Biolody - B3.4 - How Humans Can Affect the Environment

B3.4.1 - The Effects of the Population Explosion

Increasing numbers of people on th planet ~7 billion
Many people want and demand better standard of living - using up non-renewable raw materials - lots of industrial waste when producing goods - producing more waste and pollution
Reducing amount of land for animals and plants plants by building, quarrying, farming and dumping waste
Increasing population is affecting ecology of Earth
Humans polute:
- waterways with sewage, fertiliser and toxic chemicals
- air with smoke and gases, eg. SO2, contributing to acid rain
- land with toxic chemicals eg. pesticides and herbicides, which can be washed into water

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Land pollution:
- sewage must be treated to remove parasites and toxic chemicals
- toxic chemicals can leak out from landfill sites - some waste is hazardous
- farming methods can pollute land: herbicides and pesticides are poisons - can get in soil, food system and washed into rivers, chemical ferilisers to keep soil fertile can get into river
Water pollution:
- herbicides, pesticides and chemical fertilisers get washed into rivers and streams
- fertilisers and untreated sewage cause high level of nitrates in water
- toxic chemicals from landfill leak into waterways and polute water, killing organisms, eg. fish

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SO2 and other acidic gases are produced when burning fuels in cars and power stations
SO2 dissolves in water in air, forming acidic solutions - solutions fall as acid rain, often far away from where produced
Acid rain kills organisms, trees can be damaged of soaked for too long, changes soil pH - damages roots and may release toxic minerals, eg. aluminium ions, which damages organisms in soil and waterways, enzymes are very sensitive to pH so are affectecd by acid rain - when trees are damaged, food and habitats for other organisms are lost

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Deforestation: many trees cut down - large scale deforestation due to need for timber and land
Deforestation has: increased release of CO2 in atmosphere, due to tree burning or wood decay by microorganisms - reduced rate CO2 is removed by photosynthesis - reduced biodiversity due to loss of food and habitats
Deforestation occurred so crops can be grown to produce ethanol-based biofuels and to increase cattle and rice fields for food - cattle and rice produce methane
Destruction of areas of peat result in release of CO2 - occurs as peat is removed from bogs and used as compost, which is decayed by microorganisms - using peat-free composts means peat bogs won't be destroyed

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In normal natural balance, CO2 is released by respiration and used for photosynthesis - also dissolves in water - CO2 is sequestered by plants and water
Levels of CO2 and CH4 are increasing - called greenhouse gases and cause greenhouse effect - most scientists believe causes global warming
Increase of earth's temperature, even a few degrees, may:
- cause big changes in climate
- cause sea levels due to melting of ice caps and glaciers
- reduce biodiversity
- cause changes in migration patterns
- changes in distrubtion of species

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Biofuels made from - two types: ethanol-based and biogas
Ethanol-based fuels produced by fermentation - microorganisms respire anaerobically to produce ethanol using sugars from crops as energy source -> glucose produced from maize starch by action of a carbohydrase -> glucose and sugar cane juices fermented by yeast producing ethanol -> ethanol extracted by disillation -> used as fuel in motor vehicles
Ethanol could replace fossils fuels in the future - terms of greenhouse effect, ethanol is more carbon friendly
Ethanol is carbon neutral - carbon dioxide used for photosynthesis by crops is returned when ethanol is burned

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Biogas - mainly methane, produced during anaerobic fermentation by bacteria
Plants and waste material containing carbohydrate can be broken down in biogas generators - generators provide ideal conditions for bacteria to reproduce and ferment carbohydrates - must be maintained at suitable temperature in oxygen-free conditions - some generators designed to mix contents - generators either buried underground or have insulating jackets
Large scale, commercial generators use waste from sugar factories or sewage works - small scale, can be used by home or farm
Gas produced is fuel and provides energy for heating etc.
More methane in gas mixture = better quality of biogas

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Shorter food chain = less energy wasted: more efficient to eat plants than animals
Produce meat more efficiently by:
- preventing animal from moving: doesn't waste energy on movement - seen as cruellty
- keeping animal in warm shed: doesn't waste energy on maintaining body temperature

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Human population increasing - food resources at risk of running out
Sustainable food production: manage resources and find new types of food - ensuring enough food for current and future population
Fish stock monitered - quotas and certain sized nets
Fusarium (fungus) grown to produce mycoprotein - new type of food - protein-rich, suitable for vegetarians - grown aerobically on cheap sugar syrup made from waste starch and the mycoprotein harvest
Microorganisms grown on large scale in fermenters - conditions in fermenter must be controlled for maximum growth of fursarium
Industrial fermenters: large vessels with air supply of oxygen for respiration, stirrers - spread out microorganisms and keep even temperature, water-cooled jacket - microorganisms release energy which makes heat, sensors - monitor pH and temperature

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Many human activities affect global environment: deforestation - increase levels of CO2, increase rice growing and cattle farming - more CH4 released, building dams to store water - loss of habitat, drying out river below dam, reduction in fertile land
Huge amounts of environmental data from different scientists in different countries - hard to know if data is valid and reliable
Different conclusions can come from the same data - often based on scientists opinions, can be biased
Global warming has divided opinion - some think increase in temperature is due to increased greenhouse gases, others think it's part of a natural cycle

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