Compound climate extreme events threaten migratory birds’ conservation in western U.S.

In a warming world, more intense and frequent compound climate extreme events pose serious challenges to biodiversity and conservation on Earth as one of the 2030 United Nations’ sustainable development goals (SDGs): “Life On Land” (SDG 15). In summer 2020, concurrent swelling wildfires and a sudden cold snap in the western U.S. killed a massive number of migratory birds. In August 2020, the hot and humid weather in response to the wildfire radiation and the oceanic evaporation could result in killing heat stress for migratory birds along the coastal shoreline, particularly in California. The heat and smoke of wildfires forced the migratory birds to abandon such feeding grounds towards inland regions, where water and food are naturally scarce, before being physiologically ready for their long-distance flyways. Then, a cold snap during 8–11 September in the Rocky Mountain states in the western U.S. urged those already weak migratory birds to fly southward before effectively recovering their physical and mental capabilities. This durable extreme starvation finally brought the skinny migrants low in the southwestern U.S. However, such ecological cascade effects of compound climate risks have rarely been acknowledged as a serious threat to migratory birds’ conservation in both scientific literature and ecosystems’ management practice. To improve our chances of saving birds’ biodiversity on Earth, hence, conscious policies and sustained efforts must immediately be arranged through SDG 13 (“Climate Actions”) based on scientific evidence and knowledge.