Agroecosystems

• Ecosystem - The interaction between abiotic and biotic factors in the environment
• Agroecosystem - The interaction between abiotic and biotic in a farming environment

Features of a natural ecosystem	Features of an agricultural ecosystem	Reason	Environmental effect
Climax Community forms	A plagioclimax is maintained = deflected succession	Need to grow crops not a woodland	Reduced habitat diversity, reduced niches
Many plant species	One species – a monoculture	Easier to manage one crop – 2 crops in one field would make planting, weeding and harvesting harder	Removes natural predators of pests and makes crop susceptible to a pest epidemic so pesticides are essential. Pesticides may contaminate food, leach into water supplies or move up food chains, harming useful organisms – pollinating insects or pest-eating birds for example. May lead to nutrient deficiency as all individuals need same nutrients. Thus, artificial fertilisers are needed
Genetic diversity within crop species	Reduced genetic diversity within crop	Crop likely to be genetically engineered for a small number of desirable characteristics	Loss of genetic diversity that may be needed if environmental conditions change or if a new disease/pest emerges
Soil always covered by some plant species	Soil often left bare after harvesting	Not economic to plant second crop in same year/growing season may make it impossible	Soil erosion
Nutrient cycling occurs via death and decomposition of plants and animals	Harvesting removes plants. Animals are killed by pesticides or kept out by enclosures. So nutrient recycling is impossible. Nutrient additions must be made in the form of fertilisers	The crop is needed for sale. Fertilisers must be used to return the nutrients lost when the crop was removed	Nitrates high soluble so may leach. Phosphates erode. Entry of nitrates and phosphates into water course leads to eutrophication. Loss of fertilisers means more must be applied therefore more must be made which increases the use of fossil fuels
Relatively low productivity	High productivity	Crop receives huge energy input in the form of artificial fertilisers/pesticides etc	Energy is from fossil fuels, the extraction and burning of which leads to global warming. Fossil fuels are finite so system may be unsustainable and unethical – future generations will have no choice but to find alternatives or change their agriculture systems

 

Oil and Gas

• Non-renewable resources - rate of formation < rate of consumption

• Formed from dead tropical marine plankton
• Formed over millions of years in anaerobic conditions with heat and pressure
• Moves from kerogen to oil shales to tars to heavy oils then light oils then diesel and petrol and eventually natural gas
• Young oil is more viscous - doesn't run - hard to extract
• Stored in porous reservoir rocks eg. Sandstone
• Cap rock needed above to contain the deposits - impermeable rock
• California - Lake View Gusher, Micricopa
• Primary recovery whereby the oil and gas comes to the surface under its own pressure(a gusher)
• Pressure is created by water below or gas above, or both
• Secondary recovery - pumping down water or gas to increase the pressure
• Tertiary recovery - attempts to increase the mobility of the oil making it less viscous
• Involves injecting stream or detergents in to the reservoir rock to make the oil flow more readily


Problems of oil recovery:
• Young oils too viscous to flow
• Oil deep below surface (5km) difficult to reach as friction increases and pumping fluids in to carry out rock fragments becomes harder
• Oil beneath deep water (2km) hard to exploit as anchoring floating rig is hard
• Oil that is very viscous or in impermeable rock will not flow to the extraction well
• Many oil fields are too small to be exploited profitably

Uses:
• Range of different uses - very versatile
• Main uses
 - building and process heating
 - vehicle fuels
 - electricity generation and petrochemicals

Environmental Impacts:
• Exploration
 - seismic surveys - affects whales
 - explosions to test for oil - habitat disturbance
 - benthic species - sea bed species
• Extraction
 - leaks eg. BP oil spill
 - anchoring rigs - destroys sea bed - benthic species
• Transport
 - pipelines - habitat destruction
 - fuel for transport
• Process
 - air pollution - fractional distillation
 - energy intensive
• Use
 - fuels - petrol/diesel - nitrous oxide = acid rain
 - habitat destruction - building petrol stations
• Waste
 - air pollutants
 - plastics - don't biodegrade

Future:
• As oil and gas become exhausted we are needing to use technology to find and extract oil and gas in new ways
• Oil sands and shales eg. Alberta, Canada
• Drilling in deep water eg. Gulf of Mexico - deep water horizon
• Drilling in difficult environments eg. the North Sea
• Drilling in harsh climates eg. the Artic
• Fraking eg. in USA

• These less conventional methods of extracting oil are likely to have greater environmental impacts and as they are more expensive ways of extracting the resources global prices are likely to increase

Coal

Formation:
• Formed from plant or animal material buried millions of years ago
• Anaerobic conditions
• As it is buried there is increased pressure and heat

Types:
• Older deposits are generally more useful
• Older coal has a higher carbon and energy content

• Lignite (brown coal):
 - sedimentary
 - limited supplies in most areas
 - low sulfur content
 - low heat content

• Bituminous (soft coal):
 - sedimentary
 - extensively used
 - high sulfur content
 - high heat content
 - large supplies

• Anthracite (hard coal):
 - limitied supplies in most areas
 - low sulfur content
 - metamorphic
 - high heat content
 - highly desrirable


Uses:
• China is the worlds largest user of coal, followed by the USA
• China has 11% of world reserves
• Used to generate 62% of the worlds electricity
• Electricity generation
• Iron and steel industry
• Provides about 22% of the commercial energy used in the world and the US
• Used to generate 75% of the worlds steel
• Countries getting more than 1/2 of the energy they use from coal:
 - South Africa - 78%
 - China - 73%
 - Poland - 68%
 - India - 57%
 - Kazakstan - 54%


Environmental Impact:

•Extraction:
 •Open cast:
 - Noise pollution
 - Habitat destruction
 - Dust
 - Cannot access deeper deposits
 - Highly mechanised = cheap

 •Shaft mining:
 - Cave ins
 - Flooding
 - Gas leaks
 - Noise/dust pollution

•Air pollution from transportation

•Use:
 • Contains lots of sulphur:
 - acid rain
 - dissolves buildings - limestone
 - destroys trees
 - sent massive cloud of sulphur over to Norway

•Coal fired power stations:
 - UK releases 5-10 million tonnes of CO2 every year
 - Particals of toxic mercury
- 60,000 babies a year may be born with neurological damage from exposure to mercury in pregnant women


Future:

• Coal liquefaction or gasification
• World consumption is expected to increase by 49% from 2006 to 2030
• Scrubbers to reduce CO2 and particulates
• Most growth in NICs
• Moves to clean coal technology could increase even in the developed world
• CCT - treat it and wash it, turn it into a gas then burn the gas which is cleaner than the coal
• Worlds most abundant fossil fuel
• World identified reserves  of coal should last at least 225 years at current usage rate
• 65 years left of coal if usage rises 2% per year
• identified US coal reserves should last 300 years at current consumption rate
• China has 11% of world reserves which will last 300 years at current consumption rate
• Resources at the moment could become reserves as more technically becomes available
• US FutureGen programme - $1 billion - demonstrates commercial viability of near zero emission coal fuelled power
• Japan, Australia and Europe all have their own Clean Coal Technology programmes
• Carbon capture/sequestration

Energy Development

Fire
Animal power
Water power
Wind power
Fossil Fuels
Electricity

Fire:
• allowed the processing of materials - baking of clay to make pottery
• This pottery was then used as a storage for surplus grain which reduced the amount of time searching for food in shortages
• This time which was gained could be used making tools or weaving clothes
• It could also be used to clear woodland for farmland quickly or move animals

Animals:
• They replaced humans in ploughing, carrying goods and driving machinery
• This gives them more time

Wind and water power:
• These were used to drive machinery for grinding, spinning and weaving
• Wind power could be used to propel ships and pump water
• Wind power also allowed sailing so this allowed countries to trade

Smelting:
• Smelting of metals using wood and charcoal allowed useful items to be made - cutting blades, nails, wheel rims and plough
• Smelting of steel was created using coal and coke - this created sophisticated machinery - steam engines
• Coal could be transported wherever it was needed

Crude oil:
• This has increased the amount of energy available - almost all tasks performed more easily

Electricity:
• This can be used to drive more equipment than could be driven by just primary energy

Energy Definitions

Renewable resources: A resource that is reformed by natural processes fast enough for new supplies to become available within a human lifespan.

Energy density: The amount of energy in a particular mass of fuel or that can be harnessed by a particular mass of equipment

Finite resources: Resources where the total amount available is fixed

Wind, solar: Renewable resources that can never be depleted and which are reformed instantly

Wood: A renewable resource that can be depleted

Secondary fuel: An energy that is produced by converting a primary fuel

Peak Shavings: The process of storing surplus energy to satisfy later demand peaks

Deplete: To reduce the amount of a resource that is available

Non- Renewable resources: A resource that is renewed so slowly that the amount available is effectively finite.

Unreliable: An energy resource where the amount of energy available cannot be predicted

Intermittent: The word used to describe an energy resource that is not available all the time

Tidal: An energy resource that is intermittent but very reliable

Wind: An energy resource that is both unreliable and intermittent

Nuclear (Uranium): A very dense energy resource

Government Subsidy: Money made available by the government to for example promote a particular energy resource such as nuclear power in France

Energy Mix: The combination of energy resources used by a country

Reserve: The total amount of material that is exploitable given current prices and technology

Resource: The total amount of a material that is potentially exploitable now or in the future

Hormonal Growth Control

Plant Growth:

•Auxins - help vegetative propagation - stimulates root growth

•Gibberlins - shoot growth - used on cereals to produce shorter stems
 - stimulate seed germnination
 - root growth
 - increase fruit size

•Ethane or Ethylene - stimulates the ripening of fruit


Animal growth:

•BST - increases milk yield in dairy cattle
 - banned in many countries due to risks to human health

•Anabolic Steroid Hormones
 - based on steroid sex hormones
 - increases growth rate and gross growth efficiency
 - if residues of the steroid remain in meat eaten by humans it could affect human growth