Which factor influences the population of occasional pests?

The influence of environmental changes and human activity on the population of occasional pests can be understood through the various ways these factors shape pest dynamics. Environmental changes, such as climate variations, habitat destruction, and alterations in land use, directly impact the conditions in which pests thrive. For instance, changes in temperature and precipitation can create more favorable conditions for certain pests to emerge or reproduce.

Additionally, human activity often plays a crucial role in altering ecosystems. Practices like agricultural intensification, urbanization, and the introduction of non-native species can disrupt the natural balance that keeps pest populations in check. When environments are modified, pest populations may increase, leading to situations where occasional pests become more prevalent.

This understanding emphasizes the importance of monitoring environmental conditions and human practices to manage and predict pest outbreaks effectively. In contrast, the other options refer to factors that may have an influence but are not as foundational as environmental changes and human activity.