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Six billion people. That's the current human population on Earth, and the highest ever reached as well. Things start to get cramped in the cities, while there is everywhere a noticeable depressing atmosphere due to having too many people around, whether that's in a traffic jam, in shops, at public services etc. The number of six billion human lives would never have been reached if it wasn't for fossil fuels. The energy sent by the sun and received by the Earth every day could ever sustain more than two billion people. Fossil fuels combine a sort of energy saved below the surface of the planet, now extracted by humans to use this energy and cover their needs. And with all needs easily covered, humanity was and is able to rise in population. But there is a great difference of four billion people between the number of humans the planet can sustain and the number of humans existing, a fact that has a bad impact on the Earth. Using fossil fuels releases huge amounts of carbon dioxide and other greenhouse gases in the atmosphere. And since there are so many people on Earth, there are more and more gas emissions. All this leads to global warming, climate change and pollution in general. Even if overpopulation didn't cause environmental problems of that kind, there are other consequences to be taken into account. And that's because all these people need accommodation, private space, public areas and services, fields and farms to produce food. All this space needed is taken from ecosystems, mostly by deforestrating large areas. This act alone is enough to reduce the amount of oxygen produced by plants, and the space that natural habitats used to cover.

Soil covers most of the surface of the Earth's land. It occurred after the erosion of rocks, due to strong winds, water, ice and due to the activity of living organisms. Soil is usually suitable for plants and small organisms to grow and live. However, human activities have altered the natural soil environment of many areas, making it hostile to organisms. Humanity deposits many toxic substances under the ground. Most of those are radioactive materials, pesticides, heavy metals and other kind of poisonous wastes. Even if they are first deposited in lakes, rivers or the sea, waters transfer most of them in the soil, when the latter absorbs water. It happens the other way round as well, as chemicals within soil are transferred with the rain into marine ecosystems. Soil contamination is as a serious problem as any other form of pollution, but it was discovered later than them. Although it is connected with water pollution, the procedure is slow, and at first not even plants show any difference to point out pollution. If not stopped in time, it leads to desertification and destruction of the whole ecosystem. Many species lose their habitat, face extinction, or accumulate toxic substances in their body and become infected and poisonous for their predators.

There are many ecosystems on earth not rich in vegetation and other organisms. This is natural wherever there is low rainfall and hostile ground. However, there are other areas, in theory able to sustain a variety of living organisms, with enough rainfall and mild climate, but which have as little variety as the first category. Their soil remains poor and unsuitable for vegetation. Such ecosystems have been eroded by human activities, often to the point of desertification. Desertification never describes the presence of a natural desert. It is the process of making an area look like a desert, having its characteristics while it should not. It is caused by acid rain, deforestation and the setting of fires. Also, because of overgrazing when plants start to grow again after a fire. Most of the times there is a combination of some or of all those factors, which are all connected with human activities. During desertification, many animal species die or lose their natural habitat. Plants disappear and face extinction. Valuable sources are lost, as fewer plants produce less oxygen. Thus, it is connected with global warming and climate change. Moreover, desertification often results in floods, as there are no trees to keep the soil steady with their roots. Floods harm both natural ecosystems and human properties, sometimes including death tolls. Consequently, desertification is a very serious problem and should be solved. Laws ought to be passed in order to decrease the amount of trees cut down and of wooden products one can buy. Carbon dioxide emissions, by which acid rain is caused, must be reduced to prevent soil erosion. Authorities have to protect forests, by organising fire brigades and immediate reforestations. Animals that graze should be kept away from burnt areas where plants have just started to grow again.

It has been almost one year since the last big fires were set in Europe. Last summer, many square kilometres of forests were burnt into ashes, with Greece being the most serious example. One year later, authorities have taken no measures to face similar problems. Fires are rather often in Mediterranean ecosystems, due to the mild winter and the long dry summers. High temperatures and drought, in combination with dead leaves on the ground, often cause fires. But when referring to a natural process, often means every eight to ten years. Mediterranean ecosystems have developed ways of regeneration within less than ten years, because the species living there have adapted themselves to the periodical presence of fire. Most roots, for instance, remain alive and plants grow up again. But no ecosystem can regain its previous healthy state if human sets fires almost every year. And that is what happens nowadays, for various reasons. Burnt forests provide humans with the space needed for new fields, farms and houses. But the price for doing so is high. Many animals die or lose their natural habitat. Many species face extinction. Moreover, having less plants means that less oxygen is produced. Consequently, it becomes obvious that measures should be taken so as to protect forests from fires. Stricter laws ought to be passed, and especially against arsonists.

Noise can actually be a form of pollution that characterizes urban and industrial areas. It affects not only the human hearing, but all our functions. The unit for measuring how loud a sound is, is called decibel. One decibel describes the minimum difference between two sounds, so that they are audible by humans. Whispering has an intensity of 20 decibel, while the sound produced by an aeroplane taking off, intensity of 150 decibel. Noise pollution refers to annoying and even harmful levels of noise. Indeed, listening to sounds louder than 85 decibel for a long time can cause long-term deafening. Intense sounds also influence our mental health. They make people more aggressive and stressful. In addition to this, concentration is impeded and thus we fail to make the right decisions. At the same time, blood pressure rises and gastric juices' secretion increases. Those two processes can lead to ulcer. The factors that cause noise pollution are pretty much known, heavy traffic, machines, extremely loud music, explosions and shooting (weather in reality or movies). It is a problem easily overlooked as something of no importance, especially when compared to other kinds of pollution that directly harms the environment. However, it is the kind of pollution that affects humans more than any other species, and thus we have to control it. Decentralisation of authorities and services (such as pharmacies, banks, schools) will make people prefer alternative areas of living, away from towns and noise pollution. That is a good way of tackling other problems as well, like the greenhouse effect in cities.

There are many environmental problems caused by human but not widely known. One of them is eutrophication. This phenomenon cannot be entirely characterised as water pollution, as it mostly describes the process of too many plants growing in lakes, rivers and sometimes in the sea. When household and industrial wastes are disposed into the water, they increase the quantity of germs in it. Germs threaten the health of the organisms living in the water, drinking it or feeding on organisms that live in it. Moreover, huge quantities of nitric and phosphoric salts enter the ecosystem. Phytoplankton, the tiniest sea organisms that can photosynthesize and depend highly on those salts, start to grow in population at top speed, consuming oxygen. As a result, zooplankton which feeds on phytoplankton starts to increase in numbers, again consuming oxygen and producing carbon dioxide. After some time, during which those small organisms continue to consume oxygen and produce larger amounts of carbon dioxide, there is not enough oxygen to sustain bigger organisms, like fish, who actually die of suffocation. Lakes are the most usual ecosystems harmed by eutrophication. Oxygen cannot be easily diminished in the sea, and the movement of the water in rivers transfer the salts else where. The most common sign of eutrophication is the waters having a deep green colour. And as human wastes increase, ecosystems become more fragile and their living organisms more vulnerable to suffocation. Consequently, one of our first priorities, as far as those ecosystems is concerned, is to find alternative ways of removing our industrial and household waste, so that it doesn't end up in the water. The top priority, needless to say, is to reduce those wastes.

Inside the Rainforest - Cape Tribulation - Queensland - Australia. Photo: Rob Inh00d. Tropical rainforests have the largest biodiversity of all ecosystems on Earth. The soil is rather poor, but it sustains a great variety of plants. It is estimated that 65% of the known plant species are found in rainforests. During the past three decades, rainforests have been decreasing in size for various reasons, though all of them are connected with human activities. Human populations living near rainforests had the impression that the soil must have been really fertile, as it could sustain such a variety of plants. So, when human started to need more fields for cultivation, they choose rainforests' earth, and thus they set big fires to get rid of big trees and to obtain space. By the time it was understood that the soil wasn't suitable for agriculture, many square kilometres of rainforests had already gone. Apart from agricultural reasons, the rainforests are cut down in order to provide wood. Most of the paper, toilet paper or furniture manufactured nowadays is based on wood from tropical rainforests. Deforestation also takes place in order to extend cities and build roads. Increasing human needs, due to overpopulation, lead to mass deforestations all over the globe. The pace with which it's been done is so high, that every year an area of the size of half Greece is lost. 50 years ago rainforests would cover double the area they do today. Thousands of species, whether they are animals or plants become extinct and even more face extinction. Humanity also depends on rainforests. A variety of building materials, food (bananas, vanilla, coffee), and even caoutchouk come from rainforests. Medical science, from the ancient times till today, also depends on substances from plants that grow there. Quinine, a range of medicine against pain and stress are only some examples of medicine that require substances from rainforests in order to be manufactured. Nowadays, 20% of the medicines found in pharmacies are produced by the use of plants from rainforests. Researchers have studied less than the 2% of the 100,000 species of plants that grow in rainforests, and are sure that most of them can be really useful in medicine or other fields. Though most of them point out that ''potentials for the future are endless, as long as scientists and pharmacologists reach the rainforests before chainsaws...'' And let us not forget that rainforests produce oxygen. Tropical rainforests produce 40% of Earth's oxygen. Cutting them down means that oxygen levels decrease, while less CO2 is absorbed by plants and thus increases in the atmosphere, causing the green-house effect. Humanity has to re-examine its needs and reduce them, so that less quantities of substances from rainforests are used. We have to set limits on our activities, otherwise those huge forests will one day belong to history.

During a nighttime robbery, the horn of a 120-year-old stuffed rhinoceros was stolen, from the museum where it was displayed. Museum authorities warned that using this horn as a traditional medicine on the Asian black market could have lethal consequences because it was preserved by the use of the deadly arsenic and DDT. But causing immidiate death should not be the only concern. The fact that DDT is still in use is really alarming, since it is a substance that causes accumulation. As an environmental term, accumulation is the gradual increase of pollutants in living organisms by direct adsorption or through food chains. The pollutants that cause accumulation cannot be metabolized or aborted by any means, so accumulation of the substance increases while going up a food chain. DDT in particular, was used in Africa during the 60's, as a insecticide against the mosquito that causes malaria. It was later found that huge quantities of DDT existed in many african species. The most surprising part of the research was that DDT existed in penguins of Antarctica and in Eskimo's mother milk! It was decided to substitute DDT with other pesticides, but accumulation had already harmed wild animals. The egg-shells of wild birds become extremely vulnerable due to this substance, slowing down the pace of reproduction. DDT is only an example. There are many other substances known to cause accumulation, but still used in every day life. The fact that it was once banned doesn't seem to pay off, since it is still used by museums. Moreover, we should really do something about it, even those who don't care about other species. For the simple reason that human usually feeds on species from many food chains, and thus receives those substances. Forum Topic: Stuffed rhino loses horn to thieves