The Green Revolution
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AP Environmental Science › The Green Revolution
A region’s crop yields rise under Green Revolution practices, but soil organic matter declines. Which practice best rebuilds organic matter?
Planting cover crops and adding compost or manure, which increases carbon inputs to soil and supports microbial communities.
Removing crop residues after harvest, which prevents pests and therefore increases soil organic matter through reduced decomposition.
Deep plowing every season, which accelerates oxidation of organic matter and increases long‑term soil carbon storage.
Increasing pesticide applications, which adds carbon directly to soil and replaces the need for plant residues.
Explanation
Declining soil organic matter under Green Revolution practices results from intensive tillage and residue removal, which deplete carbon inputs. Planting cover crops and adding organic amendments like compost rebuilds organic matter by enhancing carbon sequestration and microbial activity. This improves soil structure, fertility, and resilience. Practices like deep plowing or bare fallow accelerate degradation instead. Restoring organic matter supports long-term productivity and environmental health.
A Green Revolution program promotes double-cropping using irrigation and fertilizers. Which environmental concern is most likely to increase?
Reduced soil erosion, because planting more often always leaves soil bare longer and increases root binding.
Soil nutrient depletion and water stress, because more harvests per year remove more nutrients and increase irrigation demand.
Increased biodiversity, because double-cropping requires planting many different native species simultaneously in the same field.
Lower pesticide resistance, because more crop cycles prevent pests from reproducing and reduce selection pressure.
Explanation
Double-cropping intensifies land use, increasing nutrient removal and irrigation needs, leading to soil depletion and water stress. The Green Revolution promoted this for higher annual yields. Without replenishment, fertility declines. Pest pressures may rise with continuous cropping. Rotation and fallows can mitigate. This concern highlights intensification's limits.
A farmer applies fertilizer just before a heavy storm. Which best predicts nutrient movement from the field?
Nutrients convert to rock minerals instantly, because storm energy catalyzes permanent binding of nitrogen into bedrock.
Complete immobilization of nutrients because storms seal soil pores, preventing any transport of dissolved nitrogen compounds.
Increased runoff and leaching of nitrates into waterways and groundwater, elevating eutrophication risk and contaminating drinking supplies.
Nutrients move only upward into the atmosphere, because rainwater forces nitrate to evaporate as a gas during thunderstorms.
Explanation
Heavy storms after fertilizer application in Green Revolution fields can cause significant nutrient runoff and leaching, leading to water pollution and eutrophication. Nitrates move into waterways, contaminating supplies and harming ecosystems. Timing applications to avoid storms reduces these risks. Ideas of nutrients evaporating or converting to rocks are scientifically inaccurate. Proper practices minimize environmental impacts.
After HYV adoption, a farming district shifts from many small plots to large mechanized fields. Which socioeconomic effect is most likely?
Reduced income inequality because all farmers can equally afford seeds, fertilizers, irrigation pumps, and tractors without credit constraints.
Potential displacement of smallholders as capital-intensive inputs favor wealthier farmers and can increase rural economic inequality.
Immediate elimination of debt because higher yields always exceed costs, making loans unnecessary for purchasing inputs.
Greater employment for landless laborers because mechanization requires more hand weeding and harvesting than traditional mixed cropping systems.
Explanation
The shift to large mechanized fields in Green Revolution districts often favored wealthier farmers who could afford capital-intensive inputs like tractors and irrigation systems. Smallholders, lacking access to credit or resources, faced displacement or consolidation of their lands into larger operations. This exacerbated rural economic inequality, with benefits accruing unevenly. Unemployment among landless laborers could rise as machinery reduced labor needs. Such socioeconomic effects highlight the uneven distribution of Green Revolution gains. Policies promoting equitable access to technology are needed to address these disparities.
A country credits Green Revolution crops with avoiding deforestation by raising yields. Which concept does this argument rely on?
Land sparing: higher yields per unit area can reduce pressure to convert additional natural habitat into cropland.
Tragedy of the commons: higher yields always cause overuse of shared resources, guaranteeing more deforestation.
Biotic potential: higher yields reduce population growth rates by increasing fertility and lowering education levels.
Ecological succession: higher yields accelerate conversion of forests into grasslands, increasing biodiversity and carbon storage.
Explanation
Land sparing suggests that intensifying yields on existing land reduces the need to clear new areas, potentially preserving forests. The Green Revolution enabled this in some regions by meeting food demands without expansion. However, outcomes depend on policies and markets. Deforestation may still occur if profits drive expansion. This concept balances production and conservation. The argument relies on efficiency gains.
A nation expands Green Revolution farming by converting wetlands to cropland. Which environmental service is most directly lost?
Stratospheric ozone formation, because wetlands release oxygen that directly builds the ozone layer and blocks ultraviolet radiation.
Ocean upwelling, because wetlands drive deep-water circulation and nutrient delivery to marine fisheries across the globe.
Geothermal energy production, because wetlands are the main locations where Earth’s internal heat reaches the surface as electricity.
Wetland water filtration and flood mitigation, since wetlands trap sediments and nutrients and store stormwater during heavy rainfall.
Explanation
Wetlands provide critical ecosystem services like filtering pollutants from runoff, mitigating floods by storing water, and supporting biodiversity. Converting them to cropland for Green Revolution expansion directly eliminates these functions, increasing flood risks and water pollution. Nutrient and sediment trapping is lost, affecting downstream ecosystems. Habitat for wildlife diminishes. Restoration efforts can recover some services. This loss illustrates trade-offs in land use decisions.
A Green Revolution irrigation scheme increases standing water in fields. Which vector-borne disease risk may increase as a result?
Malaria risk may increase if mosquito breeding habitat expands in standing water near human settlements and farmworker housing.
Tuberculosis risk may increase because irrigation water aerosolizes nitrogen fertilizer, spreading bacterial infections through the air.
Rabies risk may increase because standing water increases bat populations that transmit rabies through contaminated irrigation canals.
Scurvy risk may increase because irrigation removes vitamin C from crops, causing deficiency in nearby communities.
Explanation
Irrigation expansions in the Green Revolution created standing water, providing breeding grounds for mosquitoes and increasing risks of vector-borne diseases like malaria. Proximity to human settlements amplifies exposure, particularly for farmworkers. This highlights a human health downside of intensified agriculture in tropical regions. Other diseases like scurvy or rabies are not directly linked to irrigation practices. Proper water management and mosquito control can mitigate these risks.
Green Revolution irrigation expanded in arid regions using river diversions. Which downstream impact is most likely?
Higher downstream biodiversity because reduced flow concentrates nutrients and oxygen, eliminating stress on aquatic organisms.
Reduced river discharge and degraded aquatic habitat downstream, potentially shrinking wetlands and increasing salinity in deltas or terminal lakes.
Increased downstream flow because irrigation canals add water to rivers, raising fish populations and improving navigation year-round.
No change in river ecosystems because diversions only occur during floods, and floodplains always recover instantly afterward.
Explanation
River diversions for Green Revolution irrigation reduce downstream flow, degrading habitats and increasing salinity in deltas or lakes. Wetlands shrink, affecting biodiversity and fisheries. The Aral Sea exemplifies such impacts from cotton irrigation. Reduced discharge alters ecosystems. Sustainable allocation is needed. This highlights upstream-downstream conflicts in water use.
Which scenario best illustrates how Green Revolution inputs can increase energy use in agriculture?
Farmers replace human labor with composting, which requires no additional energy and eliminates the need for transportation or machinery.
Synthetic fertilizer production via the Haber-Bosch process uses fossil fuels, and irrigation pumping and mechanization add further energy demand.
HYV seeds photosynthesize at night, reducing electricity use for irrigation and lowering fuel consumption in fertilizer manufacturing.
Monocultures require fewer inputs, so adopting HYVs always decreases fuel use per hectare in every climate and soil type.
Explanation
The Haber-Bosch process for synthetic fertilizers is energy-intensive, relying on fossil fuels and increasing agriculture's carbon footprint. Irrigation pumping and mechanized operations add further energy demands. The Green Revolution shifted farming toward high-input systems. This raised overall energy use per unit of food. Alternatives like renewables can mitigate. The scenario shows energy-agriculture links.
A Green Revolution region shows increased soil compaction from heavy machinery. Which management practice best reduces compaction impacts?
Increasing machinery weight, which presses soil particles closer and improves pore space, raising root growth and water infiltration.
Controlled traffic farming or reduced tillage, which limits machinery passes and helps maintain soil structure and infiltration capacity.
Applying more pesticides, which dissolves compacted soil aggregates and permanently restores macropores without changing field operations.
Removing all crop residues, which exposes soil to rain impact and speeds natural loosening of compacted layers.
Explanation
Soil compaction from heavy Green Revolution machinery reduces porosity, limiting root growth and water infiltration. Controlled traffic or reduced tillage minimizes repeated compression, preserving structure. These practices maintain productivity. Crop rotation can also help. Avoiding wet field operations prevents worsening. This management addresses mechanization's downsides.