Insect declines have been reported worldwide, although the particular causes of the declines may be complex and are poorly understood. Meadow spittlebugs were one of the most abundant insects in the coastal prairie along the California coast 40 years ago but have largely disappeared. Evidence links this decline to changing climatic conditions, which have reduced survival of eggs and neonates. We identified several refugia where meadow spittlebug populations have persisted amidst unfavorable conditions. Protection from desiccating winds was the common attribute of these refugia. Following a wet year, adult meadow spittlebugs were able to disperse from one refuge that we studied to recolonize coastal prairie habitats, although populations declined over the next two drier years. Because of their previous high abundance, loss of meadow spittlebugs is likely to affect the functioning of this widespread habitat, including energy transfer, their host plants, and their predators. In addition, meadow spittlebugs are unusual in having been the subject of extensive physiological and long-term ecological data, so they can serve as a bellwether species, indicating the effects of climate change.

These data indicate the number of meadow spittlebug nymphs that were observed on cow parsnip plants at various distances away from the edge of Owl Canyon. Owl Canyon served as a refugium for this species. Surveys were conducted during the summer in 2019 (wet year), 2020 (dry year), and 2021 (dry year). During late summer 2020 we collected sweep net samples of adult meadow spittlebugs at various distances away from the edge of Owl Canyon.

The distance in m from the edge of the canyon is shown in column A for 2019. Similarly, distance from the canyon is shown in column D for 2020 and in column G for 2021. The number of meadow spittlebug nymphs per plant in 2019, 2020, and 2021 are in column B (Fig 2A), column E (Fig. 2B) and column H (Fig 2C) respectively.

The number of adult meadow spittlebugs in sweep samples is shown in column K at various distances (shown in column J) from the edge of the canyon. This corresponds to Fig. 3.