Final answer:
The statement is true, as careful preparation is critical in environmental manipulation to avoid unforeseen consequences and to ensure the preservation of ecosystems. The precautionary principle advises proceeding with caution when the effects of an activity are not fully understood.
Step-by-step explanation:
The statement 'The usefulness of environmental manipulation depends upon the degree of preparation' is true. In the context of environmental science, careful preparation is essential for any activity that manipulates the environment, especially because of the potential for unforeseen consequences. For instance, the introduction of an invasive species could dramatically alter an ecosystem. Therefore, understanding the possible impacts through rigorous research and planning is crucial.
Likewise, it is important to consider principles such as the precautionary principle mentioned in the provided reference, which implies that when the effects of an activity on the environment are not fully understood, it is better to proceed cautiously, assuming that some harm could occur. Furthermore, large-scale environmental experiments can be challenging due to the variability and complexity of ecosystems, making it difficult to apply strict experimental designs as in controlled laboratory settings.