Australia's Coast, Its Nature and Importance

7/29/2019 Australia's Coast, Its Nature and Importance

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Climate Change Risks to Australias Coast 9

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CHAPTER

AUSTRALIAS COAST ITSNATURE AND IMPORTANCE

KEY FINDINGS

The coastal zone is highly dynamic. Australias shoreline has shifted greatly in the geological past,and climate change will bring considerable further change to its position.

Australias coast has been relatively stable over the past few decades, and planning in a number of areas hasnot taken into account the extent of observed shoreline instability.

Australia has four major coastal regions, each with different geomorphology and climate characteristics.Each will be affected by climate change in a different way.

The coastal zone has immense social and economic value to Australia. It is where most Australians live andwork and it is the conduit for our export economy.

Extensive ecosystems of global and national signif cance are in the coastal zone, and the diversity of marineplants and animals in southern Australia is among the highest in the temperate regions of the world.

This risk assessment is intended to inform a national consideration of the adaptation needed to protect ourkey economic, social and environmental assets in the coastal zone in the face of climate change.

1.1 Coastal dynamicsAustralias 35,000 kilometre coastline is dynamic.The climate and the sea have always been major forcesshaping the coast, and over time the position of ourshoreline has shifted large distances. Now climatechange is driving the evolution of a new coastlinefor Australia, but the location of that coastline is notyet clear.

1.1.1 Our shifting shoreline

the geological and recent past

The coastline of Australia is continually changing.The level of the sea is regionally variable andmoves up and down as a result of changes in oceancurrents, ocean temperature, atmospheric pressure andf uctuations in the amount of water held in the greatglaciers. The land can also move. Coastal marginscan rise or fall because of tectonic forces or changesin glaciation, and the weight of sediment deposited indeltas can cause the coast to subside, as is happeningin the USA at the mouth of the Mississippi.

Over tens of millions of years, these processeshave driven major f uctuations in the position ofAustralias coastline. Palaeontologists and geologistshave found evidence that the sea reached as far

inland as Norseman and the Kennedy Ranges(some 160 kilometres inland from Carnarvon inWestern Australia). The Nullarbor Plain, the LatrobeValley and the whole of the lower Murray basin toabove the LachlanMurrumbidgee junction were onceinundated by the ocean.

Global glacial (cold) and interglacial (warmer) cycleshave been a major driver of changes in sea level overthe past 2.5 million years (the Quaternary period).Sea level during the last interglacial period120,000130,000 years ago was as much as4 to 6 metres higher than it is today. In parts of South

Australia, sand barriers left by such high interglacialseas on a tectonically rising coast can be found parallelto the current coast and up to 500 kilometres inland.1Figure 1.1 shows the extent of sea inundation during thelast interglacial near Port Stephens, New South Wales.

At the last glacial maximum (20,000 years ago),sea level was around 120140 metres lower than today,with water locked up in ice sheets. Considerable areasof the continental shelf were exposed to theatmosphere and to breaking waves, Torres Strait didnot exist, and Tasmania and Papua New Guinea werejoined to continental Australia (Figure 1.2).

Most of the great glaciers stopped shrinking around7,000 years ago, and by about 6,500 years ago the sea

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10 Climate Change Risks to Australias Coast

Port StephensGrahamtown

Reservoir

Hun

ter

Riv

er

NEWCASTLE

N e wc a

s t l eB i g h t

Tilligerry

Ck

Holocene sand barrie

r

Last Interglacial sand barrier

Last Interglacial

shoreline limit

0 5 km

Figure 1.1 Maximum extent of the shoreline in the lower Hunter region, New South Wales, during the Last Interglacial (120,000 to 130,000 years ago)

when sea level was approximately 4 metres higher than present in this embayment.

reached close to its current level around the coast ofAustralia. This coincided with the Holocene interglacialglobal warm period, which we continue to enjoy.

For the past 6,000 to 7,000 years, the sea level has

oscillated within a narrow band of plus or minus2 metres. This period of relative stability is sometimesreferred to as the stillstand period (Box 1.1).

The coast that we recognise today stabilised inthis period.2 Because of the relative stability of theAustralian continent over the Pleistocene (2.5 millionto 10,000 years ago), the sea returned to a similar localelevation after each major f uctuation. Waves and windbuilt dune systems, rocky coasts eroded to form seacliffs, coral reefs developed, and valleys repeatedlyf ooded to form estuaries.

The relative constancy of sea level over the past6,000 to 7,000 years in Australia has allowed coastallandforms and ecosystems to adapt in a comfort zoneduring this interglacial phase. Small oscillations in sealevel, where they have occurred, appear to have beenslow enough to allow shoreline and estuarine dynamicsto accommodate their impacts.

On shorter timescales, parts of the coast can betransformed by extreme weather. While the frequencyof tropical cyclones is generally low, the storms theygenerate can shift large amounts of coastal sedimentand deposit it some distance inland. Stranded storm-

generated features, such as sand and shell ridges orcheniers, and shingle and boulder ridges, can persistfor thousands of years. In northern Australia,

Sydney

Perth

Popondetta

Lae

Wewak

PortMoresby

0 1500 km

Appr ox. sca le

Continental shelf

Figure 1.2 Coastline at the last glacial maximum

(20,000 years ago).

the location of detrital coral and shell deposits suggestthat even bigger tropical cyclones have occurred in thepast than those observed since European settlement.These super-cyclones and the storm surges theygenerate are likely to pose a major threat to coastalsettlement if they recur in the future.3


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Box 1.1 Coastal stability over the past

6,000 years the Australian stillstand

The Australian coast is different from most othercontinental and island shores, which have not yetreached a relatively stable sea level position after

cessation of ice melt following the last glacialmaximum. Other countries are still subject topost-glacial rebound (resulting in uplift of landdue to the loss of an enormous weight of ice afterdeglaciation), subsidence due to sediment loading,or uplift where tectonic plates collide.

The Atlantic coast of North America is a case inpoint. There, the shoreline has been evolving as sealevels have risen over the past 6,000 to 7,000 years.There is no stillstand along these shores(Figure 1.3). Similar conditions occur in southernEngland and in The Netherlands, making such areas

very vulnerable to storm attack. In contrast, parts ofnorthern Europe and eastern Canada are undergoinguplift (due to post-glacial rebound).

Figure 1.3 Post-glacial rise in sea level as shown by an envelope of the position of rising sea level and subsequent stillstand around the Australian

coast commencing between 7,000 and 6,000 years ago compared to a more continuous rate of sea-level rise towards the present along the Atlantic

coast of the USA.

PresentMSL

4

8

12

16

20

2468

DepthbelowMSL(m)

Western Atlantic sea-level envelope

East and North Australia envelope

Time (ka)0

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1.1.2 Four coastal regions

The dynamic interactions between the sea and the landover time have led to the current Australian coastline.More than 10,000 sandy beaches make up about half

of mainland Australias coast; much of the remainderis rocky shoreline.

The Australian coast can be classif ed into four broadregional environments (Figure 1.4):

Region 1 The Muddy North: highly tidal,cyclone inf uenced and muddy

Region 2 The Limestone South and West:small tides, carbonate rocks, high wave andwind energy

Region 3 Eastern Headlands and Bays:

small tides, quartz sands, moderate wave energy,many bays

Region 4 The Barrier Reef: northernQueensland, including low-lying rocky mainlandcoasts and the Great Barrier Reef and its islands.

Tasmania and the Bass Strait islands share many of thecharacteristics of regions 2 and 3.

Each region has distinctive ecosystems and naturalassets, and each is vulnerable to a different degreeto extreme weather and to the potential impacts ofclimate change.

Reg

ion

4

Regi

on1

Regio

n3

Regio

n 2

Figure 1.4 Australia can be divided into four broad coastal regions

based on geomorphology, sediment type and tide-wave regimes.


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Region 1 The Muddy North

The mainly muddy coasts of northern Australia aresubject to high tides and the destructive effects oftropical cyclones. Cyclones shape low-relief sandand shell ridges (cheniers) on muddy shorelinesfringed by mangroves. Vast tidal f ats, often bare ofvegetation, extend up many estuaries, where mangrove

communities have adjusted to tidal levels and sedimentconditions. The region has high seasonal rainfall, sosediments f ow out of catchments during the summerwet season. Complex hydrological interactionsbetween tidal f ows, river discharge and sedimentoccur in the estuaries and wide bays and gulfs.

The estuaries and the gulfs are enriched with marine lifeimportant to Indigenous communities and commercialf shing. Offshore oil and gas resources in the regionhave been developed into major export industries.

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Cyclone-generatedsand ridge

Mangrove fringe

Mud

Figure 1.5 Typical geomorphology and sediment type of

The Muddy North.

Calcarenite

ridges

Sand

Calcarenite

reef

Shallowlagoon

Figure 1.6 Typical geomorphology and sediment type ofThe Limestone South and West.

Region 2 The Limestone South and West

The coast of the south and south-west is exposed to

the worlds most energetic waves, generated in thevastness of the Southern and Indian oceans. Sedimentsare mostly derived from marine carbonates. The tracesof previous interglacial high and glacial low sea levelshave been preserved locally as calcarenite ridges orplatforms, both above and below sea level. Calcareousbeach sands can be perched on such surfaces.

Westerly winds effectively mobilise calcareous sandsinto dunes along stretches from Geraldton to WilsonsPromontory. Elsewhere, limestone forms lengthystretches of cliff, such as near Shark Bay, the Nullarborcoast of the Great Australian Bight, and in the PortCampbell area of western Victoria. The southern tracksof tropical cyclones also inf uence coastal conditionsalong the west coast.

Calcarenite rocky reefs provide buffers to waveattack in some areas and habitat for many organisms,including the rock lobster, an important export.The southern half of Australia also supports theworlds most extensive temperate seagrass meadows.


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Region 3 Eastern Headlands and Bays

The third region extends from the east side of WilsonsPromontory in Victoria to Fraser Island in Queensland.It has a low tidal range and is exposed to swell andwind waves from the Tasman Sea and Southern Ocean.The region is also subjected to periodic high-energycyclonic activity, including tropical cyclones to the

north and extra-tropical cyclones or east coast lows.Major storms have occurred in clusters at irregularintervals, for example in 1950, 1967 and 1974.

Rocky headlands separate beach and dune stretches ofvarying lengths. Towards the north of the region, sandsin the littoral system can migrate around the headlands,moving northwards. Drowned river valleys cut intoancient uplands to form intricate estuaries and low-lyingdeltas, where settlements and farms are clustered.

Region 4 The Barrier Reef

North of Fraser Island, the Great Barrier Reef (made upof more than 3,600 individual reefs) and islands extendfor 2,300 kilometres along the Queensland coast.The modern reef is relatively young and mostly formed

in the 6,000 years since the sea level stabilised. It sitson a substrate derived from erosion of the easternmargin of Australia and deposited in previous glacialperiods when the sea level was lower, and often formsa veneer over earlier reefs.

Along the mainland coast are low-lying deltas thatare periodically inundated during cyclonic f oods.In the past, storm surges and high winds have causedenormous personal and economic devastation in theseareas. Agriculture, tourism, f shing, ports and transport,as well as ecosystems, have suffered from the impactsof extreme weather. The impacts of land-based

activities that generate nutrient and sediment f uxesare a continuing threat to the health of nearshore andreef environments.

Estuary

High sand ridge

Steep inner

continental shelf

Figure 1.7 Typical geomorphology and sediment type of the

Eastern Headlands and Bays.

Sand Shallowlagoon

Coral reef

structure

Calcarenite

Figure 1.8 Typical geomorphology and sediment type ofThe Barrier Reef.

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1.2 The importance of the coast

All Australian governments have recognised thecoastal zone as a vital national asset.4 The coast playsa critical role in driving the Australian economy andin providing ecosystem services. The cities, industriesand ports that provide most of the nations jobs arein the coastal zone. Its beaches, waterways and coralreefs are also where Australians recreate.

Since European settlement, most Australians havecongregated along the thin strip of the coastline.Only a small proportion have inhabited the sparseinland. The proportion of the population living inthe country has declined since World War II and willprobably continue to do so.5 Around, 85 per cent ofAustralians live within 50 kilometres of the coast,and all our state capitals are on the coast.

1.2.1 Economic benefits

The Australian coastal economy is driven by local,national and international demands for goods andservices. Financial f ows from primary, secondaryand tertiary industries are either generated in thecoastal zone or pass through it. Coastal industriesinclude transportation; shipbuilding and maintenance;minerals, oil and gas production; f shing; tourism;and construction. The coastal zones are also thesite of many essential services, such as health,education, sewerage and wastewater systems,telecommunications, defence and f nance.

Australian ports rank among the worlds majorexport ports, and Australia is the worlds f fth largestuser of shipping. In 200708, 789.6 million tonnesof international cargo and 119.3 million tonnes ofdomestic coastal cargo moved across Australianwharves.6 International trade continued to expand in200708 and is expected to continue to grow over thenext 20 years.7

Brisbane, Sydney, Melbourne, Adelaide and Fremantleare Australias main city ports and account for

89 per cent of total containerised trade. Ports otherthan the major city ports handle 88 per cent of totalnon-containerised shipping.8 Major regional portsand producing centres include Gladstone, Newcastle,Wollongong, Geelong, Launceston, Whyalla and thePilbara ports.

In 200708, bulk-shipped energy exports (uranium,

metallurgical and thermal coal, natural gas, LPG,crude and ref ned oil) were worth $43 billion. Of that,$24 billion was coal; Australias largest energy exportearner9 (Figure 1.9).

Major infrastructure upgrades valued at many billionsof dollars are either underway or being plannedfor many ports around the Australian coastline.The upgrades include expansions of loading facilitiesat Dampier, Port Hedland, Newcastle, Hay Point,Gladstone and Abbot Point. It has been estimated thatsome $2 billion of public investment and $2 billion ofprivate sector investment will be required over the next

30 years in the port of Melbourne alone.10

Australias coastal waters are relatively def cient innutrients, and do not support a major f shing industrycompared to other countries. However, the coastalzone is the base for a range of nearshore and deepwaterf sheries that are valuable to local economies andcommunities and to the national economy. Fishing isAustralias f fth largest food-producing industry;the gross value of f sheries and aquaculture in 200708was $2.19 billion.11

Rock lobster is the highest value f shery ($407 million

in 200708), with production occurring in WesternAustralia, South Australia, Tasmania and Victoria.It is most important to Western Australia wheretwo-thirds of the catch is taken.12 In northern waters,the prawn catch is the highest value individual f shery($74 million in 200708).

Wildcatch f sheries are diminishing worldwide. With agrowing population, the world increasingly relies onaquaculture to meet the demand for f sh. In 200708,the gross value of Australian aquaculture was

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$868 million, and the industry is expected to continue

to grow in importance.Tourism and construction, which are related economicactivities, are major contributors to coastal centres.Population growth along the coast has fostered localand regional booms in the construction of touristfacilities and housing. Many coastal communitiesdepend on these activities as rural incomes fromagriculture and f shing have declined in relative termssince the 1970s.

Tourism is not only dependent on the built environmentof the coastal zone but also the natural assets andcharacter of particular regions. Some of Australiasmost iconic attractions and World and NationalHeritage areas are in the coastal zone, including the

Great Barrier Reef, Sydney Harbour Bridge and

Opera House, Bondi Beach, Kakadu National Parkand Shark Bay. Natural attractions include coral reefs,rainforests, national parks, wetlands, mangroves,recreational f shing grounds and beaches.

Tourism creates many jobs and provides a signif cantcontribution to the economy and social fabric of localregions. In 200304, an estimated $20 billion was spenton recreation and tourist activities directly involvingcoastal and ocean ecosystems.15 Overall, tourismsdirect contribution to the Australian economy in200708 was $40.6 billion (up from $34 billionin 2003), 3.6 per cent of the gross domestic product,

employment for 497,800 people (up from 461,000in 2003), and 4.7 per cent of total employment.16

Top five fisheries, by volume

(wildcatch and aquaculture)

Top five fisheries, by value

(wildcatch and aquaculture)

Australian sardines 33,600 tonnes Rock lobster $407 million

Salmonids 25,500 tonnes Salmonids $299 million

Prawns 22,400 tonnes Prawns $268 million

Tuna 14,700 tonnes Tuna $210 million

Rock lobster 13,800 tonnes Abalone $189 million

Source: ABARE 200917

Table 1.1 Top five Australian fisheries, by volume and value, 200708.

Box 1.2 Australias ports

Australias ports vary greatly in type volume and level of activity. Melbourne and Sydney handle thegreatest value of throughput each year. Western Australian and Queensland bulk port facilities handlesignif cant volumes of material annually (up to 137 million tonnes).13

Figure 1.9 Value and volume of throughput at Australian ports 200708.

Source: BITRE 200914

Bundaberg

Fremantle

Bunbury

Dampier

Port Hedland

DARWIN

Port AdelaideMELBOURNE

SYDNEY

Port Kembla

Newcastle

BRISBANE

Gladstone

Hay Point

Townsville

Launceston

Geelong

Twofold Bay

WesternportPortland

Whyalla Port PiriePort Lincoln

Yamba

Esperance

Albany

Geraldton

Broome

Cairns

100 000 1 000 000

>1 000 000 5 000 000

>5 000 000 15 000 000

>15 000 000

Value of imports and exports

($ x thousand)

Port Bonython

HOBART

Wyndham

Weipa

Karumba

Burnie

LucindaInnisfail

Wallaroo

Port LattaDevonport

Port WalcottAbbot Po int

Yampi Sound

Spring Bay

Cape Cuvier

MackayCape Lambert

Top 5 by throughput value 200708

($ thousands)

MELBOURNE.................64,903,755

SYDNEY .........................57,662,468

BRISBANE .....................33,363,592

Fremantle/PERTH.........25,930,020

Dampier ..........................19,529,018


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Box 1.3 Great Barrier Reef

Tourism generates the largest economiccontribution in the Great Barrier Reefcatchment. The Reef has 1.9 millionvisitors annually.18

The Great Barrier Reef Tourism ClimateChange Action Strategy 20092012 states:The health of the tourism industry isinextricably linked with the health of the Reef.

Tourisms share of GDP in the Great BarrierReef catchment is 8487 per cent, and its shareof employment is 8184 per cent. In 200506,tourism contributed $6 billion to GDP andemployed 55,000 people.19

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Box 1.4 Gold Coast City

The population of the Gold Coast has grownfrom 110,900 in 197620 to 497,848 in 200821and is projected to be 900,000 by 2030.On average the city hosts more than 28,900visitors every day, 92 per cent of whom comefrom other places in Australia. Visitors fromJapan, New Zealand, Asia and China make upmost of the remaining 8 per cent.22

Between them, visitors to Gold Coast Cityspend an average of $4 billion each year.The citys tourism sector employed almost18,500 people in 2006.23

1.2.2 Social benefits

The beach is an important part of Australian cultureand identity. Beaches are public places for all to enjoyand for many Australians beaches provide a sense ofplace and offer opportunities to participate in activitiesthat stimulate and enhance wellbeing.

Since the early 1900s, there has been a growingrecognition that coastal living offered many recreationaland aesthetic advantages for city dwellers. It is perhapsno coincidence that the second national park in theworld after Yellowstone was the Royal National Park onthe coast south of Sydney. Once authorities allowed surfbathing in daylight in 1902 at Manly, the fascinationwith body surf ng and later with board surf ng took

off. The formation of surf lifesaving clubs as volunteerorganisations began a movement, that has deep roots in20th century coastal life, which continues today.

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Box 1.5 Surf Life Saving Australia

Australias and the worlds f rst off cial surflifesaving clubs were founded in 1906 at Bondiand Bronte. Surf Life Saving Australia nowincorporates 305 local surf lifesaving clubs,17 regional branches in New South Walesand Queensland, and seven state and territorycentres.25 Australian surf lifesavers have rescuedmore than 500,000 people in the 80 years thatrecords have been kept.26

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The sense of place that has attracted so manyAustralians to the coast was captured by Robert Drewewhen he wrote: Australians make or break romancesat the beach, they marry and take honeymoons at thebeach, they go on holidays with their children to thebeach, and in vast numbers retire by the sea.24

The interest in coastal living has given rise to thesea change phenomenon, which since the 1970shas driven the demographic and economic revivalof non-metropolitan coastal communities. There hasbeen growth in coastal cities such as the Gold Coastand Cairns, as well as an extension of coastal satellitecommunities within commuter range from capitalcities. A number of coastal holiday or lifestyle

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destination communities, such as Bunbury in WesternAustralia and Victor Harbour in South Australia,have also grown rapidly in the same period. In manycases the rate of population growth in such coastallocal government areas has been about double thenational average. This rate of growth has entailedpersistent challenges for land use, infrastructure andplanning. The sea change phenomenon is expected tocontinue for the next 20 years, especially as a result offurther baby boomer retirement.

The social benef ts of the coastline and individualbeaches are valued highly by Australians. The value ofAdelaides beaches has been estimated at $46 millionper year27, and the gross value of Gold Coastbeaches to tourists alone was estimated at between$106$319 million in 2006.28

Benef ts that the coast brings to people, through

aesthetics, improved physical and mental health,and culture must be factored into any considerationof the benef ts of the coast to the national good.


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Box 1.6 Population growth

Australias population is projected to reach 35 million by 2049.29 All states and territories experiencedpopulation growth in 2008. The greatest growth occurred in Queensland, followed by Victoria,then New South Wales.

Outside capital cities, the largest population growth in 200708 generally occurred along the Australian coast.30

Seventy-f ve per cent of Australias non-metropolitan population is living in coastal areas.31

200 km

Brisbane

Brisbane

Metropolitan

Area

10 km200 km

100 km

400 km

40 km

Sydney

Metropolitan

Area

Sydney

40 km

Melbourne

Metropolitan

Area

Melbourne

Hobart

Adelai de

50 km

300 km

Adelai de

Metropolitan

Area

Perth

Perth

Metropolitan

Area

500 km

100 km

Darwin

400 km

More than 20%

10% 20%

5% 10%

Population Growth 19972006

by LGA

Figure 1.10 Fastest growth local government areas, 1997 to 2006.Source: DITRDLG 200832


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1.2.3 Environmental benefits

Australia has a wide range of coastal environments,with rich and very diverse coastal ecosystems thatsupport a unique biodiversity. Coastal habitats includemangroves, estuaries, saltwater marshes, kelp forests,seagrass beds, rocky shores, beaches, sand dunes, andvegetation communities such as heath and woodland.

Even within a specif c ecosystem type there can be arich diversity of habitats along the Australian coast.For example, the mangrove f ora of Australia is one ofthe worlds most diverse, and it covers about 18 percent of the coastline. Mangroves are important nurseryareas for f sh and crustacean species, including formany commercial species such as barramundi andprawns.33 Tropical birds such as the mangrove robinand mangrove fantail are found almost exclusivelyamong mangroves, while other terrestrial birds dependon mangroves at various times of the seasonal or tidalcycle. More broadly, mangroves protect the shorelineand enrich coastal productivity by recycling carbonand nutrients. Nutrient enrichment by mangroves maybe particularly important in waters where nutrientconcentrations are typically low.

Australia has the worlds most diverse array of tropicaland temperate seagrasses. In fact, Australia hosts morethan half of the worlds 60 species and 11 of the worlds12 genera of seagrasses, with about 51,000 squarekilometres of seagrass meadows, with Shark Bay hometo the worlds largest seagrass bed.34

Australias coral reef ecosystems are unique.

The Great Barrier Reef off Queensland and NingalooReef off Western Australia are Australias coral reeficons, but there are many other coral reef ecosystemswith unique species assemblages. There aredeepwater corals, low to high latitude transitionalreefs in New South Wales and Western Australianwaters, and coral atolls in the Indian Ocean and

South Pacif c Ocean. These coral ecosystems supporta broad array of f sh and invertebrates, many of whichare endemic. They also support a range of speciesthat are important for recreational, commercial andtraditional f sheries.35

Rocky shores are one of the most easily accessiblemarine habitats and are a transition zone betweenthe land and sea. The rocky shorelines of southernAustralia contain very high numbers of endemicspecies; it has been estimated that over 90 per centof mollusc and echinoderm species (such as starf sh)and 60 per cent of seaweeds may be endemic.36

Coastal wetlands, estuaries and mangroves allperform critical functions, sustaining humanactivities, assimilating waste and purifying water byremoving nitrogen, phosphorus and other pollutantsfrom agricultural or urban runoff.37 The stabilisationof the shoreline against erosion by sea currents

Figure 1.11 A mangrove ecosystem.

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and the protection of hinterlands from storms andf oods are important ecosystem services that alsoprotect human-made assets, such as infrastructure,agricultural systems and built-up areas.

Many parts of coastal ecosystems heavily used bypeople are showing signs of stress. Land clearing,soil erosion, pollution of waterways (by industrialeff uent, sewage and nutrient runoff from farms),canal construction, overallocation of freshwatersupplies, mining of beaches and dunes, use ofpesticides and other actions have damaged somecoastal ecosystems and reduced their ability toprovide ecosystem services.

1.3 Conclusion

The coastal zone and position of the shoreline is verydynamic. Understanding past variability can helpus better appreciate how the coast could change inthe future, including as a result of human-inducedclimate change.

Human settlement has greatly modif ed the coastalenvironment over the past 100 years. Australiahas become a coastal society: around 85 per centof the population live within 50 kilometres of thecoast. Buildings, utilities, public amenities andtransport networks have been constructed in areasthat experience periodic f ooding, wind damage andshoreline erosion.

The Australian coastal zone has been developed withthe expectation that the shoreline will remain stable,extreme events will occur within a range def ned byhistorical experience, and sea level will not change.As the next chapter will show that expectation is no

longer tenable.Climate change and sea-level rise will usher in aperiod of relative instability in coastal environments,

shorelines, storm processes, beach processes,ecological systems and, ultimately, the use of coastalareas. Global warming has the potential to take theEarths dynamic system out of the comfort zoneof past glacial-interglacial cycles and to createdisequilibrium. Eventually, sea levels could rise tonew equilibrium positions not seen since the Eocene(40 million years ago) if the drivers of climate change

are left unchecked.Understanding and planning for these changesare signif cant and urgent tasks. The next chaptersummarises the latest scientif c research andprojections for the effects of climate change on theAustralian coastal zone.

Chapter 2 describes how the current climaticcomfort zone conditions may change at ratesnot experienced in the historical and geologicalpast. Temperatures and CO

2are likely to increase

beyond levels experienced in the past 6,000 years.Over centuries, sea levels will rise more than a metre

beyond existing stable tidal range positions, resultingin new inundation of land and shifts in shorelines.

Figure 1.12 A seagrass ecosystem.

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Australia's Coast, Its Nature and Importance

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