Overview
This lecture covers natural disruptions to ecosystems, focusing on their types, impacts on habitats, and the ways species respond, including migration and adaptation.
Types of Natural Disruptions
- Natural disturbances are events that disrupt ecosystem structure or function, affecting energy and matter cycles.
- Examples include tornadoes, hurricanes, fires, and asteroid impacts.
- Natural disturbances can be more significant than human-caused ones.
Time Scales of Disturbances
- Disturbances occur as periodic (regular, predictable), such as seasonal rains and droughts.
- Episodic events happen irregularly but somewhat frequently, like hurricanes or wildfires.
- Random events have no predictable pattern, e.g., earthquakes or asteroid strikes.
Natural Climate Change
- Earth's climate changes over time due to natural reasons, such as orbital shifts and tilt variations.
- These changes cause regular ice ages and warm periods.
- Natural fluctuations in atmospheric carbon dioxide and temperature occur over thousands of years.
Sea Level Rise and Ecosystems
- Sea level rises naturally due to increased temperatures and melting polar ice caps.
- Higher temperatures cause thermal expansion in oceans, contributing to sea level rise.
- Rising seas flood coastal habitats like estuaries, salt marshes, and mangroves, resulting in habitat loss and altered species communities.
Impacts on Habitats and Migration
- Environmental changes can destroy or alter habitats, forcing species to migrate or risk extinction.
- Some species follow regular migration patterns in response to predictable changes (e.g., wildebeest and rainfall).
- Climate change shifts migration timing, such as birds adjusting to earlier insect hatching.
Trends and Data Interpretation
- Students are asked to analyze a map showing changes in honeysuckle leaf-out dates across the US, considering latitude and possible reasons for observed trends.
Key Terms & Definitions
- Natural Disruption — A natural event altering the structure or function of an ecosystem.
- Periodic Event — Occurs at regular, predictable intervals (e.g., rainy seasons).
- Episodic Event — Occurs occasionally but not at regular intervals (e.g., wildfires).
- Random Event — Occurs without a predictable pattern (e.g., earthquakes).
- Thermal Expansion — Water expanding as it warms, raising sea levels.
- Estuary — A coastal habitat where saltwater and freshwater mix.
Action Items / Next Steps
- Describe the relationship between latitude and honeysuckle leaf-out dates on the provided map.
- Explain potential reasons for the observed pattern as practice for describing data trends.