[Radix] Tsunamis and Coastal Tree Barriers

[T.G.Cannon at greenwich.ac.uk]

Dear Ilan
thanks for that! Are you going to try and send it to Baird et al?

You could also mention the awful corrolary - officials in Vietnam,  
Bangladesh, Thailand etc seeing the press release on its own and  
adopting an attitude that there is no longer any need to protect (or  
replant) coastal mangroves... given the incentives and corruption they  
are subjected to, they could use this as justification for approving  
more shrimp farms and hotels etc.

Your point about links of DRR, sustainable development and livelihoods  
is crucial: the protection of coastal forests is vital. Moreover,  
since there is no evidence that coastal forests do any HARM, or make  
tsunamis or storm surges WORSE, then there is no argument for removing  
them.

good wishes to all for a safer new year...

Terry Cannon


Quoting Ilan Kelman <ilan_kelman at hotmail.com>:

>
> To Radix:
>
>
>
>
> A press release was issued about an upcoming publication
> that suggests that planting trees along coasts is not a good idea
> for reducing
> tsunami damage.  If that were taken as a
> straightforward and definite statement, which would be
> inappropriate, it could have
> significant and detrimental implications for coastal management.
>
>
>
>
> I provide below my full reaction to the press release
> followed by the press release itself.  I
> hope that this will provide a more balanced view of the topic, rather than
> leaping to conclusions.
>
>
>
>
> Best wishes,
>
>
>
>
> Ilan
>
>
>
> ----------
>
>
>
> The press release below on coastal tree barriers and
> tsunamis raises numerous concerns which are reflective of the journalistic
> nature of the article, not of the science that is being reported.
> My points are:
>
>
>
> 1. The statement that "there is, as yet, no evidence
> that coastal tree belts can provide meaningful protection against a
> tsunami or,
> for that matter storm surges produced by cyclones" is an
> exaggeration.  The scientifically correct
> interpretation of the data available is that there is not enough evidence to
> prove that statement conclusively.  Yet,
> conversely, there is not enough evidence to claim that coastal tree belts do
> NOT provide meaningful protection.
> Overall, we do not have enough evidence to make a claim either way and
> that is the message that ought to be highlighted.
>
>
>
> 2. The statement "it would be extremely dangerous to
> rely on tree planting alone to shield coastal communities in the event of
> future tsunami or storm surges" is entirely correct.  That, in fact,
> is exactly the same message
> which has been promoted for decades regarding all forms of flood risk
> reduction:  that relying on structural
> measures increases flood vulnerability and risk in the long-term
> http://www.ilankelman.org/miscellany/StructuralDefences.rtf
> However, the coastal tree barrier press
> release misses the point that coastal tree barriers have the potential for
> doing much more than simply address flood risk reduction. Ample evidence
> exists, such as from Vietnam, that if appropriately implemented as a
> development programme, coastal mangroves can not only reduce flood risk but
> also promote sustainable livelihoods.
> That element is missing from the press release:  the debate should
> not be about flood
> protection, but should be about disaster risk reduction,
> development, and sustainable
> livelihoods, all addresses simultaneously to complement each other--as
> evidenced by decades of research and practice including much
> (although far from
> all) post-tsunami work.
>
>
>
> 3. Look carefully at the language in the press release:  "barriers",
> "shield",
> "protection".  This is typical
> of the technocratic, humanity-against-nature language which is highly
> culturally biased yet which dominates much disaster risk reduction discourse,
> sending inaccurate messages regarding disaster risk reduction, development,
> environmental management, sustainability, and livelihoods.  Instead,
> it is more helpful and more accurate
> to discuss how coastal ecosystems, including those with trees, could
> be used to
> support livelihoods, development, and sustainability, including disaster risk
> reduction--with extensive evidence and case studies from research and
> practitioner publications.
>
>
>
> 4. The variables quoted as being important are indeed
> important, but connections amongst those variables (causations and
> correlations) need to be considered too.
> For example, the presence of coastal tree barriers might affect distance
> of a village from the shore and hence the height of the village above sea
> level.  That is, by planting coastal tree
> barriers, it is conceivable, although certainly not definite, that villages
> might end up being set back farther from the shore and/or farther above sea
> level--or the villages might end up closer to the shore and/or closer to sea
> level.  If this speculation is proven either
> way, then coastal tree barriers would have a direct link to tsunami and storm
> surge damage, either increasing or reduction the damage.
>
>
>
> 5. The "shape of the seabed in concentrating the
> tsunami's power" is mentioned but not the fact that most damage from
> tsunamis comes from waves that are breaking or that have just
> broken.  If coastal tree barriers cause waves to break
> earlier or cause a significant proportion of the force of the
> breaking wave to
> be spent before reaching human settlements--and these statements are entirely
> speculation--then coastal tree barriers would reduce damage.  The
> issue of where and how the waves break,
> and how coastal tree barriers affect that, including resulting
> debris in the waves, needs to be addressed in more
> detail.
>
>
>
> 6. The maximum height of the waves is also important,
> especially at the coast. Some places in Aceh apparently experienced tsunami
> heights of over 30 metres. Perhaps little could be done to avert
> damage at the shoreline in such
> circumstances. But that says little about the impacts of coastal trees on the
> velocity, debris content, breaking characteristics, and inundation zone of
> tsunamis or storm surges in cases where the water's height is less than the
> coastal vegetation's height.
>
>
>
> Two more general points:
>
>
>
> 7. It is disappointing that tsunamis and storm surges are
> not separated more.  There is far more
> evidence for storm surges than for tsunamis and that should be acknowledged.
>
>
>
> 8. This press release focused on "coastal tree
> barriers" but there is a danger that this phrase has different meanings to
> different people and could be interpreted as any coastal ecosystem,
> especially
> with the press release's inclusion of the phrase "a barrier of trees or
> coastal vegetation".  I agree that
> the evidence for or against "coastal tree barriers" is particularly sparse,
> but (i) coastal tree barriers are only one component of coastal
> ecosystems with
> trees and (ii) the evidence is far more conclusive for a wide range
> of coastal
> ecosystems supporting disaster risk reduction, development, environmental
> management, sustainability, and livelihoods.
>
>
>
> My comments should not in any way be taken as a scientific
> statement about Baird et al.'s work.  I
> am reacting to the press release, not to the full study which apparently has
> not yet been published.  A few years ago,
> a similar media article made Baird et al.'s comments look
> unscientific, but when
> I read the full scientific papers, I had no scientific critiques
> about what was
> published in the academic journals.
> Instead, Baird et al. provided insightful remarks based on the evidence
> that they had collected.  Similarly, the
> critiques in the press release of other work have scientific legitimacy and
> ought to be discussed further, but they fail to give the full story or to
> account for all the evidence across many studies.  The full report,
> though, is presumably much
> better in doing that.
>
>
>
> Overall, my concern here is science communication in terms
> of the messages being publicised and the scientific evidence being presented.
>
>
>
> Ilan
>
>
>
> -------------
>
>
>
> http://www.igovernment.in/site/Coastal-tree-barriers-cannot-stop-tsunami-Experts/
>
> Coastal tree barriers cannot stop tsunami: Experts
>
> *A team of marine scientists has dismissed claims that
> coastal tree barriers
>
> can halt the might of a tsunami as 'false and dangerous'*
>
>
>
> Published on 1/6/2009 12:40:21 PM
>
>
>
> *Sydney:* A team of marine scientists has dismissed claims
> that coastal tree
>
> barriers can halt the might of a tsunami as 'false and
> dangerous'.
>
>
>
> Shortly after the fourth anniversary of the devastating
> Indian Ocean
>
> tsunami, which claimed nearly a quarter of a million lives,
> researchers
>
> issued a strong warning against coastal communities and
> governments putting
>
> their trust in mangrove and tree barriers erected as a means
> of protection,
>
> reports IANS.
>
>
>
> "Following the tsunami scientific studies were released
> which claimed that
>
> the damage to coastal communities had been less in places
> where there was a
>
> barrier of trees or coastal vegetation," said Andrew
> Baird of the ARC Centre
>
> of Excellence for Coral Reef Studies and James Cook
> University.
>
>
>
> As a result there has been a lot of tree planting in coastal
> areas affected
>
> by the tsunami, in the hope it will protect coastal
> communities in future
>
> from such events, Baird added.
>
>
>
> "However, these studies looked only at the presence or
> absence of vegetation
>
> and the extent of damage?and did not take account of other
> important
>
> variables, like the distance of a village from the shore,
> the height of the
>
> village above sea level or the shape of the seabed in
> concentrating the
>
> tsunami's power," he said.
>
>
>
> The study concludes there is, as yet, no evidence that
> coastal tree belts
>
> can provide meaningful protection against a tsunami or, for
> that matter
>
> storm surges produced by cyclones, such as the surge that
> followed Cyclone
>
> Nargis in Myanmar last year which killed over 1.5 lakh
> people.
>
>
>
> As a result it would be extremely dangerous to rely on tree
> planting alone
>
> to shield coastal communities in the event of future tsunami
> or storm
>
> surges, they warn?and doing so could lead to further
> tragedies, an ARC
>
> release said.
>
>
>
> The findings have major implications for civil defence and
> emergency
>
> planning, the cost of restoring affected regions and in
> minimising the death
>
> and destruction suffered by some of the poorest communities
> in the world,
>
> the team says.
>
>
>
> Their study is scheduled for publication by the United
> Nations Environment
>
> Programme.
>
>
> _________________________________________________________________
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