1. Review of Carbon, Nitrogen and Phosphorus Cycles

2. The Carbon Cycle

3. Carbon Moves From: Atmosphere to plants
(C02 pulled from air to use in photosynthesis)
Plants to animals
(animals eat plants or other animals)
Plants and animals to soils
(decaying bodies release carbon into the soil)
Living things to atmosphere
(as you exhale, release CO2)

4. Concerns for Humans
CO2 is a greenhouse gas that traps heat in the atmosphere.
Burning fossil fuels has added 5.5 billion tons per year of carbon to the atmosphere (a 30% increase over the past 150 years)
The increased Carbon is causing the planet to become warmer.

5. The Nitrogen Cycle 80% of Nitrogen is in the atomosphere
(it is not in a form that humans can use: needs to be broken down by lightning, fire or bacteria)
Animals get nitrogen to make amino acids by eating plants
(when animals/plants die, decompose and return nitrogen to soil)

6. Concerns for Humans
The use of nitrogen rich fertilizers, causes too much nitrogen to be added to waterways via runoff.
Animal wastes associated with farming add more nitrogen to soil and water.
Burning fossil fuels fixes nitrogen from the air.
High concentrations of nitrogen in the water causes “algae blooms”: toxic to fish and shellfish.

7. The Phosphorus Cycle
No atmosphere connection. Phosphorus added by animal waste, runoff and rock erosion.
(Plants hydrolyze the phosphorus; animals eat the plants. Decaying plants and animals and animal wastes return phosphorus to the soil.)

8. Concerns for Humans Phosphorus run off leads to eutrophication
Eutrophication: a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae and nuisance plants weeds). This enhanced plant growth reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die.