Impacts of Urbanization
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AP Environmental Science › Impacts of Urbanization
A city increases density near jobs; which environmental benefit is most likely compared with sprawl?
More habitat conversion per capita because dense housing requires more land per person, increasing fragmentation and edge effects.
Higher per-capita water use because apartments require more irrigation and larger lawns than single-family homes.
Lower public transit viability because density reduces ridership, making frequent service economically impossible in compact neighborhoods.
Reduced vehicle miles traveled and land consumption per capita, which can lower emissions and preserve surrounding natural areas.
Explanation
Increasing urban density near job centers reduces per-capita land use and vehicle miles traveled by enabling walking, biking, and transit. This preserves natural areas and lowers emissions compared to sprawl. Dense areas support efficient public services. However, it requires good planning to avoid overcrowding. Density promotes sustainable urbanization.
A city plants street trees; which mechanism best explains reduced summer energy demand?
Trees eliminate humidity, preventing latent heat transfer and making indoor cooling systems less efficient and more energy intensive.
Trees increase wind resistance, trapping heat near buildings and forcing air conditioners to work harder throughout the summer.
Trees increase albedo of rooftops by producing reflective bark, which directly reflects most incoming solar radiation year-round.
Shading and evapotranspiration lower ambient temperatures and building heat gain, reducing air-conditioning use during hot summer days.
Explanation
Planting street trees provides shade that reduces solar heat gain on buildings and pavements, lowering urban temperatures. Evapotranspiration from leaves further cools the air, decreasing the need for air conditioning. This reduces energy demand and associated emissions. Trees also improve aesthetics and mental health in cities. Urban forestry is a cost-effective way to combat heat islands.
A city’s population doubles; which solid-waste trend is most likely without policy changes?
Total municipal solid waste decreases because larger populations always share goods more efficiently, reducing per-capita and total waste.
Landfill methane emissions stop because waste decomposes aerobically in all landfills, regardless of design or management practices.
Hazardous waste disappears because urban residents produce only biodegradable materials, eliminating the need for special disposal.
Total municipal solid waste increases, often requiring expanded landfill capacity or diversion strategies such as recycling and composting programs.
Explanation
As urban populations grow, total municipal solid waste generation typically increases due to higher consumption and waste production. Without interventions, this strains landfill capacity and increases environmental risks like leachate and methane emissions. Recycling and composting programs can divert waste and reduce impacts. Population density can sometimes improve waste management efficiency. Planning for waste in growing cities is essential for sustainability.
A city replaces wetlands with housing; which ecosystem service is most reduced?
Wetland water filtration and floodwater storage decline, increasing nutrient and sediment loads and raising flood risk during storms.
Stratospheric ozone formation decreases because wetland plants produce oxygen needed for ozone, increasing UV exposure at the surface.
Plate tectonic activity declines because wetlands no longer lubricate faults, decreasing earthquake frequency in the urban region.
Deep-ocean upwelling decreases, reducing marine productivity and causing coastal fisheries to collapse near the inland city.
Explanation
Wetlands provide essential ecosystem services like water filtration, flood control, and habitat provision, which are lost when replaced by housing. Removing them reduces natural buffering against floods, as wetlands store excess water during storms. Nutrient and sediment retention declines, leading to poorer water quality downstream. Biodiversity suffers from habitat loss. Preserving wetlands is crucial for maintaining these services in urbanizing regions.
A city uses permeable pavement in parking lots; what is the primary hydrologic benefit?
Increased infiltration and reduced runoff, which lowers peak storm flows and can enhance groundwater recharge compared with conventional asphalt.
Complete elimination of evaporation because water cannot contact air, guaranteeing more surface water storage after rainfall events.
Reduced infiltration because pores clog instantly, ensuring impermeability equal to concrete after any rainfall event.
Higher runoff because permeable surfaces repel water, sending more flow to storm drains and increasing flash flooding.
Explanation
Permeable pavement allows water to infiltrate through pores, reducing surface runoff compared to traditional asphalt. This enhances groundwater recharge and decreases peak storm flows, mitigating flooding. It also filters pollutants naturally. Maintenance is key to prevent clogging. Such innovations support low-impact development in urban areas.
A city builds near an estuary; which pollutant most commonly drives hypoxic “dead zones”?
Silica from sand increases respiration rates, consuming oxygen and creating dead zones near urban coastlines.
Helium from balloons displaces oxygen in water, creating hypoxia and causing fish kills in coastal estuaries.
Excess nitrogen and phosphorus from wastewater and runoff stimulate algal blooms; decomposition increases BOD and lowers dissolved oxygen.
Iron filings from bridges magnetize oxygen molecules, preventing them from dissolving and causing hypoxia in estuaries.
Explanation
Urban expansion near estuaries increases nutrient runoff from sewage, fertilizers, and stormwater, leading to eutrophication. Excess nitrogen and phosphorus fuel algal blooms, whose decomposition raises BOD and depletes oxygen, creating hypoxic dead zones. This harms marine life, causing fish kills and biodiversity loss. Estuaries are particularly vulnerable due to limited water exchange. Mitigation includes better wastewater treatment and buffer zones. This illustrates urbanization's role in coastal water quality degradation.
A city channels a stream into concrete; which ecological effect is most likely?
Increased habitat complexity as concrete creates riffles and pools, raising macroinvertebrate diversity and improving fish spawning success.
Higher groundwater recharge because concrete is porous, allowing more infiltration than natural streambeds and riparian soils.
Reduced stream biodiversity as channelization increases flow velocity, reduces habitat heterogeneity, and disconnects floodplains from the stream.
Lower erosion because faster water always deposits more sediment, building natural banks and stabilizing channels over time.
Explanation
Channelizing streams into concrete alters natural flow dynamics, increasing velocity and reducing habitat diversity. This homogenization limits niches for aquatic species, decreasing biodiversity. Floodplains become disconnected, affecting nutrient cycling and riparian ecosystems. Erosion may increase downstream due to faster flows. Restoring natural stream features can help recover ecological functions.
A city encourages rain barrels for homes; what is the primary environmental benefit?
Higher groundwater contamination because rain barrels add heavy metals to aquifers, increasing toxicity in municipal wells.
Reduced stormwater runoff and potable water demand by capturing roof runoff for later use, lowering strain on drainage and water systems.
Increased peak runoff because stored water is released all at once during storms, overwhelming storm drains and causing more flooding.
Guaranteed elimination of drought because rain barrels create new precipitation through evaporation and cloud formation over cities.
Explanation
Rain barrels capture rooftop runoff, reducing stormwater volume entering sewers and preventing overflows that pollute waterways. They provide non-potable water for uses like irrigation, lowering demand on municipal supplies. This eases strain on drainage systems during storms, reducing flooding risks. In urban areas, they promote water conservation amid increasing impervious surfaces. However, proper maintenance prevents mosquito breeding. This simple tool illustrates decentralized approaches to urban water management.
A suburb expands into farmland; which outcome best describes habitat fragmentation effects?
Smaller isolated patches increase edge habitat, reduce gene flow, and raise local extinction risk for area-sensitive species.
Fragmentation guarantees higher biodiversity by creating more ecotones, ensuring all species increase in abundance and distribution.
Habitat corridors become unnecessary because urban matrices are permeable, allowing safe movement for most large mammals.
Larger contiguous habitat patches form, increasing interior forest species and reducing edge effects and predator access to nests.
Explanation
Habitat fragmentation occurs when suburban expansion divides large, continuous habitats into smaller, isolated patches, which is detrimental to biodiversity. Smaller patches increase edge effects, allowing more invasive species and predators to impact interior species. Gene flow between populations decreases, raising extinction risks for species needing large areas. Fragmentation often favors generalist species over specialists, altering community structures. Conservation efforts like wildlife corridors can help connect fragments and preserve biodiversity.
Urban lawns receive fertilizer; after storms, which lake response is most likely?
Lower primary productivity because added nitrates and phosphates limit algal growth and reduce chlorophyll concentrations in surface waters.
Eutrophication as nutrient runoff stimulates algal blooms, followed by decomposition that lowers dissolved oxygen and can cause fish kills.
Thermal stratification disappears because nutrients cool the lake, increasing mixing and oxygenation throughout the water column.
Acidification as fertilizers directly release sulfuric acid, lowering pH and dissolving calcium carbonate in lake sediments.
Explanation
Fertilizers applied to urban lawns often contain nitrogen and phosphorus, which can wash into lakes via stormwater runoff after storms. This nutrient enrichment causes eutrophication, promoting excessive algal blooms that block sunlight and deplete oxygen upon decomposition. Low oxygen levels lead to hypoxic conditions, resulting in fish kills and loss of biodiversity. Preventing this requires best practices like reduced fertilizer use and buffer zones. Eutrophication illustrates how urban land management affects downstream water bodies.