Basics of Environmental Science

 

Basics of Environmental Science

Michael allaby

2 Environmental interactions, cycles, and systems The cycles proceed at widely differing rates and rates that vary from one part of the cycle to another. Cycling rates are usually measured as the time a molecule or particle remains in a particular part of the cycle. This is called its ‘residence time’ or ‘removal time’. It is worth remarking, however, that most of the gases and particles which pollute the air and can be harmful to health have very short atmospheric residence times.

Os ciclos biogeoquímicos The idea that biogeochemical cycles are components of an overall system raises an obvious question: what drives this system? It used to be thought that the global system is purely mechanical, driven by physical forces, and, indeed, this is the way it can seem.

A formação do calcário – biologicamente determ determinado inado Here, then, is one major cycle in which the biological phase is of such importance that we may well conclude that the cycle is biologically driven, and its role extends further than the production of rock. The conversion of soluble bicarbonate into insoluble calcium carbonate removes carbon, as carbon dioxide, from the atmosphere and isolates it. Since the Earth formed, some 4.6 billion years ago, the Sun has grown hotter by an estimated 25 to 30 per cent, and the removal of carbon dioxide from the air, to a significant extent as a result of biological activity, has helped prevent surface temperatures rising to intolerable levels.

O PAPEL A !"O#A $O% &"&LO% !"O'EO()*M"&O% Authorities differ in the importance they allot to the role of the biota (the total of all living organisms in the world or some defined part of it) in driving the biogeochemical cycles, but all agree that it is great, and it is self-evident that the constituents of the biota shape their environment to a considerable extent. We alter the environment by the mere fact of our existence. By eating, excreting, and breathing we interact chemically with our surroundings and thereby change them. We take and use materials, moving them from place to place and altering their form. Thus we subtly modify environmental conditions in ways that favour some species above others. In our concern that our environmental modifications are now proceeding on such a scale as to be unduly harmful to other species and possibly ourselves, we should not forget that in this respect we differ from other species only in degree. All living things alter their surroundings, through their participation in the cycles that together comprise the system which is the dynamic Earth.

3 Ecology and environmentalism

 

O P+O!LEMA A% ME",-E%. A% "$#E+P+E# "$#E+P+E#A,-E% A,-E% E O L"M"A+E% /01. 023 Where there is doubt, prudence may suggest we set thresholds very low, and in practice this is what happens. With certain pesticide residues in food, for example, the EU operates a standard of ‘surrogate zero’ by setting limits lower than the minimum quantity that can be detected.

 A polarização polarização em torno torno das decisõ decisões es para remediar remediar uma situação de dano ambiental  Where the statistical evaluation of risk is unavoidably imprecise yet remedial action seems intuitively desirable, decisions cannot be based solely on scientific evidence and are bound to be more or less controversial. Since decisions of any kind are necessarily political, and will be argued this way and that, people will take sides and issues will tend to become polarized.

Ecologia ‘Ecology’, then, is at one and the same time a scientific discipline and a political, at times almost religious, philosophy which inspires a popular movement and ‘green’ political parties in many countries.

4 History of environmental science 5 Changing attitudes to the natural world  Environmental protection always involves compromise between conflicting needs.(31) needs.( 31) O iní  cio da conserva çã o de florestas ocorreu nas regions r egions tropicais

What we would understand today as the conservation of forest habitats and wildlife began quite early in the tropics, where it was a curious by-product of colonial expansion. This led government agencies and private companies to employ scientists or, in the case of the British East India Company, surgeons, many of whom had time to spare and wide scientific interests. One of the earliest conservation experiments was begun in Mauritius in the middle of the eighteenth century by French reformers seeking to prevent further deforestation as part of their efforts to build a just society.

At about the same time, Americans were also becoming aware of the need for

 

conservation. George Perkins Marsh (1801–82), US ambassador to Italy from 1862 until his death, wrote Man and Nature while in Italy. Published in 1864, this book led to the establishment of forest reserves in the United States and other countries, but it also challenged the then accepted relationship between humans and the natural environment. Today, the love of wilderness and desire to protect it probably represents the majority view, at least in most industrialized societies. Similarly, most people recognize pollution as harmful and will support measures to reduce it, provided they are not too expensive or disruptive. As we have seen, however, these are far from being new ideas or new attitudes. They have emerged at various times in the past, then concern has waned. It may seem that public attitudes reflect some cyclical change, and this may be not far from the truth.

2. earth sciences 6 Formation and structure of the Earth

Plate tectonics exerts a very long-term influence, of course, and other factors modify climates in the shorter term, but the distribution of land and sea determines the overall types of climate the world is likely to have (HAMBREY AND HARLAND, 1981).

7 The formation of rocks, minerals, and geologic structures /143 5 O+O'E$"A

8 Weathering No sooner has a rock formed than it becomes vulnerable to attack by weathering. The word ‘weathering’ is slightly misleading. We associate it with wind, water, freezing, and thawing. These are important agents of weathering, but they are not the only ones. Weathering can be chemical as well as physical and it often begins below ground, completely isolated from the weather.

A 6O+MA,7O E &AOL"$ Hydrothermal weathering, in which hot solutions rise from beneath and react with the rocks they encounter, produces a range of commercially valuable minerals, perhaps the best known of which is kaolin, or ‘china clay’. This material was first discovered in China in 500 BC and was used to make fine porcelain, hence the names ‘china clay’ and ‘kaolin’, from kao ling, meaning ‘high ridge’, the type of landscape in which it occurred. Today it is still used in white ceramics, but most is used as a filler and whitener, especially in paper. The paper in this book contains it. Kaolin deposits

 

(www.wbb.co.uk/)Welcome.htm) occur in several countries, but the most extensively mined ones are in Cornwall and Devon, Britain.

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