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Showing posts with label Nature. Show all posts
Showing posts with label Nature. Show all posts
Saturday, May 29, 2010
Why are sunsets red?
Sunsets often have a red or orange color to them. Why is this? Sunlight (what we call "white light") is made up of all different colors of light, each having a different wavelength. During a sunset, more red light is scattered toward you because of aerosols in the lower atmosphere, compared to the amount of blue or green light. Since, at sunset, sunlight is passing through a much longer path of the lower atmosphere than when the sun is overhead, the effect of the aerosols becomes much stronger. So, you end up seeing more red light that any of the other colors of light, and the sky appears red.
Why are rainforests important?
THEY PROVIDE A HABITAT FOR PLANTS AND ANIMALS
Tropical rainforests took between 60 and 100 million years to evolve and are believed to be the oldest and most complex land-based ecosystem on earth, containing over 30 million species of plants and animals. That's half of the Earth's wildlife and at least two-thirds of its plant species!
Because most tropical rainforest grows in warm and steamy environments, it contains a huge variety of plants. One hectare of lowland rainforest may contain 1000 trees with up to 300 species. Compare this to the UK's forests which are likely to have only 5-10 species per hectare: that's 30 to 60 times more species in a hectare of rainforest! These plants in turn provide food and shelter for many rare animals that depend on the rainforest for their survival. There are many more thousands of rainforest plants and animals species still waiting to be discovered.
THEY REGULATE OUR CLIMATE
Rainforests store water like a huge sponge. In fact, it is believed that the Amazonian forests alone store over half of the Earth's rainwater! Rainforest trees draw water from the forest floor and release it back in to the atmosphere in the form of swirling mists and clouds.
Without rainforests continually recycling huge quantities of water, feeding the rivers, lakes and irrigation systems, droughts would become more common, potentially leading to widespread famine and disease.
Did you know that we also depend on trees to cleanse our atmosphere? They absorb the carbon dioxide that we exhale, and provide the oxygen we need to breathe. When rainforest trees are burnt they release carbon dioxide, which pollutes the atmosphere and contributes to global warming. Deforestation is in fact considered the second major driver of climate change (more than the entire global transport sector), responsible for 18-25% of global annual carbon dioxide emissions.
THEY HELP TO PREVENT SOIL EROSION
Surprisingly, soil in the rainforest is very poor in nutrients. This is because the nutrients are stored in the vast numbers of trees and plants rather than in the soil. Tree roots bind the soil together, while the canopy protects the soil from heavy rains. When a tree dies and its trunk falls to the forest floor, it decays and the nutrients it contains are recycled. However, if trees are removed from the forest, the nutrients are removed with it, along with the protection provided by the tree roots and the forest canopy. The unprotected soil is then simply washed away in heavy rains, causing blockages and floods in lowland rivers, while leaving upland rivers dry.
THEY PROVIDE A HOME FOR INDIGENOUS PEOPLE
Many indigenous people have been living in harmony with the rainforest for thousands of years, depending on it for their food, shelter and medicines. When oil and logging companies come to remove vast areas of forest, they bring diseases which the indigenous people have no resistance to, threatening their survival. Often they are also forced to move away from their homes to unfamiliar places, sometimes even being killed in the process.
RAINFOREST PHARMACY
It may surprise you to know that more than 25% of our modern medicines originate from tropical forest plants. Even so, we have only learned how to use 1% of these amazing plants, so imagine the possibilities if we could experiment with the other 99%!
For example, the rosy periwinkle, found in Madagascar, is used to cure leukemia, while the anti-malarial drug quinine is taken from the bark of the Andean cinchona tree. The rauvolfa shrub found in Asian and African forests is used to cure high blood pressure and mental illness. Rainforests and the native populations who discovered these medicines could hold the cure to many more diseases if we would only nurture the forests and allow their people to show us.
OTHER IMPORTANT FOREST PRODUCTS
Many foods we consume today such as nuts, bananas, coffee and spices, and industrial products such as rubber, resins and fibres, were originally found in tropical rainforests.
Tropical rainforests took between 60 and 100 million years to evolve and are believed to be the oldest and most complex land-based ecosystem on earth, containing over 30 million species of plants and animals. That's half of the Earth's wildlife and at least two-thirds of its plant species!
Because most tropical rainforest grows in warm and steamy environments, it contains a huge variety of plants. One hectare of lowland rainforest may contain 1000 trees with up to 300 species. Compare this to the UK's forests which are likely to have only 5-10 species per hectare: that's 30 to 60 times more species in a hectare of rainforest! These plants in turn provide food and shelter for many rare animals that depend on the rainforest for their survival. There are many more thousands of rainforest plants and animals species still waiting to be discovered.
THEY REGULATE OUR CLIMATE
Rainforests store water like a huge sponge. In fact, it is believed that the Amazonian forests alone store over half of the Earth's rainwater! Rainforest trees draw water from the forest floor and release it back in to the atmosphere in the form of swirling mists and clouds.
Without rainforests continually recycling huge quantities of water, feeding the rivers, lakes and irrigation systems, droughts would become more common, potentially leading to widespread famine and disease.
Did you know that we also depend on trees to cleanse our atmosphere? They absorb the carbon dioxide that we exhale, and provide the oxygen we need to breathe. When rainforest trees are burnt they release carbon dioxide, which pollutes the atmosphere and contributes to global warming. Deforestation is in fact considered the second major driver of climate change (more than the entire global transport sector), responsible for 18-25% of global annual carbon dioxide emissions.
THEY HELP TO PREVENT SOIL EROSION
Surprisingly, soil in the rainforest is very poor in nutrients. This is because the nutrients are stored in the vast numbers of trees and plants rather than in the soil. Tree roots bind the soil together, while the canopy protects the soil from heavy rains. When a tree dies and its trunk falls to the forest floor, it decays and the nutrients it contains are recycled. However, if trees are removed from the forest, the nutrients are removed with it, along with the protection provided by the tree roots and the forest canopy. The unprotected soil is then simply washed away in heavy rains, causing blockages and floods in lowland rivers, while leaving upland rivers dry.
THEY PROVIDE A HOME FOR INDIGENOUS PEOPLE
Many indigenous people have been living in harmony with the rainforest for thousands of years, depending on it for their food, shelter and medicines. When oil and logging companies come to remove vast areas of forest, they bring diseases which the indigenous people have no resistance to, threatening their survival. Often they are also forced to move away from their homes to unfamiliar places, sometimes even being killed in the process.
RAINFOREST PHARMACY
It may surprise you to know that more than 25% of our modern medicines originate from tropical forest plants. Even so, we have only learned how to use 1% of these amazing plants, so imagine the possibilities if we could experiment with the other 99%!
For example, the rosy periwinkle, found in Madagascar, is used to cure leukemia, while the anti-malarial drug quinine is taken from the bark of the Andean cinchona tree. The rauvolfa shrub found in Asian and African forests is used to cure high blood pressure and mental illness. Rainforests and the native populations who discovered these medicines could hold the cure to many more diseases if we would only nurture the forests and allow their people to show us.
OTHER IMPORTANT FOREST PRODUCTS
Many foods we consume today such as nuts, bananas, coffee and spices, and industrial products such as rubber, resins and fibres, were originally found in tropical rainforests.
Thursday, May 27, 2010
Why are most plants green?
Most plants appear green because they contain chlorophyll, a pigment within the leaf and stem structure that reflects the wavelengths of light that make up the color green. Chlorophyll absorbs other wavelengths of light and uses the energy to produce nutrients.
Why is the sky blue?
A clear cloudless daytime sky is blue because molecules in the air scatter blue light from the Sun more than they scatter red light. This scattering effect is known as Rayleigh scattering. Because the blue light is scattered in random directions, some of it reaches the planet surface, where we see it.
When we look towards the Sun at sunset, we see red and orange colors because the blue light has been scattered out (filtered) and away from our line of sight.
In the evening, the sky sometimes looks orange or red because of air pollution. dust, water vapor, and other floating particles in the air act as a filter on the sunlight. When the Sun is low, the air layer is thicker and the light is more filtered, so it looks yellow, orange and finally red.
In more detail:
Light of a particular color is characterized by its frequency and wavelenth. The higher the frequency, the more blue it appears.
Sunlight is made up of all colors that, when mixed together, produce white light. You may have seen a rainbow or the prism experiment where the white light is split up into several colors.
The earth's atmosphere is filled with minute dust and water particles that act like a filter, scattering the light rays. The rays of light with the longer wavelengths, such as reds and yellows, tend to pass more easily through the atmosphere, while the rays with the shorter wavelengths, like blues and indigos, tend to be randomly scattered more easily. These more easily dispersed shorter light rays are what give the sky its blue color.
Red skies at sunrise and sunset are caused by the same phenomenon. When the light hits the Earth at an angle it has more of the atmosphere to go through; this increases the filtering effect and that is why you see a red sky.
When we look towards the Sun at sunset, we see red and orange colors because the blue light has been scattered out (filtered) and away from our line of sight.
In the evening, the sky sometimes looks orange or red because of air pollution. dust, water vapor, and other floating particles in the air act as a filter on the sunlight. When the Sun is low, the air layer is thicker and the light is more filtered, so it looks yellow, orange and finally red.
In more detail:
Light of a particular color is characterized by its frequency and wavelenth. The higher the frequency, the more blue it appears.
Sunlight is made up of all colors that, when mixed together, produce white light. You may have seen a rainbow or the prism experiment where the white light is split up into several colors.
The earth's atmosphere is filled with minute dust and water particles that act like a filter, scattering the light rays. The rays of light with the longer wavelengths, such as reds and yellows, tend to pass more easily through the atmosphere, while the rays with the shorter wavelengths, like blues and indigos, tend to be randomly scattered more easily. These more easily dispersed shorter light rays are what give the sky its blue color.
Red skies at sunrise and sunset are caused by the same phenomenon. When the light hits the Earth at an angle it has more of the atmosphere to go through; this increases the filtering effect and that is why you see a red sky.
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