Biodiversity and Change
Explain the concept and importance of biodiversity in tropical rainforests.
Examine the causes and consequences of reduced biodiversity in this biome.
The syllabus says:
Biodiversity
The degree of variation of life forms within a given ecosystem, biome, or an entire planet.
Biodiversity is one measure of the health of ecosystems.
Life on Earth today consists of many millions of distinct biological species.
The United Nations declared the year 2010 as the International Year of Biodiversity.
New Snub-Nosed Monkey Discovered, Eaten
Myanmar species sneezes uncontrollably when it rains, experts say.
That part of the earth where all life exists.
biosphere
An interdependent community of plants and animals together with the habitat to which they have adapted.
Plants and animals (organic or biotic components) + air, rock, water and soil (inorganic or abiotic components).
Ecosystem
One particular type of organism.
Homo sapiens
species
All the members of a species living in a particular area at the same time.
population
All of the different populations of organisms which live together for
example the grasses, trees, insects, deer and birds which live in a part of a
wood.
community
The place where a particular organism or population lives.
habitat
This refers to an animal’s role in a habitat – what it feeds on and when, where it finds
shelter, etc.
niche
The factor linking the different parts of an ecosystem is the flow of nutrients and energy.
sun’s energy + = carbohydrates
producers
consumers
feeding or trophic level
Energy (90%) is lost at each stage
• Not all of the plant is eaten• Unable to digest or break down all of the material consumed• Running • Respiration• Growing
pyramid of energy
It takes a large number of primary producers to
support a smaller number of primary
consumers, which in turn provide food for an even smaller number of
carnivores.
Pyramid of numbers/ biomass
Forest ecosystems
timberfuel wooddrinking and irrigation waterfoddernon-timber products (vines, bamboo, leaves)food (honey, mushrooms, fruit, game)
Goods
removal of air pollutantsemission of oxygencycling of nutrientsan array of watershed functions (infiltration,
purification, flow control, soil stabilisation)maintenance of biodiversitysequestering of atmospheric carbon
Services
moderation of weather extremes and impactsgeneration of soilprovision of employmentprovision of human and wildlife habitatprovision of aesthetic enjoyment and
recreation
Services continued
Biomes
A distinct ecological community of plants and animals living together in a particular climate is called a "biome” (the
largest ecosystem).
The rainforests are home to more worldwide species or populations than all other biomes added together.
80% of the world’ biodiversity are found in tropical rainforests
Rainforest biodiversity
Tropical forests are characterized by the greatest diversity of species.
They occur near the equator, within the area
bounded by latitudes 23.5 degrees N and 23.5 degrees S.
One of the major characteristics of tropical
forests is their distinct seasonality: winter is absent, and only two seasons are present (rainy and dry).
The length of daylight is 12 hours and varies
little.
Tropical forest
Temperature is on average 20-25° C and varies little throughout the year: the average temperatures of the three warmest and three coldest months do not differ by more than 5 degrees.
Precipitation is evenly distributed throughout the year, with annual rainfall exceeding 2000 mm.
Soil is nutrient-poor and acidic.
Decomposition is rapid and soils are subject to heavy leaching.
Canopy in tropical forests is multilayered and continuous, allowing little light penetration.
Flora is highly diverse: one square kilometer may contain as many as 100 different tree species.
Trees are 25-35 m tall, with buttressed trunks and shallow roots,
mostly evergreen, with large dark green leaves.
Plants such as orchids, bromeliads, vines (lianas), ferns, mosses, and palms are present in tropical forests.
Fauna include numerous birds, bats, small mammals, and insects.
evergreen rainforest: no dry season.
seasonal rainforest: short dry period in a very wet tropical region (the forest exhibits definite seasonal changes as trees undergo developmental changes simultaneously, but the general character of vegetation remains the same as in evergreen rainforests).
semievergreen forest: longer dry season (the upper tree story consists of deciduous trees, while the lower story is still evergreen).
moist/dry deciduous forest (monsoon): the length of the dry season increases further as rainfall decreases (all trees are deciduous).
Further subdivisions of this group are determined by seasonal distribution of rainfall:
More than one half of tropical forests have already been destroyed.
Extremely rapid rates of nutrient transfer, due to high temps, rainfall and humidity. Biomass is the largest store of nutrients due to the vast arrays of plants found in the TRF. Few nutrients are in the litter, due to their rapid decomposition as a result of high temperatures. Leaching is rapid and more so in areas of rainforest clearance.
Tropical rainforests are located in a band around the equator, mostly in the area between the Tropic of Cancer (23.5° N latitude) and the Tropic of Capricorn (23.5° S latitude). This 4800 km wide band is called the “tropics”. Tropical rainforests are found in South America, West Africa, Australia, southern India, and Southeast Asia.
Tropical rainforests
Characteristics/adaptations
Rainforest destruction
Slash and Burn Most clearances are still by the local people and tribes needing land on which to grow crops. They clear the forest by ‘slash and burn’. Vegetation is cut down and then burned. The ash acts like a fertiliser adder nutrients to the soil. When the soil begins to turn infertile (usually after 3-5 years) the people move on. This is called shifting cultivation. It is a sustainable method of farming in the rainforest. It ensures the forest will recover.
Road BuildingTransamazon. To get to oil. To get to mahogany trees etc. (and settlers move in).
Logging Commercial logging is the major cause of primary rainforest destruction in South East Asia and Africa. World wide, it is responsible for the destruction of 5 million ha. per year. Logging roads enable landless people to enter the forest. In Africa, 75% of land being cleared by peasant farmers is land that has been previously logged.
Cattle Ranching Ranching is a major cause of deforestation, particularly in Central and South America. In Central America, two-thirds of lowland tropical forests have been turned into pasture since 1950.
Hydroelectric Power An unlimited supply of water and ideal river conditions have led to the development of hydro electric power stations (HEP Stations).
Farming There are nearly 3 million landless people in Brazil alone. The government has cleared large areas of the Amazon Rainforest and encouraged people to move there. The scheme has not been successful. Farmers stay on the same land and attempt to farm the land year after year. Nutrients in the soil are quickly exhausted as there is no longer a humus layer to provide nutrients. The soil becomes infertile and nothing will grow.
Mining The mining of iron ore, bauxite , gold, oil and other minerals have benefited many LEDCs. However, it has also devastated large areas of rainforest e.g. The Amazon.
Soya bean productionChicken McNuggets
Deforestation is causing many problems at a range of scales:
Local:Ecosystem About 80% of the rainforests nutrients comes from trees and plants. That leaves 20% of the nutrients in the soil. The nutrients from the leaves that fall are instantly recycled back up into the plants and trees. When a rainforest is clear-cut, conditions change very quickly. The soil dries up in the sun. When it rains, it washes the soil away. The rainforest never fully recovers. Wildlife and plant life is reduced. Elimination of Indian groups and their way of life. Estimates suggest that 80% of forest Indians have died since the arrival of Europeans in the sixteenth century. Most have died from western diseases such as malaria to which they have no immunity. Those remaining have been forced away by the construction of roads, ranches, mines and reservoirs. Soil Erosion. When vegetation is removed soil is left exposed to the heavy equatorial rainfall. It is rapidly eroded. The removal of top soil means little vegetation will grow. Also, soil erosion leads to flooding as soil is deposited on river beds.
National:Deforestation can consume a country's only natural resource. If deforestation is not managed in a sustainable manner a country's only natural resource could be lost forever. Global:Global WarmingRainforest canopies absorb carbon dioxide. When the rainforests are burned and cleared, the carbon is released. Also, when trees are cut down they can no longer absorb carbon dioxide. This means more carbon dioxide is in the atmosphere. Carbon dioxide allows heat through the atmosphere (suns rays). However, it will not allow as much reflected energy to escape from the atmosphere. This is called the greenhouse effect and causes global warming.
(in addition to the reasons previously stated)
Why maintain biodiversity?
Utilitarian argument
(Utility means “use”, and this justification of conservation usually refers to the economic benefit of conserving plants, animals and
their habitats).
In the mid-1980s and 90s, 40 million tons of bananas were consumed worldwide each year, along with 13 million tons of mangos.
Central American coffee exports were worth US$3 billion in 1970.
•plantations in regions that were formerly primary forest. The forest regularly saves our global food supply by offering new, disease-resistant crops. Although we have sampled only a tiny fraction of the potential foods that tropical forests offer, they already have profound influence on our diet. An astounding number (250) of fruits (bananas, citrus), vegetables (peppers, okra), nuts (cashews, peanuts), drinks (coffee, tea, cola), oils (palm, coconut), flavorings (cocoa, vanilla, sugar, spices) and other foods (beans, grains, fish) originated in and around the rainforest and are still mostly grown on plantations in regions that were formerly primary forest.
In the mid-1980s and 90s, 40 million tons of bananas were consumed worldwide each year, along with 13 million tons of mangos.
Central American coffee exports were worth US$3 billion in 1970.
Food
Tropical rainforests are called "the world's largest pharmacy” because of the large amount of natural medicines discovered in rainforests that are derived from rainforest plants.
For example, rain forests contain the basic ingredients of hormonal contraception methods, cocaine, stimulants, and tranquilizing drugs.
Curare (a paralyzing drug) and quinine (a malaria cure) are also found there.
Many of the Western medicines that we use today are derived from plants, and many more may have pharmaceutical properties. Tropical forests have given us chemicals to treat or cure inflammation, rheumatism, diabetes, muscle tension, surgical complications, malaria, heart conditions, skin diseases, arthritis, glaucoma and hundreds of other maladies.
Medicine
Much of the genetic variation used in evading the damage caused by new pests is still derived from resistant wild stock.
The forest regularly saves our global food supply by offering new, disease-resistant crops.
Conserving genetic material
Tropical forests yield some of the most beautiful and valuable woods in the world, such as teak, mahogany, rosewood, balsa, sandalwood and countless lesser-known species. These woods surround us at home, in shopping malls and in offices. Many are vital to our industries.
But only recently has the industrialized world realized the limits to timber extraction.
A healthy forest can provide a lot more than wood. Tropical forest fibers are found in rugs, mattresses, ropes and strings, fabrics, industrial processes and more.
Tropical forest oils, gums and resins are used in insecticides, rubber products, fuel, paint, varnish and wood finishing products.
And tropical oils are key ingredients in cosmetics, soaps, shampoos, perfumes, disinfectants and detergents.
Industrial products
“Everything has a right to live”.
Ethical reasons
Tourism (recreation)
Aesthetic reasons
