The
Romans built fish ponds by the sea. [1] Constructed of masonry, they
were holding tanks to provide wealthy owners of seaside villas, and
perhaps commercial fishmongers too, with access to fresh fish. As the
shallow Mediteranean tide (only a few centimetres) rose and fell the water
in the tanks was refreshed via a system of sluices. These ponds are
mentioned by Columella, writing sometime in the first century CE.
We consider that incomparably the best Fish-pond is one which is so situated that the incoming
tide of the sea expels the water of the previous tide
and does not allow any stale water to remain within
the enclosure. [1]
A
number of these tanks have survived in amazingly good condition and are
still more or less at sea level, showing the latter has not changed a
lot in 2000 years.
This tells
us something important, because in the last two decades sea level has
been rising at about 3 mm a year [3] and accelerating. If this had been
going on for the last 2000 years the fishponds would be under 6 m of
water by now. The fact that they aren't indicates that the current rate
of incease in sea level is something that has just developed very
recently. If it had been going for even as long as 200 years the
fishponds would still be under a foot of water.
So something has been happening quite recently that has made the seas rise by an unprecedented amount.
What Roman Fish Tanks Tell Us
Here's something I learned about only last week
The Romans built fish ponds by the sea. [1] Constructed of masonry, they were holding tanks to provide wealthy owners of seaside villas, and perhaps commercial fishmongers too, with access to fresh fish. As the shallow Mediteranean tide (only a few centimetres) rose and fell the water in the tanks was refreshed via a system of sluices. These ponds are mentioned by Columella, writing sometime in the first century CE.
We consider that incomparably the best Fish-pond is one which is so situated that the incoming tide of the sea expels the water of the previous tide and does not allow any stale water to remain within the enclosure. [1]
A number of these tanks have survived in amazingly good condition and are still more or less at sea level, showing the latter has not changed a lot in 2000 years.
This tells us something important, because in the last two decades sea level has been rising at about 3 mm a year [3] and accelerating. If this had been going on for the last 2000 years the fishponds would be under 6 m of water by now. The fact that they aren't indicates that the current rate of incease in sea level is something that has just developed very recently. If it had been going for even as long as 200 years the fishponds would still be under a foot of water.
So something has been happening quite recently that has made the seas rise by an unprecedented amount.
[1] https://harvardmagazine.com/2016/08/what-roman-ruins-rev
[2] Columella, On agriculture, trans. Forster and Heffner
[3] https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-14/