ACS Distance Education UK
Tropical forests are being destroyed at an ever increasing rate. The estimates of the losses vary, but at least one half of the tropical forests of the world have already been lost. If the trend continues, the remaining tropical forests will disappear within the next three decades. This is an incalculable loss, because these forests provide habitat for an estimated half of the plant and animal species of the world. In addition, these forests provide water and fuel for a large portion of the world’s population. They also have a large influence on the local and global climatic systems. Such forests are also potentially a treasure house full of previously unknown chemicals, foods, pharmaceuticals, spices and more.
Most of the deforestation is caused by commercial logging, land clearance for agriculture, ranching and fuel. Solutions to these problems include:
• The development of alternative wood supplies for fuel and timber, achieved by planting and maintaining timber and fuel wood plantations.
• Developing alternative energy sources for cooking and heating to replace wood used as fuel (e.g. solar).
• The regulation of logging.
• A consensus on the value of forest conservation over commercial development.
• More efficient use of harvested wood products.
As with tropical forests, temperate zone forests are also under threat, although in some areas such forests have actually increased in extent. Acid rain is the greatest threat to these forests in the Northern Hemisphere. This is caused by acidic pollution from factories mixing with water vapour in the atmosphere and falling to the ground as rain. The conifer forest regions of Europe and North America are the currently most severely affected by acid rain.
Agriculture – Loss of agricultural land, overgrazing, irrigation
Because of excessive increases in the world’s human population, coupled with the construction of buildings and roads, the land available for food production is steadily decreasing. In much of the remaining land topsoil is lost by erosion and production decreased due to increasing salinisation problems. Due to erosion, large scale agriculture can result in severe and unsustainable rates of soil loss. Overgrazing and the collection of firewood can cause land to become arid, eventually resulting in the spread of deserts and semi-deserts.
The problem is particularly severe in developing countries, where difficulties are caused by unsound and ineffective agricultural policies. These policies are often the result of a lack of available funds and a necessity to feed an increasing population. The United Nations estimates that if the present rate of loss continues, by the year 2000 approximately one-third of the arable land around the world will have become non-productive.
Not surprisingly there is a long list of possible environmental consequences from mining. Some of these include erosion, groundwater contamination by heavy metals, habitat destruction, sinkhole creation and acid mine drainage.
Acid mine drainage occurs where outflowing water from a metal or coal mine is highly acidic, although this can be a naturally occurring process, it is characteristic of large scale disturbances.
Exhaustion of non-renewable resources
The primary consideration here is the exhaustion of fossil fuels. Fossil fuels were formed millions of years ago through the decomposition of animal and plant material over time it formed layer upon layer under the ground, which solidified and formed a hard, black colored rock like substance known as coal. Through mining these non-renewable resources coal is processed into oil or petroleum, which forms a large part of the Australian economy through export to other countries. There is a limited supply of coal in underground reserves and is therefore considered to be non-renewable, once it is all gone, there is no more. The solution to this problem lies in the better use of the alternative fuel supplies, by increasing the efficiency of combustion, or by using alternative energy sources, such as wind, solar power and biofuels such as ethanol.
Destructive fishing methods may lead to habitat loss. Examples of this include cyanide fishing where sodium cyanide is used to kill and capture fish, the sodium cyanide damages coral, spawn and younger fish. Dynamite fishing where explosives are used to kill or stun schools of fish, this style of fishing frequently kills the coral reef supporting the fish population as well. The combination of these two can lead to large breakdown of coral reef ecosystems. Bottom trawling involves dragging a net along either the very bottom of the ocean or just above the bottom. Bottom trawling can lead to mass destruction of entire sea floor environments. Further effects include resuspension of sediment from the sea floor. This has the effect of reducing light levels leading affecting kelp growth. Additionally such sediments are often ‘sinks’ for pollutants such as DDT, effectively resuspention is allowing such pollution back into the food chain. Destruction of the seafloor environments also reduces the ability of fish populations to restore themselves due to habitat loss.
Overfishing leads to resource depletion as stocks are so overharvest that they are unable to reproduce fast enough. Overfishing can also lead to the destabilization of whole ecosystems. The ability of an ecosystem to recover from overfishing is further hampered by changes in species distribution and composition making it near impossible for an overfished species to reestablish itself. There are many well known examples of overfishing leading to collapse of species. Some of these include the collapse of the cod fishery off Newfoundland. In 1992 Canada created a moratorium on this area known as the Grand Banks. Despite this recovery is poor leading Canada to declare the Cod as an endangered species in 2003 as well as creating an indefinite closure to cod fisheries on the Grand Banks.
Bycatch is the part of the catch that is not required. Often this is discarded, the quantities are quite staggering. For example, the worst offender is shrimp trawling, it has been estimated that for every 6 pounds of shrimp, approximately 20 pounds of bycatch is also caught. By catch may include marine mammals such as dolphins, sharks, birds, turtles, crustaceans etc etc.
Water supplies worldwide are threatened with depletion and pollution. The major problem is the loss of watersheds through denudation of vegetation. The solution to this problem must come from the better use of land and the protection of crucial vegetation in the watershed areas. The decreased availability of surface and groundwater demands new approaches to overcome future water availability issues and increase water production worldwide. In Australia, improved water allocation that is environmentally sustainable is a high priority of the Council of Australian Government’s National Water Initiative which is developing new solutions to water quality and management issues for example; land use, catchment management and alternative options for surface and groundwater usage.
Currently the demand for water is increasing and the ability of many Australian cities to supply water is decreasing. Population growth and climate change are also adding increased pressure on our natural resources and the future supply of safe drinking water. Hydrology is intrinsically linked with catchment management and land use practices therefore an understanding of water flow and the hydrological system integrates with water management regimes. Flow regimes are influenced by increased irrigation, farming practices, urban and residential sprawl. Therefore the management of catchment areas is becoming increasingly important as human development encroaches, altering natural systems. Climate change and weather patterns are also adding greater pressure on catchment areas and our natural water resources.