What environmental impact can result from improper pesticide use?

The choice highlighting the contamination of soil and water sources accurately reflects a significant environmental impact of improper pesticide use. Pesticides can easily runoff into nearby water bodies during rainfall or irrigation, leading to the pollution of rivers, lakes, and groundwater. This contamination can have dire effects on aquatic life and subsequently on humans who rely on these water sources for drinking and irrigation. Additionally, when pesticides infiltrate the soil, they can disrupt soil microorganisms, degrade soil health, and lead to long-term ecological issues.

In contrast, the other options suggest beneficial effects that are not characteristics of improper pesticide use. Improved soil fertility and enhanced plant growth would typically result from proper agricultural practices, including the use of organic fertilizers and sustainable farming methods. Increased biodiversity is also a goal of sustainable practices; however, the misuse of pesticides often leads to a decline in biodiversity, as non-target species, including beneficial insects and pollinators, can be harmed or killed off. Thus, the focus is clearly on the negative implications of pesticide misuse, making contamination of soil and water sources the most accurate answer.