Geoscience Reference
In-Depth Information
century. (quoted. in. Brahic. 2008).. These. rises,. together. with. increased. storminess,.
will.cause.geomorphic.adjustments.to.coasts..In.particular,.sand.will.be.eroded.from.
the.upper.beach.and.deposited.on.the.near-shore.bottom.(Cowell.and.Thom.1994)..
This,.according.to.the.“Bruun.Rule”.(Bruun.1988),.will.cause.shorelines.to.retreat.
horizontally. at. 50-100. times. the. vertical. sea-level. rise. (but. note. criticism. of. the.
Bruun.Rule.by.Cooper.and.Pilkey.2004)..By.2100,.recession.would.range.from.4.5.
to. 88. meters. in. Australia. (CSIRO. 2002),. but. recent. stochastic. modeling. suggests.
this. is. an. underestimate. (Cowell. et. al.. 2006).. Consequently,. climate. change. will.
accelerate. the. current. global. trend. of. beach. retreat. (70%. of. beaches. are. eroding),.
stable.beaches.(20-30%).will.begin.to.retreat,.and.the.number.of.accreting.beaches.
(<10%).will.decrease.(Burkett.et.al..2001)..This.may.affect.beach.ecosystems.little.
if. a. slow. landward. retreat. is. the. only. change.. However,. if. there. are. accompany-
ing.habitat.changes.(e.g.,.to.dunes,.wave.climate,.grain.size,.beach.area,.and.slope).
or.habitat.losses.(e.g.,.narrower.beaches),.great.ecological.effects.would.occur.on.a.
given.beach..For.example,.major.intertidal.habitat.loss.was.projected.to.have.severe.
consequences. for. California. shorebirds. (Galbraith. et. al.. 2002),. and. model. simula-
tions.for.the.Humber.estuary.suggested.large.losses.of.intertidal.area.and.inverte-
brate.biomass.(Fujii.and.Raffaelli.2008)..Alternatively,.erosion.may.be.retarded.if.
the.sediment.supply.is.increased.as.the.combination.of.sea-level.rise.and.increased.
storminess.erodes.cliff.faces.
If.dunes.suffer.rapid.erosion,.vegetation.would.be.lost..This.loss.would.further.
destabilize.dunes,.creating.a.destructive.feedback.loop..Such.losses.would.directly.
affect.vegetation-dependent.dune.fauna.and.indirectly.affect.beach.fauna.via.reduced.
supply. of. organic. matter. to. the. upper. beach.. In. addition,. turtles. and. seabirds. that.
nest.in.dunes.would.be.severely.affected..If.particle.size.and.beach.slope.(i.e.,.mor-
phodynamic.state).change,.the.richness,.abundance,.and.kinds.of.macrofauna.will.
change. because. steep,. coarse-grained,. relective. beaches. are. impoverished. com-
pared.with.lat,.ine-grained,.dissipative.beaches..Similar.ecological.consequences.
may.arise.if.climate.change.enhances.along-shore.sediment.transfer.via.changes.in.
the.directional.weightings.of.the.wave.climate,.i.e.,.“Gordon.Effects”.(Cowell.and.
Thom.1994)..Shoreline.stability.is.even.more.sensitive.to.Gordon.Effects.than.Bruun.
Effects.(Cowell.and.Thom.1994).
The.ecological.consequences.of.sea-level.rise.may.be.exacerbated.by.engineer-
ing. responses. such. as. seawalls. and. groynes.. The. latter. accumulate. sand. in. their.
vicinity. but. also. lead. to. downdrift. erosion. (Peterson. et. al.. 2000).. This. downdrift.
erosion. is. likely. to. increase. under. conditions. of. higher. sea. levels,. and. more. fre-
quent.storms.will.lead.to.loss.of.signiicant.areas.of.beach.habitat.including.entire.
beaches.(Speybroeck.et.al..2006)..Where.seawalls.are.used.to.defend.societal.assets.
in. urban. areas,. beaches. may. be. lost. entirely. as. in. the. “jersiication”. of. the. coast.
(Finkl.and.Walker.2004)..However,.the.meager.literature.on.the.ecological.effects.
of. seawalls. shows. conlicting. results.. For. example,. while. the. ocypodid. ghost. crab.
Ocypode cordimanus
. appears. to. be. badly. affected. in. New. South. Wales. (Barros.
2001),.the.macrofauna.of.a.Chilean.beach.showed.no.signiicant.effects.(Jaramillo.
et.al..2002).
