Another summer of record-breaking temperatures, river closures, mega-drought, and raging wildfires throughout the American West has come and gone. The impacts, however, remain perilous for trout and will require large-scale efforts to remediate and shore up watersheds. Scientists understand these complex and often interconnected impacts, but the frequency and intensity of recent droughts requires more questions, research, and solutions.
Drought is not some new phenomenon created by climate change. Ancient civilizations starved, and mass-extinction events occurred due to droughts. But that is no reason to shrug off what’s going on today—much to the contrary. We need to understand what’s causing droughts, how it may impact our lives and ecosystems, and develop plans to create resilient watersheds.
I know it feels like climate change may be the greatest scapegoat of all time. But think about how connected weather is to our daily lives. A storm that originated in the southern Gulf of Mexico, traveled north and brought record-breaking flooding to New York City and Philadelphia. Conversely, think about Lake Mead–the reservoir behind the Colorado River’s Hoover Dam. The lake is the largest reservoir in the country and supplies water for three states and some 20 million people. Due to the ongoing mega-drought and years of below average precipitation, the reservoir is at its lowest level in history. Our changing climate affects the planet in so many interconnected, complex ways, and drought is definitely one of them.
Drought can come in many shapes and forms, but our planet is changing, and droughts appear to be worsening. According to climate scientists, human-caused climate change causes, or exasperates, droughts for a variety of factors: hotter hots, longer and earlier summers, and shorter winters. A recent National Oceanic and Atmospheric Administration report on the 2020-2021 Southwestern U.S. Drought concluded that human-caused warming has made droughts more impactful.
A hotter planet encourages and intensifies droughts through more efficient evaporation and diminished snowfalls. According to the Yale Climate Center, “what might have otherwise been a mild or moderate drought in a cooler world will become, in a warmer world, more severe as a result of increased evaporation.” Snow has this one rule that it chemically has to follow—it has to be 32 degrees or colder to remain a solid. So, a warming planet, “increases the fraction of winter precipitation that falls as rain rather than snow and also shortens the cold season, so there’s less time for snow to even occur.”
In a 2020 study in the journal Science, for example, researchers observed how human-caused climate change is contributing to the 21st-century mega-drought in the Western U.S. and Northern Mexico by evaluating trends in modeled temperature, relative humidity, and precipitation data between 1901 and 2018. According to the study’s findings, human-caused warming accounts for 46% of this drought’s severity.
In the West, a primary indicator of drought is snowpack, which is also its main supply of water. Normal to above average snowfalls supply lower elevations with clean, cold water well into the summer. In Colorado, for example, snowpack provides 70 percent of the state’s water supply. TU’s Jay Chancellor, wrote about how climate change is impacting this: “Snow is melting between 15-30 days earlier than it was 25 years ago, which is leading to increased flooding and erosion and resulting in extended periods of summer drought.”
Colorado stands to lose six to seven miles of habitat on the Dolores River due to drought and poor snowfall; those stretches of river have literally dried up. The traditional slow, gradual replenishment from snowpack is crucial for watersheds and trout alike. Without strong snowpacks, watersheds and trout become increasingly vulnerable to mortality, disease, and climate change.
Over the past few years, some of the images of wildfires more closely resembled an apocalyptic video game rather than a planet that supports eight billion people. Wildfires increase and scale as droughts intensify. That’s part of the reason why we’re seeing amazingly destructive fires coincide with the West’s mega-drought. Visually, wildfires may seem the most destructive impact of drought—and they certainly are. But for trout, increased water temperatures, poor water quality, and low flows are a deadly trio that topple even the most resilient watersheds.
Temperature and water quality play an important role in trout lifecycles, and they’re heavily influenced by drought. We all know that trout need cold, clean water to survive and produce fishable populations. With an earlier and quicker snowpack melt off season, drought will encourage warmer water temperatures and lower flows, which does not fare well for trout nor the communities that depend on a strong fishing season.
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Most species of trout begin perish or experience poor survival in waters warmer than 67 degrees, scientists have found. So, fishing in drought-stricken areas requires more attention to water temperatures, as temps may become hazardous for the fish. Additionally, as droughts increase and intensify, one can expect far more hoot owl restrictions or full-on closures.
The impact of drought on water quality is an evolving and complex field. Take for instance a dry, mud-caked hillside, A heavy rainfall in a drought year can produce intense erosion events and sedimentation, which have consequences for trout. Another consideration is how wildfire impacts a stream or river’s chemical composition. According, to the U.S. Geological Survey, wildfire can impact aquatic ecosystems by “changing in the magnitude and timing of snowmelt runoff and increased loading of streams with nutrients, dissolved organic carbon, major ions, and metals”
Additionally, droughts will put increased strain on existing water resources. This is especially true in the West, where water resources are over-allocated in normal years, let alone mega-drought years.
Is There Hope?
All this talk about mega-droughts, climate change, and withering trout is depressing, but important nonetheless. If we want to preserve trout species around the county and world, we need to understand these impacts and work together to discover ways to mitigate them. The current mega-drought will wane, as precipitation patterns change, but the drought drivers will persists and wait for the next period of low precipitation. That is why it is so essential to promote watershed resiliency efforts and responsible angling practices in drought.
“The best thing we can do is keep our waters connected [by getting rid of unnecessary dams, diversions and other impediments],” fisheries biologist and researcher Ashley Rust said. While climate change does appear to be playing a role, how we use water and alter watersheds plays a major role as well—and affects trout equally, if not more. It doesn’t take a rocket-scientist to understand that if we pump too much water from streams and rivers in normal climates, we’ll be in trouble come drought. Additionally, degraded or developed watersheds are far more susceptible to the impacts of drought. So, outside of the mammoth task of reversing climate change, creating resilient watersheds and reconnecting them will go a long way toward defending against the inevitable future droughts.
Cover picture courtesy of Josh Duplechian