Which of the following is NOT a potential impact of excessive atmospheric moisture?

Decreased humidity is not a potential impact of excessive atmospheric moisture because excessive moisture in the atmosphere typically leads to increased humidity levels rather than a decrease. When there is a high concentration of water vapor in the air, it increases the overall humidity, which can contribute to various weather phenomena such as fog, precipitation, and cloud formation.

In contrast, flooding, increased vegetation growth, and altered weather patterns are all legitimate consequences of heightened moisture in the atmosphere. Flooding occurs when water accumulates in excessive amounts due to heavy rainfall or rapid snowmelt. Increased vegetation growth can result from more available water, which supports plant life; however, this growth can also lead to challenges such as increased pest populations. Altered weather patterns may emerge as the overall climate systems respond to the increased moisture content, leading to changes in precipitation and temperature distributions. Therefore, decreased humidity stands out as the only option that contradicts the implications of excessive atmospheric moisture.