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Mangrove reports

Posted: Wed Mar 13, 2019 12:00 pm
by Matt Flynn
Given the Gulf die-off after successive poor Wets, will Top End mangroves be affected by this wet season?

The previous two years were much better Wets for the Top End, so there may be no effect. But this year was unusual in terms of low rainfall.

Anyone with observations, post 'em up :mrgreen:

Re: Mangrove reports

Posted: Mon Oct 14, 2019 2:12 pm
by Matt Flynn
A recent observation is that Gulf mangroves have been slow to recover ... ... nvironment

Re: Mangrove reports

Posted: Tue Oct 15, 2019 6:08 pm
by NinjaFish
Interesting about the mention of the trade winds and entirely possible. I’ve seen how cyclones have held water both in and out in the Gulf and I swear it gets hotter than further North. Water temps in the shallow Gulf waters boil live Mullet as you bring them in with the cast net from deeper out! No tree damage that I’ve noticed around Darwin yet but can’t see dieback from the water either.

Is it possible that even Mangrove trees need the much needed Nitrogen from rainfall like any other tree and will die back like any other tree when deprived?

Re: Mangrove reports

Posted: Tue Oct 15, 2019 7:04 pm
by ronje
Mangroves die when they have been exposed to excessive water. They'll tolerate it for a while but its certain death if its prolonged.

What happens with excessive wet/runoff is that the mangrove roots can't breath like they do when exposed to normal daily tidal influences. Exposed twice a day to allow intake of oxygen.

To put it simply, they drown.

See if the "dieback" coincided with/shortly after a lengthy run-off period or prolonged easterly wind season. They'll also die if covered by saltwater excessively.

A prolonged northerly wind in Gulf heaps up water at bottom of gulf covering mangrove roots. Prolonged n/e winds heaps up water in s/w corner. Similarly easterly wind heaps it up in western side of gulf. Mangroves drown. Not rocket science.

That's what happened with the mangroves/trees in the areas where NT farms put up levees to hold extra freshwater in the runoffs a few years ago. Mangroves simply drowned.

Happened down here with lengthy run-off in 2011. Mangroves in the run-off creeks all died and still haven't recovered. Creeks look (and are) barren.

Re: Mangrove reports

Posted: Wed Oct 16, 2019 10:06 am
by NinjaFish
Agree totally Ronje.

This particular report does mention all that but comes in from the other angle of being dry.

The mangroves were once nurseries for the mud crab, barramundi and prawn fisheries, but now consist mainly of dead trees and dusty earth.
The few live seedlings coming through are exposed, and vulnerable to damage from the fallen dead trees.
Scientists from Queensland and Northern Territory universities said one contributing factor was a temporary drop in sea levels, caused by a change in the trade winds, which left the forests unusually high and dry.
But they said another factor in the dieback along 1,000 kilometres of coastline was climate change and a sharp increase in the sea temperature.

Interesting how they measured sea level rise while the Trade Winds held the sea back. Maybe the earths tilt has displaced some seas here and there. Maybe “dead trees and dusty earth” (still?) were never Mangroves here or... sea levels are seriously dropping in the Gulf from those nasty Trade Winds.

Anyhow I know it’s all linked and I suppose if they chuck in all possible reasons we can each pick which one we want to follow and protest to. :D

Re: Mangrove reports

Posted: Wed Oct 16, 2019 7:34 pm
by ronje
Whatever the reason a carbon tax will fix it.

Re: Mangrove reports

Posted: Thu Oct 17, 2019 11:39 am
by NinjaFish
And menaced they have. True or not, a well worded opinion, stirrer and user of words this fella. I imagine he would have been hung in the town square last week if he was still here.

Carbon tax wouldn’t have happened on his watch...

”To paraphrase H. L. Mencken, the whole air of environmental politics is to keep the public alarmed by menacing it with an endless series of hobgoblins, most of which are imaginary. Pursuing an anti-CO2 agenda is pursuing a hobgoblin that will cause vast economic and environmental harm.”