Lecture 8: Global change ecology

Which carbon pool are humans modifying most directly?

Humans are most directly modifying the atmospheric carbon pool.

What is the new carbon flux that humans have created?

The new carbon flux humans have created is the massive flux of carbon from the fossil fuel pool → atmosphere through fossil fuel combustion.

How much of this extra carbon winds up in the atmosphere? How much is taken up by plants and the ocean surface?

• About 50% of the extra carbon humans emit stays in the atmosphere.
  
  

• About 25% is taken up by plants and soils (land sink).
  
  

• About 25% is absorbed by the ocean.
  
  

So roughly half stays in the air, and the other half is split between land and ocean.

What effect do you expect increased atmospheric CO2 to have on plants and net primary production (i.e., plant biomass)? Explain your answer given your knowledge of photosynthesis.

 Increased CO₂ initially increases photosynthesis and plant biomass, but the long-term effect is limited because plants become constrained by nutrients, water, or light.

What does the Loblolly pine experiment tell us regarding the ability of plants to reduce atmospheric CO2 levels? 

The Loblolly pine experiment shows that while elevated CO₂ increases plant growth at first, the effect quickly saturates due to nutrient limitations, meaning plants cannot significantly or sustainably reduce atmospheric CO₂ levels

f. How does increased atmospheric carbon affect seawater chemistry? Which types of organisms are particularly sensitive to this change in seawater chemistry? 

• More atmospheric CO₂ → more CO₂ dissolves into oceans → forms carbonic acid → lowers pH → reduces carbonate ions.
  
  

Corals, shellfish, and plankton that rely on calcium carbonate are most sensitive to this change.

What is the greenhouse effect? Was the greenhouse effect created by humans or modified by humans?

The greenhouse effect is a natural heat-trapping process in the atmosphere, and humans didn’t create it—but we have intensified it by adding extra greenhouse gases.

Identify 3 major greenhouse gases – Which of these is most potent (i.e., retains the most heat)? 

Carbon dioxide (CO₂) – most abundant from human activities (fossil fuels, deforestation)

1. Methane (CH₄) – less abundant but much more effective per molecule at trapping heat
   
   

2. Nitrous oxide (N₂O) – released from fertilizers, agriculture, and some industrial processes
   
   

Most potent

• Methane (CH₄) is the most potent greenhouse gas of the three, molecule for molecule, because it traps much more heat than CO₂ over a 100-year period (about 25–30 times more).

Of these 3 greenhouse gases, which is the most abundant?

CO2

How is “climate change” formally defined?

Long-term changes in Earth’s climate, whether natural or caused by humans.

Climate change is heterogeneous: Which locations on earth are warming fastest? Discuss the role of “albedo” in driving this effect. 

Fastest warming: Arctic and polar regions.

• Why: Loss of reflective ice lowers albedo, causing the region to absorb more heat and amplify warming.
  
  

This is why climate change is heterogeneous—warming is stronger where albedo feedbacks occur.

Climate change affects all organizational scales of ecology.

Climate change impacts organisms, populations, communities, ecosystems, and the biosphere, influencing physiology, interactions, energy flow, and global patterns.

In which direction will species’ ranges shift with global warming? Why is this the case?

With global warming, species move toward cooler climates—northward or to higher elevations—because they follow the temperature conditions they need to survive.

What is phenology? 

Phenology = the study of seasonal life-cycle events and their timing.