Environmental impacts and the potential for sustainable food supplies
To explain the environmental impacts of the global food system.To consider the potential for sustainable food supplies.To compare two contrasting agricultural systems. Learning objectivesQuestion!How much of the worlds greenhouse gas emissions is the global food system responsible for?Most emissions:Agricultural production Fertilizer manufactureRefrigeration
Also includes indirect emissions from deforestation and land-use changes.One third!20% of the UKs greenhouse gas emissions are related to food supplies!3Food travels long distances between farmer and consumer.Transportation methods have different impacts:Large volumes of food can be imported by container ships and pollution levels are low.Airplanes have high amounts of pollution for the low volumes they carry. Impacts of food transportationLook at Figure 6.24 on page 235. What is the biggest source of food transport pollution in the UK?
4The term 'sustainable development' according to the Brundtland Commission is "development that meets the needs of the present without compromising the ability of future generations to meet their own needs.What is sustainable agriculture?Sustainable agriculture refers to the ability of a farmer to produce food indefinitely without causing irreversible damage to the local ecosystem.
5Key issues in promoting sustainable agricultureBiophysicalThe long term effects of various practices on the soil, habitats, waterways, atmospheric quality and other aspects of the environment.SocioeconomicThe long term ability of farmers to obtain inputs and manage resources, such as labour.
6Unsustainable farming practicesIn Madagascar only 34% of the primary forest remains. Much of it has been destroyed due to the demand for land to grow coffee for export (cash crop).1. Deforestation
Reduction in interceptionSoil erosionFloodingGlobal warming7The root system dies, so there is nothing to bind the soil together, resulting in erosion. The top soil is washed or blown away, leading to the silting up of rivers and localised flooding.There is no canopy to protect the soil from leaching.
Lack of leaves, therefore nutrients are not returned to the soil, rendering the soil infertile and dependent on fertilisers.Other impacts involve loss of way of life for indigenous tribes, loss of wildlife, global warmingImpacts of deforestation
Traditionally, crops would have been grown on a smaller scale. Trees would have been planted around plots, providing fruit, nutrients to the soil, and roots to stabilise the ground.To increase output, boundaries have been removed, farming has become mechanised and output relies on applying fertilisers and pesticides.Environmental damage:Soils compactionLoss of habitatsSoil erosion / desertificationEutrophication2. IntensificationUnsustainable farming practicesCan you place the following labels in the correct place on your diagram?The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.
EutrophicationAnimation: http://www.youtube.com/watch?v=UGqZsSuG7ao (Eutrophication Animation)10Can you place the following labels in the correct place on your diagram?Algae dieMicrobes respire and use up oxygenAquatic animals suffocate and dieFertilisers wash into a lake or riverAlgae grow fasterSome plants diePlants shaded by algaeDead algae and plants decompose by microbesDissolved oxygen levels fallPlace the labels below on the correct place on your diagrams.Activity: Eutrophication diagram
3. Over IrrigationSalinisation is the process that leads to an excessive increase of water soluble salts in the soil, rendering the land un-cultivateable. This can be caused by human interventions such as inappropriate irrigation practices, e.g. with salt-rich irrigation water and/or insufficient drainage.Unsustainable farming practicesActivity: Unsustainable farming practicesThere are five main causes of unsustainable agriculture practice and degradation of the countryside: policy failure, rural inequalities, resource imbalance, unsuitable technologies and trade relations. Read and make notes on the information on pages 235-6.
Do the same for the four strategies that help to achieve sustainable agriculture (page 236).
A sustainable agricultural system is one that can indefinitely meet the requirements for food and fibre at socially acceptable, economical and environmental costs (Crossen, 1992)
Poly-tunnels in SpainThe Dogon plateau, MaliSustainable farming practices15Read the case studies of the Dogon Plateau, Mali and Spains Plastic Revolution.
Now complete the table you have been given. Summarise the main strategies implemented to increase food supply, then list the advantages (in terms of sustainability) and disadvantages of each system.Activity: Sustainable food suppliespages 232-33 of Ross, et al.16