Climate change is leading to more frequent, intense storm events across the globe. The recently released report from the Intergovernmental Panel on Climate Change (IPCC) indicated that among other consequences of climate change, heavy rains fueled by warmer air will increase the number of deadly floods across the planet, a trend that many researchers say is already underway. Floods are the most common natural disasters in the United States, and in many areas, they are getting worse. As climate change continues to exacerbate sea-level rise and extreme weather, our nation’s floodplains are expected to grow by approximately 45 percent by the end of the century, extending the destructive reach of these disasters.
In addition to human communities, severe weather can harm birds and other wildlife. In Florida, the wet seasons have become shorter and more intense, with the same amount of rain compressed into fewer storms with higher rates of precipitation. Heavy rainfall can reduce foraging time for many bird species. Flying insects are inactive during heavy rain, so birds such as aerial insectivores – which are experiencing strong population declines across North America – are unable to find food during storms. This means that nesting birds have less food to feed their young, causing nestling growth to slow in insectivores, such as Tree Swallows, after heavy rains.
Heavy rains also flood nests of birds that nest on beaches and barrier islands – like terns, plovers, and Black Skimmers – or on floating vegetation in wetlands, such as Seaside Sparrows, rails, and bitterns. Some experts associate these precipitation changes with the loss of forests, swamps, and marshes, which reduces evaporation of water from soil and plants into the atmosphere, and creates unpredictable weather patterns. Loss of these habitats also directly impacts breeding and wintering birds that rely on these areas to find food and nesting or roosting sites.
Elsewhere in North America, increasingly severe storms can impact birds during the most perilous period of their annual cycle: migration. Heavy rainfall and strong winds can ground birds during their journeys, requiring them to rest, feed, and build their strength back up before continuing on their migration. With intense and long-lasting rainstorms becoming more frequent, these stopover periods are likely to become longer for many birds, leading to prolonged migrations and potentially higher mortality. In addition, various studies have indicated that some migrant declines may be due to rainfall variation, the consequences of which may carry over from one stage of a migrant’s annual cycle to another. For example, recent research demonstrated that Kirtland’s Warbler first-time breeders were much more sensitive to changes in winter rainfall in the Caribbean than experienced adults, which could have important consequences for their migration timing and subsequent reproductive success during the breeding season in Michigan.
In the western United States, precipitation has been shown to be a more important predictor than temperature for understanding long-term changes in bird species’ distributions and abundances. In particular, December snowfall has carry-over effects months later since the melting snow runoff is what affects stream flows, plant growth, and insect abundance in the spring and summer. While increased precipitation generally has positive effects on western birds due to the otherwise dry conditions in the region, future changes in evaporation rates and storm timing and intensity may lead to mismatches in bird breeding times with food availability and abundance, thereby reducing productivity. For the Blue Grosbeak, timing of breeding is associated with monsoons in New Mexico, which is thought to relate to important insect populations for feeding young. The increasing variability of heavy rains because of warming temperatures means that prey populations may no longer sync up with the energetically demanding breeding times of many bird species in North America.
Without immediate action to reduce greenhouse gas emissions, climate change is projected to increase the frequency with which birds have to weather heavy precipitation events. Birds don’t have the same technology and early warning system for severe weather events like we do, but we can help birds – and communities – prepare for a storm by prioritizing the restoration and conservation of our natural infrastructure. As the impacts of climate change increase, habitats ranging from forests and wetlands to coastlines and barrier islands that absorb heavy rainfall and protect against sea-level rise become more important than ever for birds and people alike.