PAUL WEST (VOICEOVER) With so many species of fauna and flora competing for food, water, and light, for a seedling, it's a real battle for survival. Botanist Darren Crayn studies the plants here.
PROFESSOR DARREN CRAYN Only 5%, approximately, of the light that hits the canopy filters through down to the ground level here. So all of these plants are getting started. They're living their earliest years in a pretty harsh environment. Not only have they got poor access to light, but there's a lot of things down here that want to end their lives quickly.
PAUL WEST (VOICEOVER) But Darren's going to show me a tree that has developed an ingenious way to start out life. This towering giant is the strangler fig. And it has a remarkable but lethal strategy to survive.
PROFESSOR DARREN CRAYN The strangler figs do something quite amazing and really unusual. They flip the script, and they start their life up there where the light is in the forks of branches in big, old trees.
PAUL WEST (VOICEOVER) Fig seeds dropped by birds and animals high up in the light-rich canopy slowly begin to grow downwards around a host tree.
PROFESSOR DARREN CRAYN It is a real challenge being up there in the canopy. So what they do is, they efficiently draw on the nutrients released by vegetation that's rotting up in the canopy and slowly grow their roots down to the ground. But once those roots contact the soil, then it's game on for the fig.
PAUL WEST (VOICEOVER) Now feasting on the rich resources underground, the fig begins a massive growth spurt.
PROFESSOR DARREN CRAYN Where you can see the roots come in contact with each other, they can fuse. And so eventually, the fig can form a network around its host.
PAUL WEST So you mean bits like this where it's a lattice almost.
PROFESSOR DARREN CRAYN Like a lattice. Exactly. As you can see here, it grows around and completely encases the host plant and squeezes it almost like a strangulation.
PAUL WEST Hence the name.
PROFESSOR DARREN CRAYN Hence the name. It chokes the life out of it.
PAUL WEST (VOICEOVER) The fig's thick foliage blocks sunlight. And its sprawling roots steal precious nutrients from the soil. This multi-pronged attack ensures the host meets a slow, grisly death.
PAUL WEST As you look into the folds and the nooks and the crannies of the strangler fig, right in the heart, you can actually see the dead host tree that initially would have supported the growth of this young plant.
PAUL WEST (VOICEOVER) No doubt these ginormous gangster-like trees are ruthless. But they do have a less sinister side. Their size plays a crucial role in the forest's ecosystem. And the best way to see how is high up in the tree tops.
PAUL WEST That's not a tree, Darren. What is that?
PROFESSOR DARREN CRAYN That, Paul, is a canopy crane.
PAUL WEST (VOICEOVER) As the crane climbs 50 metres into the sky, a whole new world opens up.
PAUL WEST It's a totally different place in the canopy.
PROFESSOR DARREN CRAYN You see things up here that you don't imagine would exist if all your experience has been based on seeing from the ground. So there are animals up here that we're barely aware of. There are small mice, native mice. There are snails. There are snakes. There are all sorts of things that live in the canopy, things we would otherwise think of as ground-dwelling animals.
PAUL WEST It's another world.
PAUL WEST (VOICEOVER) In fact, 90% of all the forest animals live up here amongst the trees. And it's the fruit from the mighty fig that provides a lot of their food.
PAUL WEST Is this us here with those bronze, really up-pointed leaves?
PROFESSOR DARREN CRAYN That's it. Yeah. So here we are approaching the crown, the Ficus destruens, the strangler fig. And you can see here as we grab a branch, down in amongst all the leaves are all of the fruits.
PAUL WEST Wow. It's laden with fruit. So that's the fig of the strangler fig.
PROFESSOR DARREN CRAYN That's the fig. And what it is is, it's not a fruit, Paul.
PAUL WEST Yeah, right.
PROFESSOR DARREN CRAYN If you break it open, you'll see it's full of tiny, little flowers.
PAUL WEST There you go. So, I mean, that looks like a kind of scaled-down, wild version of the fruit that we see in the fruit shop.
PROFESSOR DARREN CRAYN Absolutely. Yeah. Figs are really, really important in rainforest ecology because there's almost always a fig fruiting somewhere in the rainforest. And so they provide a lot of food for a lot of other fauna. They're like a 7-Eleven. They're like a convenience store in a sense. They're available when all the other stores are closed.
PAUL WEST (VOICEOVER) This incredible tree is the 500-year-old cathedral fig.
PAUL WEST It's hard to convey just how big this tree is. It's got a 72-metre girth. That's 40 people holding hands to get around the base of this.
PAUL WEST (VOICEOVER)At 50 metres high, its majestic crown is the size of two Olympic swimming pools.
PAUL WEST It is absolutely awe-inspiring.
PAUL WEST (VOICEOVER) But it's not just about looks. Like most trees, it offers habitat for countless insects and animals and, in this case, also for plants.
PAUL WEST It's not just a tree standing alone. There's all kinds of other plants smattered up all through from the ground to the top all the way up in the canopy.
PAUL WEST (VOICEOVER) This tree alone supports over 1,000 plants. It's amazing to think that what started out as a tiny seed with murderous intent now supports so much life.