For the Juniors: How do mangrove trees survive?

NARRATOR:

This mangrove area is a very special place for Jacobi, Tyson, their dad and granddad.

BIRD:

It's a special place for me too.

NARRATOR:

You'll soon see lots of reasons why mangroves are special. Listen to that squishy sound. The ground is very wet. That's because twice a day seawater comes in and floods this whole area. This is what this mangrove area looked like about six hours ago at high tide. The water reached the branches on some of the trees. Over six hours — about the time you spend at school each day, this is what happens. This is speeded up so you can see what happens in a short time. The water gradually flows back out to sea. And now it's low tide. In about six hours, it'll be high tide again and the water would be above Tyson and Jacobi's heads.

DAD:

Grab his hand. Grab his hand, Jacobi.

NARRATOR:

Even now in some areas, the water is still a bit deep. So Tyson needs a little help from his big brother.

TYSON:

I got all wet in here.

NARRATOR:

And sometimes they both need a bit of help from Dad. Mangroves are home to many creatures. There's always so much to discover. Even the seeds of these mangrove trees are special. When they fall off the trees, they start to germinate straightaway. They grow roots and then their leaves start to sprout from the top. When the tide comes in, some seeds float away. Some will die. But others will find a good spot, put their roots down and eventually grow into a big mangrove tree.

BIRD:

Lots of little mangrove trees here.

NARRATOR:

No, they're not all little mangrove trees. The ones with the leaves on top are mangrove trees but the ones with no leaves are the mangroves' roots.

BIRD:

But roots grow down, away from the light.

NARRATOR:

That's right, but mangrove roots are special. A plant's roots need air to breathe. If they can't breathe, the whole plant dies. Most healthy plants live in soil that has gaps between the tiny grains of sand. There's air in these gaps, so the roots can breathe. But if that soil is wet all the time, there's water between the grains of sand, not air. The plant's roots can't breathe and so it will die. Mangroves grow in ground that's wet most of the time. So it doesn't have much air in it.

BIRD:

So how come these mangroves aren't dead?

NARRATOR:

Well, these roots act a bit like snorkels. They grow up through the mud. When the tide is out, like now, they absorb air. This air passes own into the mangrove's root system under the mud. Enough air is stored in the roots under the mud so that later when they're covered by water, the plant still gets the air it needs. If the roots are covered by water, mud or oil for too long, the trees won't get enough air. So they'll die. So the mangrove roots that Jacobi and his granddad are looking at are very special. And because they're so special, they have a very special name. They're called pneumatophores. And here's another special thing about these mangroves. Yellow leaves. Most plants that grow on land can't survive in salty seawater. But these mangroves are flooded with salty seawater twice a day and they're growing very well. These pneumatophores stop most of the salt from the seawater getting into the roots. If some salt does get in, it's sent up to the plant's older leaves. They store the salt until they can't hold any more. They turn yellow and then they fall off the tree. That gets rid of the salt in the plant. Those leaves gradually rot and help to feed the creatures that live in the mud. Creatures like these crabs. Can you see them? They're very well camouflaged, aren't they?