D4.3 IB DP Biology

Outline the cause and consequence of the greenhouse effect.

Certain naturally-occurring gases in Earth's atmosphere have the ability to absorb and trap infrared radiation, which causes some of the heat to stay on Earth and contribute to warming.

Outline the cause and consequence of the enhanced greenhouse effect.

Combustion of fossil fuels and some other human activities release CO2, which has contributed to a rise in atmospheric CO2 in the last century. Other sources of CO2 rise include cement production and deforestation.

List anthropogenic sources of atmospheric carbon dioxide and methane.

Agricultural ponds (e.g. rice paddies)

Cattle farming

Landfills

State what is oxidized to carbon dioxide in the atmosphere.

methane

Outline climate changes that can result from the enhanced greenhouse effect.

the Earth's surface gets warmer. This will have serious knock-on effects, such as changes in global rainfall, ocean circulation and extreme weather events, and an increase in sea level.

Explain the correlation between atmospheric CO2 and methane concentrations since the industrial revolution and global temperatures.​

By analyzing the gas composition of air bubbles trapped in the ice, the CO2 concentration and average global temperature can be determined.

The Vostok ice core data show a positive correlation between temperature and CO2. Correlation doesn't prove causation, but investigations of how CO2 absorbs infrared radiation establish a causal connection between CO2 and global temperature.

Define positive feedback.

a change in some variable in the system causes a change in the system that amplifies the original change.

Outline five examples of positive feedback cycles related to global warming.

As temperature increases, CO2 is released from the deep ocean into the atmosphere , which then contributes to the greenhouse effect, creating more warming.

Sea ice has a very high albedo (reflectiveness) compared to open ocean or land. As the temperature increases, ice melting increases and albedo decreases, which then causes the temperature to increase as more heat is absorbed by the ocean.

higher temperatures lead to higher rates of decomposition.

This has the potential to convert carbon that was once stored in the soil long term in forms like peat (partially decomposed plant matter in wetland ecosystems) into atmospheric CO2, which then increases temperatures.

Warmer climates cause permafrost in the tundra to melt. this causes two things:

1. Methane trapped in the permafrost will be released

2. Previously undecomposed organic matter frozen in the permafrost will decompose,

which causes an increase in methane which causes temperatures to rise.

Warmer climate can lead to an increase in drought in some areas, which can make wildfires more frequent. Since combustion releases carbon dioxide, this contributes to further warming.

Define tipping point.

Threshold level at which an environmental problem causes a fundamental and irreversible shift in the behavior of a system.

For example going from a carbon sink to a carbon source.

Explain changes in boreal forest carbon cycle due to climate change.

The boreal forest has traditionally been an ecosystem with high rates of photosynthesis and low rates of respiration and wildfires. It has therefore acted as a carbon sink-an ecosystem that absorbs more carbon dioxide from the atmosphere than it releases.

Warmer and drier conditions have increased the rate of decomposition in the ecosystem and increased the likelihood of wildfires, which means the boreal forest may soon pass a tipping point where it becomes a carbon source instead.

Describe impact of changes to Antarctic polar ice on emperor penguin.

Many fish species live in the water under landfast ice, and emperor penguins rely on these local concentrations of fish to hunt enough food to feed their young. The loss of landfast ice causes these fish to move on, which applies a bottom-up limit on the emperor penguin population.

Describe impact of changes to Arctic polar ice on walruses.​

Walruses feed on the ocean floor, but rely on pack ice to rest and breed. When pack ice melts, walruses are restricted to feeding sites that are close to land, which applies a bottom-up effect on the walrus population.

Outline the cause of ocean stratification.

due to differences in density, with warmer, lighter, less salty water layering on top of heavier, colder, saltier water. Mixing between layers occurs as heat slowly seeps deeper into the ocean and by the action of current, winds, and tides.

Define upwelling and current as ocean phenomena.

Upwelling is a process in which deep, cold water rises toward the surface.

current describes the motion of the ocean

Outline how a change in ocean currents and nutrient upwelling due to global warming has led to a change in ocean primary production.

Because ocean currents sink and rise to the surface, they play an important role in bringing nutrients back to the surface when they rise (upwelling). Without the ocean currents, photosynthesis in the ocean would decrease, causing impacts on marine food chains.

Explain how global warming has caused poleward and upslope shifts in habitats for temperate species.

Since temperature is an important limiting factor in species distribution, changes in temperature also cause changes in species distribution.

In the northern hemisphere, warming allows species to live in areas furthernorth than they historically did, while in the southern hemisphere this is reversed.

Similarly, species that were once limited to lowland areas are able to live further up in elevation.

Explain why tropical montane species may be more sensitive to temperature shifts that result from climate change.

These poleward and upslope shifts in species distribution are not major stressors for tropical or temperate species-if a species moves into your territory from the south, you simply move farther north as well and you can survive.

However, polar species and species that are already adapted to living at high elevations lose out in this-an arctic fox can't move any farther north than it already lives, so its realized niche simply shrinks with the added competition.

Outline the effect of atmospheric CO2 concentration on ocean pH.

Carbon dioxide reacts with water to form carbonic acid.

Rising CO2 concentration increases carbonic acid formation, which leads to ocean acidification.

Describe the impacts of lower ocean pH and higher average ocean temperature on coral reefs.

coral builds its skeleton from calcium carbonate. Carbonate (CO32-) converts into bicarbonate (HCO3-) at lower pH, which is caused by higher temperatures, which prevent coral from building its skeleton.

Explain why loss of coral causes collapse of reef ecosystems.

Because thousands of marine animals depend on coral reefs for survival, including some species of sea turtles, fish, crabs, shrimp, jellyfish, sea birds, starfish, and more. Coral reefs provide shelter, spawning grounds, and protection from predators. They also support organisms at the base of ocean food chains.

Define carbon sequestration.

the transformation of carbon from atmospheric CO2 into another form that can be stored long-term.

Describe afforestation, and reforestation and restoration of peatlands as biologically based approaches to carbon sequestration.

Afforestation involves planting trees in areas like grassland or shrubland. When a tree grows, it incorporates a large amount of carbon to build its trunk and root system, and that carbon can remain inside the tree for hundreds of years.

Debates are ongoing whether plantations of efficient non-native trees or rewilding of local species is a better approach.

Peat is an accumulation of partially decomposed organic matter. It forms in any ecosystem with low decomposition rates, like boreal forests or temperate wetlands.

Water is a poor solvent for oxygen gas, so waterlogged soils become depleted of oxygen, slowing down decomposition. Due to this, efforts to restore wetlands can help address climate change.