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Description of layers of forest

Tropical rainforests contain an enormous variety of plants and animals – approximately 90 per cent of all of the world's species. Vegetation is dense and occurs in four main layers:

• The forest floor/shrub layer. This area is dark as trees block out most of the sunlight. The forest floor is covered in a thick blanket of dead and decaying roots and leaves, known as humus. A little vegetation can grow between the trees if it is able to trap sunlight. This area is prone to flooding during torrential rainfall.
• The under canopy is the layer above the forest floor. This area is shady and cooler. As there is very limited sunlight, seedlings lie dormant until larger plants and trees die. The gap that is left in the canopy is quickly filled as new plants grow into it. Lianas, or vines, take root in the ground and climb up trees to reach the sunlight.
• The canopy is the continuous layer of tree tops that is more sheltered. The trees are normally 20 to 40 metres tall. This leafy location with fruit all year round is the habitat for most wildlife including insects, tree snakes, birds and some mammals, eg howler monkey, jaguar and sloth.
• The emergent layer consists of the tallest trees in the rainforest and they can grow up to 60 metres. They are higher because they are able to trap more sunlight to help them make more food to grow. Emergent trees are supported by buttress roots which prevent them from blowing over in high winds.

This diagram shows the four layers of rainforest vegetation and the amount of sunlight that each one receives: