[Coral-List] Is Anyone in favor of dredging in coral areas?

arthur webbarthur at gmail.com
Sun Mar 12 22:41:41 EDT 2017

Hi Nohora,

I'm not sure what challenges you are facing but I'm very sure no-one on 
the coral list is likely to say "dredging is good for coral", so I 
wonder if your email has been of much use? I've taken a bit of time out 
to write a little on this issue of dredging and reefs below, but from a 
perspective which may be seen as out of step with the majority first 
pass assessment of such a question. I worry that it's too easy to vilify 
an activity like dredging and subsequently further enforce and set up 
an, "us and them" barrier where neither the engineers want to work with 
reef scientists or vis-versa. In the Pacific Islands it is more 
important than ever that the very best of the coral science community 
are involved in what is likely to become an increasing interest in 

I have worked most of my life in the tropical pacific islands and have 
spent the greater part of my research time in the atolls. My field is 
coastal processes and I specialise in "reef mediated shoreline systems", 
so I'm more a coastal geomorphologist than coral biologist but the fact 
is in these systems "no corals = no island", so one does need a broad 
experience and understanding of the whole system and the needs of the 
communities. Anyway, as you're likely aware, pretty much everything on 
an atoll is comprised of living or once living reef debris and many of 
our atolls retain fantastic productive reefs around them and in some 
cases also in the lagoons.

A few years ago I had oversight of a project to develop a dredge 
operation in Tarawa lagoon (an atoll in Kiribati). In this case the 
dredging was undertaken to win aggregates from the lagoon basin to 
supply onshore needs for building etc. All up I would have to say that 
dredging in this case most certainly had significant net benefits to the 
community, to development and to relieve untenable pressure on crucially 
important shoreline systems. Previously the only source of aggregate was 
from mining beaches - an utter disaster in a fragile atoll environment! 
So I still would not say this dredging "is good for coral" but I can say 
based on the follow-up environmental monitoring that in the case of 
Tarawa it has little impact on neighbouring live coral areas and 
assuming the operation remains well managed, I think we can continue to 
have dredging and coral all at the same time and ultimately we can 
better retain functional beaches which protect from marine conditions.

A further similar example is in Funafuti (Tuvalu) where just last year 
the New Zealand Govt. assisted the Govt. of Tuvalu to fill massive pits 
which rendered many parts of their main land mass on Funafuti flood 
prone and useless (a legacy of the US military engineers from WW2). In 
this case a sand pump was used to harvest unconsolidated coral sands and 
gravels from the lagoon and pump this directly into the on-land pits. 
Hundreds of thousands of tonnes of material was pumped and again due to 
careful management the impact on living corals was negligible. Certainly 
the net benefits to that community by making large areas of land safe 
and usable far outweigh the limited, managed impacts in the lagoon.

Finally, and this may actually be the subject of a paper (I'll do a 
little digging) the hard ocean side reef flats of Majuro (Marshall 
Islands) were the sight of intense quarrying for limestone rock some 
years ago. I was personally aghast (from the perspective of coastal 
hazards and environmental concerns) the first time I saw these huge pits 
blasted into the intertidal reef flats and again one could not say this 
was "good" for anything living on those flats at the time. Obviously 
corals didn't grow on top of the harsh intertidal habitat but they do 
grow on the outer flanks of the atoll only a few 10's of metres away (I 
believe there are regular contributors to the list who are better 
qualified than I and who might explain better any impacts observed). 
Otherwise, I've never found any literature regarding impacts to those 
living coral at the time of quarrying and there seems to have been 
little environmental monitoring. All that said, the interesting thing is 
these deep (now sub-tidal) pits carved into the rocky reef flats have 
become home to corals which otherwise would never have gained a foothold 
in this environment, the locals indicate they also support fish, 
crustaceans and so on. From the perspective of shoreline processes they 
are still a problem because material which might have once moved from 
the reef edge to the shoreline now falls in the pits. But in this case 
maybe there is some degree of argument to say these pits were "good" for 
corals because now there are corals where once there was none? This same 
phenomena can be seen all around the Pacific Islands in dredged channels 
which have been blasted to facilitate navigation. In a number of cases 
the channels become impassable because of rapid coral recruitment and 
growth - where once there was none.

Anyway, I share these stories / observations not to suggest (on coral 
list of all places!) that disturbing reefs with dredges is good, like I 
said that's too simplistic anyway. But for those remote islands where 
choices are limited we must keep open minds because there are times we 
have to balance the needs of human populations and most importantly 
where there is a strong case to undertake dredging, I think with careful 
design, management and monitoring you actually can dredge and keep 
impacts to an acceptable limit. So why tell this story here? Because the 
people who follow the coral list and work in this field are the very 
people necessary to ensure that the very best management is implemented 
where these types of activities do occur.

For atoll communities and other small island populations with reef 
mediated shores, dredging is likely to become increasingly important, 
especially as a component of long term sea level rise adaptation. The 
land on most atolls is on average only a meter or so above high tide 
water level and it follows that for atoll communities climate change and 
associated sea level rise threatens their very ability to live on their 
islands. Worse still this is occurring in frighteningly short time 
frames. Dredging and building the elevation of some strategic islands is 
likely the only way these peoples will keep a home. Plainly, these are 
decisions only the custodians of these islands can make but when / if 
they make it, it will be critical that the coral research / management 
community stays engaged and supports those decisions to try and bring 
about the best possible balance of solutions and outcomes.

Obviously, I just can't speak to the challenges you are facing Nohora 
but I read your frustration. I do fear however that by implying on an 
open forum like the coral-list that anyone who works in this sector is a 
"hired gun" to commercial interests at the expense of ethics and the 
environment is unhelpful and mostly in my experience at least, untrue.

Arthur Webb
University of Wollongong,
NSW. Australia.

On 8/03/2017 2:27 AM, Observatorio Pro Arrecifes Coralinos wrote:
> Dear Coral-Listers
> Besides the few people hired to $ay that is ok to dredge in coral
> area$, is Anyone in the Coral-List in favor of dredging in coral
> areas?  If you advise that dredging is good for coral areas, please
> send us your scientific evidence that proves according to you that
> Dredging is not a threat to
> coral reefs.
> Nohora Galvis
> Directora Observatorio Pro Arrecifes
> Fundación ICRI Colombia
> Coral Reefs Observatory Coordinator
> Follow us on:
> Facebook.com/ICRI.COLOMBIA
> Twitter @ArrecifesCoral e @ICRIcolombia
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