The most worrisome alien pests are those we may not even know about yet. In many cases, it is not possible to predict which foreign species will become pests if they reach Hawai`i.

Many of our worst pests were introduced with good intentions but turned out to be terrible problems. Others - especially insects and diseases - hitched aboard other harmless species.

The only cost-effective approach is to choose very carefully those species we want here, and to strengthen prevention systems to stop unwanted introductions.