Environmental

• The main causes of climate change are human activities, such as burning fossil fuels, deforestation, agriculture, transportation, industrial processes, and waste management.
• Climate change leads to rising sea levels which flood coastal communities and islands, and extreme weather events such as hurricanes becoming more frequent and intense.
• Climate change is causing sea levels to rise due to melting glaciers and ice sheets, which can lead to coastal erosion, flooding, saltwater intrusion into freshwater sources, and loss of land.
• Environmental effects of reservoirs

  • Construction of a dam and reservoir creation alters the environment of the reservoir site itself and the surrounding area
• Habitat change


  • Flooding the reservoir obviously destroys the previous habitats but it also creates new and valuable ones
  • Wetlands are uncommon habitats in most regions so the reservoir may be more valuable than what has been lost
• Wildlife barriers


  • The dam and reservoir act as a barrier to wildlife that migrates along the river such as salmon and sturgeon
  • Free movement along the river is an important part of recolonising areas that have become vacant in bad years
  • The dam may prevent this
• River regime downstream of dams

  1. The reservoir may be used to regulate the river flow, holding water back during times of surplus to ensure adequate river flow in times of shortage

  2. This reduces the risk of flooding downstream but also reduces periods of lower flow which are important for some species such as river turtles that lay their eggs in sandbanks

  3. Periods of rapid flow are also important to wash away sediments from gravel river beds in which salmon and trout lay their eggs

  4. The changes in flow fluctuations can change river erosion and sedimentation and therefore the development of meanders
• Sedimentation


  • The sediments that are carried into the reservoir will settle there and not be carried further downstream
  • In the past, they may have been important to fertilise the floodplain downstream
  • They may also have built up river banks and coastlines and counteracted erosion
• Microclimates


  • The large body of water may change the local climate
  • The high heat capacity of water helps to reduce temperature fluctuations
  • It will be warmer in winter and cooler in summer
  • Water provides less friction than land, so windspeeds will be higher
  • Greater evaporation from the reservoir surface may increase humidity, cloud cover, and precipitation downwind of the reservoir
• Sedimentation


  The water is allowed to remain static to let suspended solids such as sit to settle
• Screens


  • Grils or meshes are used to remove vegetation and litter such as plastic and paper items
• Aeration


  Bubbles of air or water sprays are used to oxygenate the water and ensure a high dissolved oxygen content
• Water sources that are anaerobic may contain hydrogen sulfide from the decay of organic matter, which makes the water smell of bad eggs
• Some dissolved metals that are toxic, or give the water a bad taste, are removed by aeration as they become insoluble
• Flocculation/coagulation and clarification


  Clay particles do not settle out in the sedimentation lagoons because electrostatic charges on their surfaces cause them to repel each other. These can be neutralised by adding flocculants such as aluminium sulfate (alum) or polyelectrolytes. They are mixed quickly with the water then passed into the clarifier tank where the particles are allowed to settle
• Filtration


  Filters are used to remove any remaining suspended solids and bacteria. These often involve slow flow through layers of sand and gravel
• Activated carbon filters


  Particles of activated carbon are used to remove organic chemicals such as pesticides which adsorb onto the carbon particles
• Water treatment processes


  • Sedimentation
  • Screens
  • Aeration
  • Flocculation/coagulation and clarification
  • Filtration
  • Activated carbon filters
• Subsistence agriculture


  Poor households access their food from the market, subsistence production and transfers from public programmes or other households
• In the past rural households produced most of their own food, but recent studies have shown an increase in dependence on market purchases by both urban and rural households, in some cases reaching 90% of the food supplies
• Food expenditures can account for as much as 60-80% of total household income for low-income households in some parts of sub-saharan Africa
• Subsistence/smallholder agriculture


  • Can play an important role in reducing the vulnerability of rural and urban food-insecure households, improving livelihoods, and helping to mitigate high food price inflation
  • There is a need to significantly increase the productivity of subsistence/smallholder agriculture and ensure long-term food security
• Increasing productivity of subsistence/smallholder agriculture

  1. Encouraging farmers to pursue sustainable intensification of production through the use of improved inputs

  2. Dramatic increase in the use of fertiliser, organic inputs and conservation investments

  3. Development of well-functioning input and output markets to help farmers acquire and use improved inputs, market their (surplus) output and reduce transaction costs and risks
• Increased productivity


  Reduces pressure on marginal lands, as the intensification of cultivated land will reduce pressure to crop fragile marginal lands
• Agricultural intensification


  The process of increasing the use of capital and labour (e.g. fertilisers, pesticides, machinery) relative to land area, to increase agriculture production per hectare
• Intensification


  • Increases the pressure on the environment, due to an increase of the use of inputs
  • The actual effect of the use of inputs on the environment does not only depend on the amount of inputs used but also on how they are applied
  • Intensification does not necessarily need to lead to environmental degradation
• Agricultural extensification


  The opposite of intensification, the process of decreasing the use of capital and inputs (e.g. fertilisers, pesticides, machinery) relative to land area
• Extensification


  • Due to a decrease in inputs per land area the pressure on the environment may be decreased
  • The actual effect of a decrease in the use of inputs on the environment does not only depend on the amount of inputs used but also on how they are applied
  • Extensification does not necessarily lead to an environmentally more beneficial situation
• Aquaculture


  The controlled process of cultivating aquatic organisms, especially for human consumption
• Hydroponics


  A type of horticulture and a subset of hydroculture, which is a method of growing plants, usually crops, without soil, by using mineral nutrient solutions in an aqueous solvent
• Hydroponics


  • Terrestrial plants may be grown with only their roots exposed to the nutritious liquid, or, in addition, the roots may be physically supported by an inert medium such as perlite, gravel, or other substrates
  • The nutrients used in hydroponic systems can come from many different sources, including (but not limited to) fish excrement, duck manure, purchased chemical fertilizers, or artificial nutrient solutions
  • Plants commonly grown hydroponically on inert media, include tomatoes, peppers, cucumbers, strawberries, lettuces, marijuana, and model plants like Arabidopsis thaliana
  • Hydroponics offers many advantages, one of them being a decrease in water usage for agriculture
• Aquaponics


  A system of aquaculture in which the waste produced by farmed fish or other aquatic creatures supplies the nutrients for plants grown hydroponically which in turn purify the water
• Selective breeding


  Breeding plants (or animals) for resistance to insects is really just another form of biological pest control. Rather than finding insects to attack the pests, breeders look for genetic trails (or combinations of traits) that reduce an organism's susceptibility to attack or injury by its insect pests
• The Wealth of Nations was written

  1776
• When analysing markets, a range of assumptions are made about the rationality of economic agents involved in the transactions
• The Wealth of Nations was written

  1776
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Consumers act rationally by


  Maximising their utility
• Producers act rationally by


  Selling goods/services in a way that maximises their profits
• Workers act rationally by


  Balancing welfare at work with consideration of both pay and benefits