Read Mazingira Newsletter Every Month August, 2004 issue
Mazingira/Environment Editorial Board
Editor
Jacob Kambili
Editorial Board
Adam Cheyo
Joyce Ngallawa
Martha Tesha
Bayizi Nkugutwa
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Joseph M. Ndesika
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Miss Zabibu Amri
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Get to know kinds, sources of water pollution
By Jacob Kambili
Over 70% of the Earths's surface is covered by water, mainly ocean salt water which has limited use. This is because salt water cannot be consumed by humans or used for many kinds of industrial processes. For most human uses, as well as some commercial ones, the quality of water is as important as its quantity. Water must be substantially free of salinity, plant and animal waste and bacterial contamination to be suitable for human consumption.
Unpolluted, clean, freshwater supplies sometimes called 'potable water' have always been considered inexhaustible until very recently when it was understood that we human beings will probably exhaust our usable water supplies in some areas because of both human and natural factors. Human factors that have affected usable water supplies include a steadily increasing demand for freshwater for industrial, agricultural and personal needs.
Shortages of unpolluted, clean freshwater throughout the world can also be directly attributed to human abuse in the form of pollution. Water pollution has negatively affected water supplies in almost all of the world's densely populated industrialized nations including Japan, Europe, the former Soviet Union and North America.
Unfortunately, the outlook for the world's freshwater supply is not very promising since many sections of the world will experience shortages of unpolluted, clean freshwater in the 2000s', according to studies by the United Nations and the International Joint Commission. Although the world's supply of water is continually being replenished by rainfall, this rainfall varies significantly. Parts of the world, particularly sections of India, Europe and Mexico continue to suffer massive droughts because of long periods of extremely limited rainfall while floods result from too much rainfall in other parts of the world.
Kind and sources of water pollution:
Water pollution occurs when the use by one segment of society interferes with the health and well-being of other members. In an industrialized society, maintaining unpolluted water in all drains, streams, rivers and lakes is probably impossible. Water quality is related to the use of intended of the water. Adding material to water may cause the water to become unfit for some uses but may not affect other uses. If silt is added to a lake, the water may still be drinkable, but the lake may no longer be an acceptable place to swim. If salts are added to a lake, the water may then be less acceptable as drinking water, but the salts may not interfere with the lake's recreational value. It many not be necessary to maintain absolutely pure water.
There are also economic considerations. The cost of removing the last few percentages of some materials from the water may not be justified. This is certainly true of organic matter which is biodegradable. The most salient sources of water pollution are Municipalities, factories, accidents, and power plants.
Municipal water pollution:
Municipalities are faced with the double edged problem of providing suitable drinking water for the population and disposing of wastes. These wastes consist of storm-water runoff, wastes from industry and wastes from homes and commercial establishments.
Wastes from homes consist primarily of organic matter from garbage, food preparation, cleaning of clothes and dishes and human wastes which are mostly undigested food material and a concentrated population of bacterial such as Escherichia Coli and Streptococcus faecalis which normally grow in the human large intestine. Because these harmless bacteria can be easily identified, their presence in the water is used to indicate the amount of pollution from human waste. Since the members of these types of bacteria present in water are directly related to the amount of human waste entering the water, the greater the amount of wastes deposited in the water, the more likely that there will be small populations of disease-causing bacteria. Therefore, the harmless bacteria are indicators that other organisms may also be present.
The nonliving organic matter in sewage presents a different kind of pollution problem because it decays in the water. Micro organisms use oxygen dissolved in the water when they degrade the organic material. As the microorganisms metabolize the organic matter, they use up the available oxygen. The amount of oxygen required to decay a certain amount of organic matter is called the Biochemical Oxygen Demand (BOD). Measuring the BOD of a body of water is one way to determine how polluted it is. If too much organic matter is added to the water, all of the available oxygen will be used up. Then anaerobic (not requiring oxygen) bacteria begin to break down wastes. Anaerobic respiration produces chemicals that have a foul odour and an unpleasant taste and that generally interfere with the well-being of humans.
Although the waste water from cleaning dishes and clothing may contain some organic material, the more important group of contaminants found in this water are soaps and detergents. These are useful because one end of the molecule dissolves in dirt or grease and the other end dissolves in water. When the soap or detergent molecules are rinsed away by the water, the dirt or grease goes with them.
Until recently, many detergents contained phosphates as a part of their chemical structure. A limiting factor is a necessary material that is in short supply and because of lack of it, an organism cannot reach its full potential. Phosphates are plant nutrients and therefore, a limiting factor of plant growth. Thus, when phosphates from detergents are added to the surface water, they act as a fertilizer and promote the growth of undesirable algae populations. Algae and larger plants may interfere with the use of the water by boat propellers, clogging water intake pipes, changing the taste and odour of water and causing the building of organic matter on the bottom. As this organic matter decays, oxygen levels decrease and fish and other aquatic species die.
Because these problems are all associated with the addition of plant nutrients such as phosphates to the water, many states have banned the sale of detergents with high-phosphate content. Most domestic waste water goes through a sewage treatment plant, so it is easier to measure and control the phosphate content.
Industrial water pollution:
Frequently, a factory or industrial complex disposes of some or all of its wastes into a Municipal/City sewage system. Depending on the type of industry involved, these wastes are likely to be a combination of organic materials, petroleum products, metals, acids and so forth. The organics and oil add to the BOD of the water. The metals, acids and other ions need special treatment, depending on their nature and concentration. As a result, Municipal/City sewage treatment plants must be designed with their industrial customers in mind. In most cases, it is preferred that industries take care of their own wastes. This allows the industry to segregate and control toxic wastes and design a waste water facility that meets its specific needs. Most companies, when they remodel their facilities, include waste water treatment as a necessary part of an industrial complex. However, many older facilities continue to pollute, discharging acids, particulates, heated water and noxious gases into the water.
Power Plants:
When an industry removes water from a source, uses the water for cooling purposes and then returns the heated water to its source, may cause what is known as thermal pollution. The power plants heat water to convert it into steam which drives the turbines that generate electricity. For steam turbines to function efficiently, the steam must be condensed into water after it leaves the turbine. This condensation is usually accomplished by taking water from a lake or stream to absorb the heat. This heated water is then discharged.
Cooling water used by industry does not have to be released into acquatic ecosystems. While this is the least expensive and easiest method, it can create problems for the inhabitants of the area for some acquatic ecosystems are very sensitive to minor temperature changes.
Since ocean estuaries are very fragile, the discharge of heated water into an estuary may alter the type of plant food available. As a result, animals with specific food habits may be eliminated because the warm water supports different kinds of food organisms. The entire food web in the estuary may be altered by only slightly temperature increases.
Accidents:
Marine oil pollution has many sources one of which is accidents, such as oil drilling blowouts or oil tanker accidents. In 1993, for instance, the tanker 'Brae' loaded with 75 million litres of oil, ran into rocks off Scotland's remote Shetland Islands. The effects of the oil spill were, however, not as serious as first thought because about 40% of the oil was scattered by the heavy seas while another 40% evaporated, limiting environmental damage.
The greatest sources of all marine oil pollution are not accidental. Nearly 2/3 of all human-caused marine oil pollution comes from runoff from streets, improper disposal of lubricating oil from machines and international oil discharges that occur during the loading and unloading of tankers.
As the number of offshore oil wells and the number and size of oil tankers grow, the potential for increased oil pollution also grow. Many methods for controlling marine oil pollution have been investigated and tried. Some of the more promising methods include recycling and reprocessing of used oil and grease from automobile service stations and industries and enforcing stricter regulations on the offshore drilling, refining and shipping of oil.
Source : (Extract from a book, Environmental Science)Environment becomes degraded as populations increase
By Meshack Mpanda
The problem of mass exodus of rural people to the urban centres is on the increase in the present century. Many able-bodied youths are on the move from the countryside to the towns to look for employment. The situation is even graver in Least Developed countries like Tanzania where streets, heavily congested with people, are full of both solid and liquid wastes as a result of human activities.
Residents of urban centres in the Least Developed Countries are faced by inadequate health care and other social amenities. For instance, many of them have no access to latrines and live in areas with poor sanitation facilities, making them become vulnerable to epidemics such as cholera. Dar es Salaam City is a salient example of this disgusting situation mainly caused by an inadequate pipe water supply. It is believed that shallow wells dug in the wake of the 2001 serious water crisis that hit Dar es Salaam are linked to contaminated water found in the ground.
Population of Mwanza City:
The 2002 census place the population of Mwanza city at almost 500,000. This is more than 10 times the population level 30 years earlier, which is largely attributed to the increasing industrialization. The estimated annual growth rate of the population is around 8%. A major source of population increase is rural-urban exodus, Mwanza being the second largest city in Tanzania, serving as the administrative and service centre for the region, the Lake Zone and neighbouring countries of the 'Great Lakes Region'. Mwanza, the terminus of the national railway line from Dar es Salaam, has one of the most important and busy airports in the country and region, and has an important port. It is also a major transit centre of goods destined for neighbouring Uganda, Rwanda, Burundi and Democratic Republic of the Congo.
Environmental situation:
The increasing population and the growing, albeit most unregulated, industrialisation in Mwanza, have placed tremendous pressure on the physical environment of Mwanza as well as on the city capacity to provide for basic infrastructure and services. Key environmental issues affecting Mwanza include unplanned settlements, inadequately managed solid and liquid wastes, among others.
Unplanned settlements or squatters continue to be one of the key environmental problems in Mwanza. Present estimates point out that between 40% - 60% of the households are in unplanned areas, housing around 74% of the population.
These unplanned settlements cause considerable environmental degradation and expose their inhabitants to restricted and unhealthy living conditions. The settlements are located mostly on the slopes of such rocky hillsides as Bugando, Igogo, Bugalika, Nyasaka, Mabatini etc. which are stripped of their vegetation cover and aggravated by the mining of stones and sand for construction purposes. Some settlements, especially those that are old and centrally-located, tend to be densely populated, with plots measuring as small as 20m2. Sanitation is generally poor as the residents are mostly dependent on the shallow pit latrines, as a significant number of other settlers have no access to latrines at all. Solid waste is disposed of rather haphazardly such that most waste matter ends up in Lake Victoria untreated. The settlements are also inadequately serviced in terms of basic infrastructure like roads and drains.
Economic/human activities are generating substantial quantities of both solid and liquid wastes. Presently it is estimated that the rate of solid waste generation in the City is between 0.5 - 0.75 kg per capital per day. Thus the amount of solid waste from domestic, institutional and commercial activities is estimated at about 375,000kg/per day. Industrial solid waste, largely from factories and industries, is estimated at 500,000kg/per day. On the daily basis, therefore, about 875,000 kg of solid waste are generated in the city.
The total number of industries in Mwanza (if small enterprises are included) come to more than 100, with the total industrial effluent generation estimated at about 6,500m3 per day. Fish processing plants alone discharge vast amounts of wastewater while seed oil processes discharge residues that remain after extracting the oil. Most garages lack oil and grease raps, allowing the solid pollutants to be washed off into the lake, particularly during heavy rains. In addition, human waste, estimated at 3.5 million litres, is also discharged into Lake Victoria, through Mirongo river, untreated daily!
Most industries operating in Mwanza lack any type of wastewater treatment facilities. Some industries have installed small treatment units that are generally of limited capacity and the closeness to the lakeshore leads to the discharge of raw or semi-treated wastewater directly into the massive waterbody, leading to the poor quality of the lake water.
City Council has set aside specific areas for industrial activities but are however, located along the lakeshore, i.e. Igogo and Ilemela areas. Due to lack of land, many industries operate in the existing large storage buildings and warehouses, besides small-scale enterprises that have set up operations in areas not meant for industrial activities. According to the 1994 by-laws, Industries are required to pay fees levied on businesses to allow them to operate within the city. However, the City Council until recently, has undertaken very limited regulation of the industries in terms of controlling and managing the environmental consequences of the industrial production. Environmental audits and environmental impact assessments have rarely been carried out.
Source: Sustainable Mwanza Programme (SMWP)
By Staff Writer
Sometimes, it is not easy to categorize the relationships that organisms have with each other. For example, it is not always easy to say whether a relationship is a predator/prey relationship or a host/parasite relationship.
How would you classify a mosquito or a tick? Both of these animals require blood meals to live and reproduce. They don't kill and eat their prey nor do they live in or on a host. This just points out the difficulty encountered when we try to place all organisms into few categories.
Another relationship that doesn't fit very well is the relationship that certain birds have with other birds. Certain birds don't build nests, but simply lay their eggs in the nests of other species of birds, who are left for a foster nestling at the expense of their own nestlings, who generally die. This could be called parasitism, but it doesn't fit the standard definition.
What about grazing animals? Are they predators on the plants that they feed on? And what kind of relationships do humans have with their domesticated plants and animals? Do we have a mutualistic relationship with cows and chickens? We certainly derive benefit from the milk and eggs we get, and cows and chickens benefit from the care they are given. Or are we primarily parasites on these species? Certainly, we are sometimes predators when we kill and eat them.
It would be convenient if we were able to unambiguously classify every kind of relationship into a clear category. But this is not possible, and each relationship may change in character at different times.Source: Extract from a book, 'Environmental Science'
By Meshack Mpanda
While some people need many hours' sleep every night, this natural state of rest in which the eyes are closed and the mind and body are not active, eludes millions of others the world over. It is believed that about 35% of the Earth's population do have sleepless nights and yet they are not aware that they are diseased!
Now, the question is why do we feel sleepy in the first place? Well, the whole physical structure of a human being (or an animal) is being regulated by chemicals most of which are already known. One of the chemicals believed to be responsible for causing a wink of sleep is a hormone, called 'melatonin' produced within the brain.
Experts in the anatomy and physiology of the human body and brain believe that it is this very hormone which reduces functions of one's body before he/she feels sleepy. When produced, the temperature of the body and that of the brain-bound blood falls, making the muscles less tense and, in turn, resulting in the state in which both the mind and the body become partially inactive.
Some people, particularly those living in the urban centres contend that sleeping is time-wasting event because they become so much absorbed in a lot of business and private activities very frequently. Without regard to one's social position, everybody falls asleep only that while the poor are sound asleep, the rich and business people are simply half asleep.
Reason why we feel sleepy:
In order to understand this mystery, we have to know about what is really happening when we fall asleep. Researchers have discovered that sleep is rather a complicated process which happens repeatedly after every 24 hours. And as an old age creeps onto someone, his/her sleeping habit also changes. For instance, a newly-born baby usually sleeps for about 18 hours daily although it can sometimes sleep for three hours only to wake up later and then fall asleep again, almost immediately.
On the other hand, however, some adults do spend only a three-hour sleep night while others can sleep upto ten hours, according to the experts. Also research reveals that some youths just find it difficult to wake up earlier purely for physiological reasons because a body of an adolescent starts undergoing changes at puberty this is why he sleeps a lot at night.
Are there any advantages?
Generally speaking, sleep is advantageous because whenever one falls asleep, both blood pressure and rate at which the heart beats fall. It is during this time that hormone that stimulates to assist body growth is produced 50 times more. It also appears that sleep affects our desire for food.
In fact, scientists have established that sleep is a 'natural leisure and recreation' as Shakespeare once put it. For the brain, sleeplessness is synonymous to suffering caused by lack of food. A person lying awake for a long time, his/her body is likely to produce a little amount of hormone called 'leptin', prompting him/her to opt for foods that contain a lot of carbohydrates that are thought to make people fat.
Moreover, sleep helps one's body get rid of chemicals which cause cancer or abnormal growth of cells in the body which, in turn, often causes death. According to a study by Chicago University, eleven strong youths were allowed to sleep for four hours for six days. Thereafter, they all appeared to have become of age and amount of insulin, which controls the amount of sugar absorbed into the blood, decreased.
Sleeplessness also affects the production of white blood cells and a hormone called 'cartisol', resulting in blood related diseases. One doctor working with Bugando Medical Centre in Mwanza also mentioned other adverse effects of sleeplessness as forgetfulness, having mixed feelings, inconsistency in one's plans etc. In the long term, adverse effects of sleeplessness include getting old very fast, fatigue, becoming vulnerable to cancer and heart diseases.
September, 2003
By Staff Writer
People in Mwanza have more reason than most to be alarmed when encountering a group of prisoners armed with pangas. In Mwanza, prisoners have become strongly associated with tree felling and never more so than in the last few months when countless trees in and around the city have been lost in the name of development (and fuel to burn!). But looking at certain areas of Mwanza it is debatable whether the quantity of trees cut was really justified or whether some trees could have been simply pruned and left standing.
Why, for example, was it deemed necessary to turn Nasser Drive from a leafy lakeside drive into a highway almost devoid of any trees lining the lake. It used to be pleasant to walk from Capri Point to the town, apart from the ever present dust. Now it is slightly less dusty but a long, hot walk without any shade , as cars pass at high speeds No one disputes the need for better roads in Mwanza but Nasser Drive now outdoes the airport and Musoma roads for traffic-carrying potential when a less wide tarmac road would have provided even the occasional visiting dignitary with a smooth and pleasant ride to the State House.
So trees have to be sacrificed if Mwanza wants roads seems to be the bottom line. Well, in some cases, that is true. If a tree is plainly in the way of the selected route for the road or will interfere with drainage, regrettably that tree will have to be removed.
But what plans do the city developers, and others, have now to replace those lost trees to ensure that we don't just have a city with nice roads but little else?
But of course it is not just prisoners who are employed to cut down trees because roads are being built. In the newly gentrified Isamilo, for example, there is hardly a day goes past when the sound of a panga on wood cannot be heard as another tree is cleared by a worker of one new house owner or another. This is in the name of creating gardens or shambas but, bwana, "do you have to cut down all your trees on your plot to do this"? Apart from creating a dust-bowl for yourself you are contributing to the loss of soil, especially precious top-soil which your shamba needs.
When good top soil goes, the soil loses it nutrients, its ability to retain water, the insects which enrich it and the very vegetation and roots which bind it together. When trees are removed the soil is free to become eroded by wind and water. (People who remember the rains of two years ago will know what the force of water can do to soil and rocks when there are no trees anymore to hold the hillsides together).
Trees also support a whole variety of animals, birds and insects thereby adding to the overall biodiversity (the variety of all plants and animals which exist together in one area). People do not live in isolation from other species and biodiversity is also now accepted as THE key indicator of a healthy environment. We should be glad, therefore, to have trees in the shambas and along the roadsides and in the newly developed city-centre of Mwanza, knowing that this is helping to provide a healthy environment.
Mwanza also lacks many of the historic monuments present in other cities but there are historic trees which are landmarks and should be conserved for people now and future generations. Otherwise we and these future generations have the right to ask "who squandered our heritage (and our biodiversity) in Mwanza City"? More fundamentally trees provide shade and shelter from extremes of weather and places for people to meet and talk. Why do we want to remove these shelters/places from our City? Trees also replenish oxygen on which all life depends, act as wind-breaks and collect a lot of the dust we all complain about.
The key question now is that with so many trees lost to Mwanza already, and who knows how many more, who, exactly, is going to be responsible for ensuring that new trees are planted so that future generations can enjoy them. Moreover who is going to ensure that the right kinds of trees are planted, and planted in the right places, so that panga-swinging prisoners of the future do not have to be drafted in to cut those trees down?
It is, therefore, incumbent upon the city planners and developers, with encouragement by the regions' politicians, to draw up comprehensive plans to introduce new trees and the means by which those trees will be cared for while they take root and flourish. These same people must also call upon expert advice to ensure that these plans are not just a 'wish-list'.
Now is the time to act - trees take a long time to mature and we can't afford to lose any more in the meantime - for the sake of our soil, biodiversity and heritage.
By Jacob KambiliAll good citizens, particularly young school pupils and students have been warned of possible highly dangerous and potentially lethal disorders that are likely to befall them if they misuse drugs.
A person is abusing drugs if he/she loses control or when he/she uses drugs over the amount he/she uses or over the way he/she acts when using them.
Councilor for nominated seats, Angeline Mabula stressed that the drug misuse or abuse behaviour currently threatening the entire world has already cause untold multi-health complications.
She sounded the warning during the official launching of the 'Inter-school Drug abuse Prevention Programme', a ceremony held at Lake Secondary School recently.
The Councillor who was a guest of honour at the colourful ceremony, organised by 'Rafiki Family' under the auspices of Sekou Toure Hospital's department of Mental Health, didn't go into details.
However, Psychiatrists and Psychologists say some common signs that someone is misusing drugs that one feels he/she needs a drug to get through the day or night. The victim may use it at unusual times or places such as in the morning or when he/she is alone.
Other signs are that the victim lies about how much he/she or others use or hide it, has money problems depending on how much people even resort to crime and prostitution to raise the necessary funds to continue on their way.
People who are misusing drugs are also ashamed of their bad behaviour while using drugs, are not working as well as before or are not going to work as often and have problems with violent behaviour. A man may become more violent towards his wife, children or friends.
The Councillor didn't mention specific health problems cause by the drug abuse behaviour either.
But is has been established that people who use drugs a lot get sick more oftern and more severely than others.
According to research findings, they are more likely to have poor nutrition which, in turn, cause more sickness, cancer and problems of the heart, liver, stomach. skin, lungs and urine system including ones that cause permanent damage.
Other adverse effects of drugs on whoever uses it include brain damage or fits (seizures), memory loss-waking up not knowing what happened, and mental health problems such as seeing strange things or hearing voices (hallucinations).
Also the victim becomes suspicious of others, having flashbacks or feeling severe depression or anxiety and even death when drugs are being used too much at one time (overdose).
In addition, injuries or death from people (and often to their beloved families). This is because they make bad/wrong decisions or take unnecessary risks or because they can lose control of their bodies as a result of drugs.
If they have unprotected sex, share needless used to inject drugs, or trade sex for drugs, they are at risk for hepatitis and sexually transmitted diseases including AIDS.
But according to those who have been through the mill, the initial sensation is a remarkably pleasurable one. However, the problems is that a gradually increasing amount is needed each passing time to experience the same initial impact, making one become addicted to drugs.
In another development, the Councillor, echoeing AIDS researchers' views, also seized the occasion to warn the youths against the fatal disease saying it is spread mainly by indiscriminate sexual contacts.
"Please refrain from any undesirable sexual contacts that can expose you to HIV-infections….why cant you wait until you get married?" she appealed to the youths.
Available World Health Organisation (WHO) statistics suggests that globally the youths, aged between 15 - 25, are most vulnerable to HIV-infections and that as of December, 2002, about 40 million people are already infected with the virus on Earth! Youths make up about 68 per cent of the population of Tanzania.
Earlier on, debating about the disgusting sexual behaviour among pupils and students, some speakers claimed that some young females look sexy in their outfits, prompting their males counterparts to make suggestions.
Josephat Malezi, a form III student of Lake Secondary School, described such young girls who cause sexual desires as people of inconsiderable culture. "Learning institutions like ours should, therefore, be centres of our African culture", he stressed.
The meeting suddenly roared with laughter when another speaker, Yohana Kilimbo of form IIB of the same school said, "I rarely had sexual intercourse in my life except once when, during my childhood a few years ago, I acted as father while a village girl acted as mother…. but I've never had sex eversince".
Mwanahamisi Mzenga, the only girl to speak out against fellow female students who offer themselves for sex with school boys or older men in return for money, strongly blasted the bad behaviour saying it contributes much to the rapid spread of the scourge in Mwanza and else where in the country.
On his side, Yusuf Hidaya said indulgence in an undesirable sexual activities as one's favourite pastime will, certainly, make life a misery and blamed the school girls for indirectly 'persuading their opposite counterparts to do sex'.
The theme of discussion on the material day, besides drug-addiction and HIV/AIDS, was gender issue and the occasion drew more than a 1,000 representatives from Lake, Pamba, Taqwa and Victoria Secondary Schools, UMATI, UPENDO DAIMA, Ishi, CODAL and Mwanza Press Club (MPC) Non Gorvermental Organisations.
Some of the students of the said schools presented shows with a variety of different types of entertainment, carrying a message urging the youths to completely change their behaviour and negative attitudes towards sexual relationships and drug-abuse vice.
The three-hour occasion was also attended by Mary Nchimbi, a Regional Secretary of CCM Youth wing, popularly known in short as 'VIJANA'.
From Last Issue
Some organisms are extinct because they were regarded as pests. Many large predators have been locally exterminated because they prey on the domestic animals that humans use for food.
Mountain lions and grizzly bears in North America have been reduced to small, isolated populations, in part because they were hunted to reduce livestock loss. Tigers in Asia and the lion and wolf in Europe were also reduced or eliminated for similar reasons.
Some extinctions of pest species are considered desirable. Most people would not be disturbed by the extinction of such animals as black spiders, mosquitoes, rats or fleas. In fact, people work hard to drive some species to extinction. For example, in the Morbidity and Mortality Weekly Report the U.S. Centres for Disease Control triumphantly announced that the virus that causes smallpox was extinct in the human population after many years of continuous effort to eliminate it.
The most important cause of extinctions related to human activity involves habitat alteration. Whenever humans populate an area, they change it by converting the original ecosystem into something that supports the human population. Forest and grasslands have been converted to agricultural and grazing lands. Coupled with this has been the introduction of new species that are useful in agriculture or grazing. These new plants and animals compete with the native organisms for nutrients and living space, and often, the native organisms lose.
The African elephants and various species of rhinoceros are in danger because they are hunted for ivory or horn, but it was the original fragmentation of their habitat for agricultural purposes that first placed the animals in conflict with human.
In much of the tropical world today, rain forests are being cleared to provide grazing land or agricultural land for an expanding human population. This activity results in the destruction of existing forests and their fragmentation into small islands. Scientists studying the effects of this activity have noticed that, as a forest is reduced to small patches, many species of birds disappear from the area. The same kinds of activities certainly happened in Europe, where little of the original forest is left. Similarly, in North America, the eastern deciduous forests were reduced, which probably resulted in the extinctions of some animals and plant that previously existed there. Almost all of the original prairie in the United States has been replaced with agricultural land, resulting in the loss of some species.
Humans also cause extinction in less direct ways. The building of dams changes the character of rivers, making them less suitable for some species. Air and water pollution may kill all life in certain areas. For example, acid precipitation has lowered the pH of some lakes so much that all life has been eliminated. In other cases, indirect human activity may selectively eliminate species that are less tolerant to the pollutants being released, or the introduction of exotic species may eliminate existing ones.
If extinction is a natural event, and if those species that become extinct are those that cannot effectively cope with the activities of humans, why should we worry about them? There are several different kinds of answers to that question. First of all, strictly from a selfish point of view, many species we know little about may be useful to us. Many plants have chemicals in them that are used as medicines. If we drive a plant into extinction, we may be eliminating a potentially useful product. Also, as the human population continues to increase, the need for different kinds of food plants and animals will increase. Once they are eliminated, however, we have lost the opportunity to use them for our own ends. Most of the wild ancestors of our most important food grains, like maize (corn), wheat and rice are thought to be extinct. What would our world be like if these plants had not been domesticated before they went extinct as wild populations? Because of this concern, many agricultural institutes and universities maintain 'gene banks' of wild and primitive stocks of crop plants.
Another interesting idea is that certain organisms in some ecosystems appear to play key or pivotal roles. Accidental extinction of one of these species could be devastating to the ecosystem and the humans that use it. For examples, the sardine fishery off the coast of Southern California and the anchoveta fishery off the coast of Peru appear to have been fundamentally altered by overfishing. Although the details are not known. It is thought that once the population was significantly reduced, other organisms filled their niche, making it impossible for their population to return to its original size.
Many people also feel that all species have a fundamental right to exist without being needlessly eliminated by unthinking activity of the human species. This is a philosophical statement that has nothing to do with economic or social value but is an ethical position.
Efforts to prevent human-caused extinctions are difficult to assess. Some countries have enacted legislation to protect species that are in danger of becoming extinct. Those species that receive special protection usually are given some sort of designation, such as endangered or threatened. Endangered species are those that are presently in such small numbers that they are in immediate jeopardy of becoming extinct. Threatened species could become extinct if a critical factor in their environment were changed.
Most of the active interest in preventing human-caused extinctions comes from developed countries. In developed countries, however, the problem is less acute because vulnerable species have already been eliminated. Extinction is a greater potential problem in tropical, less developed countries, where many biologists estimate that there may be as many species of organisms in the tropical rain forest of the world as in the rest of the world combined. Unfortunately, extinction prevention is not a major issue in many less developed countries. This difference in level of interest is understandable since the developed world has surplus food, higher disposable income and higher education levels, while people in many of the less developed countries the reverse is true.
August, 2003
Over large parts of the world, the natural ecosystems that once existed have been completely destroyed and replaced with intensely managed agricultural ecosystems. This is a natural consequence of human population growth. As the population increased, more and more land was converted to agriculture. Today, very little additional land can be converted to agriculture. All of the best land has already been converted, leaving only marginal areas that have relatively low productivity. The major ecosystems affected by this conversion of agriculture were temperate forests and grasslands. What today supports wheat, rice and corn was originally prairie or forest.
Extinction is the death of a species, the elimination of all the individuals of a particular kind. It is natural and common event in the long history of biological evolution. Of the estimated five hundred million species of organisms that are believed to have ever existed on earth since life began, perhaps five to ten million are currently active. This represents an extinction rate of 98 to 99 percent. Obviously, these numbers are estimates, but the fact remains that extinction has been the fate of most species of organisms. However, the process of speciation involves the production of new species. Thus, there is a continual process of adding new species, while at the same time eliminating those that are not able to adapt to a changing environment.
Recall that a species is a population of organisms. Every individual organism is a member of a species and shares many characteristics that are typical of the species. For example, all dogs have four legs, two eyes, hair and a tail of some kind. But there is also individual variation among the individuals within the species. Some individuals are taller, can run faster, have quicker reflexes or are better able to hear, smell or see. This individual variation allows some individuals to cope better with their surroundings. Most of these characteristics are at least partly the result of the genetic material (genes, DNA) that the individuals inherited from their parents.
The individuals that have a combination of characteristics that allow them to be more successful or more likely to live long enough to reproduce and are also likely to have larger numbers of offspring. Their offspring are quite likely to have many of the characteristics that made their parents successful and will outnumber the offspring of parents that were not well adapted. The characteristics typical of the species change slightly.
If two populations of the same species are isolated from one another for a long time and the kind of environment typical of the two locations is very different, the process of natural selection can result in the two populations becoming so different from one another that they do not interbreed and would be considered different species. Keep in mind that the environment changes over time, so the same set of characteristics will not always be suitable. For example, at one time, much of Canada and the Northern parts of the United States were covered with glaciers. The climate was quite different from what exists today and the kinds of plants and animals that existed were also quite different.
Because the environment is continually changing, a species must adapt or become extinct. If this adaptation occurs over a long period, the original species may evolve into a new species. In this situation, the original species eventually becomes extinct, but before it does, many of its genes (particularly the favourable ones) are passed on to the newly evolving species. An example of this involves the extinction of the dinosaurs. As earth's environment changed, it became less favourable for dinosaurs. However, before their extinction, many of the favourable genes in this reptile line had formed the basis for the newly evolving mammals and birds. This form of gradual extinction and replacement by other, better-adapted group is common in evolutionary history. The fossil record shows many groups of organisms that flourished for millions of years before more advanced groups replaced them.
Studies of modern local extinctions suggests that certain kinds of species are more likely than others to become extinct. Species that have small populations of dispersed individuals are more prone to extinction because successful breeding is more difficult than in species that have large populations of relatively high density. Some kinds of organisms, such as carnivores at higher tropic levels in food chains, typically have low populations but also have low rates of reproduction compared to their prey species.
Organisms in small, restricted areas are also prone to extinction because an environmental change in their locale can eliminat the entire species at one time. Organisms scattered over large areas are much less likely to have their entire range negatively affected at the same time.
Specialized organisms are also more likely to become extinct then are generalized ones. Since specialized organisms rely on a few key factors in the environment, anything that negatively affects these factors could result in their extinction, whereas generalists can use alternate resources.
Rabbits and rats are good examples of animals that are not likely to become extinct soon. They have high population density and a wide geographic distribution. In addition, they have high reproductive rates and are generalists that can live under a variety of conditions and use a variety of items as food. Conversely, the cheetah is much more likely to become extinct because it has a low population density, is restricted to certain parts of Africa, has low reproductive rates and is very specialized in its food habits. It must run down small antelope, in the open, during daylight, by itself. Similarly, the entire wild whooping crane species consists of about 130 individuals who are restricted to small winter and summer ranges that must have isolated marshes. (Captive and experimental populations bring the total number of about 200 individuals). In addition, the rate of reproduction is low.
Human are among the most successful organisms on the face of the earth. We are adaptable, intelligent animals with high reproductive rates of few enemies. As our population increases, we displace other kinds of organisms. This has resulted in an accelerated rate of extinction. Wherever humans become the dominant organisms, extinctions occur. Sometimes, we use other animals directly as food. In doing so, we reduce the population of our prey species. Since our population is so large and because we have an advanced technology, catching or killing other animals for food is relatively easy. In some cases, this has led to extinctions. The passenger pigeon in North America, the moas (giant birds) of New Zealand and the bison and wild cattle of Europe were certainly helped on their way to extinction by people who hunted them for food.
We use organisms for a variety of other purposes in addition to food: Many plants and animals are used as ornaments. Flowers are picked, animals skins are worn and animal parts are used for their purported aphrodisiac qualities. In the United States, many species of cactus are being severely reduced because people like to have them in their front yards. In other parts of the world, rhinoceros horn is used to make dagger handles or is powdered and sold as an aphrodisiac. Because some people are willing to pay huge amounts of money for these products, unscrupulous people are willing to take the chance of poaching these animals for the quick profit they can realize. These activities have already resulted in local extinctions of some plants and animals and may be a contributing factor to the future extinction of some species.Continued next issue.
Source (Extract from book, 'Environmental Science).
July
2003
By Staff Writer
At one time, a human being was just another consumer somewhere in the food chain. They fell prey to predators and died as a result of disease and accident just like other animals. The tools available to exploit their surroundings were primitive so these people did not have a long-term effect on their surroundings. Minerals and energy resources were only minimally exploited. Chert, obsidian, and raw copper were mined for the manufacture of tools and certain other mineral materials, such as salt, clay and other, were used as nutrients, for making pots or as pigments. Besides occasional use of surface seams of coal or surface oil seeps, most of the energy needs of early humans were filled by biomass.
As human populations grew, and as their tools and system of use became more advanced, the impact that a single human being could have on his or her surroundings increased tremendously. The use of fire was one of the first events that marked the capability of humans to change ecosystems. Although fires were also natural events in many ecosystems, the more frequent use of fire to capture game and to clear land for gardens returned climax communities to earlier successional stages more frequently than normal.
As technology advanced, wood was needed for fuel and building materials, land was cleared for farming, streams were dammed to provide water power and various mineral resources were exploited to provide energy and build machines. These modifications allowed larger human populations to survive, but always at the expense of previously existing ecosystems.
Today, with over 5.5 billion people on the earth, nearly all the surface of the planet has been affected in some way by human activity. Even the polar ice caps show the effects of human activity. Lead residues from the burning of leaded gasoline and various kinds of organic pollutants can be identified in the layers of ice that build up from the continuous accumulation of snow in these areas, (the amount of lead is currently decreasing because some countries have been making the transition from burning leaded fuel to using unleaded fuel in automobiles).
Historical basis of pollution:
Pollution is usually defined as something that people produce in large enough quantities that it interferes with our health or well-being. Two primary factors that contribute to damage done by pollution are the size of the human population and the development of technology that 'invents' new forms of pollution.
When the human population was small and people lived in a primitive manner, the wastes produced were biological and so dilute that they often did not constitute a pollution problem. People used what was naturally available and did not manufacture many products. Human beings like any other animal, fit into their natural ecosystems. Their waste products were biodegradable materials. Biodegradable materials are a source of food for decomposers, the organisms that break the material down into simpler chemicals, such as water and carbon dioxide.
Pollution began when human populations became so concentrated that their waste materials could not be broken down as fast as they were produced. As the human population increased, people began to congregate and establish cities. The release of large amounts of smoke and other forms of waste into the air caused an unhealthy condition because the pollutants were released faster than they could be absorbed by the atmosphere.
Throughout history, there have been numerous attempts to eliminate the misery caused by hunger and disease. In general, we rely on science and technology to improve the quality of life. However, technological progress often offers a short-term solution to a specific problem but in the process can create an additional pollution problem.
The development of the steam engine allowed for machines to replace human labour, but increased the amount of smoke and other pollutants in the air. The modern chemical industry has produced many extremely valuable synthetic materials (plastics, pesticides, medicines) but has also produced toxic pollutants.
Even identifying an example of pollution is not always easy. To some the smell of a little wood smoke in the air is a pleasant experience: others are upset by the oduor. A businessman may consider advertising signs valuable and necessary; others consider them to be visual pollution. Even the presence of chemicals in drinking water can be difficult to classify as a clear-cut example of pollution. For example, a small town discovered traces of arsenic in its ground water supply. Toxic heavy metals such as arsenic certainly should be considered hazardous, but we do not know how much arsenic contamination is allowable before harm occurs. Are the small quantities of arsenic in groundwater great enough that, over a period of time, they accumulate and cause damage of individuals in the populations? Will children with smaller body masses be more affected than adults? Is the arsenic a normal part of the groundwater, or is it the result of the heavy spraying of arsenic-containing pesticides on apple trees in the past?
Certainly, if the arsenic is the result of human activity and is causing health problems, it is a pollutant. If it is a natural part of the groundwater, it may still be a health hazard to be dealt with but would technically not be a pollutant.Source: (Extract from a book 'Environmental Science')
Feature
Importance of recreational activities in urban areas outlined
By Jacob Kambili
Recreation seems to be a basic human need. The most primitive tribes and cultures all had games or recreational activities. New forms of recreation are continually being developed. In the congested urban centre, special areas where recreation can take place often must be constructed.
A major problem with urban recreation is the development of recreational activities and facilities conveniently located near the residential areas. Areas that are not conveniently located may be only infrequently used.
Large urban centres are discovering that they must provide adequate, low-cost recreational opportunities within their jurisdiction. Some of these opportunities are provided in the form of commercial establishments, such as bowling centres, amusement parks and theatres. Others must be subsidized by the community. Playgrounds, organized recreational activities and open space have usually been combined into an arm of the municipal government known as the Parks and Recreation Department. Cities spend millions of money to develop and maintain recreation programmes. Often, there is conflict over the allocation of financial and land resources. These are very closely tied because open land is scarce in urban areas, and it is expensive. Riverfront property is ideal for park and recreational use, but it is also prime land for the development of industrial, commercial or high-rise residential buildings. Although conflict is inevitable, many metropolitan areas are beginning to see that recreational resources may be as important as economic growth for maintaining a healthy community.
An outgrowth of the trend toward urbanization is the development of nature centres. In many urban areas, there is so little natural area left that the people who live there need to be given an opportunity to learn about nature. Nature centres are basically teaching institutions that provide a variety of methods for people to learn about and appreciate the natural world. Zoos, botanical gardens and some urban parks, combined with interpretative centres, also provide recreational experiences. Nature centres are usually located near urban centres, in places where some appreciation of the natural processes and phenomena can be developed. In some cases, they are operated by municipal governments. In others cases, they may be run by schools systems or other nonprofit organizations.
Outdoor Recreation:
Not all people enjoy the same recreation. Some people enjoy reading or watching television. Others prefer commercial recreational activities, such as golf, tennis, bowling, amusement areas, race tracks and skiing. Another major area of reaction, usually classified as outdoor recreation, involves using the natural out-of-doors for hiking, camping, canoeing and so forth. Millions of people want to use public lands for these activities.
Most recreational activities require the consumption of natural resources such as mineral, fuels and timber. Some activities require more resources than others, but even the backpacker, who has traditionally been considered an ecologically frugal individual, requires considerable equipment. Other activities, such as the use of off-road vehicles, require even more resources in the form of equipment and fuel. As energy and other resources become less available, we may be forced to abandon some of our more extravagant recreational activities for those that are more ecologically conservative.
Conflicts over recreational land use:
Many people desire to use the natural world for recreational purposes because nature can provide challenges that may be lacking in their day-to-day lives. Whether the challenge is hiking in the wilderness, underwater exploration, climbing mountains or driving a vehicle through an area that has no roads, people experience a sense of adventure from these activities.
All of these activities use the out-of-doors, but not in the same way. Conflicts develop because some of these activities cannot occur in the same place at the same time. For example, wilderness camping and backpacking often conflict with off-road vehicles.
There is a basic conflict between those who prefer to use motorized vehicles and those who prefer to use muscle power in their recreational pursuits. This conflict is particularly strong because both groups would like to use the same publicly owned land for their activities. Both have paid taxes, both "own" the land, and both feel that it should be available for them to use as they wish. When everyone "owns" something, there is often little desire to regulate activities.Source: (Extract from a book, 'Environmental Science')