Environmental Consequences of Agriculture
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 a number of thinking skills activities based on diagrams showing physical processes. It explores both the causes and problems of salinization in Australia, eutrophication through agro-chemical run-off and recaps groundwater pollution in the Edwards Aquifer in Texas.
What are the environmental impacts of agriculture and irrigation on water quality and what is the varying power of different actors in relation to water management issues?
Lesson Time: 1-2 Hours - Choose the activities for you
- 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 ground water storage
- To be aware of the role of different stakeholders
Starter Activity_Processes_Photograph Analysis
Annotate the photograph collage with as many visible and inferred environmental impacts of agriculture on water quality
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 have an influence on freshwater quality?
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.
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 refers to the input of agricultural chemical from fertilizers and pesticides from irrigation, infiltration and channel storages. These inputs increase the levels of nitrates and phosphates in both surface storages like rivers and lakes as well as the groundwater.
This can be seen in the following diagram:
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 exert 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 hemoglobin in 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 "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 in humans.
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 from essential oxygen and 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
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 leads 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 makes notes on how non-point source pollution affects ground water
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, to include, different environmental problems, place examples and the role of different stakeholders, including conservationists, small-scale farmers and large-scale farmers.