The first is to avoid loss of genetically unique populations because they may have unexpected economic or ecological value. The genetic diversity represented by populations like these will be the source of adaptation to environmental changes that will inevitably occur in the near or distant future. The second reason is to avoid ecological and economic risks. Results like this reveal a subtle but ultimately critical lack of genetic adaptation to the environment. Decline syndromes lead to premature death, which of course may not occur until ace 50 or 100 in a tree that would otherwise have lived for several centuries.
Widespread declines can be very important forest health issues.
Some naturalized species have succeeded so well that they harm other species and even threaten ecosystem balance. Purple loosestrife, ailanthus, zebra mussel, gypsy moth, and chestnut blight fungus are examples of aggressive, non-native species whose spread has both economic and ecological impacts. Every case represents a disruption to an ecosystem that has evolved in place for thousands of years and is, therefore, a potential threat to ecosystem health. A comprehensive policy for the protection of natural diversity should address the spread of aggressive, non-native plants and animals. Also, there is increasing use of planting of wild species to restore or recreate non-forest plant communities, such as those found in wetlands.