As the climate changes, droughts are projected to become more common throughout the United States. Decreased precipitation will be especially severe in the South. However, even in areas without decreased precipitation, higher temperatures associated with climate change will also lead to increased evaporation and loss of moisture from plants and soil. In both cases, the lack of soil moisture means that more heat from the sun goes to heating the air and soil rather than towards evaporating soil moisture, ultimately leading to hotter temperatures. Therefore, droughts actually contribute to hotter temperatures, and droughts and heat waves often co-occur as an extreme event double whammy. Droughts are also key contributors to fire weather, the ideal climate conditions that support megafires. The importance of water availability within all ecosystems, and the increasing frequency and intensity of drought, will continue to elevate it as a key threat if climate change continues unabated.
The cost of drought
Although droughts may not garner as much attention as acute extreme events like hurricanes, floods or fires, their multidimensional effects are vast. In the U.S. droughts ranked second highest in economic costs in an assessment of the costs of disaster events. Societal effects are also high, as drought related water shortages and costs can lead to disparate access to safe and affordable water, with BIPOC and low-income communities disproportionately affected.
Within the environment, drought can affect ecosystems and wildlife in a myriad of ways. Most directly, drought may cause mortality of wildlife. The combination of drought and heatwaves can push birds to their physiological limits, leading to lethal dehydration. In drought times, birds may also congregate at the remaining dwindling water spots, causing conditions ripe for the spread of disease. Indeed, during a recent California drought nearly 20,000 Band-tailed Pigeon died due to avian trichomonosis. Death may also come from starvation as food resources diminish once the plants dry out and stop growing, which also causes declines in populations of insects and other integral prey. Drought-induced malnourishment conditions may also lead to a failure to secure adequate energy stores needed for migration for some species like the endangered Whooping Crane.
The complex nature of drought can also affect wildlife indirectly. As water is a key resource integral to ecosystem function, drought conditions cascade through multiple environmental systems causing dramatic and widespread change that lead to Ecological Drought. This type of drought, especially when prolonged, can lead to systemic changes where whole bird communities are altered with species declining in abundance or disappearing altogether. Wetland birds are particularly vulnerable, as drought can diminish the amount of wetland habitat available. A multi-year drought in California has seen the number of breeding waterfowl dip 46% below average as wetlands shrink and dry up. Prolonged drought can also cause loss of habitat, such as loss of piñon pines in the southwest, where millions of trees-- between 40-80% -- have died from a combination of drought and bark beetles. Declines in bird species dependent on these woodlands followed -- a whopping 73% drop in abundance -- with species like the Western Bluebird and Broad-tailed Hummingbird dropping in abundance dramatically, while others, including the Bushtit have vanished. Long-term droughts have even been linked to the collapse of entire avian communities, where almost half of bird species have disappeared from within survey locations in the Mojave Desert.
Drought-associated declines are most often linked to persistent reproductive failure due to a lack of resources to successfully rear young. Declines in breeding success due to ecological drought are commonly documented in bird species, including Barn Owl, Snail Kite , Bridled Titmouse, and Willow Flycatcher. However, declines locally may also be attributed to outward movement rather than actual population declines. Species like the Dickcissel manage to flee drought events, dispersing north away from dry conditions in record numbers in drought years highlighting how flexibility can be beneficial to species when facing extreme weather.
What can we do?
First and foremost, we must take action now and address the underlying cause of climate change. Rallying around policies and actions that make significant and meaningful traction to reduce greenhouse gas emissions is key. Support of green energy and transportation, natural climate solutions, energy efficiency and innovations that help meet carbon goals for a stabilized climate will help curtail droughts to within normal variation. Individual actions at home can also help birds adapt to climate change exacerbated drought.
Additionally, through Audubon’s Western Water Initiative, we have a team engaged and advocating for sound water policy and management across the West, particularly in the Colorado River and Rio Grande basins as well as the many Saline Lakes and their wetlands that dot the region. It is essential that the West prepares for a drier future as 40 million people and hundreds of bird species rely on flowing rivers. When communities are unable to plan for shrinking water supplies, there is increased risk that drought response activities—such as increasing groundwater pumping or depleting river flows—will further harm habitats. As the climate warms, it is our duty to protect water resources for the generations of people and birds to come.
Planting native plants can help birds cope with drought in your own backyard, as natives are water-wise and may do better during drought conditions. Natives also support healthy insect populations, and since 96% of landbirds feed their young insects this simple action can help bolster bird populations in dire times of need. You can support birds through drought and reduce your carbon footprint at the same time by giving your garden or patio a climate makeover.