Scientists have found that some trees, including oak, are predicted to leaf earlier in the spring. The effect of earlier leafing may be detrimental to woodland plants which will receive less sunlight in crucial growth phases.

This is not the first time that the effect of earlier leafing/flowering has led to concerns. For example, many insects have evolved to emerge in spring at a time which corresponds to food availability. A warmer climate may cause the insect to emerge early when food is not yet available, or cause the tree to leaf earlier causing the insects to miss the optimum food availability. This concept, known as, phenological mismatch, could lead to population declines and disrupted ecosystems.