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 objectives

Question!

How much of the world’s greenhouse gas emissions is the global food system responsible for?

Most emissions:1. Agricultural production 2. Fertilizer manufacture3. Refrigeration

Also includes indirect emissions from deforestation and land-use changes.

One third!

20% of the UK’s greenhouse gas

emissions are related to food supplies!

• Food travels long distances between farmer and consumer.

• Transportation methods have different impacts:

o Large volumes of food can be imported by container ships and pollution levels are low.

o Airplanes have high amounts of pollution for the low volumes they carry.

Impacts of food transportation

Look at Figure 6.24 on page 235. What is the biggest source of food

transport pollution in the UK?

The 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.

Key issues in promoting sustainable agriculture

Biophysical

The long term effects of various practices on the soil,

habitats, waterways, atmospheric quality and

other aspects of the environment.

Socioeconomic

The long term ability of farmers to obtain inputs and manage resources,

such as labour.

Unsustainable farming practices

In 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 interception

Soil erosion

FloodingGlobal

warming

The 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 warming…

Impacts 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 habitats

Soil erosion / desertificationEutrophication

2. Intensification

Unsustainable farming practices

• Can 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.

Eutrophication

• Can you place the following labels in the correct place on your diagram?Algae die Microbes

respire and use up oxygenAquatic

animals suffocate and

die

Fertilisers wash into a lake or

river

Algae grow faster Some plants

die

Plants shaded by algae

Dead algae and plants decompose

by microbes

Dissolved oxygen levels

fall

Place the labels below on the correct place on your diagrams.

Activity: Eutrophication diagram

3. Over Irrigation

Salinisation 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 practices

Activity: Unsustainable farming practices

There 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 Spain The Dogon plateau, Mali

Sustainable farming practices

Read the case studies of the Dogon Plateau, Mali and Spain’s 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 supplies