The development of the population over the past 10,000 has offered many benefits to humans. Great advances have been made in the production of food , in the provision of heat , light and shelter, and the treatment and cure of some diseases . All these achievements are due to the ability of our species to manipulate their environment. However the domain of the human species, associated with modern industrial and agricultural technologies, threatens our planet in various ways, among which include:
- The rapid reduction of resources land by a growing population
- The pollution of the environment by large – scale industrialization
- The destruction of natural ecosystems
- The accelerated extinction of plants and animals
- The constant loss of productive agricultural land due to erosion and desertification.
Growth of human population
Probably the greatest ecological problem of our time is the rapid growth of the human population. During most of the time humans have lived on Earth , its population has grown fairly steadily and slowly. For example, between the years 10 000 and 500 a. JC the global population passed from 5 million to 100 million. By the year 13000 of our era it reached 500 million, and at the beginning of the nineteenth century it had doubled to 1000 million. Since then there has been a real explosion of the human population, reaching more than 5000 million in 1987. It has been late eighteenth century, the British economist Thomas Malthus,
The rapid growth of the population, especially in the last 200 years, has been due to the decrease of the mortality rate and not to the growth of the birth rate. The fact that food sources , drinking water and public health are within reach of the majority of the population has resulted in greater longevity.
In recent decades, parallel to massive population growth, has seen a significant displacement of the inhabitants of the average rural to large urban centers. In 1950 there were about 750 million people living in urban areas, which represented 25% of the total population. In the 2000s, urban areas will accumulate almost half of the world’s population, or about 28 billion people.
Most of this urban expansion has also taken place in the newly urbanized countries. The rapid growth of cities such as Sao Paulo or Bangkok have surpassed the number of jobs and housing available. Consequently many people live in marginalized neighborhoods like shanty towns of Brazil or the towns of the misery of Argentina, in inadequate accommodation often lacking in service of water supply and sewerage. In those places there is a high rate of unemployment , a poverty widespread and a lack of services basic such as schools and hospitals.
Pressures on natural resources
As the human population expands, while maintaining the pace of global economic development, the demand for food, water, fossil fuels, minerals and other natural resources grows. In many cases these resources are scarce, and increasing the competition to obtain them. The easily cultivable regions of the earth – about 11% of the ice-free land surface – are devoted to the production of food, either for humans or livestock . Fish stocks decline rapidly in many of the oceans as a result of fishing exaggerated. Oil reserves and natural gas reserves , which are easily accessible, are now being exploited or have already been exhausted. About two billion people suffer from shortages chronic water.
In developed countries, most of the landscape has been transformed due to economic development . The agriculture , forestry, industry , the construction of housing and roads of communication are just one of the uses of land that have altered or destroyed natural habitats and wildlife. There are also other forms of environmental communication related to soil, water and air , which has also damaged many ecosystems.
Many less developed countries face serious economic and social problems caused by rapid population growth and the need to finance their industries and infrastructures. These countries have to devote too much of the state’s funds to paying the interest that developed countries have given them. In this way, the valuable resources that should be used for internal development are diverted.
On the other hand, these countries are under enormous pressure to export their mineral deposits and other natural resources , such as lumber for construction. Much of the land on productive farmland is used for profitable crops such as cocoa and coffee , which can be exported to overseas markets . These pressures often lead to the transformation of traditional forms of cultivation, and local farmers are forced to work less fertile or uncultivated lands. This situation causes the occupation of semi-arid lands or clearing. The human alteration of these fragile ecosystems can have wide and record consequences.
Grounding a plot of land for the purpose of planting crops, raising livestock, or performing any other human activity generally means burning or clearing forests and virgin (natural) forests: deforesting. Before the introduction of agriculture, about 10,000 years ago, it is estimated that half the land surface was covered with trees . Of these forests and original forests, only the fourth part remains intact. The rest has been destroyed or transformed into planted forests, more uniform in their composition, and very different from the original vegetation .
The development of agriculture and – from the middle of the eighteenth century onwards – the industrial revolution have accelerated the destruction of forests and forests in many temperate countries. By the end of the Middle Ages , 80% of European forests had been felled. Similarly colonization of North America meant rapid logging.
In the United States less than 5% of forests and original forests remain. At present there are rainforests in the tropical or subtropical regions, both humid and dry, which are under a similar attack by loggers and farmers. Since the beginning of the century, about half of the world’s rainforests have been felled, and that means about 800 million hectares. In 1990, an area similar to that in the Gulf of California (about 16 million hectares) was estimated to have been destroyed each year.
This logging is the result of several activities:
- Extraction of wood for construction
- Felling of trees to obtain wood as fuel and coal
- Land degradation by displaced farmers or landless migrants
- Large- scale desolation for the breeding of livestock and planting of crop plants.
- Mineral extraction
The disappearance of both temperate and tropical forests and forests can have ecological consequences on a large scale. The forests release large volumes of water vapor into the atmosphere, and this forms clouds that precipitate as rain. In addition to reducing atmospheric water, forest and rainforest loss prevents falling rainfall from being retained locally, decreasing groundwater reserves and preventing rock moisture from recovering . This causes water scarcity and then drought.
Compared to temperate forests, tropical forests are especially fragile ecosystems. Their rich natural and plant life seems to contradict the fact that their soils are normally poor. All available nutrients are entangled in trees and other organisms, or contained in dead leaves and other remains of plants and animals, which remain on the soil surface. These reserves are quickly captured by plants and recycled, without the soil becoming rich.
Cutting and burning the trees leaves their nutrients on the ground in the form of ashes, providing fertile help that lasts little. However, the nutrients are leached by torrential rains, very common in these regions. Consequently the crops that are made can be productive only for a few years, before they deplete the reserves of the soil and the farmers are forced to leave that land.
Devoid of the cover of the dense vegetation, the soil of the forest is devastated, constituting, alluviums that obstruct the rivers and the estuaries. This phenomenon may affect local fishing. The exploitation and colonization of tropical forests is also a threat to the indigenous peoples who inhabit them. At the same time as they take possession of the lands inhabited by the Indians and break traditional ways of life, the colonizers carry diseases against which the inhabitants of the forest have few natural defenses.
The remnants of temperate forests are also rapidly ending. In Norway virtually no virgin forest has been left, and the timber industries are now making large incursions into the coniferous forests of Canada and Russia . In addition, many forests in the northern hemisphere are affected by the phenomenon called forest death .
Wood Used as Fuel
About two billion people worldwide use wood as fuel, energy for cooking, heating and other domestic uses. In countries such as Tanzania, Nepal and Mali, 90% of domestic energy consumption is hardwood. Even in newly industrialized nations, such as India and Brazil, large numbers of people, especially in rural areas, still depend more on wood than on oil , gas or other fossil fuels. Numerous trees are cut to meet the demand for fuel and in many places these trees do not recover. It is estimated that by the year 2000, one billion people will face a chronic shortage of wood.
Another factor that needs to be taken into account is the increase in the urban population. In many underdeveloped countries, most of the poor in the cities use coal as their domestic fuel. This material less heavy than wood, is less expensive transportation . But more than half of the energy contained in the original wood is lost when it is converted into coal. This means that urban consumers spend twice as much fuelwood as people living in rural areas.
The shortage of combustible wood entails a greater dedication to your search. The need to maintain valuable reserves of wood may lead to less cooked food being consumed and water boiled for less time, which may lead to increased risk of disease.
The shortage of wood can also lead to the use of dry manure as fuel and the avoidance of crops. This reduces the amount of these materials incorporated in the soil and spread as fertilizers, which causes a reduction in soil fertility. It is estimated that in Asia and Africa , 400 million tons of manure per year are burned as fuel. If it were used as fertilizer it could produce extra crops equivalent to 20 million tons of grain.
Destruction of Watersheds
Felling upland regions can have devastating effects even at great distances. The ecological damage inflicted on Himalayan watersheds in recent decades is a good example of this phenomenon. Over 40% of the forests in this region of Central Asia have been felled in the last 40 years. The ability to retain the soil that the roots of the trees have is especially important to maintain the stability of the mountain slopes.
Trees also help to retain rainwater by trapping it in its leaves and branches, where it is slowly poured into the exposed soil. When the trees disappear, water leakage decreases significantly and rainwater is washed away carrying the exposed soil. Water runs on the surface, fills the canals, causes landslides and floods. The fertile soil is lost, the terraces are damaged and the crops are buried in the mud. The wildlife and natural flora threatened by all roads.
In addition the effects are also felt at great distances. The elimination of Himalayan vegetation has greatly increased the risk of floods in India and in Bangladesh because of the rapid water from the Mohonic rains from the mountains to the lowlands. The capacity of the river channels is reduced to the large amount of mud carried from the foothills of the Himalayas. The Ganges and Brahmaputra rivers transport more than 3,000 million of soil each year to the Bay of Bengal. The extreme increase in the influx of rivers creates cycles of floods and droughts, and affects the recycling of water in large areas.
All soils are subject to some degree of erosion by wind and water. This loss, in general, is repaired naturally. But when the erosion is very marked or sudden can result in the decrease or the annulment of the productivity of the arable land. The detached soil is transposed at great distances, carried by the water by the streams, the rivers and the estuaries, causing the elevation of these watersheds.
Soil erosion is a global problem, caused by inadequate cultivation methods , deforestation or exaggerated grazing. One-third of US farmland is seriously affected by soil erosion.
Soil erosion is especially severe in the fragile ecosystems of tropical and dry regions. In many parts of Africa the cause of erosion has been the abuse of grazing . When a large number of pacing animals – such as goats, sheep, cows – are concentrated in a particular area for a long time, the vegetation cover is reduced or even disappears, leaving the soil uncovered and making it vulnerable to erosion.
Desertification is the process by which the soil loses its fertility, so that it can not be used as a cropland or grazing area. When the agent is human action , it speaks of desertification . Desertification is the typical final state of gradual degradation. The land has become arid and barren, has very little vegetation and is easily eroded. It is estimated that about six million hectares of productive land are lost each year through this process. Another 20 million hectares are impoverishing their soils to the point that growing them is no longer profitable. Currently, desertification threatens 30% of the earth’s surface,
- The main causes of desertification are:
- The clearing of forests and jungles
- Exaggerated grazing
- The intense cultivation
Felling and grazing abuse are the main factors involved in the transformation of tropical dry forests and shrub lands of deserts. The problem increases when farmers move from fertile land, where the soil rapidly depletes their nutrients if crops are not disturbed by long fallow periods. Soil impoverishment causes farmers to clear more land and extend degradation. Trees are often cut to obtain fuelwood and accelerate erosion.