Big Cyclone, poor mangrove recovery

 Fifteen years ago Category 5 Cyclone (~hurricane or typhoon) Yasi slammed into the coast just north of Cardwell on the Queensland coast in Australia.  The seven metre storm surge caused almost total mangrove death over many square kilometres.  I had not been back to this area in fifteen years.  The last time I saw the area, it was about 3 months after they cyclone, and I walked through a dead standing forest. This site once had a luxuriant Ceriops (yellow-leaved spurred mangrove) swamp.  Remains of the original trees are still standing and a new stand of mangroves is growing up below.  Fifteen years of regeneration have only filled in half the space, regrowth is only about 20% the height of the original trees and dead timber from fallen trees covers the ground.  In contrast, the beach vegetation, mainly littoral rainforest has totally recovered and it luxuriant.

Dead mangroves seen on previous visit fifteen years ago

Beach vegetation that took the seven metre deep surge with six metre waves

Getting into the swamp was a challenge as the landward fringe was filled with bushy mangroves that had retained strong dead twigs on their lower, now shaded stems.  One passed that barrier, I was in a mosaic of open ground with fallen trees and dense bushy mangroves.  The fallen timber was firm and whilst sun bleached, was not weakened by decomposition.  Absent were signs of insect attack or ship worms.  Stepping over the fallen timber would be easy for a young man, and the mud was wet and cracked but not deep or sticky.

Getting in is tough, lots of twigs and mosquitos

In the middle, there are wide spaces and bushy thickets

As far as I wanted to go, it was much the same

Only one type of crab was abundant, a small grapsid or sessarmid (Sesarma messor?) and these crabs ran from me across the surface when crabs usually run down crab holes.  It was strange behaviour that caught my eye.  Just after they cyclone a small dark red crab was everywhere, yesterday I saw just two of them.  Rakali tracks covered the ground and I think that they go down larger crab holes and attack the residents.  I don’t imagine that near complete predation of larger crabs is helping the recovery of the mangrove forest.  Tracks from feral pigs, large and small, indicated that these animals lived in the area and routinely crossed the swamps.  More than crocodiles, I fear encounters with feral pigs and even found a rubbing tree with scars from the pig’s tusks.  Wallaby and bandicoot tracks were also present.

Sesarma messor? Rather small for this species

Rakali scratches

A feral boar rubs against this tree

The one unexpected animal was a moth as large as a small bat.  I could feel the vibration from its wing beats as it flew past.  Fortunately it landed on a nearby tree and I could photograph it.

Despite a number of good years, with above average rainfall and no cyclones, the recovery of the mangroves has been very slow.  The regrowth mangroves are flowering like crazy, aware that half the space is yet to be filled.  Rainforest trees hold back on flowering to concentrate on growth as a larger tree can support many times more flowers and fruits.  It tells me something, that the mangroves are flowering and fruiting so precociously.

Heavy fruit load for such a small tree (Ceriops sp.)

Not much alive on the surface

I did not see any molluscs.  There were a few dead mangrove clams.  I also did not see bird footprints.  It seems that nothing has thrived due to the changed conditions.  The conditions twelve years ago are shown in this post https://queenslandcoast.blogspot.com/2014/06/legacy-of-cyclone-yasi.html.  These photos were taken in Girrimay National Park about 1 km north of the last car park.