[Coral-List] New study: Coral reef loss creates shoreline disequilibrium and increases coastal erosion

[Austin Bowden-Kerby]

Great work Curt!

This is a breakthrough study and ingenious way of quantifying the problem.


I have information potentially linking overfishing of sea urchins
and parrotfish into the coastal erosion equation, that might be of
interest?  Here in Fiji, back in 1999, we ran participatory workshops with
the indigenous community of seven villages in Cuvu District on the Coral
Coast, which led to the restoration of the practice of establishing no-take
Tabu areas, which had been abandoned for several generations.  In the
workshops, coastal erosion was one of the points of discussion. The beaches
were eroding badly in several areas and coconut trees were falling in.
Someone from the University had told them that it was due to sea level
rise, but there was no evidence one way or the other.  We grouped the 50-60
participants in each workshop by age, and each group produced resource maps
from memories of the time when they were most active as fishers in their
youth, focusing on changes in coral cover and marine resources.  The men
and women >70 years old were able to map reef environments that existed
before WW2!   A universal finding of these elder groups was that most fish
species that were abundant in former decades had become rare or even
locally extinct, and there was a universal agreement that the introduction
of gill nets was the root cause of the severe overfishing.
Another emergent finding from the elder fishers was that the reef flats
were considerably shallower than in past decades.  Areas of reef flat that
had been waist deep or deeper at low tide had become shallow to the point
of being knee deep and in some cases ankle deep or even dry.  I asked if
there had been a major earthquake or uplift event, and the consensus was
that there had not been.  On further discussion and visits to the reefs
with the elders, it became apparent that the former deeper tidepools had
been filled in with coralline algae "live rock", not sand, as the sand was
swept away during storms.  There were still some waist-deep areas on these
reefs, with sand covering a rocky base 3-5 cm below, which was preventing
corals from settling.  My hypothesis, which I presented to the group, was
that for the rocky areas, abundant COTS would kill the corals and without
bioerosion of parrotfish and sea urchins to break dead corals into sand,
that new corals would recruit on top of the dead ones, and when these
second generation of corals in turn died, additional recruits would settle
and so forth, until the tide pools were completely filled in with coral
rocks.  The community agreed that this might be what was happening.  So I
went on to speculate that if the reef holes were all filled in and the
corals were all gone, that the reef had become much flatter, and with no
corals or reef holes to absorb the energy of the incoming waves, the waves
would impact the beach with greater force.  So this might be what was
behind the beach erosion?  Perhaps as important was the fact that without
the parrotfish and sea urchins, the dead corals would not be ground into
sand, so the very sand formation process was likely broken. Both problems
might be the direct result of overfishing.

The community consulted and determined that banning gill nets might be
opposed, due to the investments made, and that the best thing to do would
be to bring back the Tabu areas which the former generations had spoken of,
but which the British Administration had apparently stopped.  As Mosese
Vana, the Provincial Fisheries Officer was at the workshop, he explained
that the new laws of the now independent Fiji allowed for customary
fisheries management!  So the community established three tabu areas on the
reef flats.  The areas were delineated and marked with wooden poles, each
topped with a woven coconut leaf flag.  It was a powerful experience, and
tears were shed as the community respectfully set aside these areas of reef
as their forefathers had done.  The Mana (spirit of power and action) had
returned!   The community got very busy: about 4,000 COTS were removed, a
rubbish collection system was implemented with assistance from the
Shangri-La's Fijian Resort (formerly dumped into the sea at high tide),
mangroves were planted at problematic stream mouths, and with help from
Fisheries, giant clams were restocked and fish wardens were trained.
The community also planted thousands of coconut trees to absorb
polluted groundwater in the villages.  And the news spread from village to
village, and Fiji now has LMMAs- locally managed marine areas with tabu
areas in close to 400 village sites around the country.

But here is the relevant part of the story to beach erosion:  I had thought
that it would take decades to see any real changes to the beaches, however
just two years into the project, Chief Anare of Navuevu Village flagged me
down as I was driving past.  He asked me if I had a bit of time, and so I
pulled over and got out and he proceeded to lead me to the shore.  He led
me to a beautiful beach, and with both hands outstretched, he pointed
downward at the sand, and with emotion in his voice he said:  "I am 78
years old, and this has always been a rocky beach.... some sand would come
in, but it was always taken away later by the waves.  The parrotfish have
returned, this Tabu area is working, and I am now very happy!"

We have no data and we don't even have before and after photos, but the
proof we have is in the minds and hearts of the very people who have the
most to lose from sea level rise and the death of coral reefs due to
climate change.  In 1999 a major change in the hearts and minds of the
people occurred, as they arose in village after village to resurrect long
neglected traditional systems of management, which rapidly spread
throughout the entire nation, and spilled over to neighboring countries.
As an example, some 80 no-take "aviraiu" MPAs have now been established in
Samoa, with the first ones established as word spread of the Fiji
successes.

But now two and a half decades later, bleaching is killing the corals and
compromising the fisheries habitat and wave absorbing services of the
reef.  So the challenge now is to work with these communities to support
and reinforce their Tabu areas in the face of climate change, by working
with bleaching resistant, heat adapted corals to secure and enhance the
fisheries and wave absorbing characteristics of these rather extensive reef
areas, which are often set aside directly in front of the village or
located in partnership around a resort.

UNESCO endorsed our Reefs of Hope strategies last February as an Ocean
Decade Action.  The goal is to enable those most impacted by climate change
and SLR (communities and resorts), to come to the forefront of meaningful
action.  A thousand communities acting is the best way to upscale climate
change adaptation and to reboot effective coral reproduction as surviving
corals become more widely dispersed.  It is not rocket science, and so we
have succeeded in training islanders how to select heat adapted corals in a
systematic manner:  collecting corals from what has survived mass bleaching
in the hottest areas of the reef, often from the "hot-tub layer" that often
forms at low tide.  Moving these corals where possible to cooler waters to
prevent their death in the severe marine heat waves that are now arriving,
as well as protecting them from predators.  The corals are planted into
nurseries and after a year trimmed to plant onto fish habitat enhancing
structures, with multiple genotypes planted per species to restore sexual
reproduction. We also have an alternate livelihoods program for communities
setting aside no-take Tabu areas which includes our happy chickens!  The
overall plan is to train the trainers and to let go, encourage other orgs
to take on the various strategies, and in this manner involve multiple
like-minded partner organizations and government agencies to work with
hundreds of communities of the region.   I will present more on this at the
Reef Futures conference in December.

Whatever the strategy, most importantly, we need to understand that
culturally intact indigenous communities are an important part of the
solution that we seek for the less developed world.  With the
reestablishment of the traditional no-take areas, these communities are in
fact already leading!  Our intention now is to maintain these gains by
adding coral-focused climate change adaptation focused on declining coral
species, to secure and support the important gains that these communities
have made.

There are dozens of research topics that are being generated for research
scientists and graduate students, as trial and error implementation
uncovers important factors formerly not understood.  But we can not afford
to wait until all is known before acting, as the Caribbean and Kiribati,
and now Tuvalu, and back to back bleaching years have all shown us- time
has run out!   Rescuing entire colonies of heat adapted corals from certain
death in the extreme shallows, many exposed in the air at low tide as a
severe marine heat wave approaches may sound extreme, but it certainly is
better than letting them die!  We recently saved over 1,300 colonies in
this way, while 80% of the tens of thousands of corals that were left
behind died, as the waters exceeded 35C.  Many of the survivors left behind
are now being wiped out by COTS, while those in the nurseries are secure.
So we now are working to prevent the death of these precious heat adapted
corals.  We are operating on the frontline of a battle against the dark
forces of climate change!   And we need help!  Our UNESCO endorsement does
not come with funding, and conservative reviewers of the multiple donor
agencies have turned down our many proposals.  Our proactive trial and
error non peer-reviewed approaches apparently make some people
uncomfortable!  But regardless, we operate with three small grants and
crowdfunding, have succeeded in training over 200 Pacific Island university
graduates thus far, have established partnerships with local NGOs and
government agencies, and we have coral focused adaptation sites running in
six Pacific Island nations.

If any are still reading this wordy information dump:  On a cautionary note
to those involved with facilitating the setting aside of no-take areas, at
least in the IndoPacific: without any biological controls, parrotfish can
become super-abundant and begin damaging the living corals as they chew
away and deepen the reef flat areas.  In 2000, when we tried to plant about
four bushel baskets of staghorn corals into the ~1 meter deep areas of the
Tabu MPA, they were eaten into nothingness by the parrotfish within just
two days!  Juvenile corals trying to come in were bitten repeatedly, so
that the corals could not grow erect branches.  Octopus also became
over-abundant, and the result was that monitoring showed that the open
fishing grounds had many more seashells and crabs than did the Tabu areas,
and so the pendulum swings from one imbalance to another!   We think that
one of the primary parrotfish and octopus predators of the shallow reefs
are blacktip reef sharks, which in these waters take at least a decade to
return.  We now recommend that newly closed areas be monitored during
regular COTS removal activities, and if the balance gets badly off, that
periodic octopus fishing might be allowed should they become over
abundant.  Where this is already happening, it has given the fisherwomen a
real boost, and more protein to the village!   If any Acropora planting
work (using only bleaching-resistant corals) is planned, we recommend that
this be done right away after the no-take area is established, before the
parrotfish become so abundant, or perhaps carry this activity out in the
open fishing areas nearby, as long as COTS are managed.

Regards, and thanks for all that each of you do.

Austin

Austin Bowden-Kerby, PhD
Corals for Conservation
P.O. Box 4649 Samabula, Fiji Islands

BULA REEF, the largest word ever written under the sea, spelled out in
rescued heat-adapted corals:
https://www.youtube.com/watch?v=tRrAZuimvWU
Reefs of Hope Peer-reviewed Scientific Paper:
https://www.mdpi.com/2673-1924/4/1/2
C4C's UNESCO endorsed Decade Action:
https://oceandecade.org/actions/reefs-of-hope/
C4C Website: https://www.corals4conservation.org
Film on our "Reefs of Hope" coral restoration for climate change adaptation
strategies:  https://www.youtube.com/watch?v=BG0lqKciXAA
Global Giving Donation Site:
https://www.globalgiving.org/projects/help-reefs-of-hope-expand-south-pacific-initiative/

Teitei Livelihoods Centre
Km 20 Sigatoka Valley Road, Fiji Islands
(679) 938-6437
http:/www.
<http://permacultureglobal.com/projects/1759-sustainable-environmental-livelihoods-farm-Fiji>
teiteifiji.org
https://www.globalgiving.org/projects/happy-chickens-for-food-security-and-environment-1/






On Fri, Sep 6, 2024 at 12:31 AM Storlazzi, Curt D via Coral-List <
coral-list at lists.coralreefs.org> wrote:

> New study: Coral reef loss creates shoreline disequilibrium and increases
> coastal erosion.
>
> The first part of this study was just what we expected; when we looked at
> short term studies globally, shores protected by coral reefs experienced
> less coastal erosion after storms.
>
> But then we looked at one of the best long-term (80+ years) data sets of
> shoreline change in the world and found surprising results. When we looked
> at decades of shoreline change data across more than 240 kilometers of the
> Hawaiian Islands, coral reef-lined coasts were eroding faster than
> shorelines without reefs !?!
>
> We hypothesize that ongoing coral reef loss is creating disequilibrium in
> these systems…..and probably lots of other places around the globe.
>
> Shorelines get into a long-term, dynamic equilibrium – e.g., beaches
> expand over the summer and contract over winter but stay in a more or less
> consistent place determined by protective features (and this includes
> artificial defenses such as breakwaters).  But if those defenses change –
> e.g., you lose height in your natural breakwaters (coral reefs) – then the
> beaches will change and reach a new equilibrium (e.g. a ‘thinner’ beach if
> defenses are lowered).
>
> In this case, the natural reef breakwaters continue to be lost, and this
> disequilibrium is ongoing.
>
> It should be noted that this effect is beyond what we expect from climate
> change alone, which is what we assume is a primary driver of recent,
> accelerating coastal erosion on unprotected shores.
>
> Please see: https://doi.org/10.1016/j.nbsj.2024.100174
>
> Bitterwolf, S.A., Reguero, B.G., Storlazzi, C.D., and Beck, M.W., 2024.
> “Shifting sands: The influence of coral reefs on shoreline erosion from
> short-term storm protection to long-term disequilibrium” Nature-Based
> Solutions, 6:100174, doi: 10.1016/j.nbsj.2024.100174
>
> ---------------------------------------------------
> Curt D. Storlazzi, Ph.D.
>
> U.S. Geological Survey
> Pacific Coastal and Marine Science Center
> 2885 Mission Street
> Santa Cruz, CA 95060
> +1-831-460-7521 office
> +1-831-295-3429 cell
> https://www.usgs.gov/staff-<
> https://www.usgs.gov/staff-profiles/curt-d-storlazzi><
> https://www.usgs.gov/staff-profiles/curt-d-storlazzi
> >profiles/curt-d-storlazzi<
> https://www.usgs.gov/staff-profiles/curt-d-storlazzi>
>
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