Which action is often necessary to deal with a pest that poses a serious threat to crops or livestock?

Eradication is often necessary when a pest poses a serious threat to crops or livestock because this approach involves completely eliminating the pest from an area to prevent significant damage. When pests are particularly harmful, such as those that can decimate crops or pose health risks to livestock, the goal typically shifts from merely managing the population to ensuring their complete removal.

Eradication can be a more intensive strategy that may involve a combination of practices, including the application of pesticides, cultural practices, and possibly the introduction of biological control agents specifically aimed at targeting the pest in question. This level of intervention is warranted when the pest's presence is so detrimental that other control methods may not suffice to protect agricultural outputs or livestock health.

In contrast, monitoring, regulatory control, and natural control are strategies focused on assessing and managing pest populations rather than eliminating them entirely. These methods are valuable, but they may not always adequately address urgent and severe threats.