Why are parasites and predators of pests considered beneficial?

Parasites and predators of pests are considered beneficial primarily because they help to control pest populations naturally. By preying on or parasitizing these pests, they can reduce their numbers, leading to a balance in the ecosystem. This biological control can often minimize the reliance on chemical pesticides, thus reducing the frequency and amount of pesticide applications needed to manage pests.

Utilizing natural enemies like parasites and predators not only helps in controlling pest populations but also promotes a healthier environment. This is particularly valuable in agricultural practices, where over-reliance on chemical pesticides can lead to negative effects such as pesticide resistance, harmful residues in crops, and detrimental impacts on non-target organisms including beneficial insects, wildlife, and human health.

The other options do not accurately reflect the beneficial aspects of pests' natural enemies. For instance, while they can significantly decrease pest populations, they do not eliminate the need for all pesticides; some situations may still require chemical interventions, especially in severe infestations or specific crop management scenarios. Additionally, the notion that these natural predators might increase pest populations is misleading, as their role is to naturally suppress pests. Furthermore, they are typically beneficial to the ecosystem rather than harmful, hence the idea of harm would not apply to their role as beneficial organisms.