Nutrient Cycling & Climate Change

Nutrient cycles

involve the storage (pools or reservoirs) and movement (flux) of nutrients in an ecosystem

carbon cycle

is the process by which carbon is exchanged among the atmosphere, land, and oceans, involving photosynthesis, respiration, decomposition, and fossil fuel combustion.

key points - carbon cycle

moves between organisms and atmosphere

photosynthesis removes CO2 from atmosphere

Respiration by primary producers, consumers, decomposers, returns carbon to atmosphere

Some carbon cycles rapidly between organisms and atmosphere like

photosynthesis by plants, respiration by animals and decomposition by microbes.

Some carbon cycles are unavailable for long periods of time

carbonate rocks, carbon in soil, fossil fuel

In aquatic ecosystems,

CO2 first dissolves in water before being used by aquatic producers. Once dissolved CO2 enters chemical equilibrium with bicarbonate and carbonate. Carbonate may precipitate out of solution as calcium carbonate may be buried in ocean sediments.

greenhouse effect

caused by radiatively active gases (RAGs) “greenhouse gases”

what are the greenhouse gases

water vapor

carbon dioxide

methane

ozone

nitrous oxide

chlorofluorocarbons

what is the greenhouse effect

gases that absorb infrared radiation emitted by a solar-heated earth and reemit that energy back to earth, trapping heat and raising earth’s temperature

The most abundant radiatively active gas in the atmosphere is

water vapor (60%-80% warming)

If water vapor is the most important greenhouse gas, why are scientists so much more concerned about CO₂ and CH₄?

There’s a limit to how much water can be held in the atmosphere before it precipitates. That’s not true of CO₂ and CH₄.

Humans have much more control over emissions of CO₂ and CH₄ than they do over the amount of water vapor.

After water vapor, what are the next most important RAGs

CO2 and CH4

What other factors beside the greenhouse effect also influence climate?

variation in solar activity

changes in earth’s orbit and rotation

volcanic activity

ocean currents and other natural factors

Other factors affecting climate change

axial wobble and variation of tilt - earth’s axis is not stable causing wobbling and tilt change over time. This alters amount of sunlight received by different parts of earth (occurs over 100,000 years)

climate

The long-term average of weather patterns in a specific area, including temperature, humidity, and precipitation.

weather

The day-to-day state of the atmosphere in a specific area, including temperature, humidity, precipitation, and wind.

Current climate models suggest

global warming is being produced by natural and anthropogenic processes, but humans are having a larger effect than natural processes.

How have humans altered carbon cycles?

Destroying vegetation = carbon released is then 40% fossil fuel burning

Approximately 15,000 years ago, much of the earth (including the area that is now Massachusetts) was covered by glaciers. The difference in global mean temperature between that “ice age” and today was:

approximately 5°C

How have humans altered the global carbon cycle?

Increasing the rate at which carbon enters the atmosphere

Assuming greenhouse gas emissions continue at current rates, the climate in MA at the end of this century is expected to be most similar to the current climate of:

South Carolina - hotter summers

Ocean acidification is a potentially serious problem because:

It will make it difficult for many marine organisms to produce their exoskeletons.

agricultural Implications

can adjust to climate change by moving crops around and adaptive management

though some areas can become non-productive from insufficient soil moisture

While increased CO2 increases photosynthetic rates and growth of plants

it also increases the ratio of carbohydrates to other nutrients reducing food nutrition

gulf stream

a warm and swift Atlantic Ocean current that follows the eastern coastline of the US and Canada before crossing the Atlantic Ocean towards Europe. It ensures that the climate of Western Europe is much warmer than it would otherwise be.

Climate change can disrupt gulf stream and result in

• Warmer waters: Rising temperatures make ocean waters warmer and lighter. 

• Freshwater influx: Melting ice sheets and glaciers add freshwater to the North Atlantic, making the water less salty and less dense. 

• Reduced circulation: If the water isn't heavy enough to sink, the circulation stops

decrease in dissolved oxygen in oceans

significant impacts on marine life and ecosystems,

hurt fish population and disrupt food web

Things to reduce the net emissions of RAGs

Decrease the use of fossil fuels:
- reduce the overall use of energy by reduction & conservation
- displace fossil fuels with other sources of energy, preferably renewable ones

• Stop or decrease the conversion of high-C ecosystems into low-C ones:

• conserve existing forest and grassland; these ecosystems store more C than agricultural or urban systems

• afforestation - increase carbon storage in ecosystems

What if nothing is done to stop emission of RAGs

eventually fossil fuels will run out = carbon emissions will decrease

excess carbon will be absorbed by the oceans, leading to increased ocean acidification

ocean acidification effects (pg 508)

skeletal damage

food web disruption

ecosystem changes

harmful algal blooms