Describe land-use change and its effect on carbon storage and climate feedbacks.

• A. Changes from farmland to forest always increase emissions.
• B. Land-use change has no effect on carbon storage.
• C. All land-use changes increase soil carbon.
• D. Changes from natural to human use (deforestation, urbanization) reduce carbon storage and can increase greenhouse gas emissions.

Answer: (D)

When natural ecosystems are changed to human uses, the amount of carbon stored in living biomass and soils often falls, and that loss can feed back to climate. Forests and other natural landscapes hold large carbon reserves in aboveground trees, roots, litter, and especially soil organic matter. Clearing land for agriculture or urban development removes vegetation, and the carbon that was tied up in those plants is released back to the atmosphere as CO2 (and sometimes methane or nitrous oxide, depending on conditions). Disturbing soil through tillage or construction further reduces soil organic carbon and lowers the land’s capacity to store carbon in the future. With fewer plants to absorb CO2 through photosynthesis, atmospheric CO2 can accumulate, enhancing the greenhouse effect and warming climate. That warming can then influence fire regimes, pests, and more land-use changes, creating a positive climate feedback loop. While some land changes (like reforestation or afforestation) can increase carbon storage, the scenario described—natural land becoming used for human activities such as deforestation or urbanization—tends to reduce carbon stocks and elevate greenhouse gas emissions.