Unit 5: Land and Water Use

Common-pool resource (commons)

A shared resource that is difficult to exclude people from using but is reduced by each user’s consumption (rival, hard to exclude), such as fisheries, aquifers, or the atmosphere.

Tragedy of the commons

A pattern (popularized by Garrett Hardin, 1968) in which individuals acting in short-term self-interest overuse and degrade a shared resource because they receive the full benefit of use but only a fraction of the shared cost.

Regulation (top-down management)

Government or authority rules that limit or control resource use to prevent overuse (e.g., fishing seasons/catch limits, grazing permits, groundwater pumping limits).

Privatization (property rights)

Assigning ownership to a resource so the owner has an incentive to manage it sustainably; can be difficult or ethically controversial for resources like water, fisheries, or biodiversity.

Community-based management (local governance)

Local users create and enforce rules, monitoring, and sanctions tailored to local ecology; works best when the group is clearly defined and compliance is enforceable.

Public good

A good that is difficult to exclude people from using and is non-rival (one person’s use doesn’t reduce availability), such as national defense or basic public information.

Clear-cutting

A timber-harvesting method where all trees in an area are cut at once; commonly causes habitat loss, increased runoff/erosion, microclimate warming/drying, and reduced carbon sink capacity.

Edge effect

Changes in environmental conditions and species composition along habitat boundaries (e.g., after clear-cutting creates forest edges), often harming interior-forest species.

Deforestation

Conversion of forested land to non-forest uses (e.g., agriculture, mining, development, plantations), often increasing erosion/runoff, CO2 emissions, fragmentation, and biodiversity loss.

Uneven-aged forest management

A forestry approach that maintains trees of multiple ages (rather than removing all at once), generally reducing ecological disruption compared with clear-cutting.

Habitat fragmentation

Breaking large, continuous habitats into smaller patches (often by logging, roads, or development), which can reduce biodiversity, isolate populations, and increase edge effects.

Subsistence agriculture

Farming primarily to feed the farmer and local community; typically lower external inputs and often lower yields per hectare than industrial systems, but can be locally adapted.

Commercial agriculture

Farming primarily for sale in regional/global markets; often uses mechanization, irrigation, synthetic fertilizers, and pesticides to maximize yield and profit.

Agricultural productivity

Producing greater output with less input (greater efficiency), which can lower costs and increase food availability but may involve environmental tradeoffs depending on inputs used.

Monoculture

Planting a single crop over a large area; efficient for mechanization but reduces biodiversity and can increase vulnerability to pests/disease.

Polyculture

Growing multiple crops (or raising multiple species) simultaneously; can increase resilience, improve soil health, and reduce pest outbreaks compared with monoculture.

Intercropping

A type of polyculture where more than one crop is grown at the same time on the same land area, helping slow pest spread and improve resource use.

Green Revolution

The spread of high-yield crop varieties and high-input farming practices (especially 1940s–1980s) that greatly increased food production using HYVs, fertilizers, irrigation, pesticides, and mechanization.

High-yield varieties (HYVs)

Crop varieties bred/engineered to produce greater yields per area, typically requiring higher inputs (fertilizer, irrigation, and often pest control) to reach potential yields.

Synthetic (inorganic) fertilizer

Manufactured or mined nutrient sources (e.g., nitrogen/phosphorus compounds) that boost plant growth but can drive runoff/leaching and downstream water pollution.

Eutrophication

Nutrient enrichment of water (often from nitrogen and phosphorus runoff) that increases algal growth and can lead to oxygen depletion and ecosystem damage downstream.

Genetically modified organism (GMO)

An organism (plant, animal, or microbe) whose DNA has been altered using genetic engineering to add or change traits not found naturally in that organism.

Rangeland

Native grasslands, woodlands, wetlands, or deserts used for grazing by livestock or wildlife; often managed through grazing pressure and prescribed fire rather than intensive farming inputs.

Overgrazing

Grazing plants faster than they can recover (including regrazing before roots recover), weakening vegetation cover, increasing erosion, and potentially reducing root growth dramatically (up to ~90%).

Desertification

A human-driven (often climate-interacting) decline in productive potential of arid or semiarid land, commonly described as conversion to more desert-like conditions (often ≥10% productivity decline).

Slash-and-burn agriculture

Clearing land by cutting vegetation and burning it; ash can provide short-term nutrients, but repeated use can cause deforestation, CO2 emissions, and long-term soil degradation.

Tillage

Plowing and breaking up soil to prepare for planting; can improve short-term planting conditions but often increases erosion and disrupts soil structure and organisms.

Soil erosion

The physical movement of soil or weathered rock by wind, water, and human activity; loss of nutrient-rich topsoil reduces productivity and can pollute waterways with sediment.

Soil degradation

A broader decline in soil condition due to improper use or poor management (agricultural, industrial, or urban), including loss of structure, fertility, and biological function.

Salinization

Buildup of salts in soil, often from irrigation in dry climates when water evaporates and leaves dissolved salts behind, reducing crop yields via osmotic stress.

Contour plowing

Plowing along the natural contours of a slope to slow runoff and reduce water-driven soil erosion.

Cover crops

Crops planted (often in the off-season) to protect soil from erosion, reduce nutrient loss, and add organic matter to improve soil quality.

No-till agriculture

A soil conservation method that leaves soil largely undisturbed and keeps crop residues on the surface, reducing erosion and often improving soil structure and moisture retention.

Drip irrigation

An irrigation method that delivers water directly to the root zone through tubing at a controlled rate; typically the most water-efficient, reducing evaporation and runoff.

Pesticide resistance

An inherited increase in pest survival after pesticide exposure due to natural selection: resistant individuals survive and reproduce, making the pesticide less effective over time.

Pesticide treadmill (pest trap)

A cycle where rising pesticide resistance leads to increased pesticide use (more frequent/higher doses or more toxic chemicals), which can further accelerate resistance and environmental harm.

Persistent organic pollutants (POPs)

Long-lasting organic chemicals that resist breakdown and can accumulate in fatty tissues of organisms, often biomagnifying through food webs.

Bioaccumulation

The buildup of a chemical (often fat-soluble) within an organism over time because intake exceeds the rate of elimination.

Biomagnification

The increase in concentration of a chemical at higher trophic levels of a food web as predators consume contaminated prey.

Integrated Pest Management (IPM)

An ecologically based pest-control strategy combining monitoring, prevention, and multiple control methods; uses targeted chemical pesticides only as a last resort to limit non-target impacts and slow resistance.

Concentrated Animal Feeding Operation (CAFO)

An intensive livestock facility where large numbers of animals are confined for >45 days/year; concentrates manure, increasing risks of nitrogen/phosphorus pollution and releasing gases (e.g., ammonia, methane, hydrogen sulfide).

Bycatch

The unintended capture of non-target species (e.g., sea turtles, dolphins, juvenile fish) during fishing, which can cause major ecological impacts even when target catches are regulated.

Aquaculture (mariculture)

Fish farming: raising aquatic organisms commercially by stocking, feeding, and harvesting; can reduce pressure on wild fisheries but can create waste, disease/parasite spread, and escape/genetic risks.

Acid mine drainage

Acidic runoff formed when mining exposes sulfide minerals to oxygen and water, producing sulfuric acid that can leach toxic metals and severely degrade water quality.

Impervious surfaces

Urban surfaces (roads, roofs, parking lots) that prevent infiltration, increasing runoff and decreasing groundwater recharge.

Urban runoff

Stormwater flow from cities that carries pollutants (oil, metals, sediment, nutrients, trash, fertilizers, pesticides) into waterways and increases flooding/erosion risk.

Urban heat island

Higher temperatures in urban areas due to heat-absorbing surfaces and reduced vegetation/transpiration, which can warm local air and sometimes contribute to thermal pollution in waterways.

Smart growth

Compact, mixed-use, transit-oriented development designed to reduce sprawl, lower car dependence, preserve open space, and support long-range regional sustainability planning.

Ecological footprint

A measure of human demand on ecosystems: the biologically productive land and sea area needed to provide resources a population uses and to assimilate associated wastes.

IPAT equation

A conceptual relationship for environmental impact: I = P × A × T, where impact depends on population (P), affluence/consumption (A), and technology (T).