Stream invertebrates often serve as indicators of stream habitat quality because of their responsiveness to environmental change. A recently published study co-authored by Center for Watershed Sciences Senior Researcher Jonathan Walter leveraged 4 decades of measurements in the Llyn Brianne Stream Observatory (Wales, UK) to understand how stream invertebrate communities responded to climatic variation. Focusing on effects of the North Atlantic Oscillation, a major driver of climatic variability in Europe, the phases of which provide analogs of climate change, showed stream invertebrate populations to be less stable during positive NAO phases. Positive NAO phases are warmer and wetter than average, mimicking projected future climates in this region.

The primary cause of instability during warm, wet periods was increased synchrony, both with respect to the dynamics of populations of the same species across different streams, and with respect to the dynamics of different species in the same stream community. When populations fluctuate synchronously, meaning that their increases and decreases in abundance tend to coincide in time, they may be at higher risk of extinction, and the total abundance of stream invertebrates—considering all species and streams—fluctuates more erratically than if the populations were unsynchronized. Hence, in the warmer, wetter conditions expected to become increasingly common for Wales as a result of climate change, stream invertebrate communities will likely be less stable.

The paper, “Climatic effects on the synchrony and stability of temperate headwater invertebrates over four decades,” has been published in Global Change Biology, as a collaboration between researchers at the Fondazione Edmund Mach, the Water Research Institute at Cardiff University, and the UC Davis Center for Watershed Sciences.