DP Environmental systems and societies

Topic 3 Human population carrying capacity and resource use

3.4 THE SOIL SYSTEM

Soil system

How does the soil system interact with all the other systems?

• Review nitrogen cycle

• Review phosphate cycle

Soil horizons• Decomposing

litter/humusOrganic

• Well mixed mineral and organic A

• LeechedEluvial

• Deposition of minerals and organicB

• Weathered rockC

• RockbedR

•Soil profile•Soil horizons•Soil formation

Soil profile

The best soil type: loam

Soil degradation

• Water erosion makes 60% of soil degradationErosion

• Overgrazing, overcropping, increasing erosionOveruse

• Slash and burn techniques leave nutrient poor soils unproductive after several crop cycles, increasing erosionDeforestation

• Also called toxification, releases toxic metalsAcidification

• Minerals in the water concentrate in the soil in dry or coastal areasSalinization

• Spreading of desert into once productive areasDesertification

• Increasing all the above problems due to change in land use and hydrology

Climate change

Deforestation

Interaction of soil and water systems

Salinization

Erosion

Soil conservation

Reduce water flow• Contour ploughing• Terracing• Gullies and ravines fenced and planted with trees

Erosion control after harvest• Keep crop cover as long as possible• Keep stubble and root structure after harvest• Plant a grass crop or crop rotation

Long term• Smaller fields• Grow a tree crop• Wind barriers• Stop use of marginal lands• Use of lime or organic material to improve soil condition

What issues can you see here?

Bad:• Slope

increased erosion

• Fields very large

• Monoculture – crop rotation?

Good:• Tree buffers

that can absorb surface runoff, lower wind erosion

• Harvest does not allow soil to be exposed

• Contour ploughing

Soil management

Subsistence farm• Only enough food for family or small community• Labor intensive• Linked with poverty• Good for the environment• no GMOs, polyculture, limited selective breeding

Soil management

Commercial farm• High technological input• Low labour• High yields• Bad for the environment• GMOs, monoculture, selective breeding

Another way to describe farming:

Extensive farming – Farms that are large in comparison to the money and labour put into them eg. large cattle ranches

Intensive farming – Farms that are small but have high output (due to capital and labour) eg. feed lots for cattle

3.5 FOOD RESOURCES

Food production

(2009, $US)

Food distribution

Terrestrial vs Aquatic systems

Harvest mainly from

lower trophic levels

(high efficiency)

Due to cultural

preferences may have

higher tropic levels (1st

level consumers)

Large range of products

produced

Harvest mainly from

higher trophic levels

(low efficiency)

Also less efficient due to

sunlight absorbed and

reflected by water

Food production systems

North American cereal farming

Inputs:

High technology, high fertilizer use, low labor

System characteristics:Genetically modified organisms,

monoculture

Environmental:Clearance of natural ecosystems, loss

of species diversity, soil erosion

Outputs:Low hectare efficiency output as is

extensive not intensive, but high farmer output

Subsistence farming in SE Asia

Inputs:

Low technology, natural fertilizers, high labor

System characteristics:Polyculture, crop rotation

Environmental:Sustainable

Outputs:Only enough to feed family or small

community, high efficiency

Food production systems

Intensive beef production in

MEDCsInputs:

High technology, heating, food

System characteristics:Selective breeding, intensive farming

Socio-cultural:Ethics of restrained animals

Environmental:Greenhouse gases, waste, transportation

Outputs:High relative to extensive beef farming

Maasai tribal use of livestock

Inputs:

Low – no fences, only human input

System characteristics:Nomadic form of subsistence farming

Socio-cultural:Cattle the source of all social roles and

status

Environmental:Low impact, but social gains of wealth and

quantity can lead to overgrazing and desertification

Outputs:Low – subsistence farming, efficiency high

Food production systems

Commercial salmon farming in Norway/Scotland

Inputs:

High use of antibiotics and steroids

System characteristics:Monoculture, high selective breeding

Environmental:Food taken from ecosystem depleting other species, good in that it leaves wild stocks of

salmon alone to breed

Outputs:High efficiency and high output per

hectare and per farmer

Rice-fish farming in Thailand

Inputs:

Low technology, high labor, fish stock

System characteristics:Polyspecies

Environmental:More natural ecosystem but relies on

introduced species

Socio-cultural:Competition from poultry, beef, pork, and

marine fish

Outputs:High output per hectare, low output per

farmer

3.6 WATER RESOURCESWater resources

Earth’s water budget

Water system

Case study

Punjub region the bread belt for India

Relies on groundwater for irrigation

Increasing population and intensive agriculture

Unsustainable use of water - water table dropping 1 meter a year

Agricultural output in decline