Tree species diversity is an important determinant of the capacity of forests to support biodiversity and provide multiple ecosystem services. Tree diversity is also an important determinant of the ecological stability or vulnerability of the forests against disturbances, such as insect outbreaks or pathogen epidemics. Forest management decisions regarding the tree species diversity are therefore at the very core of successful adaptation of forestry to climate change and for sustainable forest management to meet the energy and raw material needs of the circular bioeconomy. In this chapter, we focus on three strategies that have been suggested as measures for adapting the forest management to climate change and that have the potential to influence tree diversity in forests, viz. introduction of diversity using non-native tree species, assisted migration, or use of admixtures. We discuss the forest health risks of these strategies and some avenues that can help to mitigate these risks in future forest management.