Stressors of Environment, Lecture notes of Environmental Science

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Unit 4 Lecture 1

Environmental

Stressors

4. Critically examine the damages to the environment caused by human activity. 1. Describe the nature and causes of environmental stress and explain how ecosystems respond.

4. Analyze the chemical composition of precipitation and interpret how acidity can impact freshwater organisms.
5. Identify and outline the major sources of emission of air pollutants.
6. Explain the physical basis of Earth's greenhouse effect and how humans contribute.

Course Learning Outcomes

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• Types of Environmental Stress

Types of Environmental Stress

Chemical stress Pollution from chemicals, heavy metals, fossil fuels, acid rain, volcanic ash etc… Physical stress Changes in temperature, climate, light, plate tectonics, water availability, natural disasters (i.g earthquake) etc… Biological Stress Invasive species, overpopulation, starvation, diseases etc…

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• We have seen numerous examples where we have seen the Earth change

Earth is Constantly Changing

• For billions of years the Earth has experienced natural change/ environmental stress

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• This can become a complicated topic because environmental stress leads to change, and this has consistently been apart of the Earth system
• Change is natural, so is environmental stress, but over geologic time this isn’t always a huge issue.
  • However, over human time scales this can be a major issue!

Stress or Natural Change?

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• Four types of Environmental Stress

Types of Environmental Stress

Anthropogenic Stress Human activities such as deforestation, urbanization, resource extraction, pollution etc…

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• Since the Earth has experienced quite literally billions of years of change and environmental stress, the Earth has some incredible healing mechanisms, and also mechanisms to restore balence
• Different systems of the Earth will reach a state of dynamic equilibrium until there is a large enough stress where change will occur

Earth’s Healing Mechanisms for Stress

Dynamic Equilibrium

Dynamic Equilibrium Example 1:

Carbon in the Atmosphere

• For example, CO 2 is naturally released into the atmosphere through the respiration of animals and fungi, and geologic processes
• CO 2 is also being absorbed from the atmosphere through the respiration of plants and other photosynthesizes as well as geologic processes

Dynamic Equilibrium Example 1:

Carbon in the Atmosphere

• So even though hour by hour, or day by day, or month to month, there are changes in the amount of CO 2 in the atmosphere, over time the amount of CO 2 in the atmosphere remains relatively stable
  • Even though there is change, the system has reached a state of dynamic equilibrium

Dynamic Equilibrium Example 2:

Ecosystems

• Let’s explore an example an ecosystem that has reached dynamic equilibrium
• This will be done in-class

Dynamic Equilibrium Example 3:

Forest Succession

Dynamic Equilibrium Example 3:

Forest Succession

• Imagine there was an environmental stress like volcanic activity, this would leave behind bare rock
• Lets start off with a forest ecosystem

Dynamic Equilibrium Example 3:

Forest Succession

• The first organisms that will colonize the bare rock will be lichens