1.0 Eutrophication1.1 IntroductionEutrophication, is theartificial enrichment of a water body or aquatic system with phosphorus andnitrogen nutrients, usually with an excess amount of nutrients. This processcause an excessive growth of plants and algae and due to the biomass load, mayresult in oxygen depletion of the water body.
For example, as aresponse to increased levels of nutrients, there is a great increase of phytoplankton whichis called algal bloom occurs in the water body .Thenutrients can be come from the animal wastes, fertilizers that are often usedin farming and sewage which are washed by rain or irrigation into the waterbodies through surface runoff. This willincrease the nutrient level and contribute to eutrophication. Eutrophicationcan be divided into cultural eutrophication which is caused by human activityand natural eutrophication which is a natural process. Culturaleutrophication is the process that speeds up natural eutrophication because ofhuman activity. Due to clearing of land and building of towns andcities, land runoff is accelerated and more nutrients such as phosphates and nitrate are supplied to lakesand rivers, and then to coastal estuaries and bays. Extranutrients are also supplied by treatment plants, golf courses, fertilizers,farms and untreated sewage in manycountries. Natural eutrophication is a natural process.
Eutrophication occurs in many lakes in temperate grasslands. Paleo limnologists nowrecognise that climate change, geology, and other external influences arecritical in regulating the natural productivity of lakes. Some lakes also demonstratethe reverse process, becoming less nutrient rich with time. The main differencebetween natural and anthropogenic eutrophication is that the natural process isvery slow, occurring on geological time scales. 1.2 Why it happens ? Eutrophication is mainly caused by human action due to their dependenceon using fertilizers. Agricultural practices and the use of fertilizers onlawns, golf courses and other fields contribute to phosphate and nitratenutrient accumulation.
When the concentration of nutrients increases until theground is no longer able to assimilate them, the nutrients are carried by raininto rivers and groundwater that flow into lakes or seas. The plankton, algaeand other aquatic plant life are then well fed and their photosynthesisactivity is increased. They grow and reproduce more rapidly, resulting in densegrowth of algal blooms and plant life. This will disrupt the normal ecosystemfunctioning and causes many problems. (Referappendice-1) On the other hand, eutrophication can be caused by the input ofuntreated sewage as well as discharge from sewage treatment plants.
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We can seethat the sewage water is directlydischarged into water bodies such as rivers, lakes and oceans in variousparts of the world, especiallythe developing nations. The result of this is the released of a highquantity of chemical nutrients whichstimulates the disproportionate growth of algae and other aquatic plants that threatens the survivalof aquatic life in many ways. Some countries may also treat the sewage water,but still discharge it into water bodies after treatment. Although the water istreated, but it can still cause the accumulation of excess nutrients and leadto eutrophication. (Refer appendice-1) Besidesthat, it is also caused by aquiculture.
Aquiculture is a technique of growing shellfish, fish and evenaquatic plants in water containing dissolved nutrients. Hence, the unconsumedfood particles together with the fish excretion can significantly increase thelevels of nitrogen and phosphorous in the water if aquiculture is not properlymanaged. This will results in the dense growth of microscopic floating plants. Lastly, eutrophication may be caused by natural event such as floods andthe natural flow of rivers and streams. The excess nutrients will be washed offfrom the land and flow into the water systems that causes the excessive growthof algal blooms. Also, as lakes grow old, they naturally accumulate sediments suchas phosphorus and nitrogen nutrients which contribute to the explosive growthof phytoplankton and cyanobacterial blooms.1.3 How it happens ? Firstly, the excess nutrients are applied to the soil.
Then, they getdrained into the ponds, lakes, or rivers. This encourages the rapid growth ofphotosynthesising organisms, especially algae. This results in a populationexplosion known as algal bloom. The algal bloom blocks the light of the sunfrom reaching the bottom of the water body. As a result, the aquatic plantsbeneath the algal bloom die because they cannot get sunlight to photosynthesizeand this further decreases the supply of oxygen in water. Eventually, the algalbloom dies and sinks to the bottom of the lake, decomposing microorganisms,especially aerobic bacteria, grow rapidly and use up oxygen for respiration atfast rate. The aerobic bacteria use up oxygen faster than it can bereplenished. This cause the biochemical oxygen demand (BOD) to increaseresulting in the depletion of oxygen in water.
Due to the lower level of oxygenconcentrations, the larger life forms, such as fish, suffocate are not able to survive.In extreme cases, if the oxygen level continue to drop until the water becomecompletely deoxygenated, aerobic bacteria will growth and releases toxic gasesthat are harmful to aquatic life. This body of water can no longer support lifeand this process is called eutrophication. (Referappendices-2) 1.4 Effectsof eutrophication with some examples For aquatic plants, they need twoessential nutrients togrow such as nitrogen (N) and phosphorus (P). In a healthy lake, thebiochemical oxygen demand (BOD) must be low which indicates the better waterquality and the nutrients must occur in small amounts for the survival ofaquatic plants. Inversely, major water pollution problemwill results if the nutrients are in large quantities.
Too many nutrients willstimulate the rapid growth of plants and algae, clogging waterways andsometimes creating a serious algal bloom. If the situation happens, thesurvival of fish and other aquatic life forms will be threaten. The algal blooms that caused by theexcessive nutrients in the water body will limit the amount of dissolved oxygenrequired for respiration by the aquatic life forms. When the algae and aquaticplants die and decompose, it will encourage the growth of detritus and oxygen depletionhappens. When the dissolve oxygen reaches hypoxic levels, the animal and plantspecies under the water such as shrimp, fish and other aquatic biota suffocatewill die. In extreme cases, the anaerobic conditions encourage the growth ofbacteria that produces toxins which are deadly to the marine mammals and birds.The growth of phytoplankton also causes the light penetration into the water tobe reduced. This can bring about aquatic dead zones, loss of aquatic life andit also lessens biodiversity.
(Refer appendices-3) Furthermore, it results in the deteriorationof water quality and limited access to safe drinking water. This is because algal blooms are highlytoxic and once the water reaches the anaerobic conditions, the growth of moretoxic bacterial is promoted. Extensive deterioration of water quality and decline in theavailability of clean drinking water will be the consequence.
Due to the densegrowth of algal blooms and photosynthetic bacteria in surface waters, the watersystems will be blocked and thus availability of piped water become limited. Onthis regard, toxic algal blooms have shut down numerous water supply systemsacross the globe. For example, in 2007, more than 2 million residents of Wuxi,China could not access piped drinking water for more than a week due to severeattack by algal blooms on Lake Taihu.
(Refer appendices-4) Moreover,it is poisoning which will causeseveral negative impact on human health and animalwhen ingested the water in drinking water. Even at very low concentrations, the cyanobacteriawhich generates red tide will release very powerful toxins with high poisonlevels in the water. Besides that, the toxic compound is doubled by the anaerobicconditions which created by the explosive plant growth in the water. It isharmful to humans and animals even at the least concentration when ingested indrinking water. In addition, algal blooms can threaten livestock health. Forexample, the first recorded incidence of animal poisoning from a blue–greenalgal bloom was in Lake Alexandrina , Australia in the late 1800s. (Refer appendice-5) Cattle, horses, pigs, sheep anddogs died after drinking water covered by a scum of the blue–green algae. The majorcause of deaths in animals is from liver poisoning and neurotoxicity that leadsto respiratory failure.
This is because the toxic compounds can make their wayup the food chain, contributing to various negative health impacts such ascancers. The shellfish accumulate the poison in their muscles and then poisonshumans upon consumption. Other than that, high nitrogen concentration indrinking water will have negative effects on infants. For example, the infant will suffer blue baby syndrome. This isbecause the drinking water with high nitrogen concentration is associated with theability of inhibiting blood circulation in infants. Hence, the baby will takeson a bluish hue because of poorly oxygenated blood resulting in blue babysyndrome.
Lastly, it endangers fishing. This is due to the increasedgrowth of floating plants such as algae and photosyntheticbacteria which is the obstacle that limits the movement of boat to a locationand the fishing vessels. We will also have some difficulties to set the fishingnets in water because of the accumulation of floating plants on the surface ofwater. 1.5 Solutions for eutrophication Eutrophication mainly arises from the use of nitrate and phosphate fertilizers. Hence, composting can be the effective solutionfor eutrophication. This is because composting is a substitute for fertilizers.It is a practice of converting organic mattersuch as food residues and decaying vegetation into compost manure.
Nutrients inthe compost manure do not contain the phosphorus and nitrates that cause algaeto bloom, so when there is run-off, it does not harm the quality of water. Incompost fertilizer, all the essential elements are broken down and synthesizedby the plants thereby not creating the cycle of eutrophication. This method ofcontrolling eutrophication is termed as nutrient limitation. (Refer appendices-6) Other than that, limiting pollution is an easy and effective method of cutting back on the amount of nitrogen andphosphates discharged into water systems. Big manufacturing companies andmunicipalities ought to reduce pollution and desist from discharging waste intowater systems to reduce the amount of toxins and nutrients ending up in thewaters that feed the algae and other microscopic organisms. If industries andmunicipalities can cap their waste discharge and pollution to a lower level, then nutrient content is reducedin the water systems which can subsequently control eutrophication. Last but not least, strengthening laws andregulations against non-point water source pollution is also a solution that can substantially control eutrophication.
The amount of nutrients entering the aquatic ecosystems can essentiallylessening by minimizing non-point pollution. The laws should aim at enhancinghigh water quality standards and zero-tolerance to non-point solution. With thesupport of policymakers, citizens, pollution regulatory authorities and thegovernment, it is easy to control eutrophication.2.0 Deforestation2.
1 IntroductionDeforestationis the thinning or clearing of a forest or stand of trees. (Refer appendice-7) Deforestation is done by humanwhere the land is then used for agriculture and development. Forexamples, the forestland or woodlands is converted to farms, ranches,or urban use. Recent and present deforestation mainlyoccurs in tropical rainforests.About 30% of Earth’s land surface is covered by forests. Moreover,deforestation on a major scale had been occurring in both developed and developingcountries since about 1700 when it is estimated that forests covered as much as4.
5 billion hectares of the planet. If this estimation is correct, total forestcover has declined by about 1.0 billion heactares or 23% during last 300 years.During war, deforestation has been used to deprive the enemy of vital resources andcover for its forces. Modern examples of this were the use of Agent Orange by the British military in Malaya during the Malayan Emergency and the United States military in Vietnamduring the Vietnam War.As of 2005, net deforestation rates have ceased to increase in countries with aper capita GDP ofat least US$4,600. Deforested regions typically incursignificant adverse soil erosion andfrequently degrade into wasteland.
The problem of deforestation is becomemore serious from years to years. According to the United Nations’ Food andAgriculture Organization (FAO), an estimated 18 million acres (7.3 millionhectares) of forest, which is roughly the size of the country of Panama, arelost each year. Besides, about half of the world’s tropical forests havebeen cleared. On the other hand, according to the research, about 30% of theworld’s land mass can be found to be covered by the forests. Recently, forestloss has contributed between 6% and 12% of annual global. Furthermore, World Wildlife Fund (WWF) found that about 36football fields worth of trees lost every minute. 2.
2 Causes ofdeforestation Thereare various factors that can caused deforestation. First of all, deforestationcan be caused by agriculture activities (Refer appendices-8). Amajor cause of deforestation is agriculture plantations.
Due to the increasingpopulations, the demand for food products such as soybeans and palm oilincreases dramatically. This causes a large quantity of trees or forests arecleared at an unnerving rate to grow crops and for cattle. In some extremesituation, the farmers will clear a forest area until the soil is completelydegraded and then move to a new woodland to continue the process. The abandonedland, will eventually reforest but it will take many years to return to itsoriginal condition. Next, mining also results in deforestation(Refer appendices-9). Deforestation occurs in BrazilianAmazon particularly since the 1980s with miners oftenclearing forest to open the mines (Referappendice-10).
This requireconsiderable amount of woodlands. They often use them for building material,collecting wood for fuel and subsistence agriculture. In addition, due to therising demand and high mineral prices, mining on tropical forests increases. These projects areoften accompanied by large infrastructure construction, such as roads,railways, and power systems.Thewaste that comes out from mining pollutes the environment and affects the nearbyspecies.
Lastly, logging is also contributed todeforestation (Refer appendice-11). Logging is the process ofcutting and processing trees to produce timber and pulp tosupply the world’s markets for furniture, construction, paper, andother products. Wood-based industries such as paper,matchsticks, and furniture need a large quantity of wood. Cooking and heatingprocess required coal and lumber which can used as fuel for burning and half ofthe illegal removal from forests is used as fuelwood.
Large areas of forestswill be cleared to construct roads for the large trucks to enter the loggingsites. Logging is important toregional economies and rural communities. However, if it is not managedproperly, it can contribute to deforestation and forest degradation. 2.3 Effects of deforestation with examples One of the devastating effect that caused bydeforestation is the loss of animal and plant species due to the loss of theirhabitat. Most of the animals and plants live in forest and manycannot survive and caused the removal of the bases of numerous food webs.
Thetrees of the rainforest provide shelter for the species and provide canopy thatregulates the temperature. However, deforestation thins theforest canopy which is meant to block sun rays during the day and holds in theheat at night. This will lead to extreme condition.
In conclusion, animals andplants will began to extinct due to the loss of their habitat and extremetemperature that are harmful to them. For example, Indonesia and Malaysia produce more than 85% of the world’spalm oil and are the only remaining home to orangutans. Fewer than 80,000 ofthese animals survive today, their habitats under constant threat of deforestation.Apart from that, trees areimportant in absorbing greenhouse gases that fuel global warming. If the treesare cut, burned or removed, the amount of trees will reduced which means largeramounts of greenhouse gases entering the atmosphere. It is foundthat deforestation is responsible for around 20% of greenhousegas emissions and 1.5 billion tons of carbon is released every year by tropicaldeforestation.
Hence, deforestation can cause the increased of greenhouse gas emissions.Furthermore,deforestation can cause landslides, soil erosion, and flash floods. Without aproper planning and development, a land stripped of its vegetations is subjectto soil erosion. This is because the trees are used to retain water andtopsoil, if there are noplant root systems, it will cause the soil structure become unstable. Whenthere are heavy rains for a long period of time, the soil will crumble andwashes away. This leads to landslide on steep hillsides. (Refer appendices-12)Then, the eroded soil is carried by the flow of the waterto the river and deposited in the bottom of river. If this continue for tohappen, the water catchment areas will deplete and causes flash floods duringrainy seasons.
Ina nutshell, deforestation disrupts the normal weather patterns, creatinghotter, drier weather and causing the change in climate. The removal of treesreduced respiration, rainfall and the rate at which plants absorb carbondioxide from atmosphere during photosynthesis. This leads to an increase in theconcentration of carbon dioxide in the atmosphere. This will prevent heat fromescaping from the atmosphere. Burning of trees normally adds around 25% morecarbon dioxide to the atmosphere.
