Human Impacts on Earth Systems

Habitat: The specific place where an organism lives, including living and nonliving factors.
Extinct: Describes a species that has died out completely with no individuals remaining on Earth.
Point-Source Pollution: Pollution originating from a single, identifiable site, such as a factory.
Nonpoint-Source Pollution: Pollution coming from many sources, often carried by rainwater moving across land.

Natural Changes: Occur through repeating patterns (tides, seasons) or sudden events (forest fires, flooding).
Human Changes: Altering land shapes, damming rivers, or removing trees to meet human needs.
Resource Depletion: Using resources faster than they can be replaced.
Pollution: Harmful substances added to the environment that cause undesirable changes.

Hydrosphere: All water on Earth.
Geosphere: The solid part of Earth.
Atmosphere: The mixture of gases surrounding the planet.
Biosphere: All living things on Earth.
System Connectivity: Human activities affecting one subsystem often indirectly impact others (e.g., burning fossil fuels in the atmosphere leading to acid rain affecting the biosphere).

Hydrosphere: Water use leads to scarcity; point and nonpoint pollution contaminate water supplies.
Atmosphere: Combustion of fossil fuels releases colorless gases and suspended particles; results in acid rain that kills crops and acidifies surface water.
Geosphere: Reshaping land for farming and mining can lead to soil degradation and erosion; mitigation includes terracing and planting.
Biosphere: Over-harvesting through hunting and fishing can lead to extinction; urbanization causes habitat fragmentation.

Fragmentation: Urbanization since the 1600s split large habitats into smaller, disconnected areas.
Population Statistics: Listed as endangered in 1967 with about $20$ individuals in the 1970s; conservation increased the number to nearly $200$ by 2014.
Light Pollution: Nighttime images show light pollution in the southeastern United States is directly correlated with human activity.

Human Structures: Levees and lock-and-dam systems are built to control flooding and maintain shipping routes, but they prevent natural sediment deposition.
The Dead Zone: A seasonal area near the river mouth in the Gulf of Mexico where oxygen levels are too low for most organisms to survive.
Algal Blooms: Caused by fertilizer runoff and contaminants from the Mississippi River watershed; the resulting dead zone averages almost $6,000\,\text{square miles}$ .

Incident (1986): An accident at the Chernobyl Nuclear Power Plant in Ukraine released massive amounts of radioactive material.
Human Impact: Approximately $115,000$ people were initially evacuated, followed by $220,000$ more in subsequent years.
Environmental Result: Humans have been absent for over $25$ years; wildlife populations have increased despite the presence of radiation within the $30\,\text{km}$ exclusion zone.

Question: How can farming on land contribute to the growth of algal blooms in the ocean?
Answer: Rainwater picks up pollutants such as fertilizers from farms (nonpoint-source pollution) and carries them into watersheds that eventually empty into the ocean, fueling algae overgrowth.
Question: Describe the environment of the algae shown at the beginning of the lesson. How are algae connected to their environment?
Response: Algae live in aquatic habitats where they rely on nutrients and light; their growth is directly impacted by the materials (like runoff) entering the hydrosphere.
Question: What materials might runoff in the Mississippi watershed contain that could contribute to algae growth in waterways?
Evidence: The runoff contains contaminants from roadways and nitrogen-rich fertilizers applied to crops.