The potential role of coastal ecosystems in

risk management:

What lessons from the2004 tsunami?

Roland CochardInstitute of Integrative Biology(ETHZ, Zurich)& Zurich Financial Services

1. Short theme intro

2. Tsunami protection functionsof coastal ecosystems – somepapers and some thoughts

3. Restoration (failure) of mangrove ecosystems in Aceh

4. Concluding notes

The 2004 tsunami:

A natural disaster of global dimensionswith up to 300‘000 human casualties~ 5% of the Acehnese population killed

Sri Lanka, India, Southern Thailand heavily affected

in Aceh Province:

>900 sqkm coastal land affected

~13.2% of paddy fields flooded

in and near Banda Aceh town:

40‘000 houses destroyed

99% of aquaculture ponds destroyed

70% of fishing fleet destroyed

The event was followed by thelargest international aid effort ever

Reconstruction was meant to decrease thevulnerability of coastal communitiesto future disasters…

…but implementation was not always exemplary…

~10 cm

for example…lots of donatednot-so-usefulfishing boats

for example…

…lots of new (empty) housing

close to the seafront

(within the tsunami hazard zone?)

for example…

…costly and not-very-helpfulengineered coastal defence measures

MangrovesSea Grass Beds

Coral Reefs

Beachesand Beach Vegetation

Natural Coastal Ecosystems

buffer wind-driven waves and provide highlyvaluable fishing grounds and fish nurseries

provide coastal stability and protectionagainst wind and salt spray

are natural (non-engineered), rich of biodiversity and beautiful !!

PreciousMangrove Forests

Lacking expertiseprevents successfulforest restoration

„According to IUCN the effects of theIndian Ocean Tsunami were mostdramatic in locations where mangrovebelts had previously been destroyed.“

„While it may be a good investment to establish earlywarning systems for the next tsunami, it could be far more effective to restore and protect mangrove forestsand other natural defenses in parallel.“

Dahdouh-Guebas et al. 2005

„We are concerned that promoting green belts as barriers, particularly in preference to tsunami early-warning systems, as suggested by some scientists (e.g., Dahdouh-Guebas et al. 2005), may lead to substantial loss of life in a future event.“

Kerr & Baird 2007

Question 1:How useful are (were) coastal ecosystemsas defence systems against tsunamisand other sea-borne disasters?

Q1 > Risk Assessment Framework

Q1 > Risk Maps

Q1 > Risk Preparedness Plan

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tsun

amir

isk

Q1 > Indicator-based risk assessment

Q1> Scientists making progress

„We used a zero intercept in our statisticalanalysis where this should not have beenthe case…“

SUMMARY:

THIS(e) STUDY(ies) DID NOT PROVIDE EVIDENCE FOR A PROTECTION FUNCTION BY

VEGETATION !

Q1> Science making progress

„Areas withmangroves and shelterbelts weresignificantly lessdamaged than otherareas“ (Chi squaretest: p<0.01).

SUMMARY:

NO PROOF PROVIDED !

62 sample locations in affected countries

Q1 > The UNEP study

Q1 > The UNEP study• source distance (3 variables) • bathymetry (18 slope and orientation variables)• terrestrial geomorphology (10 variables)

• bio-physical variables (% coral protection and reef orientation, land cover resistance index 1–5, % mangroves, % seagrass protection)

=> multiple regression analysis

Q1 > The UNEP study

Adj. R²= 0.621, N = 56 sites

Variables coeff sign p-level

Distance from fault line - ***Average depth at 10 km - *Length of proximal slope + **Percentage of seagrass - ***Percentage of corals + ***

mangroves and vegetation index non-significant

… but clustered locations > spatial auto-correlation ?!?

Q1 > The UNEP study

„How broad does a tsunami protectionforest need to be in order to be effective?“Question at a Workshop in 2006 on „Protectionfunctions of coastal ecosystems against the 2004 tsunami“

Q1 > Issues of complexityVariability of run-up (~bathymetry)

Q1 > Issues of complexityLocation of ecosystems and assets at risk

Q1 > Issues of complexityWave funneling in bays

Q1 > Issues of complexityWave channelling in mangrove estuaries

Q1 > Issues of complexityDifferent hydraulic resistance of species

Q1 > Issues of complexityRisks of debris flow !

Q1 > Conclusion

The science basisis - as yet - not

adequate to supportserious tsunami riskmanagement using

greenbelts.

October 2006: „Mangroves For theFuture Project“ received 62 million $$

„In the Philippines on average only 10-20% of replantedmangroves survive. This is mainly due to a lack of scientificexpertise in reforestationprogrammes.“

Question 2:

Why did mangrove plantingcompletely fail in Aceh? (Aug. 06)

75% dead 98% dead

100% dead 100% dead

Q2 > Issues of complexityLoss of frontal sand spits

Q2 > Issues of complexityLoss of wind breaks > wind waves

Q2 > Issues of complexityDeposition of marine sediments on mudflats

Q2 > Issues of complexityLoss of mangrove infauna (crabs et al)

Q2 > Issues of complexity

Quickbird image taken 12 days afterthe tsunami

Land subsidence !?! (and/or other effects)

Q2 > Issues of complexityLand subsidence and uplift

Do we really actuallyneed to replant?

Who knows…?

Serious investmentsrequire proper planning; proper planning requiresquality baseline research. Invest in applied research!

Overall Conclusion 1

Timeplan of the Reconstructionand Rehabilitation Agency forAceh and Nias, ending 2009

$$ ??

Serious investmentsrequire time. Forests do notgrow overnight!

Overall Conclusion 2

$ £ €at least 30 years +

Overall Conclusion 3Seriousinvestmentsrequire fertile grounds, sustainabletenure and management. Invest in education of local students! en

thus

iast

icm

angr

ove

rese

arch

er

Overall Conclusion 4

Investments aremost efficient ifsynergies aretapped!

e.g. academic institutionsshould workclosely with aidagencies

Fill theknowledgegaps!– but… in the absenceof knowledgestick to thereliable tools.

Conclusion 5

Question 2 > Subsidence and upliftCorals are ancient sea level loggers!!