Natural Resources and Environmental Science: Watersheds, Conservation, Wildlife, and Energy
This domain covers the hydrologic cycle and watersheds, soil erosion and conservation practices, water-quality issues, wildlife habitat and population management, forestry, and renewable energy. Expect quantitative items on carrying capacity and conceptual items on erosion and pollution sources.
Water and watersheds
- Hydrologic cycle: evaporation, transpiration, condensation, precipitation, infiltration, percolation to groundwater, and runoff.
- A watershed is all land draining to a common outlet; ridges and divides separate neighboring watersheds.
- Nonpoint source pollution - sediment, nitrogen, phosphorus, and pesticides carried by runoff - is the leading cause of water-quality impairment. Point sources come from a pipe or outfall. Riparian buffers, cover crops, and nutrient management reduce nonpoint losses.
- Eutrophication: excess N and P trigger algal blooms, oxygen depletion, and fish kills.
Erosion and conservation
- Water erosion types: sheet (uniform), rill (small channels), gully (deep, cannot be crossed by equipment). Wind erosion dominates dry, bare, fine-textured soils.
- The Universal Soil Loss Equation: A = R × K × LS × C × P, where C (cover management) and P (supporting practice) are the factors a producer controls most directly.
- Practices: contour farming, terracing, strip cropping, no-till, cover crops, grassed waterways, windbreaks, and crop rotation.
Wildlife, forestry, and energy
- Habitat requires food, water, cover, and space. Carrying capacity is the maximum population an area sustains; stocking rate is what the manager applies. The proper use factor leaves roughly half the forage for the resource.
- Succession runs bare ground → grass and forbs → shrubs → young forest → mature forest. Edge habitat often boosts diversity.
- Water rights: riparian doctrine ties use to land bordering water; prior appropriation follows "first in time, first in right."
- Renewable options: biomass, methane digesters, solar, wind; ruminant methane and fertilizer nitrous oxide are key greenhouse gases.
Worked example
200 acres × 3,000 lb forage/acre = 600,000 lb of forage. With a 50% proper use factor, usable forage = 300,000 lb. A 1,000-lb cow with calf consumes about 9,000 lb/year. 300,000 ÷ 9,000 = 33 cow-calf pairs. If drought cuts production to 1,800 lb/acre, usable forage falls to 180,000 lb and capacity falls to 20 pairs.
Traps that cost marks
- Confusing sheet with gully erosion, or point with nonpoint pollution.
- Skipping the proper use factor and overstating carrying capacity.
- Treating carrying capacity as fixed despite drought and succession.
- Mixing riparian and prior appropriation doctrines.