The fossil record allows the inference that the intrinsic attributes engendering survival of wild forest trees originated over millions of years of natural selection following physical, chemical and biological tests. Current thinking is that tolerance of, hence survival in, ever-changing environments is a physiological attribute influenced by both synecological associations and autecological changes. However, in terms of genetics and biochemistry, the fundamental basis for survival fitness remains incompletely known.

In association with the rapid rate of global climate change, there are now increasing incidents of forest mortality. Global sustainability of healthy forests requires ongoing survival fitness of forest organisms, in particular that of trees. Over the last century, tree-improvement programs selected and crossed individual mother trees having desired traits, to produce seed orchards and clones for reforestation/afforestation and related purposes. However, selections of preferred genotypes were based on their growth performance under earlier environmental conditions, and cultivars were selected mainly on the basis of commercial attributes rather than on their ability to survive extreme events. Consequently, the possibility exists that survival fitness of preferred cultivars and their progeny has been compromised, relative to wild types. The needed research remains to be done, but a solid scientific foundation to manage future forests is clearly lacking at present. This presentation reviews the current state of knowledge about these concerns and suggests future research priorities. The limits of tolerance of trees to unpredictable extreme events can begin to be estimated by subjecting seedlings to controlled environmental tests.