The advance in the timing of spring events is well documented in scientific research. However, changes have not been the same for all species and can even differ among populations of the same species in distinct locations. A team of researchers compiled an extensive dataset of phenology observations from the published literature and from phenology networks including USA-NPN. They estimated whether the average date that a life cycle stage occurs has shifted since 1980, assessed the extent to which those shifts were driven by changes in temperature or precipitation, and explored whether climate change was increasing the likelihood of phenological mismatches for species that occur in the same location. The authors found that for plants, spring and summer events like leaf out, flowering, and fruiting are occurring earlier than they did 40 years ago, with later stages like flowering and fruit ripening advancing faster than earlier stages. Climate had much weaker effects on the timing of animal activity, which has implications for mismatches in the timing of plants and animals that rely on synchronization of their life cycle stages.

Plants growing in the forest understory, including spring ephemerals, which are short-lived herbaceous plants, are important members of the forest plant community. A team of Appalachian Mountain Club scientists evaluated observations of leaf out and flowering in 11 understory plant and 14 tree species to help address the outstanding question of which plant group is shifting their springtime activity more. Overall, understory plants are advancing the timing of their activity twice as much as trees under warmer conditions. Interestingly, plants of the mid-Atlantic region – comprising the “middle” section of the Appalachian Trail – showed substantially more advancement than plants to the north or the south. And finally: when they looked at differences among the plant groups by region, they only saw evidence of greater advancement among understory plants in the north. The findings of this analysis are good news for the understory plants. Greater advancement in the springtime activity of these plants compared to leaf-out in the overstory canopy means more time for them to grow prior to being shaded out by the larger trees.

Understanding how climate change is affecting species is especially important for threatened or endangered species, which already exhibit perilously low species numbers. A research team led by Jeremy Yoder at California State University, Northridge sought to determine the environmental conditions that Joshua trees must experience to trigger flowering. Using over 10,000 images of Joshua tree contributed to iNaturalist, the team predicted whether and when Joshua trees flowered in years past, back to 1900, and tested the performance of the model in predicting the timing of flowering by comparing the predictions to observations contributed to Nature’s Notebook. They determined that over the past 120+ years, the trees have increased how frequently they flower, as a result of progressively warmer temperatures and more variable rainfall over the period.