integrated lec 24 Flashcards
Main Threats to Biodiversity:
Habitat Destruction: Deforestation and land conversion for agriculture or development.
Overexploitation: Unsustainable harvesting of wildlife (e.g., primates for bushmeat).
Invasive Species: Non-native species outcompeting or predating native species.
Pollution: Examples include mercury contamination and microplastics.
Climate Change: Intensifies other threats and disrupts ecosystems.
Synergistic Effects:
These threats often interact, amplifying their impacts on biodiversity.
Provide examples of synergistic effects between threats to biodiversity.
Deforestation + Climate Change: Habitat loss + altered climate shrink species’ ranges (e.g., orangutans).
Overfishing + Pollution: Depleted fish + weakened ecosystems (e.g., coral reefs).
Invasive Species + Habitat Loss: Fragmentation aids invasives (e.g., Hawaiian birds).
Agriculture + Pesticides: Habitat destruction + pollinator declines (e.g., bees).
Climate Change + Ocean Acidification: Warmer seas + weaker shells stress marine life (e.g., corals).
Key: Combined threats magnify biodiversity loss.
climate change basics
Cause: Human activities release CO₂, intensifying the greenhouse effect and causing global warming.
Evidence of Climate Change:
Rising atmospheric CO₂ levels (Scripps Institution data).
Increasing global temperatures (NASA data).
Other Effects:
Stronger and larger Hadley cells, pushing desert belts poleward.
Increased frequency of extreme weather events (e.g., hurricanes, droughts, fires).
responses of organisms to climate change
Possible Responses:
Acclimation: Phenotypic plasticity to cope with environmental stress.
Adaptation: Evolutionary changes in response to selective pressures.
Range Shifts: Moving to areas with suitable climate conditions.
Extinction: When acclimation, adaptation, or migration are insufficient.
Acclimation in Porcelain Crabs:
Experiment: Crabs acclimated to cold temperatures improved cold tolerance but gained minimal high-temperature tolerance.
Takeaway: Acclimation is limited and species may struggle to cope with rapid warming.
Snowshoe Hares and Coat Color Mismatch:
Background: Snowshoe hares rely on seasonal coat changes for camouflage.
Findings (Mills et al., 2013):
Snow arrives later and melts earlier, increasing mismatch between coat color and background.
Current plasticity in coat change timing is insufficient to avoid this mismatch.
Survival declines with mismatched coat color, potentially slowing population growth.
Projections: If emissions remain high, mismatches will worsen, increasing extinction risk (Zimova et al., 2016)
Range Shifts in Pikas:
Observation: Pikas are moving upslope as temperatures rise.
Challenge: Limited space at mountain tops (“death zones”).
Status: Some populations are healthy (e.g., Rockies), while others are extirpated (e.g., Great Basin).
Why is coat color mismatch a threat to snowshoe hares?
Coat Color Mismatch in Snowshoe Hares:
Seasonal Camouflage: Snowshoe hares molt their fur to match the seasonal environment—white in winter (snow) and brown in summer (no snow).
Climate Change Effect: Warming temperatures lead to earlier snowmelt and shorter snow seasons, creating a coat color mismatch.
Threats from Mismatch:
Increased Predation: Hares with white fur on bare ground are more visible to predators.
Reduced Survival: Higher predation decreases hare populations, impacting species that rely on them as prey.
Evolutionary Lag: Hares may not adapt quickly enough to rapidly changing snow patterns.
Conclusion: Coat color mismatch disrupts camouflage, exposing hares to greater predation and threatening their survival.
How are range shifts impacting species like pikas?
What’s Happening: Climate change is causing species like pikas to shift their ranges upward in elevation or latitude to find cooler habitats.
Impact on Pikas:
- Habitat Loss:
Pikas rely on cool, high-altitude environments. As temperatures rise, their suitable habitat shrinks and moves upward.
At the top of mountains, no higher habitat remains, leading to “range pinning.” - Thermal Stress:
Pikas are highly sensitive to heat and can die if exposed to temperatures above ~77°F (~25°C) for prolonged periods. Warming forces them to retreat into cooler microhabitats, reducing foraging time. - Fragmentation:
As lower-elevation populations are extirpated, pika populations become isolated. This limits gene flow, increasing vulnerability to extinction. - Food and Seasonal Mismatches:
Warming disrupts the growth of vegetation pikas depend on for food storage (haypiles), reducing survival during harsh winters.
Example: In the western U.S., many low-elevation pika populations have already disappeared due to rising temperatures, illustrating the risks of upward range shifts.
Key Threat:
Pikas face extinction in regions where their habitat is disappearing due to climate change.
extinctions and biodiversity loss
Global Extinction Risk (Urban, 2015):
-Models predict climate change could drive many species to extinction.
-Caveat: Most models ignore factors like species interactions, dispersal, and evolution.
Why Biodiversity Loss Matters (E.O. Wilson):
-Irreversible and unpredictable consequences.
-Earth’s biota is largely unstudied and underappreciated.
solutions to climate change
Mitigation Strategies:
1. Reduce Carbon Emissions: Transition to renewable energy and improve energy efficiency.
2. Protect and Restore Ecosystems: Forests, wetlands, and coral reefs can act as carbon sinks.
3. Global Cooperation: Policies based on scientific evidence are essential.
Call to Action: Requires individual, societal, and governmental efforts
What are synergistic effects in biodiversity loss?
A: When multiple threats interact, amplifying their impacts (e.g., climate change worsening invasive species spread).
Why are microplastics a growing environmental issue?
A: They contaminate ecosystems and food chains, affecting both aquatic life and humans.
How does CO₂ contribute to global warming?
A: It intensifies the greenhouse effect by trapping more heat in the atmosphere.
