Final answer:
Biological pest control is often more successful on islands because these locations have isolated ecosystems which are easier to manage, clear authorities for implementation, and less chance of reinvasion. This method is non-toxic, cost-effective, and can lead to permanent solutions for pest issues.
Step-by-step explanation:
Biological pest control is often more successful on islands due to several interconnected ecological factors. Islands generally have lower migration rates, supporting limited numbers of species with fewer incoming predators and parasites from the mainland. This isolation also means that once a biocontrol agent is introduced on an island, there is typically less chance of additional pests or competing species entering the system to disrupt the newly established ecological balance. Moreover, islands often have clear lines of authority and containment measures can be more effectively implemented to control and monitor the success of biological control agents.
Successful biological control measures have led to the eradication of various invasive species, ensuring that these populations don't rebound. Key to these successful eradication efforts include having sufficient resources, clear authority, understanding the biology of the target organism, and ensuring that reinvasion is unlikely—conditions that are more easily met on islands. An example of successful biological control is the introduction of the South American lady beetle to control a tropical American scale insect threatening the endemic gumwood tree on St. Helena.
Aside from the practical benefits of preventing pest reintroduction, biological pest control agents have the advantage of being inherently non-toxic, leading to protecting human health and the environment from the adverse effects of chemical pesticides. They also tend to offer a permanent solution, which over time is generally less expensive as the control agents continue to exert their effects without the need for reapplication, as is the case with chemical controls.