Pine tree representing an elevational tree-limit rise of 105 m over the period 1915�. Nipfjallet, SwedenIf climatic factors such as temperature andprecipitation change in a region beyond the tolerance of a species phenotypic plasticity, then distribution changes of the species may be inevitable.There is already strong evidence that plant species are shifting their ranges in altitude and latitude as a response to changing regional climates.When compared to the reported past migration rates of plant species, the rapid pace of current change has the potential to not only alter species distributions, but also render many species as unable to follow the climate to which they are adapted.The environmental conditions required by some species, such as those in alpine regions may disappear altogether. The result of these changes is likely to be a rapid increase in extinction risk.Adaptation to new conditions may also be of great importance in the response of plants.Predicting the extinction risk of plant species is not easy however. Estimations from particular periods of rapid climatic change in the past have shown relatively little species extinction in some regions, for example.Knowledge of how species may adapt or persist in the face of rapid change is still relatively limited.Changes in the suitability of a habitat for a species drive distributional changes by not only changing the area that a species can physiologically tolerate, but how effectively it can compete with other plants within this area. Changes in community composition are therefore also an expected product of climate change.

The timing of phenological events such asflowering are often related to environmental variables such as temperature. Changing environments are therefore expected to lead to changes in life cycle events, and these have been recorded for many species of plants.These changes have the potential to lead to the asynchrony between species, or to change competition between plants. Flowering times in British plants for example have changed, leading to annual plants flowering earlier than perennials, and insect pollinated plants flowering earlier than wind pollinated plants with potential ecological consequences. A recently published study has used data recorded by the writer and naturalist Henry David Thoreau to confirm effects of climate change on the phenology of some species in the area of Concord,