organic matter per km2 every year.
Activity
Watch the video above and produce a food web for a coral reef ecosystem
For each of the four coastal ecosystems make a list of all the physical factors that lead to their formation.
Practice drawing cross sections of these four coastal ecosytems, include in your digrams different stages of development and succession
Coral reefs are the most productive of all ecosystems and support when in a healthy state an abundance of marine life. They produce over 2500 tones of organic matter per km2 every year.
Activity
Watch the video above and produce a food web for a coral reef ecosystem
For each of the four coastal ecosystems make a list of all the physical factors that lead to their formation.
Practice drawing cross sections of these four coastal ecosytems, include in your digrams different stages of development and succession
Threats to Coastal Ecosystems
The threats to coastal ecosystems can really be summarised under two main headings, population growth and coastal development. Firstly as population grows more and more land is needed to support agriculture and human settlement. This results in projects such as wetland drainage for agriculture. As populataion size increases so does the need to develop the coast further. Accoring to the WWF half of the world wetalnd environments inlcuding saltmarshes and mangroves have been lost since 1900 they state that conversion of wetlands for commercial development,, extraction of minerals and peat, overfishing, tourism, sedimentation, pesticide discharge from intensive agriculture, toxic pollutants from industrial waste, and the construction of dams and dikes, often in an attempt at flood protection, are major threats to wetlands everywhere.
Threats to Mangroves
The following PowerPoint resource develops the threats to mangroves in detail
Threats to Mangroves
The following PowerPoint resource develops the threats to mangroves in detail
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Threats to Coral Reefs
There are many threats to coral reefs, Globally the main threat is due to a lsow warming and acidification of the ocean. This causes coral bleaching. However specific local threats damge reefs ind different regions. the following map shows the pattern of these threats.
There are many threats to coral reefs, Globally the main threat is due to a lsow warming and acidification of the ocean. This causes coral bleaching. However specific local threats damge reefs ind different regions. the following map shows the pattern of these threats.
Activity
Using the map and data above answer the following questions.
1. Using the map state the threat impacting the most coral reefs
2. From the graph showing major threats to reefs which factor has the highest threat?
3. Which region of the world has seen the biggest loss of coral reefs
4. Using all the infomration explain your answer to 3.
Using the map and data above answer the following questions.
1. Using the map state the threat impacting the most coral reefs
2. From the graph showing major threats to reefs which factor has the highest threat?
3. Which region of the world has seen the biggest loss of coral reefs
4. Using all the infomration explain your answer to 3.
Coral Bleaching
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Over Exploitation
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Sedimentation
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Case Study: The Management of the Great Barrier Reef
The following resource has been adapted from a presentation given by John Doy provides an outstanding an overview of the the management of the GBR. Just click on the image below. Another good website with a multitude of resources on the management of the GBR is here.
Conflicts
Conflict at the coast occurs between different interest groups. However the main conflict is between conservationists and interests groups whose activities threaten marine ecology and biodivesrity. A good example of a coastline experiencing conflicts is the Daintree Coastline in Queensland Australia.
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Coastal Retreat and its Management.
There are a number of factors that can lead to fast rates of coastal retreat. These includes exposed cliffs with soft rocks and large fetch. Human management can also accelerate rates of erosion. Coastlines can be mangaged through both hard and soft engineering.
Sea Walls
Sea walls are an example of hard engineering. They are built of resistent concrete and are normally used to protect coastal resorts and important infrastructure. They are effective at preventing erosion and give people security from flooding. However they are expensive and costly to maintain. Another disadvantage concerns the way they reflect wave energy back on to the beach. This causes erosion of the beach and the sea wall to be undermined. This reduces its lifespan and maintenance costs. Cost - €4-5000 per meter Rock Armour Rock armour is made of resistant rock and piled up to protect the coastline. They are effective for reducing erosion as wave energy is absorbed by rock armour as it can move through gaps between the rocks and the boulders themselves can sway with the impact. On some coasts they make for a more natural aesthetic but on other coasts they are quite an eyesore and can make beach access dangerous. There is less maintenance costs but if rock is imported then costs rise. Cost -€3-4000 per meter Groynes Groynes are used to intercept the transportation of beach material via long shore drift. In doing so the size of the beach builds up and creates a larger buffer to absorb wave energy, reducing coastal erosion where they are used. They also create a larger recreational space for tourism, which brings a lot of money to the local economy. Wooden groynes are cheap but don't last long. Rock armour groynes are longer lasting but more expensive. The big problem with groynes is that they speed up rates of erosion down drift. Cost - Wooden groynes €8000 each Rock Armour Groynes - up to €200 000 each Revetments Generally wooden slatted structures constructed towards the backshore. They are built ona angle to help absorb and disiapte waven energy. They are effective at reducing rates of erosion at the base of the cliff and and they reduce erosion of the beach compared to sea walls. They are considered by some to have less visual impact compared to sea walls. The main problem is that they don't last long as look terrible when in a poor state of repair. They also become more dangerous. Cost - €2000 per meter Breakwaters These are large concrete blocks and boulders placed parallel to the shore in the nearshore area. The purpose is to change the direction of waves and reduce longshore drift. They also help absorb wave energy. As a conequence beaches build up in the low enrgy zone directly behind the breakwater. Howver due to wave refraction beach erosion takes places between the breakwaters leaving a narrower than average beach. Breakswaters are also considered unattractive Cost - €200 000 - €500 000 each Gabions Gabions are metal cages filled with rocks. The main purpose is to privide stability and support to the slope of a cliff. They are not strong structures and cannot withsatnd the strongest waves but are very cheap. They also allow vegetation to grow within them and so have a lower visual impact on the coast. Cost - € 400 per meter Beach Replenishment This involves the delivery of fresh beach material to increase the size of the beach. It is considered a softer approach as it relies on the size of beach to act as a buffer against waves and it doesn't necessarily interfere with coastal processes. It also creates a natural looking coastline. However dredging beach material form offshore can increase rates erosion in other areas of the coast and it has a big impact on the natural ecosystem. It's nt as cheap as you think though! Cost - €20 per cubic meter Salt Marsh Restoration With increasing costs of hard engineering and predicted sea level rise in the future authorities need to consider cheaper alternatives. Saltmarsh restoration returns previously drained areas of coast back to salt marsh. This creates available space for rising tides to flood and it reduces the impacts of erosion and flooding in other areas of the coast. It creates a very natural coast with big benefits for biodiversity. This is also attracts tourists, which bring money to the local economy. It is relatively cheap and long lasting. The only costs involved come from the dismantling of the old sea walls. There may be a cost for the land as well. |
Case Study: Coastal Erosion and Management
The Holderness Coast in eatern England is one of the fastest eroding coasts in Europe. It has a number of physical and human causes and there is a great variety of management methods being deployed.
Activity
Using the rsources below explain the causes of erosion at Holderness Coast.
Discuss how human management is part of the problem
Explain the impacts of erosoion and management along the coast.
Activity
Using the rsources below explain the causes of erosion at Holderness Coast.
Discuss how human management is part of the problem
Explain the impacts of erosoion and management along the coast.
Exam Tip!
It should be possible for this latter question to develop 2 or 3 different towns along the Holderness coast. There is also the opportunity to develop scale, such as local factors. e.g. tourist towns, regional factors, e.g. Main road at Mappleton and national factors e.g. gas terminal, in Easington.
A second structure rleated to impacts could be social, economic and environmental.
It should be possible for this latter question to develop 2 or 3 different towns along the Holderness coast. There is also the opportunity to develop scale, such as local factors. e.g. tourist towns, regional factors, e.g. Main road at Mappleton and national factors e.g. gas terminal, in Easington.
A second structure rleated to impacts could be social, economic and environmental.