Returning once-forested pastures to natural tree cover, through tree planting or natural regeneration, can improve a city’s water security. Trees stabilize soil, reduce erosion, and prevent fertilizer and manure runoff that can lead to river and stream pollution. This measure shows the amount of pasture that would need to be reforested to reduce nutrient or sediment loading by 10 percent.
Lower numbers are better, since for less work you still get a 10 percent reduction: high potential (< 1,000 hectares), medium potential (1,000-10,000 hectares) and low potential (>10,000 hectares). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this strategy.