Environmental Consequences of Agriculture
Introduction
This page provides a 4-page printable PDF that includes activities that run through the challenges of irrigation and agriculture for managing freshwater resources. It covers a starter activity on photo analysis and then develops several thinking skills activities based on diagrams showing physical processes. It explores both the causes and problems of salinization in Australia, eutrophication through agrochemical run-off and recaps groundwater pollution in the Edwards Aquifer in Texas.
Enquiry Question
What are the environmental impacts of agriculture and irrigation on water quality and what is the varying power of different actors about water management issues?
Lesson Time: 1-2 Hours - Choose the activities for you
Lesson Objectives:
- To understand the causes and problems of salinization from irrigation
- To understand the causes and problems of eutrophication from agro-chemical run-off
- To understand the causes and problems of contaminants from groundwater storage
- To be aware of the role of different stakeholders
Teacher Notes:
1. Processes_ Photograph Analysis starter - Students should study the photographs on the PDF worksheet (project it too) and annotate it to identify different types of visible and inferred environmental impacts on freshwater.
Then ask students what they think the connecting theme is - Pollution from irrigation and agriculture
2. Power and Possibilities_Read the extract concerning the CEO's dilemma
3. Spatial Interactions_Causes of salinization - Hand out the PDF worksheet and students can begin by looking at the relationship between agriculture and salinization. They should annotate the diagram.
Then show them the answer sheet
4. Processes_Then show the diagram showing different causes of salinization and for each statement they should attempt to explain the link to salinization. The answers are in the drop-down box
5. Place exemplification - Students should then watch the video and make notes in the space provided on:
a) Why Australia has a significant problem with soil salinity
b) The role of different stakeholders
6. Processes_Comprehension - Students should then read the text on agro-chemical run-off in the PDF worksheet and highlight the environmental impacts on water quality
7. Processes_Explaining eutrophication - Watch the video on the Roskilde Fjord and students should make notes on
- a) The causes of eutrophication
- b) The role of different stakeholders
Then students can add an explanation to the algal bloom cycle diagram in their students should their PDF worksheet
8. Processes_Sequencing - Then get students to connect the statements to the correct diagram to sequence the explanation of eutrophication. The answer is in the drop-down box
9. Then you can recap groundwater contamination using the video watched last lesson on Edwards Aquifer in Texas. This time students should make a note on how non-point source pollution affects groundwater.
10. Spatial Interactions_Explaining human impacts - Finally get students to annotate the diagram to show how agriculture pollutes groundwater storage.
11 Power and Possibilities _Student Assessment - Mind Map - Students should mindmap the environmental pressures of agriculture on freshwater, including, different environmental problems, place examples and the role of different stakeholders, including conservationists, small-scale farmers and large-scale farmers.
Starter Activity = Processes - Photograph Analysis
Annotate the photograph collage with as many visible and inferred environmental impacts of agriculture on water quality
Annotation Activity
Student Activity - Power and Possibilities - The CEO's Dilemma
Read the following extract to your students and then ask them the following questions:
- Why is the river being polluted?
- Who is responsible for the river being polluted?
- What different stakeholders influence freshwater quality?
A CEO of a global company was taking a picnic with her family close to a popular river in her local area one weekend. Whilst relaxing after the dinner one of the children came running back to her to report that there were several dead fish in the river. On closer inspection there were indeed several dead fish and the colour of the water seemed stained with an orange-brown contaminant. On further investigation, the family traced the effluence back to an outlet pipe from a local factory. Everyone in the family was upset. Later that evening the CEO was reflecting on what they had witnessed and her leadership of her company. Did the CEO of that company want to pollute the river? Did the workers of that company want to pollute the river? Did the stakeholders of the company want the river polluted? Her children certainly didn't want to see the river polluted. The answer in each case was no, so why was the river being so badly polluted?
Salinization
Salinization refers to the increased salinity of the soil and groundwater. It can be caused by both natural factors such as through the weathering of rock and through wind and rain processes or it can occur due to human causes
Student Activity - Spatial Interactions - Human Causes of Salinization
Study the following diagram and suggest reasons why agriculture has helped create salinization.
Salinization
Student Answer:
A Pumping and use of saline water
Deeper groundwater has higher concentrations of salt.
B Leaking channels
Leaking channels cause a rise in the water table.
C Irrigation in inappropriate soils
Some soils cannot store water so the water table rises. Over-irrigation adds more salt to the soils
D Increased evaporation rates from over-irrigation
Evaporation of water leaves salt deposits behind increasing the concentration in the soil.
E Evaporation draws saline water upwards through capillary rise
Capillary rise involves the movement of water upwards through the soil pores. This is drawn upwards from the loss of soil moisture on the surface due to evaporation.
Student Activity - Processes - Irrigation and Salinisation
Study the following diagram and for each statement attempt to explain the link to salinisation.
Source: Adapted from Slinger and Tenison (2007)
Agro-chemical run-off
Agro-chemical run-off refers to the input of agricultural chemicals from fertilizers and pesticides from irrigation, infiltration and channel storages. These inputs increase the levels of nitrates and phosphates in both surface storage like rivers and lakes as well as the groundwater.
This can be seen in the following diagram:
Source: Wikipedia
Student Activity - Spatial Interaction and Place - Salinisation in Australia
Watch the following clip based on Australia and make notes on:
a) Why Australia has a significant problem with soil salinity
b) The role of different stakeholders
Student Activity - Processes - Agro-chemical run-off
Read the following excerpt taken and adapted from Scienc.jrank.org and highlight the different environmental impacts.
Excessive use of fertilizers, for example, can lead to the contamination of groundwater with nitrate, rendering it unfit for consumption by humans or livestock. Water containing large concentrations of nitrate can poison animals by immobilizing some of the haemoglobin in the blood, reducing the ability to transport oxygen. In addition, the run-off of agricultural fertilizer into streams, lakes, and other surface waters can cause an increased productivity of those aquatic ecosystems, a problem known as eutrophication. The ecological effects of eutrophication can include an extensive mortality of fish and other aquatic animals, along with excessive growth of nuisance algae, and an off-taste of drinking water.
The use of pesticides can also result in environmental problems. As was previously noted, pesticides are used in agriculture to reduce the abundance of species of pests (that is, the "targets") to below a level of acceptable damage, which is economically determined. Unfortunately, many non-target organisms can be exposed to the pesticide. This occurs on the treated site, and also on nearby off-sites as a result of the "drift" of the sprayed agrochemical. These non-target exposures cause many unnecessary poisonings and deaths of organisms that are not agricultural pests.
In addition, there is a widespread, even global contamination of the environment with some types of persistent pesticides, especially with organochlorines such as DDT, dieldrin, and aldrin. This contamination involves the widespread presence of pesticide residues in virtually all wildlife, well water, food, and even humans.
Eutrophication
Eutrophication or Cultural Eutrophication occurs when excessive fertilizers run into lakes and rivers. This encourages the rapid growth of algae (algal bloom) and other aquatic plants. Following this, overcrowding occurs and plants compete for sunlight, space and oxygen. Algae bloom essentially starve other freshwater organisms of essential oxygen so biodiversity falls and mortality increases
Student Activity - Processes, Power and Possibilities - Eutrophication
Watch the following clip that explains the process of eutrophication and
a) Make notes on the causes of eutrophication
b) The role of different stakeholders
Student Activity - Processes - Sequencing Explanation of Eutrophication
Place the statements provided in the correct place in the diagram to sequence the explanation of eutrophication.
Source: Adapted from Science Tech Entrepreneur
Student Answer:
The Pollution of Groundwater
The pollution of groundwater from agriculture is effectively the result of the above factors already discussed. Extraction of water from aquifers and irrigation can lead to salinization of groundwater. It can also lead to increased concentrations of other harmful substances such as nitrates and even cyanide. Heavy use of fertilizers and pesticides leach nitrates, phosphates and other chemicals into the aquifer, which can be harmful to life. Other factors such as seepage from animal sewage tanks either through breaches to storage tanks or through spraying on fields lead to rapid increases in nitrates.
Most agricultural inputs to groundwater can be classified as non-point source pollution.
Student Activity - Processes - Groundwater Pollution Recap
Watch the following clip on aquifer pollution and make notes on how non-point source pollution affects groundwater
Student Activity - Spatial Interactions - Groundwater Pollutants
With the help of the diagram explain how agriculture contributes to polluting groundwater.
Student Assessment - Power and Possibilities - Mind Map of Environmental Impacts and Stakeholders
Mind map the environmental pressures of agriculture on freshwater, including, different environmental problems, place examples and the role of different stakeholders, including conservationists, small-scale farmers and large-scale farmers.
