Climate change is expected to affect mountain ecosystems in many ways. Scientists predict that warmer summers may result in earlier snowmelt, more frequent forest fires, and changes in distributions of plants and animals. Although some ecosystem changes (e.g., melting glaciers) have already been observed, many future impacts remain uncertain. Monitoring provides a way to document ecosystem changes, anticipate future changes, and improve management of protected lands.
Butterflies are sensitive indicators of climate change because temperature influences the timing of an individual’s life cycle and the geographic distribution of species. As individuals develop from egg to larvae to pupae and finally to mature butterfly, temperature thresholds may trigger these changes. Annual temperature patterns are often the primary determinant of the distribution of “generalist” butterflies.
Generalist butterflies are species that can utilize many different plant species for nectar, larval development, and egg deposition. Specialist butterflies depend on a few plant species for food and development and they can be directly and indirectly influenced by climate (temperature and precipitation). An example of indirect influences is when climate limits the growth of the butterflies’ “host” plants; when the quality or number of these plants decline, so do the number of butterflies.
Recently, studies in Europe and California have documented range shifts in butterflies in response to changing temperatures. As average annual temperatures have increased, some species have responded by moving northward or to higher elevations to follow optimal temperature ranges. However, scientists still have a lot of unanswered questions about the long-term survival of these species. For instance, even if butterflies are able to fly to higher elevations in response to warming temperatures, will they be able to establish as breeding residents? Will host plants be able to migrate up quickly enough to support butterfly populations, or will some species become extinct?