1. Natural Resources Perpetual Renewable Non-renewable

2. Natural Resources Perpetual: Available forever (in “human time” perspective ) Perpetual energy sources? Solar Radiation TidesWind Rivers (hydro)? perhaps...

3. Natural Resources Renewable: Rate of replenishment by natural processes ≥ Rate of consumption Renewable energy sources? Wood* Other biomass* *but there’s a catch...

4. Natural Resources Non-renewable: Rate of replenishment by natural processes < Rate of consumption Non-renewable energy sources? Natural Gas Coal Oil Nuclear Geothermal -- a “tweener”

5. Sustainable Able to continue a certain behavior indefinitely. Sustainable Yield The maximum rate at which humans can use a resource over a long time period (i.e., without reducing the possible level of yield).

6. What class(es) of natural resources could be used sustainably? Renewable (e.g. timber/wood, water, clean air, fisheries, etc.) Perpetual (but not in danger of being used unsustainably)