Global warming is often seen as a very negative thing; after all increasing the temperature of the atmosphere will cause sea levels to rise, which in turn will cause more frequent and higher intensity extreme weather events. For example hurricanes need a surface sea temperature of at least 28 degrees Celsius to form and maintain themselves, global warming will ensure that these conditions can be met more easily. It is also causing glacier retreat which is raising sea levels (this is potentially very dangerous for countries which are not very far above, or even under (for example in the case of parts of Holland) sea level, especially when combined with warmer oceans, meaning that attacking waves will have more energy when battling against sea defences). Global warming will also mean that some animals and plants will no longer have the niche environment that they can survive in, this could mean the extinction of entire species. However global warming also has some positive outcomes like new trade routes through areas of ocean that were previously non-navigable, and access to resources under the North Pole.
In Brazil the rainforest is being cut down at the enormous rate of about the size of Belgium each year. This land is being used for a variety of different uses, but in particular the land around Carajas in east Brazil is being converted into a massive iron ore mine. Brazil is desperate to “open up the rainforest” since its population has doubled in the last 40 years and it needs room to stretch its legs, unfortunately this has meant cutting into the lungs of the earth, although there are massive moral and political issues with whether Brazil should be allowed to do this at the expense of the rest of the world, for now it is tolerated (to an extent). Deforestation in the rainforest has had many negative environmental impacts. Firstly an awful lot of the world’s trees are in the Amazon rainforest, and when they are cut down it increases the level of carbon dioxide in the atmosphere, since trees convert carbon dioxide into oxygen, meaning that all animals have a smaller oxygen supply. This could be avoided if the rainforest was cut down in a sustainable way, by planting trees elsewhere as you cut them down. The loss of trees has also meant a loss of habitat for many animals in the rainforest.
Areas of the rainforest have been cut down and designated for agriculture, this is a good idea in principal since the rainforest is very nutrient rich however, rainforests have nutrients replaced very quickly, and once the trees are cut down the soil will become infertile quickly, the heavy rain experienced in the rainforest climate also means that any top soil will be washed away, previously this wasn’t a problem because the canopy would protect the ground below by interception.
The Aral Sea is on the boarder of Kazakstan and Uzbekistan in Eastern Europe, the land around it should be semi desert, however it was used to grow a mono-culture cash crop, cotton. Cotton is a very thirsty crop and requires a large amount of water which was taken from the Aral Sea, a lot of pesticides and chemicals were used in the growing of cotton, which all ended up in the Aral Sea, this resulted in dwindling fish stocks. Since the area surrounding the Aral Sea was communist all the farmers received their water for free so they were very wasteful with it, and the Aral Sea shrank. In 1987 the Aral Sea split into two lakes, one small and one large with a 25 meter wide dyke separating the two. The water level dropped so much that villages were now miles away from the sea when before they had been on the coast. It was decided by local government that the larger lake could not be saved from shrinking but the smaller one could. Various measures were taken to protect the smaller lake, this is an example of where land use change has had initial negative consequences for the physical environment, for example an increase of dust and salt storms, degradation of delta ecosystems and the lowering of fish numbers, but this impact was partly corrected since wildlife began to return to the smaller lake and the water level has risen from 35meters to 38meters and is still rising.
Near Cirencester in the Cotswolds in the south west of the UK 50 years ago extraction began of gravel. The gravel was very cheap to extract since it was only one meter below the surface, there has been an average of 2 million tonnes of gravel extracted each year, with another 50 years to go until the resource runs out. These gravel pits were left to naturally fill with water to become lakes, and there are now 137 lakes in total. It is now an SSSI and used as a water park, each lake is sold to the highest bidder as long as it is in keeping with the general aim of the people who manage all the lakes (the Cotswold water park society) to keep a careful balance between development, recreation and nature conservation. Initially the extraction of gravel cam be detrimental to wildlife since there is noise pollution which can frighten the animals, and also remove their habitat, however the gravel pits are left with sloping sides (to make it easy for animals to enter and leave the lakes) and have created a new habitat for animals. This has been so successful that beavers have bred there for the first time in the UK for over 500 years.
In conclusion a lot of land use changes are negative for the physical environment, they can cause pollution and a loss of habitat, but man is not always bad, there are numerous cases where SSSIs and nature parks have helped preserve the environment, or enrich it.
