Rainforests

• Tropical rainforest


  Hot, wet ecosystem found on and near the Earth's equator
• Tropical rainforests contain far more species of plants and animals than any other biome
• Tropical rainforests cover approximately six per cent of the Earth's surface
• Tropical rainforests get 2,000 mm of rain per year and temperatures range from around 27 to 32°C, so conditions are wet and hot all year round
• Why it is hot & wet in a rainforest

  1. The sun's rays shine directly on the land and sea at the equator

  2. The sun's heat warms the land, the air and the sea and causes water to evaporate into the air

  3. The warm air can hold a lot of water

  4. As the air rises it cools and the water turns back into rain, creating clouds
• Emergent layer


  • The tallest layer - over 40 metres. Contains only a few tall trees which grow taller than the trees of the canopy. The plants are made for living in dry conditions because it's very sunny. They have small, waxy leaves to prevent them drying out.
• Canopy


  • The second highest layer - 30-45 metres. The canopy blocks out the sun from lower layers and intercepts (catches) rainfall. It contains the most plant species. This layer contains the most animal species.
• Understory


  • Low light conditions (2-15%). Plants adapted to low light grow here. Birds, butterflies, frogs, snakes and lots of insects live here.
• Forest floor


  • Very little light reaches the forest floor (2%) - so plants grow slowly. The ground is covered in fallen leaves, rotting branches and twigs and a network of shallow roots. Lots of insects live here.
• Adaptations of plants in tropical rainforests

  • Thick, waxy surface of leaves protects against hot sun, heavy rain, and strong winds
  • Epiphytes (plants which live above the ground growing on tree trunks and branches, e.g. orchids, ferns, mosses)
  • Buttress roots (wide roots that stop tall trees from falling over and wind above the ground looking for food and nutrients)
  • Tree trunks (don't waste time growing branches as they could use this energy to grow faster and reach the sunlight first)
  • Lianas (climbing woody vines that drape rainforest trees and have adapted to life in the rainforest by having their roots in the ground and climbing high into the tree canopy to reach available sunlight)
  • Drip Tip leaves (allow rain drops to run off quickly to avoid growth of fungus and bacteria)
• Adaptations of animals in tropical rainforests

  • Sloths (use camouflage and move slowly to avoid predators, feed at night to save energy)
  • Spider Monkey (has long, strong limbs to help it climb through the rainforest trees)
  • Flying frog (has fully webbed hands and feet, and a flap of loose skin that stretches between its limbs, allowing it to glide from plant to plant)
  • Toucan (has a long, large bill to allow it to reach and cut fruit from branches that are too weak to support its weight)
• Tropical rainforests have extremely high biodiversity, containing around 50% of the world's plant and animal species
• The removal of trees from forests is called deforestation
• Main threats to tropical rainforests

  • Cattle ranching (70% of deforestation)
  • Agriculture and farming (25% of deforestation)
  • Logging (3% of deforestation)
  • Other activities such as mineral extraction, road building and dam building (2% of deforestation)
• Since 1978, over 750,000 km2 (3 times the size of the UK) of the Amazon rainforest has been destroyed
• Population growth and migration to the Amazon rainforest area is putting pressure on the rainforest, as the Brazilian Government offers land to poor people to reduce overcrowding in cities
• Environmental impacts of deforestation in the Amazon

  • The Amazon stores around 100 billion tonnes of carbon, so deforestation contributes to global warming and climate change
  • Brazil is losing 55 million tons of topsoil every year because of soil erosion caused by farming
  • In the Amazon, 1 million species are threatened as human activity expands deeper into the rainforest
• Economic benefits of deforestation in the Amazon

  • Farming makes lots of money for Brazil (e.g. $7 billion from trading cattle in 2008)
  • Brazil is now the 5th biggest exporter of food in the world as it has expanded agriculture into the Amazon
  • 3,000 people are employed in the mining industry in the Amazon
  • Logging accounts for 7% of Brazil's GDP (wealth), and Brazil accounts for 3% of all forestry produce
  • The money created from these enterprises allows Brazil to generate foreign income, which can then be used to pay off debts or be invested in further development projects
• Deforestation is responsible for 15% of global CO2 emissions
• Importance of managing tropical rainforests

  • TRF store ¼ of the world's carbon
  • TRF provide fruit, spices and rubber that are sold worldwide
  • The TRF is used as a tourist site and generates jobs and income
  • More than 20% of the world's oxygen supply is provided by the TRF
  • TRF is rich in biodiversity with 6 million different species
  • Around 25% of all medicines come from TRF plants
  • TRF are home to 350 million people around the tropics, providing shelter, health and food as well as being an intrinsic part of their cultures and traditions
  • ¼ of the world's fresh water is stored in the Amazon basin
  • TRF are part of a global irrigation system that helps form clouds and distribute fresh water around the planet
• Ways to manage tropical rainforests sustainably

  • Selective logging (only some trees, e.g. just the older ones, are cut down, and the rainforest canopy is preserved)
  • Afforestation (new trees are planted to replace the ones that are cut down)
  • Ecotourism (environmentally friendly tourism that protects the environment, educates visitors, employs local people, and reinvests profits into conservation)
  • Debt reduction or conservation swaps (poorer countries have portions of their debts wiped out or paid for by richer nations or charities in exchange for promising to protect or conserve large parts of their forests)
• There are international agreements on the uses of tropical hardwoods and logging, such as the International Tropical Timber Agreement set up in 2006 to "promote the sustainable management of tropical timber producing forests"