What coastal dunes have to offer?
After moving to Cape Town, I have never experienced so much wind in all my life. My house is near the sea where there are quite a few dunes scattered along the coastline. Whenever it’s windy, it blows the sand into the road, like being in a mini sand storm. Once the wind lifts, piles of sand cover the edges of the road and this is precisely how coastal dunes move and regenerate themselves. I think out of all the environmental habitats coastal dunes are the least popular and unknown; however, these sandy yet grassy habitats are incredibly significant to coastal areas.
Coastal dunes have provided people with essential services such as raw materials; coastal protection; water catchment and purification; maintenance of wildlife; carbon sequestration, tourism, recreation, and education. Along many sandy coastlines, coastal dunes form the first line of defence against the sea. The growth and evolution of coastal dunes depend on sediment supply, vegetation effectiveness and climatic variables such as wind climate, sea level, and wave conditions. Concerning water resources, coastal dunes act as freshwater aquifers and recharge areas, the freshwater that accumulates below the dunes locally reduce the aquifer salinity. Dune systems, as freshwater resources in the coastal zone, are becoming increasingly crucial as freshwater availability is decreasing under the pressure of land use and climate. The dune environment is a dynamic system that is vulnerable to many natural and human factors. A change in one of these factors has consequences for dune development and its functioning.
The fragility of coastal dunes
Physical stressors on dune plants include high air temperature, shifting sand, nutrient limitation, and high levels of airborne salt spray and overwash due to storm surges. These daily, seasonal and episodic stressors have significant consequences for growth, reproduction, and the survival of plants. Dune species have evolved numerous adaptations to cope with environmental stressors.
Coastal dune ecosystems are threatened worldwide due to the human reduction of natural-land area and its modification. Coastal dunes are attractive locations for human settlement and recreation. For example, nearly 75% of Mediterranean coastal dunes have been lost in the last 30 years, and in New Zealand, coastal dunes have decreased from 129,000 ha to 39,000 ha (~70% of the habitat lost) over the past 100 years due to land conversion and erosion. Similar losses are observed in North America, Australia, Europe and Asia. In particular, during the past decades, tourism, the expansion of urban areas, and the spread of agriculture and afforestation activities have strongly shaped coastal landscapes. Beaches on highly disturbed areas are subject to human activities (e.g. trampling, sand removal, and mechanical cleaning), which threaten the natural biodiversity of sandy shore ecosystems.
I see people walking across the dunes all the time, sometimes with their dogs in tow It may seem strange, but the vegetation that grows on dunes are susceptible, particularity new shoots as they haven’t become established yet, it’s hard to settle down when the earth below you is literally changing and moving all the time. To compound this problem, people walking all over you. Another way tourism affects dunes is by the development of commercial beaches, including raking and building permanent structures. When permanent structures are made, the dune loses some of its ability to regenerate itself. Without the ability to restore itself, the dune is at risk because any damages done will have lasting effects. Coastal dunes are also highly susceptible to biological invasions, especially by plants intentionally introduced for dune stabilisation.
Nations with extended and densely populated coastlines risk high costs for the socio-economic damages and the reconstruction of coastal areas affected by extreme events. Climate change will increase sea-level rise in the coming decades, causing landward ingression of the sea and modifying the coastal aquifer recharge dynamics and freshwater availability. In particular, in the lowland coastal area, a low rate of sea-level rise will lead to a drastic reduction of the beach-dune system and aquifer recharge area, which will cause an inland shift of saline groundwater. Also, changing precipitation regimes and groundwater recharge rates may cause a similar landward shift of the saltwater-freshwater interface, thus increasing the salinity of surface water bodies and coastal wetlands. Natural environments can sustain disturbances up until a threshold, and recently, coastal dunes have been reaching their threshold due to the rise in tourism.
Unfortunately, despite their importance, habitat loss and degradation due to land-use change has continued and is expected to quicken as sea levels rise with a changing climate. On top of this, the general public is often unaware of the importance of these vegetative sandy habitats, and this fact does not help to implement appropriate conservation strategies. Coastal dune habitat needs to be highlighted for conservation and restoration to amend past degradation and to allow coastal dunes to persist into the future. A couple of years ago, a hotel on the beachfront, on the western cape decided to level a dune which had formed in front of the restaurant area preventing guests from admiring the sea. They did this without consulting any environmental organisation. Once the authorities found out, they had to pay a fine and restore the dune themselves.
Managing coastal dunes involves, the stability and dynamics of these systems which are controlled by an interaction between wind erosion, sand supply, and vegetation dynamics. Restoration efforts need to put emphasis on plant species that are constrained to coastal dunes, because they are ecologically unique and provide essential ecosystem services for human populations. The loss of these endemic coastal dune plants is a problem because they contain vital ecosystem services, such as being a safe refuge for animals, soil stabilisation and improved soil fertility. Reintroductions are often needed because natural reestablishment of endemic species is unlikely because their habitat is often fragmented. Research suggests that rehabilitating plant communities will require more than ten years to restore species diversity.
Restoring coastal dunes
Restoration projects of coastal dunes in urban areas have been implemented in some parts of the world aimed at restoring ecosystems and enhancing the resilience of beaches to erosion and loss of service. Although the number of projects has increased in recent years, strategies to recover dunes are still fragmented. Community engagement in dune restoration projects in urban areas are under enormous pressure. This community engagement is crucial to their success because it promotes within the community, a perception about the importance of these ecosystems and their environmental services, inviting more allies for the conservation of green urban areas.
The Coastal Community Engagement Program (CCEP), is a partnership initiative between the City of Gold Coast and the Griffith Centre for Coastal Management to maximise community understanding of natural coastal processes and management strategies for the local beaches, foreshores and dunes. BeachCare aims to provide an opportunity for individual community members to contribute to caring for their local coastal environments. One of BeachCare’s objectives is to restore, with community input, dunes affected by severe erosion in an area that is vulnerable to extreme climate events. The volunteers are involved with planting and watering endemic/native plants, or removing weeds.
Today, coastal dunes are recognised as a cost-effective method of protecting community infrastructure from storm damage. Despite the value of dunes for shore protection and environmental benefits, their role in providing these benefits aren’t always well understood or appreciated by coastal landowners and beach users, and therefore sometimes not incorporated into design conditions.
Take home message
Like I said at the beginning of this post, coastal dunes are very underrated, especially if you don’t live on the coast. Saying this, they are significant ecosystems which are very sensitive to change. If they disappear, not only will animals, plants and birds suffer but ultimately we will be more exposed to elements such as storm surges and increased salinity in the water table. So spread the news, and let’s save these picturesque ecosystems.
By – asbpa.org. http://asbpa.org/wpv2/wp-content/uploads/2016/03/dunes_84_1.pdf
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