Final answer:
Biological control introduces new species as natural predators to pests, often as a pesticide alternative. Although effective in some cases like New Guinea's water hyacinth, there are risks such as non-target impacts. Effectiveness varies by region, necessitating careful planning and ecological consideration.
Step-by-step explanation:
The practice of introducing a new species to prey on pests, known as biological control, is an alternative to using pesticides. While there have been notable successes, such as the control of water hyacinth infestations in New Guinea using weevils, and the protection of gumwood trees in St. Helena by a predatory lady beetle, there are significant risks involved. One of the main critiques is that non-target impacts can occur when the introduced species preys on species other than the intended pests, potentially harming local ecosystems or even causing extinctions.
Moreover, the effectiveness of biological control agents can vary widely based on the local environment, as demonstrated by the weevils in Florida, which had minimal impact on controlling water hyacinth compared to their effectiveness in New Guinea and Lake Victoria. Pesticides, despite their use, can also pose problems by killing non-pest species, leading to resistance in pest populations, and potentially endangering human health and wildlife. Thus, the implementation of biologically based pest control must be conducted with great caution and thorough understanding of the ecological dynamics of the area.