Short- and long-term changes in wild bee diversity following a catastrophic flood

Natural disturbances such as flooding, drought, and wildfire, can promote biodiversity by creating new opportunities for species colonization. However, disturbances that occur too frequently or severely limit an ecosystem’s ability to recover and may lead to a decline in species diversity. Current climate models predict an increase in both the frequency and severity of disturbances in response to anthropogenic climate change. In 2013, a 100-year flood hit Colorado’s Front Range. This disturbance event provided a rare opportunity to assess the impacts of a severe natural disturbance on a particularly important group of animals: wild bees. Wild bees are essential for plant recolonization following a disturbance event through the pollination services, yet little is known about their response to flooding. One year before the flood, we conducted a comprehensive survey of the wild bees along the St. Vrain Greenway, an 8-mile long urban trail following an east-west riparian corridor in Colorado. We resampled in 2014 to quantify flood impacts on wild bee diversity, and again in the field season of 2020 assess short- and long-term changes in diversity following the flood. The first two years of data show significant declines in bee species diversity (-36%) and preliminary analyses of 2020 data show an increase in wild bee diversity. This research provides crucial baseline data about changes in wild bee diversity in response to catastrophic storms that are predicted to increase in the future and has implications for restoration efforts following large disturbance events.