The System of Dunes

Describe about the Coastal Regions around Darwin?
 

The system of dunes including the foredune, primary foredune, secondary foredune and tertiary foredune contribute to the system of dunes across the coastal regions around Darwin. Indeed, the depth of the soils across various dune systems ranges between 5 – 200 metres around the coastline. The foredune region invaded by sand layer and therefore lacks nutrients and supports the growth of colonizer plants. However, the tertiary dune enriched with rich nutrients encapsulated under dense layers of soil resulting in sustained growth of forests and woodland community across that region. Similarly, the primary foredune occupied with grasses, spinifex and mat plants in accordance with the thickness of soil (i.e. 3 cm) and its nutrients capacity. Furthermore, the region of secondary dune supports the growth of woody scrubs and small tress adding to the biodiversity of the dune ecosystem.

The foredune regions remain invaded by space and track (including berm and swale) with the soil depth of 5 – 10 metres. However, the primary dune composed of superficial layer of sand and thick layers of soil beneath the sand stream extending until depth of 75 metres. The secondary dune indeed extends until the depth of 150 metres and contains the layers of moist dark soil beneath the superficial layers of sand particles. In fact, the soil under the tertiary dune acquires the depth of 200 meters making this region as the deepest of all dunes across the coastline. The soil of the primary foredune region remains occupied by Casuarina equisetifola tree, as evident in the diagram. The branches of this tree terminate in sharp edges in the form of needle, with toothy appearance of leaves. The conical structure of fruits and appearance of conical prominences beneath the tree include the prominent features making it easily identifiable across the primary dune region. The secondary dune region indeed, occupied with Pandanus spiralis with extended surface area across the soil. This tree features like palm with leaves appearing as spiky clusters, thereby providing it a unique appearance across the coastline. The tertiary dune region indeed, succeeded by monsoon rainforest with intermittent wetland. This geographical confinement is also known as tropical deciduous forest in context to the occurrence of intermittent dry and wet seasons, and identifiable through existence of tall bamboo trees.

                                                    (Casuarina equisetifola)                                                          (Pandanus spiralis)

The city of Darwin identified for its geographical biodiversity in context to the variety of coastal ecosystems around the region. Wolanski (2006:p. 435) reveal the coexistence of wet and dry ecosystems predominated by cyclonic and monsoonal occurrences intermittently across Port Darwin and Shoal Bay throughout the year. The coastal bioregions across the northern territory (of Darwin) correspond to the locations including Shoal Bay, Mindil Beach, Vesteys Beach, Fannie Bay, East Point, Nightcliff, Rapid Creek and Buffalo Creek Management Areas, Charles Darwin, Stuart Park, Lamaroo Beach, Casuarina Coastal Reserve, Tree Point Conservation Area and Esplanade. The academic literature reveals the acidic nature of soil in regions of Shoal Bay across Darwin Coastal (Prasad & Power, 1997:p.72). The Shoal Bay indeed known by the sand dunes scattered consistently around the shores. The National Geographical Intelligence Agency’s findings illustrate the soil depth range of 18.3 – 22 metres constituted by sandstone particles across the entrance, and turning rapidly to 7.3 metres following the distance of 1 miles from the point of entry of the Shoal Bay (NGIA, 2004:p.71). The vegetation of the Shoal Bay comprises of monsoon vine forests and rainforests occupying the coastal bioregions. However, the Casuarina coastal territory comprises of wide sand dunes with depth range in accordance with the 7-meter tide resulting in the formation of expandable beach (Short & Farmer, 2012:p.45). Wolanski (2006a:p.451) reveals the terrestrial habitats of Casuarina Reserve constituting the coastal vegetation across Darvin Harbour. The flora of the Casuarinas Coastal Reserve enriched with the botanical species including Rotten Cheese Fruit, Screw Palm, Ghost Gum, Leichhardt Tree, Beauty Leaf, Banyan Fig, Tamarind, and Poison Peach.  However, the trees and plants including Peanut Tree, Indian Beech, Pink Paperbark, Northern Black Wattle, Beach Hibiscus, Cluster Fig, Coastal Sheoak, Paperbark, Cheesewood, Milky Pine, River Red Gum, Tape Vine, Lacewing Vine, Native Grape, Snake Vine, Little Cheeses, Lime Berry, White Grape, Arrowroot and Kapok Tree further add to the terrestrial habitation across the Casuarinas’ region. Indeed, these findings from the academic literature reveal the biological diversity in terms of variations across ecosystems in coastal regions around Darwin. The marine ecosystems including mangrove forests, coral reefs and grassy meadows pertain to the biological invasions diversifying the various ecosystems across the Darwin’s coastal regions. This diversity in coastal ecosystems attributes to the gradual and sustained expansion of the coastal wetlands facilitated by the rich vegetation across the coastal regions (Perillo et al, 2009:p. 9). Indeed, the role of bio-films in stabilizing the mudflat assists in establishment of thick mangroves vegetation leading to considerable reduction in soil erosion by the tidal currents. This results in proportionate slowing of the tidal currents leading to reduced erosions of the wetland across the coastal regions.

Vegetation and Biodiversity

The destructive influences on the coastal ecosystems include the impact of rapid urbanization on the sustainability of the costal habitat (Miththapala, 2013:p.22-28). Indeed, the increased human encroachment on the coastal regions results in the degradation of the tidal flats resulting in gradual destruction of the coastal bioregions across Darwin. Furthermore, the academic literature reveals the negative influence of human activities including dam construction and dredging of rivers on the sustainability of coastal ecosystems in terms of degradation of the tidal flats. Indeed, the chemical by-products and the industrial effluents contaminate the marine ecosystems leading to coral bleaching and smothering of coastal vegetation (Lorenz et al, 2013:p.270).

The destructive waves resulting from the cyclones lead to massive soil erosion across the coastal regions, thereby destabilizing the ecosystem in terms of disruption of the flora and fauna under the coastal confinements. In fact, the strong impact of the destructive waves across the coastal line pulls back the sand dunes from the beach as tidal flats unable to absorb the high energy of the waves resulting in backwash and degradation of the coastal ecosystem.

The coastal ecosystem further degraded by the adverse influence of Wave Refraction and Longshore Drift (Hyndman, 2011:p.388). The process of Wave Refraction results in bending of the waves toward the shore with the rapid movement of wave currents in the deeper water resulting in gradual dredging of the sand dunes from the shore. Similarly, the Longshore Drift results in elimination of the sediment particles from the beach under the influence of wave currents challenging the sustainability of the beach while striking it repeatedly at an angle.

The academic literature documents the negative influence of ocean acidification, habitat destruction and natural calamities on the sustainability of the coastal ecosystems (Roundtable on Environmental Health Sciences, Research, and Medicine, Board on Population Health and Public Health Practice, Institute of Medicine, 2014). Indeed, the research studies indicate the decreased survival rates of coastal plants and animals due to increased acidification of the marine water from the industrial toxicities. Additionally, the disappearance of the coastal habitat resulting from elevated sea level and coastal development by humans leads to loss of biodiversity across the coastal regions surrounding Darwin. The recurrent blowouts due to natural calamities or human interference result in formation of parabolic dunes leading to loss of vegetation and consequent disruption of biodiversity of the coastal ecosystems (Martinez et al, 2013:p. 3).

The primary, secondary and tertiary foredunes across the Darwin coastline eroded due to various coastal processes and environmental influences. The physical, biological and chemical influences of weather eroded various dunes across the coastline leading to the gradual destruction of gun placements while leaving the marine debris near the shore. Indeed, the intertidal, backshore and offshore zones gradually disrupted under the influence of climatic fluctuations across the coastal region. The following diagram reveals the patterns of dunes drifting induced by the action of coastal waves. The consistent physical impact of the coastal waves on sand dunes gradually degrades them, thereby resulting in long-term recession of the frontal and incipient dunes.

Coastal Bioregions of Northern Territory (of Darwin)

The constructive influences warranted to maintain the coastal ecosystem include the creation of Riprap across the beaches. Indeed, the protective methodology of riprap assists in preventing the erosion of sand dunes and vegetation across the coastal lines (Schwartz, 2005:p.531). The rocks employed to safeguard the coastal ecosystem assist in preventing the erosion by assimilating the energy of water currents, thereby reducing the capacity of the waves to capture and erode the coastal vegetation.

Indeed, the sand drift fencing is another protective mechanism necessary to conserve the sand dunes across the coastal regions (Dixon, 2011:p.30). The sad drift interception fencing facilitates trapping the high velocity winds across the vicinity of sand dunes at coastline, thereby challenging the movement and affinity of sand particles toward the water currents. Consequently, the biodiversity of the coastal ecosystem preserved with the installation of the interception fencing system due to its potential affect in preserving the sand erosion across the coastline.

The employment of vegetation and plant protection devices facilitate in stabilizing the primary and secondary sand dunes across the coastline (Dixon, 2011a:p.29). The physical protection to plants in terms of installing protective coatings prevents their degradation under the influence of the high velocity wind currents. Moreover, implanting extensive vegetation assists in sustaining the sand dunes and proportionately enhancing coastal flora across the target system.

The other constructive measures employed with the intent of protecting the coastal dunes include configuring walkways to cease the foot traffic across the dune areas (Beckman, 2013:p.80). Indeed, these walkways are highly effective in preventing dune blowouts under climatic influences resulting in the preservation of the natural flora and biodiversity of the coastal ecosystem.

The construction of costal protective structures including Groynes and Sea Walls assists in safeguarding the beach materials and enhancing the coastal biodiversity (Mitra, 2013:p.153). The Groynes constitute the concrete barriers implanted perpendicularly from shore to the seawater for protecting the sediment from moving toward the water currents. Similarly, the sea walls constituting the concrete material efficiently bounce back the high-energy waves to the sea to prevent erosion of sand dunes and coastal vegetation under the influence of floods and storms.

Indeed, sustainable coastal management warrants employing constructive approaches to preserve the biodiversity across coastal ecosystems in Australia (Kenchington et el, 2012:p.29). The perspectives of ecological conservation require thorough consideration over and above the commercial ideology in context to prioritizing safety and preservation of flora and fauna across the Australian coastal regions. Stringent jurisdictions need strategic implementation to protect the coastline from human invasion and natural calamities, thereby leading to secured and sustainable coastal bioregions across the Australian subcontinent.

References:

Beckman, D 2013, Marine Environmental Biology and Conservation, Jones & Bartlett, Burlington

Dixon, K 2011, Coastal Plants: A Guide to the Identification and Restoration of Plants of the Perth Region, CSIRO, Australia

Hyndman, D & D 2011, Natural Hazards and Disasters (3^rd edn.), Cengage, USA

Kenchington, R, Stocker, L & Wood, D 2012, Sustainable Coastal Management and Climate Adaptation: Global Lessons from Regional Approaches in Australia, CSIRO, Australia

Lal, R, Lorenz, K, Hüttl, R, Schneider, B & Braun, J 2013, Ecosystem Services and Carbon Sequestration in the Biosphere, Springer, NY

Martínez, L, Gallego-Fernández, J & Hesp, P 2013, Restoration of Coastal Dunes, Springer, NY

Miththapala, S 2013, Tidal flats, IUCN, Sri Lanka

Mitra, A 2013, Sensitivity of Mangrove Ecosystem to Changing Climate, Springer, New Delhi

National Geographical Intelligence Agency 2004, North, West and South Coasts of Australia (8^th edn.), Prostar, Annapolis

Perillo, G, Wolanski, E, Cahoon, D & Brinson, M 2009, Coastal Wetlands: An Integrated Ecosystem Approach, Elsevier, Netherlands

Roundtable on Environmental Health Sciences, Research, and Medicine, Board on Population Health and Public Health Practice, Institute of Medicine, 2014, Understanding the Connections Between Coastal Waters and Ocean Ecosystem Services and Human Health, The National Academies Press, Washington DC

Schwartz, M 2005, Encyclopedia of Coastal Science, Springer, Netherlands

Short, A & Farmer, B 2012, 101 Best Australian Beaches, New South, Australia

Wolanski, E 2006, The Environment in Asia Pacific Harbours, Springer, Netherlands

Wolanski, E 2006a, The Environment in Asia Pacific Harbours, Springer, Netherlands