Bbc planet earth 08 — jungles
This is our planet's hothouse. The jungle. The tropical rainforest. Forests like these occupy only three percent of the land yet they're home to over half of the world's species. But how do so many different kinds of plants and animals find the space here to live alongside one another?
On the dark, humid forest floor the jungle appears to be lifeless. Often the only signs of life are what you hear. A male blue bird of paradise is advertising for a mate. It's quite a performance but he's not the only bird of paradise here keen to make an impression. There are nearly forty different kinds on the island of New Guinea each with a display seemingly more bizarre than the rest. A riflebird of paradise. Like many jungle animals, birds of paradise avoid competing with each other and these do so by living in different parts of this jungle covered island. The six plumed bird of paradise displays in his special clearing, on the forest floor. The magnificent bird of paradise favors the low branches of bushes. His female is modestly dressed.
The male has a good set of lungs but he'll have to do more than flutter his eyelids, if he wants to impress her. It'll all depend on his performance. The females may be dull looking but they're very picky and it's time for a really close inspection. His right side looks fine… but what about his left? Pretty impressive, but is he magnificent enough? Oh dear. Her departure says it all. Generations of choosy females have driven the evolution of these remarkable displays. The more extravagant a male is, the more likely he'll be noticed.
New Guinea lies in a warm tropical belt that girdles our planet around the equator. With abundant rainfall and twelve hours of daylight three hundred and sixty five days a year, it's here that rainforests flourish. Surprisingly only two percent of the sunlight filters down to the forest floor. Down here seedlings struggle to grow but the gloom is not eternal.
The death of a forest giant is always saddening but it has to happen if the forest is to remain healthy. The sudden blaze of sunlight will bring life to the forest floor. A single hectare of rainforest may contain as many as 250 species of tree. That's nearly ten times the number that grow in Britain and the thirst for light triggers a race for a place in the sun.
There's no time to waste. A seed that may have fallen only a few days ago, now bursts through the leaf litter.
With so many competitors, getting a good start is critical but each plant has it's own particular strategy for making the most of this rare opportunity. The seeds of hardwoods are quick to germinate but, like the fabled tortoise, their strategy is to be slow and steady. Vines and other climbers put all their energy into rapid vertical growth, rather than girth though they'll need to be well supported. The climbers' strategy looks chaotic but there's method in their madness. Their growing tips circle like lassoes, searching out anchors for their spindly stems. They put coils in their tendrils so that if their support moves, they will stretch and not snap. But the frontrunners at this stage, the first to fill the clearing, are pioneers like the macarangas. Their immense leaves capture huge amounts of sunlight, so fueling their growth. As a result the macarangas grow a remarkable eight meters a year surging ahead of almost all their rivals.