California’s drought isn’t just a human crisis. It’s also disrupting nature – with some potentially severe consequences for people and wildlife alike.
To a certain extent, Californian wildlife and habitats are adapted to drought, a normal cycle in the state’s climate. Many species adapt by roaming to find food, water and shelter. Others adapt by having fewer offspring so they have fewer mouths to feed.
But many animals have trouble adapting because humans have altered their ecosystems so much.
In three months last autumn, for instance, state wildlife officials responded to 108 black bear sightings in Bakersfield, a city of 360,000 people. Before the drought, there were only one or two such sightings each month. Nine of the bears had to be captured and relocated. One died shortly after being captured at an apartment complex. The bear’s cause of death could not be determined even though officials performed a necropsy.
Black bears aren’t normally a threat to people. But they can be unpredictable, especially when they feel cornered or threatened.
The bears showed up in Bakersfield looking for food and water because their usual habitats had dried up. It’s normal for some animals to travel great distances during drought, especially to lower elevations where converging streams keep things moist and there is still plenty of vegetation.
But these are often the same places where people chose to build cities, creating lots of potential for conflict.
Some types of fish face more serious consequences, because drought changes their world even more dramatically. Declining river flows shrink their habitat. Drought also increases water temperatures to lethal levels and may boost the concentration of dangerous pollutants. Sometimes this can spell the end of a species.
One species facing just such as threat is the Red Hills roach, a minnow-size fish that lives in a small number of streams in the central foothills of the Sierra Nevada. In the summer of 2014, biologists located only 200 of the fish in one shrunken stream in Tuolumne County. It’s unclear if the species will survive another drought year.
Winter-run Chinook salmon on the Sacramento River, an endangered species, are also in trouble.
Salmon begin to suffer when water temperatures exceed 56 degrees Fahrenheit, and are likely to die at temperatures above 58 degrees. Before dams were built, salmon could reach colder waters at higher elevations, and could time their downstream migration to match natural runoff pulses. Now the dams – most built without fish ladders – keep the fish in lower-elevation waters that get dangerously warm in summer. So the fish depend on humans trying to estimate when and how much of the cooler dam water to release.
In years when there is enough rainfall and snowmelt, there’s usually enough cold water stored deep in California’s reservoirs for officials to release into the rivers below the dams so the salmon can complete their downstream migration. But in drought years, reservoir supplies are depleted and officials can’t release enough cold water to help the salmon migrate.
In 2014, wildlife officials estimated that 95 percent of juvenile winter-run salmon died migrating downstream because the Sacramento River became too warm.
The die-off occurred even though the U.S. Bureau of Reclamation tried to save cold water in Shasta Reservoir on the Sacramento River, the largest reservoir in the state, for the salmon migration. With that lesson in mind, the State Water Resources Control Board in May ordered Reclamation to save even more water in Shasta Reservoir to prevent a similar disaster for this year’s salmon run.
A drought also leads to severe fire risk because there is so much dead vegetation and trees. In the first five months of this year, state fire crews responded to 60 percent more wildfires than the average for the same period over the previous five years. And this is before the start of the summer months.
The extreme dry conditions are killing many trees, worsening the fire risk. Additionally, recent mild winters mean an abundance of bark beetles, which kill trees by tunneling through the inner layers of bark, eventually killing the tree. Sap flow in healthy trees can repel the beetles, but trees can’t produce enough sap without adequate water. This year is so dry that even some tree species normally resistant to drought “such as knob cone, grey pine and bishop pine“ are beginning to die.