How people change the environment: forests, rivers, cities and pollution

Grade 9 Social Studies Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Card F, cities (EPA)

   In the United States, urban areas are about 1–7°F warmer by day and 2–5°F warmer at night than outlying areas, a heat island. Pavement and buildings soak up heat, and cities have fewer trees. A 2025 review of 115 studies found that urban trees generally cool the air more than other plants. Card G, changes in the United States from 1970 to 2025 (EPA): gross domestic product (GDP) up 349%; vehicle miles up 197%; energy use up 46%; population up 67%; emissions of the six main air pollutants down 78%. In 2025, about 115 million people lived in counties where pollution was above a national air-quality standard. Card H, chain: more vehicles and factories can release more air pollution; cities offer jobs and services that draw people in.

2. 1.

   GDP rose 349% and population rose 67% from 1970 to 2025. Does that mean each person's share of GDP rose 349%, Noah asks?

   • About 282%, since 349% minus 67% is the rise in the share for each person of the nation
   • About 6 times, since GDP rose 4.49 times and population rose 1.67 times, and the two ratios add to about 6
   • No: population grew too, so GDP per person rose by about 169%, since 4.49 ÷ 1.67 is about 2.7
   • Yes: GDP rose 349% and each person gets a share of it, so each share rose by the same percent
3. 2.

   How can emissions be down 78% since 1970 and 115 million people still live where pollution is above a standard, Ren asks?

   • A 78% fall is a change since 1970; a standard is a fixed level, so air can be far cleaner and still above it
   • The 115 million is a small number, so it does not matter next to the 78% fall in emissions
   • Emissions fell in the counties that meet the standard, and rose in the counties that do not
   • The 78% fall must be wrong, since 115 million people could not live above a standard if emissions had fallen
4. 3.

   Card F gives 1–7°F by day and 2–5°F at night for U.S. urban areas. Which statement is supported, Tala asks?

   • A city is 7°F warmer by day, since 7°F is the top of the range and the range is the same in each place, in each year
   • The night gap is the bigger gap, since 2–5°F has a higher floor than 1–7°F and so wins
   • Cities are warmer by night than by day, since the night range starts at 2°F and the day range at 1°F
   • Across U.S. urban areas the day gap varies more, 1–7°F, than the night gap, 2–5°F, and the night gap is at least 2°F
5. 4.

   A planner says more street trees will help cool a city. What do the cards support, Zee asks?

   • Trees generally cool the air more than other plants in cities, though 'generally' leaves room for exceptions
   • Other plants cool the air more than trees, since pavement and buildings soak up heat from trees
   • Trees cool by soaking up the heat from pavement, so planting them right beside the buildings and roads works well
   • Trees remove the heat island, since the review of 115 studies shows trees cool the air in cities and remove the problem
6. 5.

   Card H says cities offer jobs and services that draw people in, and also that more vehicles can release more pollution. What does that mean for a growing city, Ari asks?

   • Growth raises pollution in a city, since more vehicles mean more pollution in the air
   • The draw of jobs and services can bring more vehicles, so growth carries a chance of more pollution
   • The draw of jobs and services ends once vehicles release more pollution, so the two cannot go together
   • The jobs and services offset the pollution, so the city comes out ahead whenever it grows
7. 6.

   Card H says more vehicles can release more pollution, yet Card G shows vehicle miles up 197% and emissions down 78%. How do they fit, Bo asks?

   • The totals are wrong, since more vehicle miles must mean more emissions, as the chain says
   • Both fit because vehicle miles fell while emissions fell, and the chain is about fewer vehicles
   • The chain is wrong, since vehicle miles rose and emissions fell, so vehicles do not release pollution
   • The chain says more vehicles can mean more pollution, but the totals show the net result: a large fall
8. 7.

   Esme's note: 'Cities grew from 1970 to 2025, so air pollution got worse.' Which fix fits Card G?

   • Population rose 67%, but emissions of the six main air pollutants fell 78%, so growth did not make it worse
   • Change 'cities' to 'vehicles', since vehicle miles rose 197% and that is what made the pollution worse, as the miles show
   • Keep it, since 115 million people still live above a standard and so pollution must have grown
   • Change 'worse' to 'better', since emissions fell 78% and so the air is clean for people everywhere now
9. 8.

   Jun's note: 'Heat islands exist because people in cities use more energy.' Which fix fits Card F?

   • Card F points to pavement and buildings that soak up heat and to fewer trees, not to the energy people use
   • Change 'energy' to 'trees', since cities have more trees and the trees hold the heat in the city
   • Change it to say heat islands are caused by pollution, since vehicles and factories release air pollution
   • Keep it, since energy use rose 46% from 1970 to 2025 and so cities got hotter as a result
10. 9.

    A headline says U.S. driving 'nearly doubled' from 1970 to 2025. Is it right, using Card G, Kira asks?

    • Yes: 197% is nearly 200%, which is twice as much, so the headline is a fair way to say it
    • No: up 197% means about 197 times as many miles, since a percent counts how many times a total grew
    • Yes: vehicle miles rose less than GDP, 197% against 349%, so doubling is a fair description of it
    • No: up 197% means nearly three times 1970's miles, since the new total is 1 + 1.97 times the old one
11. 10.

    Card H says cities draw people with jobs and services, and Card F reports heat islands. Which statement weighs both, Milo asks?

    • The jobs make up for the heat island, since the draw of a city is bigger than any cost it has
    • The heat island will stop people coming, since a city that is warmer by day loses its draw
    • The heat island is the one effect of growth that the cards report, so planners can ignore the jobs and services
    • Growth brings jobs and services that draw people and a heat island of 1–7°F by day, so planners weigh both