Environmental Science Agriculture and Food Production 1 — Questions and Answers
Question 1: The Green Revolution of the mid-20th century primarily involved:
- A global shift from meat-based to plant-based diets
- Development of high-yielding crop varieties, increased irrigation, and synthetic fertilizer use that dramatically raised food production (Correct answer)
- International agreements to protect tropical rainforests from agricultural expansion
- Organic farming methods that eliminated the need for pesticides
Correct answer: Development of high-yielding crop varieties, increased irrigation, and synthetic fertilizer use that dramatically raised food production
The Green Revolution (1940s-1970s) introduced high-yield varieties of wheat and rice, expanded irrigation, and dramatically increased fertilizer and pesticide use, averting famine in much of Asia and Latin America.
The Green Revolution, led by scientists like Norman Borlaug, developed semi-dwarf, high-yielding varieties of wheat and rice that responded well to fertilizer. Combined with expanded irrigation, mechanization, and synthetic inputs, food production in developing countries increased dramatically. It prevented widespread famine but also drove environmental problems: aquifer depletion, soil degradation, pesticide resistance, and loss of crop genetic diversity.
Question 2: Monoculture farming poses environmental risks primarily because:
- It requires more land than polyculture for the same yield
- Genetic uniformity increases vulnerability to pests, diseases, and climate variability (Correct answer)
- Monocultures cannot be harvested by mechanized equipment
- Single crops deplete soil carbon faster than no-till methods
Correct answer: Genetic uniformity increases vulnerability to pests, diseases, and climate variability
A single genetically uniform crop planted over large areas is highly vulnerable to a single pathogen or pest that overcomes its defenses, risking crop failures.
Monoculture reduces the ecological complexity that buffers against pests and disease. When all plants share the same genetic susceptibility, a virulent pathogen or new pest can devastate an entire crop. The 1970 Southern Corn Leaf Blight wiped out ~15% of the U.S. corn crop; the Irish Potato Famine of 1845-52 killed ~1 million people. Monocultures also degrade soil through nutrient depletion, erosion, and loss of microbial diversity.
Question 3: Contour plowing reduces soil erosion by:
- Plowing in the same direction as slope to channel runoff quickly off the field
- Plowing across (perpendicular to) the slope so furrows act as barriers that slow water flow (Correct answer)
- Deep plowing that buries topsoil below the erosion-prone surface layer
- Using mechanized equipment to minimize soil disturbance during planting
Correct answer: Plowing across (perpendicular to) the slope so furrows act as barriers that slow water flow
Contour plowing runs furrows horizontally across a slope, creating ridges that intercept rainwater, reduce runoff velocity, and hold soil in place.
Contour plowing involves plowing and planting across the slope rather than up and down it. The ridges and furrows created act as a series of small dams that trap runoff and allow water to infiltrate rather than flowing downslope and carrying soil particles. Combined with strip cropping, terracing, and cover crops, contour plowing can reduce erosion by 50-75%. It is especially effective on moderate slopes (2-12%).
Question 4: The primary cause of hypoxic dead zones in coastal marine ecosystems is:
- Thermal pollution from power plant cooling water
- Nutrient runoff (nitrogen and phosphorus) from agriculture that causes algal blooms and oxygen depletion (Correct answer)
- Plastic debris that blocks sunlight and prevents photosynthesis
- Overfishing that removes organisms that would otherwise oxygenate the water
Correct answer: Nutrient runoff (nitrogen and phosphorus) from agriculture that causes algal blooms and oxygen depletion
Excess nitrogen and phosphorus from fertilizer runoff stimulate algal blooms; when algae die and decompose, bacteria consume oxygen, creating hypoxic zones where fish and invertebrates cannot survive.
Eutrophication from agricultural nitrogen (primarily as nitrate) and phosphorus causes dense algal and phytoplankton blooms. When blooms die and sink, decomposition by bacteria consumes dissolved oxygen faster than it can be replenished, creating hypoxic zones (< 2 mg/L O2) or anoxic zones. The Gulf of Mexico hypoxic zone (from Mississippi River nutrient discharge) varies from ~5,000-20,000+ square km annually. Other major dead zones occur in the Baltic Sea, Chesapeake Bay, and Yellow Sea.
Question 5: Integrated Pest Management (IPM) is defined as an approach that:
- Eliminates all pesticide use in favor of biological control agents exclusively
- Combines biological, cultural, physical, and chemical controls to manage pests with minimal environmental impact (Correct answer)
- Relies on genetically modified crops that are resistant to all common pests
- Applies pesticides on a fixed calendar schedule regardless of actual pest populations
Correct answer: Combines biological, cultural, physical, and chemical controls to manage pests with minimal environmental impact
IPM uses monitoring and economic thresholds to determine when intervention is needed, then applies the least-harmful effective control before escalating to synthetic pesticides.
Integrated Pest Management (IPM) combines multiple pest control tactics: cultural practices (crop rotation, resistant varieties, timing of planting), biological controls (natural predators, parasitoids, pathogens), physical controls (traps, barriers, cultivation), and chemical controls (pesticides as last resort). IPM uses economic thresholds to time interventions. It reduces pesticide use, slows resistance development, and protects beneficial organisms and human health.
Question 6: Which farming practice best describes no-till agriculture and its primary environmental benefit?
- Planting crops without using any synthetic fertilizers, relying on natural soil nutrients
- Seeding crops directly into undisturbed soil, preserving soil structure and reducing erosion (Correct answer)
- Irrigating crops only when soil moisture sensors indicate water stress
- Rotating crops annually to prevent nutrient depletion in the soil
Correct answer: Seeding crops directly into undisturbed soil, preserving soil structure and reducing erosion
No-till (conservation tillage) leaves crop residues on the surface and disturbs the soil as little as possible during planting, dramatically reducing erosion and retaining soil moisture and carbon.
No-till agriculture uses specialized planters to seed directly through crop residue into undisturbed soil. Benefits include: dramatically reduced soil erosion (up to 90% less compared to conventional tillage); improved water infiltration; increased soil organic matter and carbon sequestration; lower fuel consumption; and preservation of soil biota. Challenges include increased reliance on herbicides to manage weeds and risk of compaction.
Environmental Science Agriculture and Food Production 1
The Green Revolution of the mid-20th century primarily involved: