Question

which human activity most significantly impacts the flow of carbon by moving stored carbon from the geosphere directly into the atmosphere?
deforestation, which increases the rate of cellular respiration by decomposers.
agricultural runoff, which increases the amount of dissolved carbon in the hydrosphere.
burning of fossil fuels, which releases carbon compounds stored over millions of years.
planting large areas of new forests, which increases the rate

Explanation:

To solve this, we analyze each option:

• Deforestation: Increases decomposition (respiration of decomposers) but not a direct move from geosphere (fossil fuels are geosphere - stored over millions of years) to atmosphere.
• Agricultural runoff: Affects hydrosphere, not geosphere to atmosphere carbon flow.
• Burning fossil fuels: Fossil fuels are carbon stored in geosphere (from ancient organisms, over millions of years). Burning them releases \(CO_2\) (carbon compounds) directly into the atmosphere. This matches moving stored carbon from geosphere to atmosphere.
• Planting forests: Increases photosynthesis (removes \(CO_2\) from atmosphere), not moving from geosphere.

Answer:

Burning of fossil fuels, which releases carbon compounds stored over millions of years.