Chapter 5: Ecology5.2: The Greenhouse Effect

5.3 Populations

Carbon CycleShow how carbon is recycled throughout the

environment Show transformation of carbon from organic

forms and inorganic formsIncludes:

Photosynthesis - removes carbon from atmosphere

Cellular respirationCombustion - adds carbon to

atmosphereFossilization

Analyzing Changes in Atmospheric CO2

Average CO2 concentration has increased from ~315 ppm to ~380 ppm in a span of just over 40 years.

Fluctuations within the year are due to seasons. When trees lose their leaves, they will not be able to remove CO2 from the environment

Relationship between greenhouse gases and the Enhanced Greenhouse Effect

The above graph show that global temperatures have been rising

Shows a correlation between rise in carbon dioxide levels and temperature rise.

But is this causation?

Ice samples taken from Antarctica contain small pockets of air, that can be analyzed for composition.

The deeper the ice sample, the “older” it is

The Greenhouse EffectOf all the light energy that reaches the Earth

from the Sun, ~30% is reflected back into space and ~70% will warm up the Earth’s surface and eventually radiate out as infra red radiation.

The Greenhouse Effect is the concept that some of this infra red radiation will become trapped in the Earth’s atmosphere by (greenhouse) gases, thus warming the Earth

The trapping of this energy is essential to life on Earth – it makes Earth habitable planet with temperatures suitable for sustaining life.

These naturally occurring greenhouse gases have been around for a long time, but with an increase in industry, population, and land development, the level of these greenhouse gases has been increasing

Greenhouse GasesCarbon Dioxide CO2Methane CH4 (contributes 20x more than

CO2 )Nitrogen oxides NOx

These gases absorb the long wavelengths of infra red light, keeping them in the Earth’s atmosphere longer.

This causes a Global Warming

Consequences of Global Warming on Arctic EcosystemsMelting of the Polar Ice Caps

as the ice caps melt, they add fresh water to the ocean’s salt water

Thus, they alter the salinity. This can disrupt ecosystems This can alter ocean currents, which can alter wind

currents, which can alter climate and result is drastic climate change

Increase the volume of water in the ocean This can cause severe flooding in coastal cities

Consequences of Global Warming on Arctic EcosystemsThe white snow and ice in the Arctic reflect a

lot of the Sun’s radiation.When the snow and ice melt (bc of global

warming), the Artic will warm up even faster (bc light will be absorbed rather than reflected)

Melting of the permafrost in Siberia would release methane gas (a greenhouse gas) thus making the planet even warmer

Positive Feedback!

Consequences of Global Warming on Arctic EcosystemsThe warmed Arctic climate causes a change in

the Arctic habitat, thus changing the migration and feeding patterns of various species

Includes: polar bears, seas, caribou

Native Americans who hunt these animals would find it difficult due to changing migration patterns

Some villages have had to relocate because of swampy conditions created with the warming

Consequences of Global Warming on Arctic EcosystemsEffects on Polar Bears?High temperatures melt the snow in polar

bear dens, shortening their hibernation periods.

Lack of ice mass mean polar bears have to swim longer distances and expend more energy to reach prey or travel.

Polar bears drowning???

Consequences of Global Warming on Arctic EcosystemsThe plant species that live and prosper in the

Arctic are adapted to the environment

Milder climates mean that more species would be able to survive in the Artic – increases competition.

Native species can become vulnerable and possibly at risk because of this competition

Consequences of Global Warming on Arctic EcosystemsPOSITIVES?

More plant species means higher biodiversityMore food for Arctic herbivores

There are a lot of gas reserves in the Arctic that remain largely inaccessible.

The melting of the ice would allow us to tap into this resource for oil and gas

However, would that lead to positive feedback?

Precautionary PrincipleIf we are not sure what the consequences of

a change in our behaviour would be, then the people who want this change should prove that it will not be harmful.

Ex: If you want to introduce a new medicine in the market, you must first prove that it is safe and doesn’t cause harm

In some cases, the people resisting change must prove that the change will cause harm

This can be difficult

Criticisms to the Precautionary PrincipleIncludes assumptions of consequences that have

not been provenThe principle is more concerned with the degree

of the seriousness of the consequences and not the actual chance of them occurring

Sometimes only applied to new technology and not the technology it would replace. (ex wind turbines)

Used to scare people

Precautionary Principle and The Greenhouse EffectSince we’re not sure what the exact effects of

increasing CO2 levels are, the precautionary principle can be applied

Countries could agree to reduce greenhouse emissions and boycott trade with countries that do not complyThis can be problematic for poorer countries.It may not be possible to reduce greenhouse

emission without delaying economic growth.Can lead to increased hunger and premature death

in these countries

PopulationsFactors that affect a population

Natality (birth rate)Mortality (death rate)Immigration (moving in)Emigration (moving out)

Limiting FactorsAny population has the potential to increase

its numbers quickly.

In most natural situations, this increase in numbers is controlled by limiting factors

Limiting FactorsAnimal Population

Food availabilityPresence of a parasite/diseaseAmount of predationAvailable nesting sites

Plant PopulationAmount of sunlightAmount of waterAmount of carbon dioxideTemperature

Sigmoid Growth Curve

Exponential Growth Phase - Unlimited growth due to lack of limiting factors

Transitional Phase- Limiting factors start influencing the rate of increase in the

population- Population still increasing, but not exponentially

Plateau Phase- Population no longer

increases due to limiting factors

- Natality + Immigration = Mortality + Emigration

- Population has reached its carrying capacity (the max number of individuals that can be supported by the environment)

Carrying Capacity