1HERSA1 A010

570 reasons to care about our harbour and coastlineSIGN-UP NOW it’s free »

You will receive the latest news and happenings at SIMS

www.sims.org.au

SIMS aims to be a world-class marine research and training institute

All donations of $2 and over are tax deductible

supporting our marine ecosystems

There are at least 570 species of fishes andthousands of species of other marine creaturesin Sydney Harbour, making it biologically oneof the most diverse harbours in the world.Now SIMS is inviting you to play an importantrole in helping preserve NSW’s unique marineenvironment for the future.

Photo Ezequiel Marzinelli

10 TUESDAY, DECEMBER 4, 2012 smh.com.au The Sydney Morning Herald

EDITORIAL FEATURE IN ASSOCIATION WITH THE SYDNEY

INSTITUTE OF MARINE SCIENCE LIVING HARBOUR: DYNAMIC SCIENCE

Northern shore identified as flood riskResearch into 21 kilometres of Manly and Middle Harbour shoreline has found areas under greatest threat from sea-level increases, erosion or severe storms, writes Melinda Ham.

This would affect alarge number ofseafront properties.

WAVES lash, tides drag the sandaway and the sea levels riseincrementally. Coastalproperties across Australia are atthe mercy of the elements, but isit something to lose sleep over?

A study by engineers from theUniversity of NSW’s WaterResearch Laboratory (WRL) hastried to quantify this risk in themost in-depth study to date,focusing on the ocean andharbour beaches in the Manlylocal government area.

The study looked at thepresent and future implicationsfor 21 kilometres of shorelinewithin Middle Harbour andNorth Harbour, including17 sandy beaches fromQuarantine Beach in the SydneyHarbour National Park to theSpit Bridge.

‘‘The areas most at risk, wherethe seawalls need upgrading, areat Clontarf Reserve and Ellery’sPunt Reserve near the Spit,’’ saysAlessio Mariani, who co-authored the report with fellowengineer James Carley.

These areas are alsovulnerable to inundation, whichmeans they are low-lying andliable to be flooded in future sea-level-rise scenarios and stormsurges.

Mariani says that in a worst-case scenario, such as a once-in-100-years storm with massivewaves, if seawalls and otherprotection works fail, the landbehind the wall will quickly erode.

‘‘The erosion would reachbetween five and 30 metresinland, depending on the area,’’he says. ‘‘This would affect a

large number of roads in theManly local government areaand a large number of seafrontproperties – public as well asprivate – which we can’t name asour report is still with theminister. The erosion would nottake minutes but hours, whichwould give emergency servicestime to put up sandbags toprotect the properties.

‘‘In general, Sydney Harbour isvery resilient,’’ Mariani says.‘‘The oldest seawalls date back tothe 1800s and early 1900s. Theyare an accepted part of the builtenvironment and do a good job.

‘‘While they have beensuccessful for nearly 100 years,our study recommended thatthey be maintained andupgraded to face future risks.Seawalls only prevent erosion to

progress further inland,however, the erosion processstill continues at sea.’’

Using computer modelling,the engineers factored inprojected sea-level rises of40 centimetres by 2050 and90 centimetres by 2100 to

extrapolate different scenarios.They also looked at what

would happen if the seawallscollapsed, and the possibleeffects of major storms (usuallyonce in 20 years or more), such

as the Sygna storm that hiteastern NSW in May 1974.This storm was named aftera shipwrecked Norwegiancargo ship.

According to a Manly Dailyarticle from the time, during theSygna storm, winds reached166km/h, whipping up wavesnine metres high, which in turncaused a massive 2.37-metretide level and a 0.23-metre stormsurge, which barraged its wayinto Manly, damaging the wharf,destroying the Manly HarbourBaths and ripping up the335-metre boardwalk to theManly Aquarium, as if it weremade of matchsticks.

Ray Mathieson, 67, clearlyremembers the Sygna storm.He’s lived in the Manly area sincethe early ’70s and has owned a

waterfront house in Little ManlyCove for the past two decades.

‘‘The Sygna storm was reallynasty and [caused] quite a bit ofdamage especially because logsfrom the Sygna washed into theharbour,’’ he says.

Again in August 1996,Mathieson’s property wasbashed by another storm. ‘‘In’96, one storm was quite severe.A king tide and a storm surge anda big southerly washed away allour pool equipment, the poolwalls cracked and we got a boatwashed up into our pool.

‘‘I think about nine boatsin Little Manly Cove broketheir moorings.’’

But have these storm surges,possible coastal erosion andpredicted sea-level rises causedMathieson to worry about his

property? ‘‘I am quite optimisticabout the effects of globalwarming,’’ he says. ‘‘I have myown water-level gauge and I’veseen no change at all in the timeI’ve been here. It’s not that I’mnot worried about theenvironment but there are otherbigger issues, like sewagetreatment and dumping rawsewage in the ocean; to mymind, that’s something to getworked up about.’’

Manly Council is taking theWRL report seriously, thecouncil’s deputy generalmanager, Stephen Clements,says. The report is with the NSWMinister for the Environment,Robyn Parker, and the council hascommissioned another reportabout flooding from rainfall in theManly local government area,

which is due to be completed byAugust next year.

‘‘We want residents tounderstand what we are doing –that they have been through thejourney with us – and we don’twant to alarm anyone or feelthey haven’t been part of it,’’Clements says. ‘‘The study hasinvolved a lot of door-knockingand surveying residents, so theycan give us anecdotal evidenceabout flooding in the past.’’

But, in general, are residentsin the Manly Council area reallyconcerned? ‘‘We have scepticsabout climate change; people infavour and against but . . .waterfront properties are stillchanging hands for more than$10 million, so maybe they’renot that bothered about thefuture,’’ he says.

One of the good guys ... the reintroduced native bush rat seems to be holding its own, breeding again and moving into new locations.

Native rat stakes claim on former turfThe reintroduction of an indigenous rodent to foreshore areas couldhelp keep feral invaders at bay, writes Keeli Cambourne.

Outsider ... the black rat.

THE first record of black rats inSydney is from the 1860s and,like the plague they carried, theintroduced rodent has left awake of destruction in its path.

But a study by a SydneyUniversity academic that’snearing completion may havefound a way to combat the blackrat, while reintroducing a nativespecies as part of a conservationinitiative in conjunction withthe Sydney Institute of MarineScience.

Early this year, an associateprofessor in conservation

biology at Sydney University,Peter Banks, beganreintroducing the native bushrat into areas it once inhabitedaround Sydney Harbour.

‘‘The black rat brought with ita bunch of diseases, such as ratlungworm, and as it is arboreal,it can climb trees and itdecimated native birdpopulations by raiding theirnests,’’ Banks says.

‘‘The bush rat probablydisappeared around 1901 whenthe plague came, and it wasaround that time that

Sydneysiders went on a rat-killing frenzy.

‘‘It is the black rats that livearound humans and in houses.What we are trying to do is reversethat pattern and see if we canblock the reinvasion of black rats.’’

During a 10-day period, Banksset traps at four locations inbush beside the harbour. Histeam caught 40 to 60 rats perone-hectare plot and, althoughit made only a dent in the feral-rodent population, which isestimated to be in the tens ofthousands, it was enough to

create a gap in their breeding.‘‘In August, we reintroduced

about 100 native rats into thosesites – around North Head,

Bradleys Head and Middle Head– to see how quickly the blackrats may reinvade,’’ Banks says.

‘‘The science is ongoing butthe bush rats seem to be holdingtheir own. They are breedingagain and have moved into newlocations as well.’’

The National Parks andWildlife Service previouslythought the only way toeradicate black rats was toconstantly bait them, Bankssays, but he is hopeful that oncethe study has been assessedunder peer review, it could helpminimise the use of poisons inthe bush.

The Australian WildlifeConservancy has also beenwatching the project and its

regional ecologist (south-east),Matt Hayward, says it is excitingfor native fauna.

‘‘This study is movingconservation forward in Sydney.Although it’s a bit early to seewhether we can call it a success,the early signs are verypromising, and the most recenttrappings indicate there is morecontrol of the black rat,’’ he says.

‘‘Native species, includingbirds and bats, have not evolvedto cope with this type ofpredator, and allowing nativerodents to re-establish gives theecosystem more resilience. Byreintroducing native species andremoving feral predators, it givesus an insight into what Australiawas like before settlement.’’

Invasion ... it looks pretty but the sea squirt is one of the many non-indigenous species making Sydney’s waterways home. Photo: SIMS

A helping handfor local speciesGuy Wilkinson

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

A RAPIDLY escalating globalpopulation, climate change andan increase in worldwideshipping trade mean moreartificial structures are beingbuilt around coastlines thanever before.

According to a scientificresearcher at UNSW and theSydney Institute of MarineScience (SIMS), Dr KatherineDafforn, about 50 per centof Sydney Harbour’s foreshorehas been modified by man-made structures.

Although the significance ofthis may be lost on many, theconsequences beneath thewater’s surface are of particularinterest to scientists.

Dafforn has been monitoringthe impact of non-indigenousspecies as a threat to estuarineecosystems. Marine creaturessuch as barnacles, mussels andother invertebrates – collectivelyknown as ‘‘fouling species’’ – areoften delivered to major portssuch as Sydney Harbour viarecreational and commercialvessels. These creatures then findtheir way on to structures such aspilings and pontoons, causingecological problems as theycompete with native species forresources such as food and space.The result is increasedmaintenance and cleaning costsfor marina owners.

Working with a seniorresearch scientist at the NSWDepartment of PrimaryIndustries, Dr Tim Glasby, and

Associate Professor EmmaJohnston, Dafforn hasundertaken a series of subtidaldive surveys on artificial andnatural structures aroundSydney Harbour. She has alsoexamined nearby natural rockyreefs and was able to determinethat the reefs were moreresistant to foreign invadersthan man-made structures.

By identifying andunderstanding ecologicalchanges associated withartificial structures, Daffornhopes to influence the futuredesign and management of thistype of construction.

‘‘By working with relevantagencies and involving thecommunity of local marinas andboat owners, I’d like to continueinvestigating bioengineeringdesign options for artificialstructures that aim to mimicnatural habitats and mitigate theimpact of artificial structures,’’she says.

‘‘For example, in Europe,experiments have attempted to‘seed’ artificial structures withnative algae to create habitatopportunities for threatenedspecies. It would be interesting toinvestigate some of these ideas inthe local Sydney context.’’

Glasby agrees the researchcould have an important part toplay in designing structures thatare less susceptible tocolonisation by invasive species,while being good surrogates fornatural habitats that areincreasingly under threat fromhuman development.

SIMS and the SIMS Foundationgratefully acknowledge thesupport from the following:SIMS sponsors: DuncanDovico, DMS Maritime, GadensLawyers.SIMS major supporters:Department of Industry, Innov-ation, Science, Research andTertiary Education, The IanPotter Foundation, Sydney

Harbour Federation Trust,James N. Kirby Foundation.SIMS Foundation foundingpartners: The Sydney MorningHerald, Sergeants Mess, ThyneReid Foundation, Orion Exped-ition Cruises, Vincent FairfaxFamily Foundation.SIMS Foundation supporters:The Horizon Foundation, TheTrust Company.