Sustainability & Human Impact
What are the three pillars of sustainability?
Environmental, Economic, Social
What are the four main components of a system?
Storages, Flows, Processes, Feedback Mechanisms
Define pollution
Introduction of substances that disrupt environmental balance.
What is a model in environmental science?
A simplified representation to study a system.
Define carrying capacity.
The maximum population an environment can support without resource depletion.
Give an example of an environmental challenge related to sustainability.
Deforestation, climate change, pollution, etc.
What is an example of a closed system in environmental science?
Earth, because it exchanges energy but not matter. (or other examples)
Name three types of pollution and their sources.
Air - vehicles, Water - industrial waste, Soil - pesticides.
Name the three types of models in environmental science.
Physical, Conceptual, Mathematical.
What are two factors that influence carrying capacity?
Resource availability, waste assimilation, habitat health, etc.)
What is the difference between intrinsic and instrumental value in environmental science?
Intrinsic: has value because it exists; Instrumental: valuable because humans use it.
What is the difference between a positive feedback loop and a negative feedback loop in environmental systems?
Positive feedback loop makes changes bigger or worse (example: melting ice → more heat → more melting).
Negative feedback loop helps bring the system back to balance (example: sweating when you’re hot to cool down).
Closed system, because it recycles nutrients and water.
Why is not all waste considered pollution?
Pollution happens when waste is released harmfully, but proper waste management prevents it.
How do climate models help predict environmental changes?
They simulate interactions of variables like CO₂ levels and temperature.
In 2018, Cape Town almost ran out of water. Population growth and drought reduced supply.
How was carrying capacity passed, and what could help prevent this?
Passed because water use was too high for what nature could give.
Fix: Water-saving rules, reuse wastewater, and limit new development.
China built the world’s biggest hydroelectric dam. It gives clean energy but flooded towns, farms, and natural habitats.
What are two problems with this, and how can the project be made better for people and nature?
Problems: Destroys forest and wildlife; people lose homes.
Solution: Study the impact first, protect animal paths, and involve the community in planning.
Fertilizer runoff from farms near Lake Erie caused toxic algae blooms. It poisoned drinking water and killed fish.
Question: What two parts of a system are shown here? What’s the feedback loop?
Parts: Nutrient runoff (flow), algae growth in lake (storage).
Feedback: More nutrients → more algae → oxygen loss → fish die → worse water quality (positive feedback).
How does improper waste disposal affect carrying capacity?
Reduces resources, increases contamination, lowers sustainability.
What is a limitation of models in environmental science?
They simplify real-world complexity and may not include all factors.
How can human innovation increase carrying capacity?
Technology, resource management, vertical farming, and renewable energy.
In 2017, Kenya banned plastic bags to protect nature. But poor vendors had trouble affording reusable bags.
What is the problem with this, and what’s a better, fair solution?
Problem: Helps the environment, but makes it hard for small shops.
Solution: Give free or cheap reusable bags to small shops to help them adjust.
Singapore uses green roofs and rooftop gardens to cool the city and reduce energy use.
Question: How does this system help the environment and create a feedback loop?
Helps by reducing heat and cleaning air.
Feedback: Cooler city means less energy used for air conditioning → less pollution → even cleaner city (negative feedback).
What is the Bortle Scale, and how does it relate to pollution?
Measures light pollution and how much artificial light affects visibility of the night sky.
London used traffic and pollution models to plan Low Emission Zones, where dirty vehicles are limited.
How did the models help, and why test them in real life?
Help: Predicted less air pollution and better health.
Real-world testing: Confirms the model works and helps improve future planning.
A city has a freshwater supply of 500 million cubic meters per year. Each person in the city consumes 120 cubic meters of water annually.
A. What is the maximum population that this city can sustain?
B. If the population grows by 2% annually, how many years until water demand exceeds supply?
Question Recap:
Total water supply = 500 million m³
Each person uses 120 m³/year
Answer 1: 4,166,666 people is the maximum population the city can sustain.
Answer 2: Water demand will exceed supply in approximately 20.27 years, if population grows at 2% per year.