Question

building understanding
one way to measure the amount of organic matter in soil is by measuring soil carbon. look at table 2.2, which shows how soil carbon is affected by different land uses.

table 2.2: effect of land use changes on soil carbon
land use change | change in soil carbon
crop to secondary forest | +53%
crop to pasture | +19%
crop to planted trees | +18%
native forest to pasture | +8%
pasture to planted trees | −10%
native forest to planted trees | −13%
native forest to crop | −42%
pasture to crop | −59%

what do you think are the long term impacts of these changes? support your answer with evidence from table 2.2.

your answer

Explanation:

To determine long - term impacts, we analyze the soil carbon changes:

1. Increases in soil carbon (e.g., Crop to secondary forest, + 53%): Higher soil carbon means more organic matter. This improves soil fertility (better nutrient - holding capacity), enhances water retention, and supports more diverse soil organisms. It also helps in carbon sequestration, mitigating climate change as soil stores carbon.
2. Decreases in soil carbon (e.g., Pasture to crop, - 59%): Lower soil carbon reduces soil fertility, makes the soil more prone to erosion (as organic matter binds soil particles), and decreases the soil's ability to sequester carbon, contributing to higher atmospheric CO₂ levels. For example, converting native forest to crop (- 42%) or pasture to crop (- 59%) leads to large carbon losses, which can degrade soil health over time and increase greenhouse gas emissions.

Answer:

Long - term impacts relate to soil health and climate:

• Positive impacts (when soil carbon increases): Land use changes like “Crop to secondary forest” (+53%) and “Crop to pasture” (+19%) increase soil carbon. This boosts soil fertility (more organic matter for nutrients), improves water - holding capacity, and aids carbon sequestration (reducing atmospheric CO₂, fighting climate change).
• Negative impacts (when soil carbon decreases): Changes like “Pasture to crop” (-59%) and “Native forest to crop” (-42%) reduce soil carbon. This degrades soil health (lower fertility, more erosion), and reduces carbon sequestration (increasing atmospheric CO₂, worsening climate change).

Evidence: Table 2.2 shows that land uses converting to more natural or semi - natural states (e.g., crop to forest) increase soil carbon, while converting natural/pasture land to cropland decreases it.