Environmental Change & Its Impact on Organisms and Ecosystems

Essential Vocabulary

• Drought – extended period with little to no precipitation
• El Niño – periodic warming of Pacific Ocean that alters global weather patterns (↑ rainfall SE U.S./Peru; ↓ rainfall Indonesia/Australia)
• La Niña – periodic cooling of Pacific Ocean that reverses El Niño patterns (↓ rainfall SE U.S./Peru; ↑ rainfall Indonesia/Australia; warmer Great Plains/SE U.S.; colder NW U.S.)
• Forced Migration – relocation of organisms when local resources/habitat are lost
• Global Warming – long-term rise in average near-surface temperature
• Ice Age – geologic interval of widespread glaciation & lower global temps
• Solar Energy – amount of energy the Sun emits that reaches Earth
• Speciation – evolutionary process by which new species arise
• Tectonic Plate – large segment of Earth’s lithosphere that moves over asthenosphere
• Tsunami – large, fast-moving ocean wave usually caused by under-sea earthquakes

Levels of Biological Organization Referenced

• Organism – single living thing (e.g., one elk)
• Population – group of same-species organisms in an area (elk herd)
• Community – all populations (plants, animals, microbes) in an area
• Ecosystem – community plus interacting abiotic factors (water, soil, climate, topography)

Time-Scale Categories of Environmental Change

• Short-Term (minutes → hundreds of years) – rapid onset; immediate biological effects; little time for evolutionary response
• Long-Term (thousands → billions of years) – gradual but persistent; drives evolutionary change & alters genetics of populations

Short-Term Environmental Changes & Their Impacts

• Natural disasters (rapid, unpredictable)

• Earthquakes: land fissures, landslides ⇒ infrastructure collapse; organisms killed/injured; $\text{Populations} \to \text{Forced migration}$
• Volcanic eruptions: lava burial; ash reduces surface sunlight ⇒ ↓ temp a few °C; habitats smothered; ash pollutes water bodies
• Forest fires: destroy vegetation, nests, burrows; leave nutrient-rich but habitat-poor ash
  • Hydrologic extremes
• Floods: drowning, nest loss; repeat flooding can drive endemic species to extinction
• Tsunamis: coastline inundation within minutes; mass mortalities, habitat scouring
• Droughts: water scarcity, soil desiccation; non-xeric species die/migrate; harder to predict & often prolonged
  • Atmospheric/oceanic oscillations
• El Niño / La Niña cycles: redistribute rainfall & temperature; marine species shift range; fisheries disrupted
  • Extraterrestrial impacts (small)
• Small asteroid/comet: local craters; immediate kill‐zone destruction

Human Preparedness for Short-Term Events (Drought as example)

• Learn local risk data (monitoring agencies, drought indices)
• Draft & follow drought response plans (state, municipal)
• Conserve water: repair leaks, xeriscape, shorten showers, shut tap while brushing
• Build storage: dams, reservoirs, rain-harvest systems

Long-Term Environmental Changes & Their Impacts

• Ice Ages (≥ 5 major in Earth history)

• Glaciers carve landforms, create lakes; cold-adapted species flourish; warm-adapted either adapt, migrate, or go extinct
  • Global Warming
• Rising mean temperature: shifts phenology (migration dates, flowering); melts sea ice ⇒ polar bear habitat loss; range shifts ⇒ ↑ inter-specific competition
  • Tectonic Plate Movement & Mountain Building
• Continental drift relocates biomes (e.g., Antarctica once tropical)
• Break-up of supercontinents isolates populations ⇒ allopatric speciation
• Orogeny (mountain formation): cooler, wetter upslope climate; organisms must adapt to rugged topography & thin atmosphere
  • Large Asteroid/Comet Impacts
• Global dust veils ⇒ photosynthesis shutdown; mass extinctions (e.g., dinosaur extinction event)
  • Changes in Solar Energy Output
• ↑ solar irradiance ⇒ warming; ↓ irradiance ⇒ cooling; organisms must adapt or face extinction

Evolutionary Consequences of Long-Term Change

• Natural Selection: differential survival of traits (peppered moth industrial melanism)
• Adaptation: beneficial traits accumulate (brown grasshopper in drought-browned grassland)
• Speciation: populations diverge genetically when isolated or under new selective pressures
• Extinction: failure to adapt leads to total species loss

Combined Effect Pathway (Short-Term → Long-Term)

Short-term disturbance (e.g., wildfire) may trigger habitat shifts that persist, thereby initiating long-term evolutionary responses in surviving populations.

Human-Caused Environmental Change

• Pollution: air haze (London skyline), water contamination (mining waste turning lake orange), oil spills → organism toxicity, food-web collapse, coastal habitat degradation
• Habitat Destruction / Clear-Cutting: removes vegetation, depletes soil, eliminates shelter & food ⇒ forced migration or death
• Introduction of Invasive Species: zebra mussels transported via ballast water filter out plankton ⇒ decline in native fish larvae
• Anthropogenic Global Warming: accelerates ice melt, sea-level rise, acidification
• Human-Caused Extinctions: current rate $1000\text{–}10\,000\times$ background; black rhino declared extinct 2011

Short- vs Long-Term Human Effects

• Short-Term: immediate die-offs, habitat loss, forced migration
• Long-Term: altered climate regimes, permanent loss of biodiversity, evolutionary pressures, potential mass extinction

Coevolution & Biosphere–Geosphere Feedbacks

• Definition: reciprocal evolutionary change between living organisms & Earth systems
• Coral Reefs / Coastlines
  • Reefs build storm-wave barriers; reduce wave energy by $97\%$
  • Prevent $\$1.8\text{ billion}$ annual U.S. flood damage
  • Reef growth modifies erosion/deposition patterns; coastline shape feeds back to reef habitat diversity
• Outcome: greater species richness → higher productivity & ecosystem stability

Typical Biological Responses to Environmental Change

1. Behavioral change (store food, new shelter, diet shift)
2. Forced migration
3. Habitat loss
4. Adaptation (physiological/structural)
5. Speciation
6. Death of individuals / Population decline
7. Extinction

Case Studies & Predictive Scenarios

• Grassland Drought (Wildebeest)

• Lack of water & grass ⇒ herd migrates
• Non-migratory organisms suffer starvation/dehydration
• Apex predators (lions) lose prey; may starve
  • Ocean Oil Spill
• Plankton, algae, bivalves die ⇒ food-web collapse
• Birds coated in oil: hypothermia, poisoning
• Marine mammals: blowhole obstruction, suffocation
• Coastal wetlands suffocated; vegetation loss leads to shoreline erosion
• Chain reaction: habitat loss → forced migration → population declines

Adaptations Matched to Disturbances (Examples)

• Drought-prone zones → water storage tissues (succulent plants, camel humps)
• Fire-prone forests → burrowing ability, thick bark, serotinous cones

Study Tips & Connections

• Link short-term changes to immediate ecological effects; link long-term changes to evolutionary consequences.
• Remember classic natural-selection example: peppered moth reflects reversible trait frequency shift with pollution levels.
• Relate tectonic plate movement to biogeography (e.g., marsupial distribution in Australia vs. placental mammals elsewhere).
• Recognize human parallels: oil spill ≈ tsunami of toxins; clear-cutting ≈ long-term habitat fragmentation.
• Use timelines:
  $\text{Minutes → Hours}$ earthquake, tsunami, oil leak rupture
  $\text{Days → Years}$ drought onset, El Niño cycle
  \text{\ge 10^3 yrs} ice ages, mountain uplift, continental drift

Quick-Reference Equations & Quantitative Data

• Coral reef wave-energy reduction: $E<em>{after} = 0.03 \times E</em>{before}$
• Extinction acceleration: $R<em>{human} \approx 10^3\text{–}10^4 \times R</em>{background}$

Practice Questions

1. Classify the following as short- or long-term: volcanic eruption, mountain building, El Niño, solar output reduction.
2. Describe two possible adaptations enabling survival in an ice-age environment.
3. Explain how a drought can initiate a trophic cascade in a grassland ecosystem.
4. Outline three ecosystem services provided by coral reefs.

Key Take-Aways

• All environmental changes—rapid or gradual—cascade through organisms, populations, communities, and ecosystems.
• Short-term changes are acutely disruptive; long-term changes restructure evolutionary trajectories.
• Human activities now rival or exceed natural processes in driving both short- and long-term environmental change.
• Biodiversity, adaptation, and coevolution underpin ecosystem resilience; their loss heightens system vulnerability.