What is a potential environmental risk of aerial pesticide application?

The selection of drift of pesticides to non-target areas as the correct answer highlights a significant concern in aerial pesticide application practices. When pesticides are applied from an aircraft, there is a likelihood that not all of the targeted substance will land on the intended crops or areas. Due to wind and other environmental factors, pesticides can easily spread beyond the target site, impacting surrounding ecosystems. This unintentional dispersal can harm beneficial insects, plants, and even humans in nearby locations, leading to negative environmental outcomes.

In contrast, the other options do not represent risks associated with aerial pesticide application. Increased soil fertility is generally a desirable outcome of appropriate pesticide use, not a risk. Air pollution from aircraft emissions does occur, but it is more directly associated with the operation of the aircraft rather than the pesticide application itself. Lastly, improvement of local biodiversity would typically be seen as a positive effect, not a risk, and is unlikely to be associated with the use of pesticides, which can actually lead to a reduction in biodiversity if not managed carefully. Thus, drift to non-target areas remains a key environmental concern in this context.