• UNIT 3: EFFECT OF HUMAN ACTIVITIES ON ECOSYSTEM

    Key Unit Competence Evaluate the effects of human population size, resource use, and technology on environmental quality.

    Learning objectives

     – Explain how modern agricultural technology has resulted in increased food production

     – Explain the negative impacts to an ecosystem of large scale monoculture of crop plants

     – Explain the reasons for habitat destruction (agriculture and extraction of natural resources) 

    – Explain the undesirable effects of habitat destruction

     – Explain the sources and effects of the pollution of air, water and land 

    – Explain the causes and effects of acid rain, eutrophication and nonbiodegradable plastics – Explain the main methods of the conservation of resources

     – Describe an example of conservation in action

     – Assess the negative impacts to an ecosystem of intensive livestock production

     – Conduct shows and dramas on wildlife conservation

     – Research the effects of the excessive use of fertilisers on the environment

     – Assess the different methods of the conservation of nature

     – Carry out a research project on recycling sewage

     – Carry out research on the African species endangered by human activity 

    – Evaluate the reasons for conserving wildlife

     – Demonstrate ways of reducing pollution and protecting the environment

     – Organise clubs focused on environmental and wildlife protection

     – Suggest ways in which one could take positive action to help conserve biological resources

     – Appreciate the balance between society, environment and the economy 

    – Recognise that extinction is a natural part of the evolution of life on earth but has taken place in an unprecedented rate, mainly as a result of human activities

     – Support the Rwandan government policy of protecting the environment

     – Adapt regulations designed to prevent overfishing into action

    The increase in human population size causes changes in natural ecosystems. Intentionally and unknowingly, human activities on Earth have negative impacts for all kind of life form of an ecosystem. This unit intends to describe different human activities on the Earth’s natural ecosystems and their effects. It also informs different biodiversity conservation methods and indicates how disturbed ecosystems can be restored. It raises the awareness towards the restoration of degraded environments as well as biological conservation. 

    3.1 Modern agricultural technologies for food production

    The increased population size brought changes in different sectors of any country including agriculture, one of the most human activities that is practiced on ecosystem for increasing food supply. Currently, agriculture is practiced with advancement in science and technology where contemporary farming methods were invented and adopted mostly in monoculture and intensive farming. Modern agriculture is named mechanized agriculture or mechanized faming. It uses different equipment including; tractors, trucks, sprayers, harvesters, aeroplanes and helicopters depending to their manufactured purposes. It even uses computers in junction with satellite imagery among others for easy and effective management and monitoring of land and crops. 

    The agricultural equipments are used in all process of farming starting from preparing the land to crop storage. Beside efficient production, mechanisation encourages large-scale production and sometimes it can improve the quality of the land. Despite their role in increasing food production, mechanized farming intentionally or due to unskilled farm labour and awareness harms the soil, biodiversity, water and air.

    Apart from farming machineries, there are chemical fertilisers that are used on farm land to boost levels of soil nutrients needed by plants for growing faster and producing more food. Some of the most used fertilisers are nitrogen, phosphorus, and potassium or a combination of them. Use of fertilizers is expensive and improper use can harm the environment. If too little is added, crops will not produce as much as they should. If too much is added, or applied at the wrong time, excess nutrients will run off the fields and pollute streams and groundwater. These are the reasons why the right amount chemical fertilizers have to be used at the right time, to avoid potential negative effects to the environment.

    Modern agriculture uses also pesticides which are organic compounds or substances. They include; insecticides, herbicides and fungicides, used with the purpose of killing unwanted plants, insects or fungi which might harm the plants. Utilization of pesticides escalate food production in case of their effective use.  However, some of the pesticides present negative effects on the environment. Examples include the 3, 5, 6-Trichloro-2-pyridinyloxyacetic acid which inhibits soil bacteria that transform ammonia into nitrite, Glyphosate (C3H8NO5P) which reduces the growth and activity of free-living nitrogen-fixing bacteria in soil, and oryzalin and trifluralin which inhibits the growth of certain species of mycorrhizal fungi. Insecticides can contaminate non-targeted organisms including; insects, fish, or plants through the spray onto eroding soil or when heavy rain falls right after an application.
     
    The last but not the least among the modern agricultural technologies is the selective breeding also called artificial selection. It is used in order to produce varieties of plants or animals having phenotypic traits suitable to a particular area and of high productivity. It allows natural evolutionary process, eliminates diseases, influencing the production of food coming from plants in a positive way, giving to plants the ability to grow on lands that are previously not suitable for farming, sustainability of food chain, creation of higher-quality products, and contributes to the availability of animals and plants that produce higher yields.

    3.2 Impacts of human activities on ecosystem


    3.2.1. Negative impacts of large scale monoculture on ecosystem

    Intensive cropping practices and its impacts on ecosystem

    A key component of agricultural intensification is monoculture, the cultivation of a single crop species in a given area. Unlike traditional polyculture (which mix crop varieties or intersperse crops with trees or domesticated animals), monoculture allows farmers to specialize in crops that have similar growing and maintenance requirements. Monoculture is increasingly adopted by farmers to achieve higher yields through economies of scale. However, monoculture may negatively impact biodiversity, soil, water and air.

    a. Impacts on Biodiversity

    By reducing natural plant biodiversity to include only one crop, monoculture affects the composition and abundance of associated biodiversity. For example, the balance of plant pests and their natural enemies that may exist in polyculture fields can be disrupted in monoculture systems, which provide habitat for a narrower range of insects. Populations of; bees, flies, moths, bats, and birds, which provide important pollinating and pest pressure services to crops, also tend to be lower in monocultures than in fields containing diverse forage and nesting sites.

    b. Impact on soils

    Continuous cropping impacts soils properties whereby soil fertility declines as consecutive crop cycles reduce the amount of nutrients from soils. As plants grow, they absorb nutrients from the soil such as nitrogen, phosphorous, potassium, and calcium. Harvesting crops is another mechanism contributing to the removal of these nutrients from the soil. In addition, when monoculture is continuously applied in the same area, it affects soil organisms due to soil pesticides. Natural soil properties including aeration and water infiltration might be affected due to the loss of soil organisms that increase these soil properties and hence soil fertility.

    In addition, due to population pressure and land scarcity, farmers in some areas are increasingly adopting intensive cultivation methods on hillside areas characterised by steep slopes with the soils often inherently poor quality. As rainfall hits loose or unprotected soil on cultivated sloping land, soils erode and carry away sediments and nutrients. The resulting redistribution of nutrients may leave upward sloping soils less fertile than lower areas, and fertilizers or other chemical particles in run-off may negatively impact aquatic ecosystems and water quality.

    c. Greenhouse effects

    Tillage as one of the practice in continuous cropping, impacts on greenhouse emissions whereby increases carbon dioxide (CO2) emissions by causing decomposition of soil organic matter (SOM) and soil erosion. Intensive tillage practices also emit CO2, a greenhouse gas that contributes to climate change. Mechanical tillage release CO2 and stimulates CO2 emissions by enhancing decomposition of soil organic matter. The tendency for tillage to increase erosion also contributes to CO2 emissions. A large percentage of soil carbon particles carried by erosion are emitted into the atmosphere as CO2 rather than buried and sequestered in deposit sites.

    Intensive livestock farming and its impacts on ecosystem

    Livestock play an important role in agricultural systems. Cattle, sheep, and goats can provide manure for soil fertilization and a diversified source of food and income generation. Traditional livestock management involves mixing animals and crops on the same farm or grazing livestock on grasslands.Intensive livestock systems exacerbate the impacts that livestock activities have on the environment, including effects on soil conditions, biodiversity, water quality and quantity, and greenhouse gas emissions.

    a. Impacts on Soils

    Increased animal stocking rates puts pressure on grazing lands, leading in some cases to soil compaction, erosion, grasslands degradation, and desertification in semi-arid areas. Concentrated “hoof action” compacts wet soils, making them less able to absorb water and more prone or more likely to run-off and erosion. Livestock grazing between land and streams can destabilize stream banks and release large amounts of sediment into fragile aquatic ecosystems. Additionally, high rates of nitrogen contained in bovines’ manures can lead to topsoil acidification.

    b. Impacts on Biodiversity

    Intensive grazing impacts biodiversity in several ways. Populations of birds, rodents, and other wildlife that depend on grasslands for food and habitat may decline as livestock densities increase. In addition, intensive grazing often involves reseeding natural meadows, resulting in a loss of native grassland plants. Higher rates of organic or inorganic fertilizer application typically accompany reseeding, which may degrade water quality through nitrogen or phosphorous leaching. Nutrient contamination in water bodies reduces oxygen levels and harms fish and plant populations.

    Leaching of nitrogen and other fertilizer nutrients into fresh and saltwater environments can lead to a state of eutrophication (overabundant nutrient concentrations), resulting in increased algae blooms and oxygen depletion. Thus, dead zones may develop in these areas, whereby decreased oxygen levels dramatically reduce fish populations and species diversity.

    c. Impacts on water quality and quantity

    Untreated livestock waste causes high nutrient concentrations in water bodies, also known as eutrophication. Untreated livestock waste can significantly impact water quality. Livestock manure contains high amounts of nitrogen, phosphorous, and potassium and may enter water directly when livestock graze near streams or indirectly through run-off or percolation into groundwater. Confined livestock systems present high risks of water pollution due to difficulties containing and treating large quantities of manure. Degraded water quality may also pose health risks to humans who rely on water for drinking and household uses.

    d. Impacts on greenhouse gas emissions

    Enteric fermentation and livestock manure are significant sources of methane (CH4) and nitrous oxide (N2O) greenhouse gases emissions. Ruminant livestock such as cattle and sheep release CH4 during enteric fermentation and the microbial digestion of fibrous plants. Animal manure emits N2O and CH4 during storage and after application to croplands or grazing areas. Additional activities related to raising livestock are responsible for emissions such as releases of CO2 in producing fertilizer for grazing lands and animal feed, N2O emissions from applying fertilizer, and CO2 emissions from overgrazing and land degradation.

    e. Impacts on air quality

    Nitric gas contributes to smog, ozone, and acid rain. During the microbial processes of nitrification and denitrification that take place in fertilized soils, nitric gas is released. Nitric emissions impact local and regional air quality by contributing to the formation of smog, ozone, and acid rain.

    Fishing and their impacts on the ecosystem 

    Techniques for catching fish include hand gathering, spearing, and netting, angling and trapping. It is normally done in fish farms including ponds, rivers, lakes, seas, oceans where fish are raised commercially. With the advancement in technology, rearing of aquatic animals is known as “aquaculture” aiming at producing more aquatic food due to the drastic increase of the population. Despite the significance of fish farming and harvesting technologies, fisheries are in danger of collapsing, due to overfishing and pollution.

    Fishing nets called ghost nets used by fishermen are sometimes left or lost in oceans whereby they can entangle fish, dolphins, sea turtles, sharks, dugong,crocodiles, seabirds, crabs, and others. These living things are restricted from movement which led to laceration (cut in skin), infection, starvation and suffocation sometimes causing the death. Other effects include overfishing which is a form of overexploitation where fish stocks are reduced to below accepted levels. It can result in resource depletion, reduced biological growth rates and low biomass levels. Since organisms ecologically depend each other, overfishing of one species decreases the presence of other species and favour the invasive species. For example, with the shark population reduced, in some sea places almost totally, the rays have been free to dine on scallops to the point of greatly decreasing their numbers.  Since then, a variety of sharks have fed on rays, which are the main predator of scallops.

    Deforestation and its effects on ecosystem

    Deforestation is the permanent clearing or removal of trees and undergrowth. Deforestation happened in the past and continues extensively today particularly in tropical area. The forests are cut mostly for mainly searching agricultural land. In Rwanda like elsewhere, deforestation was driven by the need for food, charcoal, and timber, especially for commercial products. Worldwide agriculture continues to be the main cause of the loss of natural forests. Other reasons include supplying firewood as fuel, constructing houses, industrial buildings, roads, and dams, removal of trees for pulp and paper, cutting trees for timber used in the construction industry, replacement of native trees with fast growing species such as conifers, eucalyptus, and rubber trees.

    a. Effects of deforestation on biodiversity

    Deforestation has the dramatic effect on biodiversity particularly in tropical rainforests. Complete replacement of native plantations with introduced species or keeping only a few native species, leads to a reduction in biodiversity. Organisms are being driven to extinction by the loss of their suitable habitat. In tropical rainforest, attention should be paid to species with great human value including medicines, where forest plant products are used as anticoagulants, tranquillisers, and antibiotics.

    b. Effect of deforestation on nutrients cycles

    Deforestation is contributing to an increase in carbon dioxide due to the removal of forests which actually use this gas for photosynthesis. Forests burning release huge amounts of carbon dioxide directly and very quickly into the atmosphere and is probably a major contributor to rising carbon dioxide levels.  Burning trees was also found to significantly reduce the nitrogen held in the ecosystem. In addition, tree roots bind soil particles together, and tree canopy prevents rain beating down on the soil. Deforestation therefore causes nutrients to be lost through leaching and runoff.

    c. Desertification

    Deforestation is also one of the process speeded by deforestation even though some scientists believed that it was caused mainly by climatic changes. Deforestation disrupts water cycle and soil structure. Reduction in tree cover means reduced transpiration, few clouds, and less rain fall in the area. Removing trees increases the risk of flooding following heavy rains. Agricultural land becomes heavily populated, it is likely to be over cultivated or overgrazed, and the soil will be less fertile and more easily eroded during periods of droughts.

    Mining and industrialization

    a. Effects of Mining on the Ecosystem

    Mining as one of economic activity applied on natural ecosystem plays an important role to humans. It is at the same time affecting environmental ecosystem through soil compaction, lowering overall soil fertility, erosion, soil pollution and minimizing the availability of nitrogen and phosphorus. Soil compaction is one of the most severe effects mining has on ecosystems and it is often the result of large machines. As the soil is compacted, there are fewer pore spaces for oxygen and water to move through the soil profile, minimizing the potential for plant establishment. Mining operations often contaminate the soil with toxic heavy metals and acids, preventing plants and soil micro-organisms from thriving

    b. Effects of industrialization on ecosystem

    Industrialization contributes for the nation economic development and prosperity by providing employment opportunities and generating wealth. It is also one of the human activity that negatively deteriorates ecosystems. The major negative effects of industrialisation include depletion or reduction of natural resources, air, water and soil pollution, global warming and climatic changes. Industrialization expose living organisms to acid rain and it is among the major causes of land degradation. Thus poor land quality, and issues generated by hazardous waste lead to some diseases including silicosis and pneumoconiosis, tuberculosis, skin diseases and deafness.

    By metallic contaminant like Cd, Zn, Hg, radioactive industrial pollutant bacteria and beneficial micro-organisms in the soil are exposed to death.  There is also a number of undesirable effects caused by toxins from industrial wastes that enter in the food chain. Moreover, industrial effluent damages the natural biological purification mechanism of sewage treatment causing several soil and water borne diseases.

    3.3 Pollution


    Pollution refers to the introduction of substances or energies into the natural environment that cause adverse change. A pollutant may be physical (for example; noise, heat, and other form of radiation), chemical (such as heavy metals in industrial wastes), or biological (sewage for example). A pollutant may be a substance of natural origin present in excess (such as a volcanic dust or particles of sea salt)), but the term is more used often used to describe changes brought about by human activities such as the emission of industrial pollutants, or the discharge of domestic wastes. The pollutant can be in any part of the biosphere: in air, land, or water.

    Air pollution and its effect on the ecosystem

    Air pollutant can be in form of gases (such as carbon monoxide from car exhausts), or aerosols (soil or liquid particles suspended in the atmosphere). Pollutants have many and different effects on the health of humans and other organisms, as well as on the natural and built environments. Oxides of nitrogen and sulphur emitted as industrial gases can form acid precipitation. Some pollutants can cause the greenhouse effect as well as ozone depletion.

    a. Greenhouse effect

    Solar energy reaches the Earth in the form of short-wave radiation. When the radiation strikes a surface, much of its energy is converted into heat, a form of radiation which has a long wavelength. CO2, H2O vapour, and other gases present in the atmosphere absorb and retain long wave radiation or reflect it back toward the surface of the earth.  These gases therefore act like panes of glass in a greenhouse, letting light in, but retaining some of the heat before it escapes into space, hence the term greenhouse effect.

    The retention of heat by the greenhouse effect is a natural process, essential for the evolution of life on the earth. It has been calculated that without it, average surface temperatures would be between -17 and -230C; the actual average surface temperature being +150C. However, the greenhouse effect appears to be increased by emission of certain industrial gases, called greenhouse gases, the most important being carbon dioxide, water vapours, chlorofluorocarbons, methane, and ozone.

    b. Global warming

    The increase in the concentration of greenhouse gases in the atmosphere cause a rise in global temperatures, and hence could bring about changes in climate. The global warming was detected to rise the sea levels, increase melting of ice, cause changes in vegetation, and contributes to unusual weather patterns.

    c. Acid precipitation


    The burning of wood and fossil fuels, including coal and oil, releases oxides of sulphur and nitrogen that react with water in the atmosphere, forming sulphuric and nitric acid, respectively and forming acid precipitation or rain, snow, sleet, or fog that has a pH less than 5.2. Acid precipitation lowers the pH of streams and lakes and affects soil chemistry and nutrient availability.

    d. Depletion of Atmospheric Ozone

    Life on Earth is protected from the damaging effects of ultraviolet (UV) radiation by a layer of atmospheric ozone (O3) layer located in the stratosphere, around 17–25 km above Earth’s surface. Like carbon dioxide and other greenhouse gases, ozone has also changed in concentration because of human activities. The destruction of atmospheric ozone results primarily from the accumulation of chlorofluorocarbons (CFCs) widely used in refrigeration and manufacturing. In the stratosphere, chlorine atoms released from CFCs react with ozone, reducing it to molecular O2. Subsequent chemical reactions liberate the chlorine, allowing it to react with other ozone molecules in a catalytic chain reaction.

    The decrease of ozone thickness in the stratosphere increase the intensity of ultraviolet (UV) rays reaching Earth’s surface. The consequences of ozone depletion for life on Earth may be severe for plants, animals, and microorganisms. Some scientists expect increases in both lethal and nonlethal forms of skin cancer and in cataracts among humans, as well as unpredictable effects on crops and natural communities, especially the phytoplankton that are responsible for a large proportion of Earth’s primary production. The most severe consequence of ozone depletion is DNA damage which could occur if ozone layer is continually destroyed or when filters to decrease or block the UV radiation in sunlight are not used as ecologists reported based on their experiments using filters

    Water pollution and its effects

    The source of pollution may be industrial, domestic, or agricultural, and the pollutant maybe thermal, chemical or nuclear.

    In many industries, water is used as a coolant. Excess heat is discharged into a nearby waterway, causing thermal pollution. Discharges from power stations, for example, may raise the temperature of rivers and estuaries by several degrees above their normal level. Warm water may carry much less oxygen than cooler water. Thermal pollution can therefore kill fish by depriving them of oxygen. It may also cause their death indirectly by encouraging the increased growth of parasites.

    Water is also polluted by industrial sewage from abattoirs, factories, hospitals and or domestic waste such as human faeces, urine and detergents. Adding organic material to water stimulates the growth of microorganisms which feed on the material. As the density of microorganisms increases, their demand for oxygen also rises. Water that is very heavily polluted with raw sewage become deoxygenated and this can lead to the death of aerobic aquatic organisms such as fish.

    Eutrophication occurs when organic material or inorganic nutrients, especially nitrates or phosphates, enter a freshwater habitat, either naturally or as a result of pollution by sewage or agricultural runoff containing fertiliser.

    Oxygen depletion and eutrophication are not only caused by sewage pollution, they may be caused by any pollutant containing high concentrations of organic or inorganic nutrient, such as fertilisers (inorganic or organic), slurry (animal faeces and urine), or silage (a fermented grass product used to feed cattle in winter) effluent which can leach off farmland and pollute water. Marine water like fresh water is contaminated by agricultural fertilisers which have negative effects on aquatic livings.

    Soil pollution and its effects

    Soil is polluted as a result of human activities. It is polluted by both inorganic and organic pollutants. These two main soil pollutants are human-made chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals, or improper disposal of waste such as plastics bottles and bags. Contamination is correlated with the degree of industrialization and intensity of chemical usage

    3.4 Biological conservation and restoration

    To date, scientists described and formally named about 1.8 million species of organisms. About 10 million more species are not yet identified. A greatest portion of species is found in tropics particularly in the tropical forests. Additionally, over half of all accessible surface water is used for different purposes.  Throughout the biosphere, human activities altered trophic structures, energy flow, chemical cycling, and natural ecosystem processes. Considering the above background, it is now time to rethink about and seek how to preserve life on the Earth.

    a. Biological conservation

    Biological conservation integrates; ecology, physiology, molecular biology, genetics, and evolutionary biology to conserve biological diversity at all levels. It is aimed to maintain the quality of natural environments and their biological resources. Unlike preservation which tries to prevent human interference, conservation involves actively managing biotic and abiotic components to ensure the survival of the maximum number of species and genetic diversity. Common reasons for conserving wildlife are:

    Utilitarian reasons: Species are conserved due to their benefits to humans in terms of food, medicines including quinine and codeine among plants, and snake venom used as anticoagulants and anaesthetics, aspirin to antibiotics are made from natural resources, and alkaloids that inhibit cancer cell growth), industrial use (timber, fuel, gums, dyes, and oils), natural genetic resistance to pests, and whether they provide new variety.

    Aesthetic reasons: Wild animals and plants biodiversity are conserved for the pleasure they provide human well-being.

    Ecological reasons: Biodiversity is conserved due to the complex ecosystem goods and services they provide including network of relationships which maintain biogeochemical cycles in the biosphere and the energy flow in an ecosystem.

    Ethical reasons: Most of the people conserve biodiversity due to the moral duty to look after the environment and that all species have right to live. It is therefore morally wrong to destroy ecosystems   or to allow species to become extinct.

    b. Conservation methods

    Zoned reserves or protected areas approach

    A zoned reserve is an extensive region that includes areas relatively undisturbed by humans surrounded by areas that have been changed by human activity and are used for economic gain. In Rwanda, there are now four national parks namely, Akagera National Park, Nyungwe National Park, Volcano National Park, and MukuraGishwati National Park which are the reserves for natural wildlife.  The key challenge of the zoned reserve approach is to develop a social and economic climate in the surrounding lands that is compatible with the long-term viability of the protected core. These surrounding areas called buffer zones continue to be used to support the human population, but with regulations that prevent the types of extensive alterations likely to impact the protected area. As a result, the surrounding habitats serve as buffer zones against further intrusion into the undisturbed area. The neighbouring communities should be involved in ecotourism activities as one way of benefiting from ecosystem services.

    Eco-farming approaches

    Eco-farming is a modern method for conserving natural ecosystems. It combines science and innovation with respect for nature and biodiversity. It ensures healthy farming and healthy food. It protects soil, water and the climate from pollutants. It does not contaminate the environment with chemical inputs or use genetically engineered crops. And it places people and farmers, consumers and producers at its very heart rather than the corporations who control the food now. It is envisioned for sustainability and food sovereignty in which food is grown with health and safety first and where control over food and farming rests with local communities, rather than transnational corporations. The methods have seven principles which are:

    – Food sovereignty in which producers and consumers, not corporations, should control the food chain and determine how food is produced.

    – Rewarding rural livelihoods for ensuring food security and fighting poverty in rural development.

    – Smarter food production and yields which aimed at creating higher yields to help feed the world.

    – Biodiversity for promoting diversity in crops, instead of monocultures like corn and soy, essentially to protecting ecosystem.

    – Sustainable soil fertility is improved using eco-farming methods and refraining from chemical fertilizers and inputs.

    – Ecological pest protection where farmers can control pest damage and weeds effectively through natural means instead of chemical pesticides.

    – Food Resilience where diverse and resilient agriculture, not monoculture crops, is the best way to protect communities from shocks from climate and food prices

    Other conservation practices

    In additional to the conservation methods, there are other practices that can be applied for biological restoration since the above methods may be difficult and expensive for some countries. They include:

    – Restricting urban and industrial development and reclaiming abandoned sites or other areas.

    – Legally protecting endangered species and prohibiting the release or introduction of non-native animals and plants into an area.

    – Controlling pollution in sensitive environments in which species are at risk of extinction.

    – Recycling materials such as paper, glass bottles, clothes, and limiting the exploitation of renewable resources to sustainable yields.

    – Restricting trade of endangered species and providing breeding programs for endangered species for example in zoos and botanic garden.

    – Avoiding poaching and forest fires and voids habitat loss.

    – Not introducing new species or exotic species and avoid overharvesting and or overfishing.

    – Preventing global change through practices like afforestation.
    Biodiversity conservation improves the quality of life for local people and leads to a sustainable development. Many nations, scientific societies, international and local NGOs embraced the concept of sustainable and economic development that meets the needs of people today without limiting the ability of future generations to meet their needs. In Rwanda, the Rwanda Environmental Management Agency (REMA) and Rwanda Development Board (RDB) aims at protecting and conserving ecosystems. The main conservation initiatives include forbidding people to use swamps, not cultivating near the streams, rivers, and lakes, reforestation, ecotourism, buffer zones, polythene or plastic bags not allowed to be used and enter in the country are highlighted.

    UNIT 2: CONCEPT OF ECOSYSTEMUNIT 4: THE CIRCULATORY SYSTEM