Eutrophication

Eutrophication is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system. One example is the "bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Negative environmental effects include hypoxia, the depletion of oxygen in the water, which induces reductions in specific fish and other animal populations.

Eutrophication can be human-caused or natural. Untreated sewage effluent and agricultural run-off carrying fertilizers are examples of human-caused eutrophication. However, it also occurs naturally in situations where nutrients accumulate or where they flow into systems on an ephemeral basis. Eutrophication generally promotes excessive plant growth and decay, favouring simple algae and plankton over other more complicated plants, and causes a severe reduction in water.Eutrophication also decreases the value of rivers, lakes, and estuaries for recreation, fishing, hunting, and aesthetic enjoyment.

High Tech Farming

As there is an increase in population, there is also an increase in the demand of food supplies. High tech farming is a commercial farming which means that it is profit motivated. It is to also overcome the problem of a shortage of land for farming and also to not be too dependant on other countries for food. It is found in densely populated areas such as Singapore where there is limited land and costly land.

In high tech farming, computer technology is used to manage water, fertilising and pest control to ensure high quality. It is sold locally and exported. Professionals are employed for this job and computers and automation devices are used to control the temperatures and watering. High tech farming consists of hydroponics and aeroponics.

Factors determining success

As there is high investment cost for high tech farming, high levels of capital are needed to invest in the technological facilities. Also, there will be competition from other imported products. This makes high tech farming a commercial farming that has to compete with other industries. Lastly, though little labour is required for high tech farming, its success will still be affected if there is a large shortage of workers and people who are able to operate the machinery.

Impacts

High tech farming is environmentally friendly. Little or no pesticides are used and it conserves land and water by using suspended troughs and controlling water. As they are located nearer to markets and production monitoring in comparison to those crops planted in soil, there will be lesser wastage and transport.

    

   pictures of crops from high tech farming

Shifting Cultivation

It is also known as “slash and burning farming” where the forest is burned.

Firstly, a suitable site for cultivation is found. Then, wood and weeds are burned to make a clearing. The ash left on the land is used as fertiliser. Simple tools are used to prepare the land for cultivation and after 3-4 years when the soil diminishes in fertility, the farmer then moves to another plot of land

Shifting Cultivation is practiced by primitive tribes in the forested highlands of the Amazon Basin, Congo Basin, Papua New Guinea, etc. While cultivated using shifting cultivation, tropical rainforest nutrient is mainly locked up in the biomass with little nutrient in the soil. Also, the cycling of nutrients is rapid.

The tribe first selects a small patch of rainforest.  To create a clearing on the forest, the tribe selectively slashes the natural vegetation by simple tools and burns the logs, so the nutrients are released as ash which dissolves and is washed by rain into the soil as natural fertilizers.

A variety of food crops are grown on the land such as rice, maize, cassava . The crops grow very quickly, some are ready to harvest after four to six months. After 2 or 3 years, due to decline in soil fertility, the yield of successive crops declines and weeds grows extensively.

Impacts

Shifting cultivation is an agricultural system used in tropical countries, in which a forest is cut, the debris is burned, and the land is then used to grow crops. Shifting cultivation conversions are relatively stable and long-term in nature, and they are the leading cause of tropical deforestation.

Usually, some type of shifting cultivation is used when extensive areas of tropical forest are converted into large scale, industrial agriculture, usually intended to supply commodities for an export market, rather than for local use. Shifting cultivation is also widely used by individual, poor farmers when they develop agricultural land for subsistence farming and to supply cash goods to a local market.

Factors determining success of shifting cultivation

There must be fertile soil that will be able to last for three to four years. As the same plot of land will be used for about four years, the soil fertility must be good. Farmers get their fertilisers from burning the biomass in the forest to get the nutrients. Thus, soil fertility is the key to growing good crops. There should also be enough workers working in the cultivation.

       

  pictures of the burning process.

Population Change

Population change is affecting people. With a figure of 6 billion and increasing, comes with an increase in starvation, having to compete with natural resources and space. However, the increase of world population may also mean more talents and ideas. So is the change in world population good or bad?

  In less developed countries, lack of access to birth control, as well as cultural traditions that encourage women to stay home and have babies, lead to rapid population growth. The result is ever increasing numbers of poor people across Africa, the Middle East, Southeast Asia, and elsewhere who suffer from malnourishment, lack of clean water, overcrowding, inadequate shelter, and AIDS and other diseases.

  In developed countries, such as America which takes up only 4% of the world population, uses 25% of all resources. Industrialized countries also contribute far more to climate change, ozone depletion and overfishing than developing countries. And as more and more residents of developing countries get access to Western media, or immigrate to the United States, they want to emulate the consumption-heavy lifestyles they see on their televisions and read about on the Internet.

  Though China and India are developing countries, they are the two most populous countries. Why is the birth rate in developing countries much higher than developed countries?

 Population density is total area population / land area in square kilometres. Small countries like Monaco and Singapore have the highest population density. Also because Singapore has a stable government and has job opportunities, thus resulting in people migrating to Singapore.

 The country with the world's lowest population density is Mongolia with a population density of approximately 4 people per square mile. Mongolia's 2.5 million people occupy over 600,000 square mails of land. Mongolia's overall density is limited as only a tiny proportion of the land can be used for agriculture, the vast majority of the land can only be used for nomadic herding. Thus causing a dispersed population. 

temperate forests

Deciduous forest

  We’ve learnt that deciduous leaves fall off in autumn in preparation of winter to minimize the amount of water loss when transpiring. It is also known that the leaves turn brown during this period. However, you may asked one question. How do the leaves turn brown?

  It is because during the shorter days and cooler weather of autumn, green chlorophyll in the leaves begins to decompose, revealing orange, yellow, and red.  This is because the plant has limited sunlight and water thus the leaves are unable to continue producing chlorophyll. Actually, these colors were present in the leaves all year long, but had been hidden by the green pigment of the chlorophyll.  

Since there is no more chlorophyll, how do the trees survive without leaves during the winter when they cant make food?  

To prepare for winter, deciduous trees and plants become dormant. They lose their leaves and seal the places where leaves were attached with a protective covering called a leaf scar. If they kept their leaves, the water in the leaves would freeze into ice, damaging the leaves and leaving the plant vulnerable to bacteria or fungi. Plants also make a concentrated sugar solution to stop water from freezing in their stems.

How does the tree know when to start growing leaves? The longer days and warmer weather of spring signal to the trees to grow new leaves and begin photosynthesis again.

Then how does the environment have an effect on such adaptation? The trees get a lot of sunlight in summer and thus are able to get energy to make food for the plant. Some food is stored in the roots for the next spring. However, when the temperature gets lower, the tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk. This is why trees get limited supply of water and sunlight during autumn. Finally, when the temperature get warmer, the leaves then start growing back.

We also learnt examples of tress like the Oak Tree. Leaves are big and broad to increase surface area to get as much sunlight as possible in summer. However, these leaves also losses a lot of water during transpiration making then shed their leaves in the autumn.

Knowing this, I have a question I can’t seem to find the answer to. Why do the trees have such big leaves if they lose a lot of water during the winter? Is it because they need to get a lot of sunlight during the summer? However, small leaves also can capture sunlight and make food for the plant. If this is so, why is it that the plant has big leaves instead of small leaves that will help decrease the amount of water loss during the winter? If they had small leaves, won’t they be able to make food even in the winter and don’t have to stay dormant?

Many of us have seen leaves found in temperate forests and tropical forest. There is a distinct difference in leaves for both climates. Then, what effect does climate have to the edge of the leaf?

Leaves in temperate deciduous forests mostly have toothed edges but the leaves in tropical rainforest have smooth entire edges. This is because climate and leaf margin are closely tied. The leaves of tree species native to colder climates usually have more teeth cut more deeply into the leaf; they are more dissected on their edges so they have a higher perimeter-to-area ratio. The presence of a toothed edge seems to assist in unfolding young leaves from buds so they can maximize photosynthesis when breaking winter dormancy.

The forest floor grows rapidly in summer and spring and disappears during winter. Another question I couldn’t find an answer to is, why the plants on the forest floor disappear when they can get as much sunlight as they want during autumn and winter when the leaves drop and they can get a lot of sunlight? Is it because its too cold? Is it also because of water loss?

Coniferous forest

We learnt that the coniferous forest is evergreen. They have cone shaped structures to allow snow to slide off and needle-like leaves to lessen water loss. They also have supple braches don’t break easily so the tree won’t fall off because of imbalance of weight. The leaves are evergreen because they do not lose much water during transpiration as they have small surface area. Thus the leaves always stays green and does not need to fall off.

We also know that there is only one type of plant in the coniferous forest, but why is that so? Is it because not many plants cant adapt to such a climate thus resulting in low diversity?

The soil in coniferous forests is not fertile unlike the soil in temperate deciduous forest. Why?

In the deciduous forest,it is not evergreen and the leaves drop very autumn thus resulting in very fertile soil. This is also the reason why their leave litter is so thick. Remember the trip to bukit timah? The leaf litter there, a tropical rainforest is already quite thick; but the leave litter in the deciduous forest is thicker because the leaves drop more. However in coniferous forests, it is evergreen and the leaves hardly drop thus not providing any nutrients. Thus, the soil isn’t fertile.

Bukit Timah Nature Reserve(:

Haha, this is some information about the BTNR that we're going tmrw. Yay:D Haha so cool.

 

 

Singapore, lying within the tropical zone, and blessed with high temperature and high rainfall all year round, was once covered with tropical rainforests. It has been estimated that primary rainforest once covered about 82% of the land area of Singapore, approximately 442 km² or 44,200 hectares (ha).

However, ever since people have settled on the island, more and more of the original natural vegetation has been cleared, to make way for settlements and for agriculture and plantations. Today, only 192 ha or 0.43% of the original forest cover remains. Most of the surviving primary forest is restricted to the more pristine areas of the 163ha Bukit Timah Nature Reserve (BTNR), and in scattered patches throughout the 3,043 ha Central Catchment Nature Reserve (CCNR). The remainder of these two nature reserves is occupied mostly by secondary forest.

The Bukit Timah Nature Reserve contains the largest patch of primary rainforest left in Singapore. Bukit Timah Hill, at about 163.63 metres above sea level, is the highest point in Singapore.

Importance of Tropical Rainforests in Singapore
Even though we do not possess very large areas of tropical rainforests, as compared to other countries like Malaysia, Indonesia, Congo and Brazil, our few remaining rainforests are still very important, for various reasons.

• Tropical rainforests have taken hundreds of years to develop and once cleared, they are almost impossible to replace. There are many species of plant and animal in the rainforests, most of which are found nowhere else in the world. And when they are destroyed, some species may become extinct and be lost forever. These include plants with medicinal value which have not even been identified and tested. So, rainforests in Singapore now perform the very important role of providing a place for many species to thrive and grow.
• Rainforests in Singapore also provide us with an idea of what Singapore was like at the beginning of the nineteenth century. Singapore was once covered by tropical rainforests. Hence, by looking at the rainforests now, we get a glimpse of what Singapore might have been like then.
• The rainforests form our water catchment areas. When rain falls, the rainwater is trapped by some of the leaves on the trees. The rainwater then drains slowly into the ground and may be collected in the nearby reservoirs. In this way rainforests help us 'catch' the rain and add to our water supply.
• As Singapore becomes increasingly built up, rainforests act as giant 'lungs' by absorbing large amounts of carbon dioxide and producing oxygen in exhange.
• The rainforests are beautiful and scenic, with fresh air and natural surroundings. They provide us with a peaceful alternative to the busy city, and these last bastions of wilderness are places of peace and quiet where Singaporeans can go to enjoy and appreciate nature at its best. They can also be a tourist attraction.
• The rainforests are a legacy of our natural heritage, and it is important to protect and conserve them, keeping them intact for the country's future generations to learn and appreciate the richness of our country's heritage.

Shock Absorber.

I was reading the notes about the measures to adapt and respond to earthquakes and was thinking about the part which they wrote about designing new infrastructure. A question popped up, how do the shock absorbers actually work? How exactly does the shock absorbers actually 'absorb' the tremours?
I found this on Wikipedia:

Structures
Applied to a structure such as a building or bridge it may be part of a seismic retrofit or as part of new, earthquake resistant construction. In this application it allows yet restrains motion and absorbs resonant energy, which can cause excessive motion and eventual structural failure.

After reading this, I don't really get it. What do they mean by 'yet restrain motion and absorb resonant energy'? They also mentioned that it can cause structural failure, that what is the use of it?

To sum up this whole post, it's about the some questions about the shock absorber.

Corinne & Alison.

This is the Wikipedia website: http://en.wikipedia.org/wiki/Shock_absorber