[Coral-List] Atoll Good News

[Dennis Hubbard]

Hi all:

I'm not sure whether I sent the following to the list or just to Doug.

Thanks Gene:

These are difficult papers to put into context. All that "p-fish poop" is
also removing carbonate from the reef, so if the production values are
going down, the reef has to lag behind. At that point, wave action is going
to disproportionately remove intertidal sediment from the platform. The
reef is both the basement for island building and the source of the
sediment. Increased grazing might seem to just increase island supply, but
the problem is that the carbonate budget is only as healthy as what is "put
into the bank". Whether or not fish grind more of to to make it available
to the island is less important than the volume of carbonate available. So,
if less carbonate is being made, more of it is being ground away and a
higher percentage is being exported, the end result is a problem for the
budget.

The one potential issue with the second paper (I'd need to read it
carefully, so take this as the off the cuff response that it is) is that
these studies are often based on plan (i.e. map, air photo) measurements
and therefore report results in square meters. Perhaps the second paper
took elevation into account, but many that I've seen recently have not -
stay tuned. In this methodology, an eroded area 5 meters high is treated as
equal to a depositional area only a meter or so ihigh. As a result, the
area stays the same, but volume is being lost. Also, most of the studies
that have also characterized the positions of the islands on the atolls
show island masses gradually moving toward the center of the atoll. As the
islands encounter to slope down into the lagoon, the island will
increasingly have difficulty - the same as if the seds were doing down the
front. And.... many excellent papers have shown that the increasing
inundation due to greater storm surge will leave many (not all) islands
uninhabitable long before they are underwater.

As with corals where we confuse calcification, linear extension, density
and "growth rate", the issue with islands is how we define "drowning".
Waiting for the highest point on the tallest dune is much different than
the point where the island has been rendered uninhabitable. There is an
interesting wrinkle in the Law of the Sea. Once an island becomes "an
uninhabitable rock" it legally ceases to be sovereign territory and the
former inhabitant's claims (or their government on a nearby island) to
offshore sovereignty likewise disappears. This will mean that there are
going to be a bunch of mining companies waiting in line to treat nearshore
shelves as international waters. There is no practical usefulness for
science without a reason for doing it, but there is no good management
without both good science and a full understanding of the vagaries of
policy and politics. That's a discussion for another day.

Best,

Dennis



-- 
Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"