Atmosphere & change
For the Earth’s climate to remain constant there needs to be a balance between insolation (incoming solar radiation) & the energy re-emitted. Light reflected from the earths surface (albedo rate) and atmospheric reflection remain as short wave radiation and can pass back through the atmosphere easily.
Any changes in the factors shown in the diagram will alter the energy balance & change the state of the climate.
Increased emissions of greenhouse gases (CO2, CFCs, methane, water vapour, ozone & nitrous oxides) from industry, power stations, cars (burning fossil fuels). These thicken the layer of these gases known as the greenhouse layer.
The greenhouse layer allows solar radiation (insolation) to pass through easily but traps longer wave radiation. Longwave radiation results from the absorption of solar energy by the earths surface, this heats up and releases longwave heat energy. More of the heat emitted from the earths surface is being trapped in the atmosphere leading to increased atmospheric temperatures.
The greenhouse layer is essential for human life on earth to exist, without it, the atmospheric temperatures would be much lower.
Theory stating that the increased pollution levels in the atmosphere are having a cooling effect on the climate due to increased atmospheric reflection. This is in part to the extra particles in the atmosphere but also due to the particles acting as condensation nuclei in clouds & increasing cloud reflectivity.
Solar Radiation Variations
The sun has cycles of increased activity (solar maximum) & decreased activity (solar minimum) that may affect the amount of radiation reaching the Earth & therefore influence the energy balance.
Variations in the Earth’s orbit around the sun & its tilt on its axis are argued to lead to changing climate patterns over long periods of time (Milankovitch Cycles).
Environmental Consequences of Global Warming
- Increased melting of polar & glacial ice – leading to reduced albedo rates & more surface absorption.
- Rising sea levels due to polar ice melt & expansion of the seas as they warm – countries such as Tuvalu (South Pacific) and the Solomon Islands are already suffering flooding during high tides.
- Increased storms/hurricanes due to warmer sea temperatures – storms are likely to be more powerful aswel.
- Possible disruption to ocean current systems as polar ice melts – this changes the salinity of the sea as melting freshwater flows into the oceans..
- Thawing of areas of permafrost – peat bogs are predicted to release huge amounts of methane as they thaw.
- Damage to coral reefs due to acidification of the oceans and rising temperatures. Increasing sea levels will also reduce the light reaching the coral reefs. Coral reefs are vital to ocean ecosystems – providing breeding grounds for many species.
Soil & Change
- Soil degradation: includes the actual loss of soil (erosion), the depletion of its nutrient content and the contamination/pollution of soil.
- A third of the world’s arable land has been lost due to erosion or pollution over the last 40 years. This puts increased pressure on the remaining land to provide food for an increasing global population.
- Erosion: once soil is exposed it becomes very vulnerable to wind and water. Soil takes a long time to regenerate naturally which makes erosion a costly and time-consuming problem replace the soil.
- Salinisation: increase in salt levels in top soil – this occurs in arid areas with high evaporation rates which draws deeper saline water upwards through capillary action.
- Leaching: water passing through soil removes nutrients. Irrigation can lead to increased leaching of nutrients.
- Eutrophication: leaching of fertilisers and animal slurry into rivers can cause excess growth of algae; this can deplete the river of dissolved oxygen & block out sunlight causing the death/depletion of many other plants & fish in the river.
Causes of Degradation
Overgrazing: increased livestock numbers overgraze the land, leaving bare patches of soil which are then eroded by wind & rain. Trampling by livestock kills vegetation & compacts soils.
- Deforestation: removal of trees for agriculture/timber reduces interception of rain & leaves soils exposed to erosion. Many of the nutrients are stored in trees.
- Monocultures: plantations of single crops remove specific nutrients which are not replaced as the vegetation is taken away to be sold.
- Irrigation: in arid areas high evaporation rates draw water upwards and this brings salts with it causing salinisation.
- Loss of fertility: increased pressure on agricultural land leads to its over-use & nutrient depletion. Fertilisers are then required to keep up crop yields.
- Fertilisers: increase farming costs & so increase food costs. They also leach into water supplies which can cause eutrophication as well as health issues.
- Land prices: soil degradation reduces the value of land, so fertile land becomes more valuable/expensive which leads to higher food prices.
- Rural – urban: migration: increases as land becomes less productive.
- Diet: less crops – less food & variety of food, can cause malnutrition.
Soil Management Strategies
Terracing: reduces surface run-off, slowing down erosion. Allows more intense farming on slopes.
- No-till farming: ploughing fields (tilling) and removing the remaining stalks and roots from previous crops damages soil structure and leaves it exposed to the wind and rain – making it vulnerable to soil erosion. No-till farming leaves the old crop residues in place. The soil structure remains more aerated, has greater biodiveristy in the soil and is protected from erosion.
- Afforestation: trees increase rain interception, roots hold soils in place and trees act as wind-breaks reducing wind erosion of soil.
- Crop rotation: different crops require different nutrients from the soil, rotating crops allows soils to replace lost nutrients.
- Contour ploughing: ploughing along the gradient of the slope avoids channels facing down the slope & reduces surface run-off.
- Hedges: provide protection from the wind & reduce wind erosion of bare soil.
Location: In the Himalayan mountain range between China and India.
- Poor country with majority of people living through subsistence agriculture. Steep land.
- Increases in deforestation due to demand for timber for fuel & building. Clearance of trees to allow farming.
- Monsoon rains major cause of soil erosion in deforested areas (including terraced slopes).
- Tree-planting schemes to stabilise soils (afforestation)
- Using alternative fuels (animal dung) – although this then reduces organic fertilising of the soil by dung.
Water & Change
* Physical water scarcity: where water resource development is approaching or has exceeded unsustainable levels; it relates water availability to water demand and implies that arid areas are not necessarily water scarce.
* Economic water scarcity: where water is available locally but not accessible for human, institutional or financial capital reasons.
Patterns & Trends in Water Scarcity
* Water scarcity is an increasing issue in many parts of the world, although arid areas such as the Middle East, Africa and Southern Asia are likely to suffer the most in the future as increasing demands are placed on water resources.
* LEDCs are likely to experience water scarcity as they lack efficient & comprehensive water infra-structure & the cost of implementing it is very high. They will experience economic water scarcity, as it would be available if they could pay.
Environmental Factors Affecting Water Scarcity
Climate change: reductions in rainfall are being experienced in some regions.
* Other places are experiencing rain in heavier downpours which increases run-off and decreases infiltration.
* Increased global temperatures are increasing evaporation rates.
Human Factors Affecting Water Scarcity
These are the most significant factors.
- Rapid population growth: particularly in LEDCs is requiring huge increases in available drinking water.
- Industrial development: as countries such as China & India industrialise, their industries consume vast quantities of water.
- Agriculture: feeding increasing populations requires more crops & more water. Irrigation is dramatically depleting rivers & aquifers, leaving less water for drinking. LEDCs increasing meat consumption in also driving up water-use to feed livestock.
- Water Management: use of water from rivers & building dams is causing populations downstream to have less water available – this is leading to conflict.
- Tourism: tourist developments typically use huge amounts of water and are depleting underground aquifers in many places.
Factors Affecting Access to Safe Drinking Water.
- Industrial pollution:industrial waste is often discharged or spilt into rivers making the water undrinkable; aquifers have also been contaminated.
- Agricultural pollution: leaching of fertilisers & pesticides into rivers & groundwater supplies.
- Contamination of water supplies with diseases such as cholera, or sewage (can cause dysentery).
* Location: Mediterranean coast, Southern Spain.
* Physical water scarcity: Rapid tourism development since the 1970s has seen water usage exceed sustainable levels. With over 150 developments, most including swimming pools, & more in construction the trend is set to continue.
* Economic importance: Benidorm contributes 1% of Spains GDP through tourism & is very important to the economy.
* Aquifers: Benidorm relies on underground water supplies but as these become depleted salty water from the sea is seeping in & contaminating them. Salinisation of the water supplies is damaging surrounding farmland.
* Solutions: The economic importance of tourism means numbers are unlikely to be limited. Water is being diverted from the river Tajo & piped to Benidorm. Desalinisation of seawater is also being considered but is very expensive.
Biodiversity in Tropical Rainforests
Importance of Biodiversity in Rainforests
- Over half the planet’s species live in rainforests.
- Trees & plants stabilise the loose soils.
- Rainforests release huge amounts of moisture into the atmosphere.
- Rainforests capture vast amounts of carbon from the atmosphere.
- Many species of insect exist that have not been identified.
- Potential medical properties of many plant/animal species in rainforests.
Causes of Decreased Biodiversity in Rainforests
Deforestation due to:
- Logging – legal & illegal for hardwood timbers, worth $ billions each year.
- Cattle ranching – in Latin America – high rainfall & initially fertile grasses.
- Palm oil & rubber – monoculture plantations with high export values
- Fossil fuels – oil & coal reserves exist under large areas of many rainforest regions.
Consequences of Reduced Biodiversity in Rainforests
- Burning of trees when clearing rainforest areas releases carbon dioxide into the atmosphere (Greenhouse Effect).
- Reduced ability of nature to capture carbon dioxide from the atmosphere.
- Trees in rainforest contain most of the ecosystem’s nutrients so removing them removes vital nutrients from the ecosystem.
- Loss of species habitat & possible extinction of certain species (orangutans under threat).Sumatran Orangutan Rescued
- Increased soil erosion which reduces the land’s fertility but also silts river beds & increases flooding risks.
- Reduction in moisture released into atmosphere creating changes in climate for places.
- Loss of potential medical benefits, but also recreation opportunities.
Sustainability & the Environment
* Environmental Sustainability: ‘meeting the needs of the present without compromising the ability of future generations to meet their needs’ UN definition.
This concept can be applied in a range of ways (certain activities e.g. tourism, agriculture) & scales (global, regional, biomes).
Location: South Pacific Ocean, just north of Australia.
Issue: Deforestation for timber exports & palm oil plantations, leading to soil degradation, loss of biodiversity & impact on fresh water supplies. Loss of land & lifestyle of indigenous populations (the Maisin).
- Protected land: land used by the Miasin (indigenous population) has been excluded from logging or agricultural concessions.
- Cottage industries: development of nut harvesting, cloth manufacturing & tourist souvenirs.
- Eco-tourism: Promotion of Eco-tourism.
- Sustainable forestry: local communities have been trained in community-based sustainable forestry management.