Though generally used to refer to our natural biological environment, the environment is all that is around us. It provides us with what we need to survive and thrive. Environmental problems are not just about protecting other species, they are about how easy or hard it is to get the things we need. And how we suffer when we cannot get them. One of the reasons we look after the well-being of other species is that they are a sign of our well-being. For instance, if river water is not clean enough for fish to live in, chances are it is not good enough for us to drink. One way to judge the severity of environmental problems is to see how many people would be negatively affected by the problem.
A lot of environmental problems become more or less important depending on where you live and how well-off you are. Most are much worse for the poor and can be avoided if you are rich enough.
The world and all the living things in it are interconnected in a web; disturb the web at one spot and the disturbance will also be felt somewhere else.
1 Climate change/global warming
The world is getting warmer by our actions The biggest environmental problem facing the world today is probably global warming. Average global temperatures are likely to increase by 1.4°C-5.8°C over the period 1990-2100. Global warming is not only a serious problem in itself, but, as it progresses, other environmental problems worsen. We can only guess at the number of new problems that could arise out of global warming.
The earth is warmed by the sun and by some geothermal activity. At night, much of this heat is radiated out into space and the earth cools down. Unlike other planets in our solar system, the earth has a blanket made up of air that traps some of the heat so that it does not get too cool. So, the earth remains a perfect temperature -- not too hot, not too cold. Though the earth's temperature varies from being hot in the tropics and sub-zero at the poles, the average has been fairly stable for a few thousand years.
Global warming occurs when 'anthropogenic' (caused by humans) changes cause the protective blanket around the earth to get 'thicker', trapping too much heat. This is slowly heating up the globe, changing the earth's physical characteristics. These changes affect the biological world we live in. Human activity brings about the release of gases -- called greenhouse gases (GHGs) -- into the air. These gases keep the earth warm; they act like the glass roof of a greenhouse.
The main GHG is carbon dioxide, which is a waste product of burning organic matter like petrol, diesel, coal or wood. Such organic matter is known as a fossil fuel because it is made up of long-dead organisms. People use fossil fuels every day to run their cars, buses, trains and aeroplanes. They power our factories, and we use them to produce electricity, with which we run all our other gadgets. People and countries that use the most fossil fuels are the ones most responsible for climate change. They are the ones that need to give up their energy-intensive lifestyles to try and ensure that global warming does not worsen.
Though it has less than 5% of the world's population, the United States of America is the biggest source of carbon from the burning of fossil fuels -- 24% of the world's total.
One of the most obvious changes taking place on the earth is the actual warming itself. All life as we know it today, from tiny one-cell plants to huge animals weighing several tonnes, exists and reproduces within a narrow range of temperature and weather, a range that is specific to each species. They may be able to survive at lower or higher temperatures, but they cannot then go about their usual patterns of behaviour and reproduction. This means that if the earth gets too warm many species will die out, some of these being the ones we depend on for our food or medicines. Other species will widen the area in which they live, which is not always a good thing. For example, mosquitoes will be found in areas where earlier it would have been too cold for them to survive. Along with them will come the parasite that causes malaria, meaning that this killer disease will be more common and more widespread than it once was. Currently, malaria infects more than 500 million humans each year, killing approximately 2.7 million; with global warming these numbers can only increase.
Some of the physical effects of global warming are already being felt -- local weather patterns are changing, there is more rain, and more storms. One of the biggest threats is the rise in sea level -- as it gets warmer the ice in the north and south poles will start melting, adding more water to the seas and raising sea levels everywhere. Global sea levels will rise by about nine centimetres by 2100. This means that low-lying areas will be flooded; low-lying countries like Bangladesh will suffer the most as will people living on islands. All over the world some of the biggest cites are built along the coast. When sea levels rise most of them will be under threat.
Climate changes may also increase the susceptibility of food crops to some pests, which in turn could intensify food shortages and malnutrition. A concurrent problem is a rapid expansion in the number of 'environmental refugees'; territorial wars will increase as people migrate looking for new homes.
Many of the important rivers in India are formed and flow due to the melting of glaciers that are replenished with ice every winter. Scientists have noticed that as it gets warmer, glaciers are melting faster and not getting properly replenished. Some are in danger of disappearing altogether, meaning that the rivers they supply will dry out.
Another problem is that as the polar ice melts, ocean currents, which are powered by temperature differences in the oceans, will change direction or die out. These currents are responsible for local weather patterns, so seasonal changes in weather that we depend on, like the monsoons, will change, and with it the agriculture that India depends on.
2 Air pollution
Every day we release more and more dangerous things into the air we breathe One of the biggest killers of people the world over is respiratory illnesses. These are illnesses related to our lungs, and many are caused by the quality of air we breathe. In other words, air pollution. Each year, air pollutants adversely affect the health of 4-5 billion people.
Air pollution is created by human activities like mining that release harmful dust particles into the atmosphere. But the most common source of air pollution is the burning of fossil fuels and waste material. Air pollution levels in the 20 largest cities of the world are higher than what the United Nation's World Health Organisation (WHO) recommends. Lead, benzene and smoke consisting of small particles of unburned or unburnable matter are especially dangerous to human health.
Air pollution is increasing because of the increasing use of fossil fuels in factories, increased emissions of industrial chemicals, and the increased use of cars, trucks, buses, aeroplanes and trains. Cars are a major source of air pollution and, sadly, their numbers are growing three times faster than the world's population. Though pollution regulations ensure that each car pollutes less, the increase in car numbers means that total air pollution levels continue to rise. In India and other developing countries, this problem is made worse because we use older cars and motorcycles whose engines may not be so efficient, therefore more polluting.
Air pollution makes asthma worse, which can sometimes cause death. Globally the number of people suffering from asthma has increased nearly 50%. Globally, deaths of children younger than five years of age from acute respiratory infections have gone up from 2.2 million in 1985 to approximately 5 million.
One aspect of air pollution that is quite important in developing countries is indoor air pollution caused by burning fuel for cooking and heating in badly ventilated homes. It is mostly women and children who suffer from this form of pollution. Globally, but especially in developing nations, approximately 4 billion humans suffer continuous exposure to smoke. This smoke, which contains large quantities of particulate matter and over 200 chemicals, including many cancer-causing ones, results in dangerously high pollution levels. It is estimated to cause the death of 4 million children each year worldwide.
3 Water scarcity
We are overusing one of the basic necessities of life The earth is the only planet in our solar system with water in liquid form, and life as we know it would not have been possible without it. All living things have water in them; human beings are mostly composed of water. For a planet which is mostly water too, it's surprising just how little water there actually is (we are talking of clean and pure freshwater which can be used by humans). [Chart needs to be inserted here will make and send later]
Of all the water on earth, only 3% is freshwater. Two-thirds of this freshwater is locked in ice caps in the world's polar regions, leaving only 1% (of all water) for plants, animals and 6 billion-plus people. For comparison, if a large bucket could hold all the salt water on the planet, an eggcup would hold the freshwater locked in ice caps and glaciers, and a teaspoon would hold all the available freshwater.
This teaspoon is a finite resource; human beings do not really create or destroy much water. The problem with this resource is that we are changing natural water cycles and thus less and less clean water is available to us. The supply of freshwater is continually recycled, as it is a part of the earth's hydrologic cycle. Each day, the sun evaporates 1,000,000,000,000 (1 trillion) tonnes of water, which returns to the earth from the atmosphere in the form of rain and snow.
There is only so much water circulating in the world's hydrological cycle. Already most of Africa and the Middle East , India and the rest of the subcontinent, much of western United States and northwest Mexico , parts of Chile and Argentina , and nearly all of Australia suffer water shortages. Scientists say that even in 1990, 28 countries with a total population of 335 million people were already facing water shortages. By 2025, water shortages may affect 52 countries and as many as 3.2 billion people. The water problem in India, for instance, has worsened as is obvious from the successive decrease in the number of hours that we get drinkable tap water in Indian cites. Excessive pumping of groundwater has caused the water table to drop close to 30 metres in a decade. In the state of Uttar Pradesh, the number of water-short villages soared from 17,000 to 70,000 in two decades; of the 2,700 water wells supplied by the government, 2,300 have dried up.
We get water from rivers, lakes, and deep underground aquifers. Some of these underground aquifers took thousands of years to build up, but we are exhausting them within a generation. All these sources are drying up as we use more and more water. We bathe much more, use flush toilets, use water in our factories, and most important, we use water to grow food - about 70% of all water withdrawn every year is used in irrigated agriculture. In many cases the food we grow is not even the right food for the area; we prefer to grow crops that need more water in order to sell the produce for cash, rather than grow those that might use less water but would be sufficient to feed us. Sixty-seven per cent of the water is withdrawn to support agriculture, 19% for industrial purposes and 9% for household use like cooking, bathing and washing.
The water that we take out also has a big effect on other species, which also need water to live. Some of the worst-affected are species that live in water, including fish, freshwater dolphins, and many insect species. The water that we do not use is polluted by our waste products.
4 Water pollution
We are dumping diseases and poisons into something we cannot live without Water pollution happens when we see the seas, rivers and lakes as places to dump our waste. This waste comes from factories and farms, and households and livestock. Some of the most serious water pollution occurs when water from our toilets, our bathrooms and our kitchens ends up in surface water that is also our freshwater source. Though wastewater may be collected in sewers, in India , for example, most cities and towns have sewers that empty straight into the nearest water source. Of India 's 3,119 towns and cities, just 209 have partial treatment facilities, and only eight have any form of wastewater treatment facility.
Such pollution kills fish and other animals that live in water.
However, there is another reason that draws our attention to the pollution problem. Un-sanitised wastewater carries bacteria, viruses and other disease-carrying organisms that are very dangerous: waterborne infections account for 80% of all infectious diseases worldwide, and 90% of all infectious diseases in developing countries, including typhoid, cholera and hepatitis. In developing countries, 90-95% of sewage and 70% of industrial waste is dumped untreated into waters where they pollute the usable water supply.
This lack of sanitation contributes to approximately 2 billion human infections of diarrhoea, resulting in approximately 4 million deaths each year, mostly babies and young children. Even in developed countries, waterborne diseases are serious. In the United States , they account for 940,000 infections and approximately 900 deaths each year.
Worldwide human infections and deaths from water-related diseases each year
Number of infected people
Number of deaths
Typhoid and paratyphoid
Farms also contribute to water pollution because agricultural runoff has pesticides and fertilisers meant for crops, which then get into our drinking water and also kill aquatic animals and plants that normally help keep the water clean. As these animals and plants die, other species start growing faster until they finally take over a waterbody, killing themselves in the process. Their dead remains clog up the river or lake, choking and killing it until nothing can survive in it and finally the water dries up too.
Today, 1.5 billion people rely on groundwater resources. People are increasingly relying on groundwater as a major source of water, primarily because it is less likely to be affected by pollutants that have contaminated a large percentage of surface water. However, that is changing; groundwater is not just being rapidly depleted it is also being polluted by leaky sewage pipes, underground storage tanks, bad septic systems and ordinary runoff containing lots of commonly-used chemicals like those in soaps and detergents. Pesticides are also being found deep underground.
5 Solid waste disposal
We are creating too much trash This is a new problem but one that is reaching critical levels. We use so many things and are so often changing them that there is no place left to throw them when we are finished using them. Waste is any unwanted or undesired material left over after the completion of a process. In earlier times in cities, as is still the case in some rural areas, we used things that were degradable, meaning that over a period of time, if left untouched, they would break down into smaller and smaller particles till they disappeared entirely. Some things like wood, cotton or wool were 'biodegradable', meaning that when it was thrown away other organisms could use it as food. Even most metals like iron or bronze slowly corroded and eroded over time, returning to the earth. Also, many of the things we used were built to last and did not need to be replaced so often.
Much of the material we use today is artificial; no animal or plant can use it as a source of food. And science comes up with lots of things that do not corrode or disintegrate easily or quickly. Many substances, when they do break down, leave behind chemicals that are dangerous to people, animals and plants. Added to this is the fact that we live in a consumerist society where we have to keep buying new things constantly, where we keep lots of disposable things that are designed for single-use only, and as soon as something is not in fashion we throw it away and buy new stuff. We also like things that are nicely packaged and easy to carry away from the shops; the packaging is then conveniently thrown away.
So what happens to all the stuff that is thrown away? Since it does not break down, where does it go? This is the problem of solid waste disposal and it is a rapidly growing problem. From car bodies to TV sets, from plastic bags to computers, we are filling up the world with our refuse.
Normally this solid waste problem is solved by landfills -- large areas far outside the city where waste can be dumped. But it is not enough to just dump it, it has to be looked after since we have to ensure that as the waste breaks down none of the break-down chemicals seep into the earth and leak into our water supply; that heavy rains or earthquakes do not expose it to people; that it does not contaminate surrounding areas; that it does not catch fire because it may contain wastes that react chemically when they come together; and that people do not come into contact with the more dangerous stuff. How long does it have to be looked after? Until the last things are degraded, which, in many cases, is over 10,000 years, longer than many cities have been in existence.
As cities grow larger, some landfill sites become quite valuable property, but such land also puts prospective residents/users at risk as it may be contaminated.
One idea was to burn everything. But the problem with this is that a lot of commonly-used materials, when burned, give off poisonous gases. The ash that is left behind also contains poisonous elements. Incinerators emit small but noticeable amounts of lead, cadmium, mercury and other toxic substances into the air we breathe, including organic compounds called dioxins. Burning is resorted to when the solid waste is too dangerous to be left lying around, like hospital waste.
The most common industries associated with hazardous substances are those producing agro-chemicals (pesticides), building materials, leather, petro-chemicals, pharmaceuticals and bio-technology products, pulp, paper and textiles.
An average person living in a developing country produces a tiny amount of waste compared to a person living in the United States or Europe . It takes 25 urban Nigerians, or a family of 10 in Mumbai or Manila , to produce the same quantity of waste as does a family of three in California , USA . But we are catching up fast. Manila 's waste climbed between 60-90% between 1982 and 1991. Solid waste in Istanbul went from 3,600 tonnes in 1979 to approximately 9,000-10,000 tonnes by 1992.
6 Population growth
There are too many of us for the earth to support In 1830, there were 1 billion human beings on the earth. A hundred years later, in 1930, there were 2 billion. Just 30 years on, in 1960, the third billion was reached. The next billion was in 1975 -- only 15 years later. Twelve years later, in 1987, we reached the fifth billion. October 12, 1999 , was the birth date of the 6 billionth human being on our planet. At the end of each day, the earth holds about 250,000 more people than it did the night before.
Scientists are still trying to figure out just how many human beings the earth can support. Supporting means providing them with food to eat, water to drink, absorbing and cleaning up the waste they throw out, enough space to accommodate their houses, and some space to relax in, have fun and play. But what they do agree about is the impact that so many people are having on the environment. Every individual human, just like any other living thing, has some effect on its environment. But other species have natural checks, such as disease, shortage of food, or too many predators. So there are never too many of that species for the environment to support. Human beings, with their medicines, guns, fertilisers and pesticides, have no such checks. Our numbers just keep on growing. We are using up resources rapidly and squeezing out other species as we meet our increasing demand for food and other products. We are cutting down forests and taking over more and more land; causing rivers and lakes to dry up as we take out water for agriculture, industries and to drink and bathe in. We pollute more and more, until the earth has no more space to clean up or even to store all our wastes!
The better and more comfortable our lifestyles get, the worse it is for other life forms and the earth itself. How much of the environment you use depends on how well-off you are. If you use a bullock cart, you need wood for the cart, a bull, and food for the bull. The dung the bull produces is a fertiliser returning nutrients to the soil and hence helping plants grow, which the bull then eats. If you drive a car, you need steel, glass, plastic, petrol to power it and other oil products as lubricants; you need well laid out roads, you need petrol stations, and ships and pipelines to bring petrol to the stations. You need mines to produce the steel and glass, and deep oil wells to pump out the oil (for petrol). You also need trees and other plants to absorb the gases that your car gives out. All these activities harm the environment and are slowly destroying the world and us. Though population is a big problem, what is also important is how much we use and how big a piece (of the earth) we need to live. We need to control both our numbers and our impact.
7 Bio-diversity loss
We are killing off species that are and could be useful to us Bio-diversity is a shorter way of saying biological diversity and refers to the wide variety of living things that share the world with us. These plants, animals, bacteria, fungi and viruses live in the boiling waters of hot springs, in sub-zero Antarctica, in the black sunless depths of the sea and in the desert sands. Life seems to be able to survive everywhere on earth, but can it survive human beings? This biological variety is slowly disappearing, killed by our actions and our destruction of the world they live in.
More than 10,000 species become extinct each year. Scientists believe that the rate of species loss is greater now than at any time in human history. Though there is a lot of discussion about the exact numbers, studies show that every year between 17,000 and 100,000 species vanish from our planet, and up to one-fifth of all living species could disappear within the next 30 years.
Many of the plants we use for food are disappearing: since 1900, nearly 75% of agricultural crop varieties have been lost. For example, in India , there will soon be only 30-50 rice varieties, where once, 30,000 existed. In China 10,000 wheat varieties were in use in 1949, and only 1,000 by the 1970s. In the US , of the 7,098 apple varieties in use between 1804 and 1904, nearly 86% have been lost; as have 95% of cabbages, 91% of corn, and 81% of tomato varieties.
These species are the bricks that make up our home, the earth. Without other species human beings would not be here today. They make the oxygen in the air we need to breathe to stay alive, they purify the water we need to drink, and provide all the food that we need to eat to survive. They give us the wood to build our houses, fibre to make our clothes. And all these species exist because yet other species create the environment that these species, which are directly useful to humans, need to live. They create the soil, prevent erosion, recycle nutrients so plants can live. They pollinate many plants that give us fruits. They provide the vital ingredients that we make medicines from. Some species provide us with pets, recreation and ornaments. We need other species to sustain us and to improve the quality of our lives.
In spite of our dependence, we are destroying this bio-diversity because we are only concerned about our own lives and the few species that we directly depend on. We do not realise how important the rest are and how they are connected in the web of life. For example, we use pesticides to protect our crops to ensure that there is enough food for us, but the same pesticides are killing the bees we need to pollinate other food plants, and the birds that eat many of the food pests. Killing the birds means we need more pesticides since there are more pests continuing the cycle.
How many species are there totally? No one can say for sure. About 1.4-1.8 million species have so far been studied and named by scientists, though there are many more that have not yet even been recorded, so there may be anywhere from 2 million to 100 million, with a best guess of perhaps 10 million. There are over 750,000 species of insects only, and 250,000 of flowering plants.
What is the worth of other lifeforms to us in monetary terms? One estimate of the total value of these species was calculated by economist Robert Costanza and colleagues -- between $ 18 trillion to $ 62 trillion a year. Compare this to how much business the entire world does in a year: just $ 47 trillion .
We need bio-diversity for two reasons: Firstly, because all species have some kind of function in an ecosystem. They can capture the sun's energy and store it, produce organic material which other species eat, decompose organic material, help recycle water and nutrients, control erosion or pests, fix atmospheric gases like nitrogen, or help regulate climate. These functions are important for human survival.
Secondly, bio-diversity plays an economic role in our lives whether we realise it or not. Bio-diversity is where everything we need in our everyday life comes from. It provides food such as crops, livestock, forestry, and fish; it gives us medication (this is especially true in India where we have traditional systems of medicine like ayurveda, which directly uses plants and animal for medicines). Our industries also use bio-diversity -- for example, fibre for clothing, wood for shelter and warmth. Many industrial products are biological in origin, such as oils, lubricants, perfumes, fragrances, dyes, paper, waxes, rubber, latexes, resins, and cork. Other important animal origin products are wool, silk, fur, leather; animals are also used as a mode of transport.
Bio-diversity is a source of economic wealth in many areas because of the tourists it attracts to places where wild nature and animals still exist in their natural state. Many people come to India for its wildlife, bringing in foreign currency.
8 Forest cover loss
Forests are more than just wood, but we are chopping them down One of the places where we can really see bio-diversity is forests. But forests all over the world, from tropical rainforests to northern boreal forests, are being cut down for wood. For our industries, to make space for agriculture, and to meet the needs of our ever-growing cities.
Forests are not just trees; they also contain other plants and animals that live along with the trees. When you cut the trees you are killing the other species by destroying their homes and getting rid of their breeding grounds and sources of food. More than 1% of forests disappear every year along with their rich ecosystems.
Commercial timber and other wood products are worth well over $ 400 billion per year, and the demand is growing. However, the value of forests lies in much more than the timber they contain. Forests provide fuelwood: globally 3 billion people depend on them for almost all their household energy. As forests are cut down and disappear, people have to go further and further to collect wood. Many rural families now spend between 1.5 and 5 hours each day collecting fuelwood. Wood collection is done mostly by women and children; the extra time they spend collecting wood could be better spent if they went to school or worked on the crops.
Forests also provide homes to many species. While covering only 6% of the planet's land surface, tropical forests contain at least 50% of all species found on earth. Many of these are valuable; forest plants are the original source of one in four medicines.
Forests provide environmental services that are often more important than the materials they supply. For example, forests protect water supplies and keep streams and rivers alive and flowing. They do this by preventing siltation; by keeping the soil together and not letting it get washed away, and stopping the soil from drying out completely, they keep the hydrological cycle going; roots and dead leaves store water, allowing year-round water flow. In the Ganga basin, which supports over 500 million farmers in India and Bangladesh , the annual costs of deforestation in India alone were estimated as far back as the early-1980s at more than $ 1 billion . This effect is worsened by the fact that because trees add moisture to the atmosphere when they respire, deforestation sometimes results in reduced rainfall too.
The global warming effects of deforestation are also extremely important: since carbon dioxide gas is the major greenhouse gas and trees use the carbon in the gas to build their bodies, forests play a big role as 'carbon sinks'. Without them global warming would have taken place faster. Forests currently hold some 1,200 gigatonnes (billion tonnes) of carbon in their plants and soils (out of 2,000 gigatonnes in all terrestrial plants and soils), as compared to the 750 gigatonnes held in the atmosphere. Around half of the forest carbon is located in boreal forests, more than one-third in tropical forests, and roughly one-seventh in temperate forests. Siberia 's forests alone absorb 10% of human carbon dioxide emissions annually.
9 POPs (including pesticides)
Chemicals we made are now killing us Persistent Organic Pollutants (POPs) are man-made organic chemical substances that do not break down in the environment as most other organic chemicals do. Most POPs are dangerous to humans and other animals. Unfortunately, there are so many of them around that there is no way to actually get rid of them all; what we can do is try and not develop any more, and limit the damage caused to the environment by the existing ones. Even small quantities of POPs can wreak havoc on human and animal tissue, causing nervous system damage, diseases of the immune system, reproductive and developmental disorders, and cancers.
POPs are produced by industrial processes, waste products or by-products, either from the manufacturing process or the product itself, leaks and spills, and the burning of fuels and waste material . Many are breakdown products of other substances such as pesticides and plastics. So, for example, when plastics are burned POPs are produced. There are hundreds of compounds in these groups, the worst 12 of which are known as the 'Dirty Dozen'.
Most POPs, like the pesticide DDT, have already been banned in some countries. But they have long lives, which is why they are called persistent, meaning that they do not naturally disappear. When they enter a human or animal body they do not leave it, instead they are stored in fat. They also magnify, which means that their concentration increases when small animals, which have some POPs in their system, are eaten by bigger ones, which in turn are eaten by still bigger ones.
Once POPs are released into the environment, either intentionally as in the case of pesticides, or accidentally in chemical spills or waste burning, they are nearly impossible to clean up. They can travel great distances either through the air or in the bodies of animals that have ingested them, or on water currents. A pesticide used in Asia can easily move to Europe . They are also passed on from mother to baby.
Many POPs are also 'endocrine disrupters'. The bodies of humans and other animals have certain chemical messengers called hormones. These are produced by the endocrine glands and control how an organism develops and functions. Some POPs mimic these natural hormones and confuse the body and prevent true messages from getting through. They stop the normal body processes. Endocrine disrupting chemicals can be hazardous in extremely low doses and pose a particular danger to babies exposed in the womb. During pre-natal life, endocrine disrupters can alter development and undermine the ability to learn, fight disease and reproduce. Wildlife researchers over the last few years have unearthed a variety of endocrine disrupter-related effects: interrupted sexual development; thyroid system disorders; inability to breed; reduced immune response; and abnormal mating and parenting behaviour.
Once the problem of POPs was known many of them were banned. DDT, for example, was banned for general use a long time ago in many countries. But pesticides are used to kill pests and increase food production. So doing without them is also a problem.
Most countries use pesticides and stopping them would dramatically alter food-growing targets; many people would face economic hardships. There are replacements but these are sometimes expensive so many developing countries continue to use dangerous pesticides.
Today, POPs are found almost everywhere -- in our food, soil, air and water. Because of their constant use it can be said that nearly everyone, all over the world, has some persistent organic pollutants in their body.
10 Soil degradation and desertification
We are losing the living earth beneath our feet Soil is not just 'dirt', it is a living structure, an ecosystem created by living things as they live, die and decompose. Each shovel of soil holds more living things than all the human beings ever born. Soil has all that plants need to grow. And there would be no animals without plants. So if soil disappears, the plants living on it would disappear and soon the animals too would vanish.
Plants need nutrients such as nitrogen, phosphorus and potassium to grow. They obtain these from the soil -- the thin skin that covers the land. They derive micronutrients from organic material, again present in the soil. Scientists classify soil into different layers: the uppermost layer is called the 'topsoil'; this is the organic layer where plants grow and animals live. When plants and animals living in the topsoil (and above it in the branches of trees or in the air) die, decomposers recycle their bodies into material that is used by other plants. The recycled material, humus, is vital for plants. Even in the most fertile areas the topsoil is less then a metre thick.
The layer below the topsoil is called the 'subsoil'. This is a mix of mineral particles and organic material. Though, compared to the topsoil, the subsoil layer is low in organic matter, this is where most of the soil's nutrients are found. Minerals released at the surface sink into this layer as the water percolates downwards. Below the subsoil we find 'weathered parent material' with no organic matter, just rock particles full of minerals. Beneath this layer is the bedrock made up of solid rock which through millions of years of geological activity and erosion formed the smaller rock particles of the parent material.
The soil formation process carries on endlessly unless we interfere with it. All plants and animals depend on this huge ecosystem lying beneath our feet, yet we take very little care of it. Soil degradation occurs when we overuse the soil, depleting it of its nutrients. Or when our farming practices make it too salty (a process known as salinisation), killing off things that do not tolerate too much salt. We also pollute the soil by using too much fertiliser or pesticides.
Experts estimate that worldwide nearly 2 billion hectares of land (22% of all cropland, pasture, forest, and woodland) has been degraded since the mid- 20th century. Some 3.5% of this 2 billion are estimated to be so severely degraded that the condition can be reversed only through costly engineering measures, if at all. Over 10% have been moderately degraded, reversible only through major on-farm investments. Of the nearly 1.5 billion hectares in cropland worldwide, about 38% is degraded to some degree. Various sources suggest that 5-10 million hectares are being lost annually to severe degradation.