What is the primary difference between Weak and Strong Sustainability models?

Weak sustainability models show the three pillars as overlapping circles where capital can be substituted. Strong sustainability models show the economy and society as nested within the environment, emphasizing that human systems cannot exist without a healthy natural base.

How does sustainable yield differ from unsustainable yield in terms of regeneration?

Sustainable yield involves harvesting a resource at a rate equal to or lower than its natural regeneration rate. Unsustainable yield occurs when the harvest rate exceeds regeneration, leading to the eventual depletion of the resource.

What is the difference between a resource being 'renewable' and being 'sustainable'?

Renewable refers to the nature of the resource (it can replenish itself), while sustainable refers to the human management of that resource. A renewable resource like timber becomes unsustainable if it is cut down faster than it can grow back.

What is a common misconception regarding the scope of sustainability?

A common error is believing sustainability only concerns the environment. In reality, it requires the integration of social equity and economic viability; without these, environmental protections often fail due to human necessity.

Why is it incorrect to assume that high crop yields always indicate sustainable agriculture?

High yields might be achieved through the overuse of fertilizers and pesticides, which can degrade soil fertility and contaminate water in the long term. Sustainability requires maintaining the health of the soil and water, not just maximizing short-term output.

What error occurs when analyzing human population growth without considering resource consumption per capita?

Focusing only on the number of people ignores the fact that different populations have different environmental impacts. Sustainability is affected by both the total population size and the rate at which each individual consumes resources.

Define 'Sustainable Yield'.

Sustainable yield is the amount of a renewable resource (such as fish or timber) that can be harvested regularly without depleting the resource's ability to replenish itself for future use.

What are 'Environmental Sustainability Indicators'?

These are measurable metrics, such as biodiversity levels, $CO_2$ concentrations, and soil nutrient status, used to monitor the health of the environment and the effectiveness of sustainability efforts.

What is 'Biological Diversity' (Biodiversity) in the context of sustainability?

Biodiversity refers to the variety of life in an ecosystem. It serves as a key indicator of sustainability because higher biodiversity generally leads to greater ecosystem stability and resilience against environmental changes.

Why is soil fertility considered a sustainability indicator for food production?

Soil fertility measures the nutrient levels required for plant growth. If farming practices deplete these nutrients faster than they are replaced, the land becomes less productive, threatening the long-term ability to feed the population.

Sustainability | College Board AP Environmental Science

Revision Notes

College Board

Environmental Science

Unit 5: Land & Water Use

Sustainability

Summary

Sustainability is the practice of managing Earth's resources to meet current human needs without compromising the ability of future generations to meet their own. It requires a balanced integration of environmental health, social equity, and economic viability, often measured through specific indicators like biodiversity and resource regeneration rates.

1. Definition & Core Concepts

Sustainability is defined as the use of Earth's natural resources in a manner that prevents depletion and ensures long-term availability. It focuses on the concept of intergenerational equity, where the current population acts as a steward for the resources required by those in the future.

The core objective of sustainable practices is to maintain a healthy planet by balancing competing needs. This involves the efficient conservation of natural resources, the reduction of waste through responsible consumption, and the protection of global ecosystems to ensure climate stability.

2. Underlying Principles: The Three Pillars

Sustainability is built upon three interdependent pillars: Environmental, Social, and Economic. For a system to be truly sustainable, it must address the health of the natural world, the well-being and fairness of human society, and the viability of economic activities simultaneously.

These pillars are interdependent, meaning a failure in one often leads to the collapse of the others. For example, an economic system that destroys its environmental base will eventually run out of the raw materials needed to function, proving that long-term economic success requires environmental protection.

Diagram of the Strong Sustainability Model showing the economy nested within society and society nested within the environment.

3. Methods & Techniques: Environmental Indicators

4. Key Distinctions: Models and Yields

It is critical to distinguish between Weak Sustainability and Strong Sustainability models. Weak models suggest that the three pillars merely overlap and that manufactured capital can replace natural capital, while Strong models argue that the economy and society are wholly contained within and dependent upon the environment.

Concept	Sustainable Yield	Unsustainable Yield
Definition	Harvesting at a rate equal to or less than regeneration.	Harvesting at a rate that exceeds natural replenishment.
Outcome	Long-term resource availability for future generations.	Resource depletion, scarcity, and ecosystem collapse.
Example	Regulated fishing quotas based on reproduction rates.	Overfishing that removes breeding populations.

5. Exam Strategy & Tips

6. Common Pitfalls & Misconceptions