@ucsusa: Global Warming in the Arctic — A Sensitive Climate Gone Off the Rails


From the Union of Concerned Scientists (Erika Spanger-Siegfried):

It is polar night in the Arctic—a darkness that lasts from early October to early March. Temperatures rarely escape freezing in that darkness, averaging -30° F until the light begins to return in spring. Right now, however, temperatures across much of the Arctic are 36 degrees F above normal. Large areas are well above freezing. And instead of rapidly expanding, sea ice extent is in decline.

Taken together, this is not unusual. It’s unheard of.

The degree to which current Arctic conditions are straying from the norm may prove to be the greatest change yet measured there—the latest signal from the Arctic that all is not well.

And while the frozen top of the world may seem remote and unimportant at the moment, what happens there matters greatly to both our immediate and long-term future.

2016 temperatures (Kelvin) above Latitude 80. The green line shows daily mean historic average temperatures from 1958-2002. The red line shows the daily mean average from 2010 to present. The blue line is 32 degrees F, or freezing. Recent days have seen departures from the long-term average of up to 36 degrees F. At and above this latitude, roughly days 1-45 and days 300-365 are spent in darkness. Source: Danish Meteorological Institute
2016 temperatures (Kelvin) above Latitude 80. The green line shows daily mean historic average temperatures from 1958-2002. The red line shows the daily mean average from 2010 to present. The blue line is 32 degrees F, or freezing. Recent days have seen departures from the long-term average of up to 36 degrees F. At and above this latitude, roughly days 1-45 and days 300-365 are spent in darkness. Source: Danish Meteorological Institute

Breaking down the Arctic breakdown

The Arctic plays an important role in moderating global climate. When heat from the tropics is delivered north to the Arctic by winds and ocean currents, the region exerts a cooling effect on both. Without this distribution of energy, the lower latitudes would overheat. Sea ice and snow- and ice-covered land (known as the “cryosphere”) help the Arctic to stay cool by reflecting most of the incoming solar energy back to space.

But the Arctic, like the rest of the planet, is warming, and unlike the rest of the planet, warming in the Arctic can feed rapidly on itself.

To describe one of the feedbacks: Warmer temperatures drive greater melt of sea ice, which exposes open ocean, and exposed water absorbs heat from sun that was previously reflected. Ocean temperatures rise as a result, and when winter comes, the sea ice has a harder time rebounding amidst warmer air and water temperatures. The following year, the melt season begins with sea ice cover that is thinner and smaller in extent.

There are other feedbacks, and all are complex. For a closer look at these reinforcing cycles, see my colleague’s blog on Why the Arctic Matters. As the National Snow and Ice Data Center puts it:

A small temperature increase at the poles leads to still greater warming over time, making the poles the most sensitive regions to climate change on Earth. According to scientific measurements, both the thickness and extent of summer sea ice in the Arctic have shown a dramatic decline over the past thirty years. […] The loss of sea ice also has the potential to accelerate global warming trends and to change climate patterns.

Okay. With this in mind, let’s look at the state of the Arctic at this time.

Sea ice extent

In the polar night, Arctic sea ice historically rebounds from summer melt as both the water and air cool. In recent decades, the ice has been declining in both extent and volume.

This year, with warm ocean temperatures and continued delivery of warm air from the lower latitudes, the ice is struggling to rebound. October saw new record lows for Arctic sea ice extent.

Global sea ice extent began 2016 (thick red line) at low levels. Just in recent days , the Arctic has lost more than a million square kilometers of sea ice, reaching a new record low and contributing to a steep decline in November’s total global sea ice extent. Antarctic sea ice extent is also at record low levels.  Source: Arctic News
Global sea ice extent began 2016 (thick red line) at low levels. Just in recent days , the Arctic has lost more than a million square kilometers of sea ice, reaching a new record low and contributing to a steep decline in November’s total global sea ice extent. Antarctic sea ice extent is also at record low levels. Source: Arctic News

In November, Arctic sea ice extent remains well below average for this time of year. In each of the last three days, a time of year when sea ice is normally growing, it has shrunk instead (see figure below). Arctic sea ice is melting up there in the polar darkness.

According to experts following this closely, as of Sunday, November 20, Arctic sea ice is now ~1.1 million square kilometers below the previous record low.


Sea surface temperatures

With larger areas of the Arctic ice-free each year, and for longer periods of time, the Arctic Ocean is absorbing more heat.

This fall, sea surface temperatures are well above average, with anomalous warmth persisting into November as seen in the figure below. Scientists have reported ocean temperatures 25° F above average in some locations.

Sea surface temperatures are unusually high and well above freezing in some areas of the Arctic, contributing to ice melt. Credit: Climate Change Institute
Sea surface temperatures are unusually high and well above freezing in some areas of the Arctic, contributing to ice melt. Credit: Climate Change Institute

Air temperatures

The chart below looks at this warmth by a different measure: “freezing degree days.” By many available measures, the oncoming Arctic winter is in a nose dive unprecedented in recent record keeping.


A weakened polar vortex and wobbly jet stream have been identified as factors in recent anomalous winters, both colder and warmer, and indeed, meandering winds are currently delivering warm air far northward to the Arctic, and a deep, snowy freeze in Eurasia.

The combination of factors driving Arctic air temperatures today has resulted in a stunning temperature anomaly—persistent, vast areas of 36° F above normal, shown in the map below.


Wild cards, like the unusual cyclone that struck the Arctic last winter, driving temperatures 50 degrees above normal, may compound and accelerate ice loss, according to a recent NASA study.

It’s as if the Arctic is trying to be heard. It’s hard to imagine stronger signals to send.

City’s stormwater inspectors keep an eye out for violations — The #Colorado Springs Independent

Channel erosion Colorado Springs July 2012 via The Pueblo Chieftain
Channel erosion Colorado Springs July 2012 via The Pueblo Chieftain

From The Colorado Springs Independent (Pam Zubeck):

[Stormwater enforcement actions represent] a 10-fold increase over 2015 and a dramatic uptick from a time when the city largely ignored violations of its own stormwater regulations. And this could just be a start — the city is also looking at a new program that would give it even more muscle against violators.

The ramp-up is due in part to Mayor John Suthers’ response to pressure from the Environmental Protection Agency and the Colorado Department of Public Health and Environment. Those agencies issued two highly critical reports of the city’s stormwater maintenance and regulation enforcement in recent years, and on Nov. 9 the EPA filed a lawsuit alleging the city’s lax approach violates its MS4 permit and the Clean Water Act. The lawsuit could bring multi-million-dollar civil penalties and federal monitoring.

In early 2007, City Council imposed stormwater fees on property owners, raising about $16 million a year for drainage projects and maintenance.

But in 2009, the Council defunded the program after voters approved a measure aimed at killing the fees. After that, the EPA lawsuit states, the city’s stormwater program limped along on an average of $1.6 million a year from 2011 to 2014.

Despite a scathing EPA report in 2013, then-Mayor Steve Bach did little, and even opposed a citizen-driven ballot measure for drainage that failed in 2014. Without more money, city officials have said, they couldn’t effectively track down violators.

That neglect had ramifications: In addition to possible EPA fines, uncontrolled drainage enraged officials in downstream Pueblo County, who in turn threatened agreements on Colorado Springs Utilities’ Southern Delivery System pipeline. So, earlier this year, Suthers and Council adopted a $460-million, 20-year stormwater program to fend off fines and cope with the city’s extensive drainage problems. One part of that program: oversight to verify compliance by contractors. Last year, the city’s stormwater staff numbered about 20. Today, it stands at 56, and another 10 will be added next year. Many of those are inspectors who troll for violators…

Though stormwater program manager Rich Mulledy says inspectors fan out over the city, most offenses were spotted on the city’s northeast side where development is brisk, records show…

Mulledy stresses the city would rather gain compliance than punish builders. He doesn’t like the word “crackdown” to describe the city’s approach in enforcing its MS4 permit, which requires erosion control for all projects larger than one acre.

“Just because of the number of houses being built, we’ve really stepped up,” he says, quickly adding that the industry has proven a willing partner. The city, he notes, has the authority to issue summonses that carry fines of $500 per day, but no fines have been levied so far.

“We’ve had compliance,” he says, “We’re committed from the city’s standpoint to make sure we’re doing the right thing to meet our permit going forward, and I feel the industry is supportive going forward. We have to meet the federal permit for sure, but we want to do the right thing and still have developers make progress and be able to do business.”

Builders and developers are all in, says Tim Seibert, president of the Housing and Building Association of Colorado Springs.

“Obviously, just like the mayor stated, we’re not pleased to hear the EPA has filed a lawsuit,” Seibert says. “We think there is a better solution. But at the end of the day, we want to be at the table and be sure we’re in compliance.”

Seibert says the HBA hosts monthly “Wet Wednesday” meetings at which its members are instructed in stormwater regulations, such as erosion control and best management practices.

“With the recent enforcement, we’ve stepped that up,” he adds. “We’ve made it more thorough. We’ve gotten a lot of cooperation from the city telling us, ‘These are the practices we need to see.’ I think that’s been very helpful for them to get in contact with guys in the field doing the implementation.”

The HBA also added a monthly meeting with Mulledy at which design standards are discussed. “We want to make sure we’re not getting ourselves in trouble, and we don’t want the city to get in trouble,” Seibert says.

He also says that as the city shapes its program to satisfy federal authorities, HBA members realize more enforcement is coming.

Mulledy won’t discuss details of the new program — still being worked out — but says it will clarify enforcement steps, and allow officials to “jump steps” if a violation poses an immediate threat to the city’s stormwater system or downstream. Currently being reviewed by stakeholders, the program will be introduced within a few months.

“In general,” Mulledy says, “it’s going to be more specific and give us more tools.”

#Drought news: Finally some snowfall, no change in depiction for #Colorado

Click here to go to the US Drought Monitor website. Here’s an excerpt:


This USDM week began with an upper-level trough exiting the Northeast. Another trough moved across the country during the week, dragging a low pressure system and cold front across the country and giving the Central Rockies, Central Plains, Upper Midwest, and Northeast a blanket of snow. A third trough moved across the West and into the Plains as the week ended. Precipitation for the week was above normal across parts of California, the Southwest, southern Texas, Central to Northern Rockies, Central Plains to Upper Mississippi Valley, and Northeast. Rains fell along the front from Texas to the Great Lakes, but amounts were mostly below normal. The troughs moved through a dominant upper-level ridge which kept weekly temperatures above normal for most of the contiguous U.S. (CONUS), with only Florida and the coastal Southeast averaging cooler than normal…

The Great Plains

A large blanket of snow fell across the Plains of Colorado to the Upper Mississippi Valley, with half an inch to an inch of precipitation across parts of Nebraska and the Dakotas. Coastal and northeastern Texas also received half an inch or more of rain, but the rest of the Plains was mostly dry this week. D0-D3 were adjusted in Texas, D0-D3 expanded in parts of Oklahoma, D0 expanded in North Dakota, and an oval of D1 was added to south central North Dakota. As summarized by the National Weather Service, from an agricultural perspective, farmers and ranchers across extreme northeast Texas have already had to supplement winter hay as the pastures were dormant even before the first frost/freeze this past weekend, stock ponds are very low/dried up, and right now, one rancher in western Bowie County has stated that winter wheat probably will not come up if planted now. As noted by the Oklahoma State Climatologist, reservoirs in central Oklahoma have seen significant decreases in storage, producing significant water impacts. Lake Hefner and Overholser were 6 and 5 feet down, respectively, for this time of year, and Draper was down 12 feet, which is a bit drastic…

The Rockies and Far West

The upper-level troughs brought welcomed precipitation to parts of the West, with 2 inches or more of precipitation falling along the coast from central California to Washington, and 2-4 inches in favored upslope regions further inland. The troughs left half an inch to an inch of moisture across parts of the Southwest and Central to Northern Rockies, which was above normal in these regions and in parts of California. Precipitation amounts were less than half an inch in other parts of the West, and these translated to below normal for the week. Mountain snow water content increased from 4 to 12 inches at many of the SNOTEL stations. But this is early in the snow season, so no change to the drought depiction was made in the West. The ecosystem continued to show the impacts of the multi-year drought. According to an analysis released November 18 by the U.S. Forest Service, the Forest Service estimates, based on aerial detection surveys conducted throughout 2016, the number of dead trees on California’s forested lands grew to a cumulative total of 102 million on 7.7 million acres since 2010. In 2016, 62 million trees died, representing more than a 100 percent increase in dead trees across the state from 2015, when 29 million trees died. This scale of die-off is unprecedented in California’s modern history. Millions more drought-stressed trees that are not yet dead are expected to die in the coming months and years. Five consecutive years of severe drought in California, a dramatic rise in bark beetle infestation and warmer temperatures are leading to these historic levels of tree die-off. The majority of the 102 million dead trees are located in ten counties in the southern and central Sierra Nevada region. The Forest Service also identified increasing mortality in the northern part of the state, including Siskiyou, Modoc, Plumas and Lassen counties. Dead and dying trees can pose a significant risk to communities if a wildfire breaks out in these high hazard areas…

Looking Ahead

An inch or more of precipitation is forecast to fall November 23-28 from eastern Texas to the Great Lakes as the latest front and low pressure system move across the CONUS. Three or more inches are expected from northeast Texas to eastern Arkansas, and an inch or more is progged for the Northeast. Meanwhile, another Pacific system will drench the West Coast with up to 10 inches or more of precipitation from northern California to Washington, and an inch or more as far inland as the Northern Rockies. No precipitation is forecast for southern California to southwest New Mexico, but the rest of the country may see a tenth of an inch or more. Temperatures should be warmer than normal for most of the CONUS, except for parts of the extreme Southwest. For November 28-December 6, odds favor cooler-than-normal temperatures for the West and warmer-than-normal temperatures for the East and Alaska. Much of the CONUS from the Plains to the East Coast, the Southwest, and Alaska are expected to be wetter than normal, while odds favor drier-than-normal weather across the Far West and the Rio Grande Valley.

#Snowpack news: The slow, snowless start to ski season — The Mountain Town News

Westwide SNOTEL November 22, 2016 via the NRCS.
Westwide SNOTEL November 22, 2016 via the NRCS.

From The Mountain Town News (Allen Best):

Going into Thanksgiving , Vail has had almost no snow. That’s not remarkable, but the recent warm weather is.

In 1962, the ski area’s inaugural year, it was dry, too. Ski area marketing boss Bob Parker got the bright idea of recruiting Ute Indians to conduct a snow dance. It did start snowing almost immediately. That was in December.

Since then, Vail has had more slow starts to winter, particularly in droughts in 1976-77 and 1980-81. Instead of recruited Utes, though, Vail—like most ski areas—invested heavily in snowmaking.

Just one problem with this autumn. It’s been too warm to make snow at many places. Vail delayed opening until the day after Thanksgiving. And at Beaver Creek, a few miles from Vail, World Cup races had to be punted. Mike Imhoff, the chief executive of the Vail Valley Foundation, the organization that puts on the races, said the venue has a “remarkably sophisticated snowmaking system. However, the cold weather did not come in time this year.”

Warm weather was the problem at Telluride, too. Chief executive Bill Jensen announced a delayed opening until the Monday after Thanksgiving. “There aren‘t enough snowmaking hours over the next week to 10 days to make the quantity of snow necessary to achieve our planning opening day,” he said.

Indeed, temperatures in Denver last week hit 80 degrees, a record for the date and tying the record high for November, which was set in 2006.

In Salt Lake City, it was warm, too. Even though it snowed, the temperature didn’t fall below freezing. The Salt Lake Tribune noted that the city had been frost-free for 242 days, breaking a record set in 1915.

Expect more temperature records to tumble, say scientists at the National Center for Atmospheric Research in Boulder, Colo. New research announced this week in the Proceedings of the National Academy of Sciences” says Americans will see, on average, about 15 daily maximum temperature records for every time that the mercury notches a record low.

This compares, during the last decade, with two record high temperatures for every record low temperature.

The United States has experienced unusual warmth lately, as indicated by this July 22, 2016, weather map showing much of the country facing highs in the 90s and 100s and lows in the 70s. New research indicates that more record high temperatures may be in store. (Weather map by the National Oceanic and Atmospheric Administration’s Weather Prediction Center.) via The Mountain Town News.
The United States has experienced unusual warmth lately, as indicated by this July 22, 2016, weather map showing much of the country facing highs in the 90s and 100s and lows in the 70s. New research indicates that more record high temperatures may be in store. (Weather map by the National Oceanic and Atmospheric Administration’s Weather Prediction Center.) via The Mountain Town News.

If temperatures were not warming, explained Gerald Meehl, a senior scientist at NCAR and lead author of the paper, the ratio of record highest to record lows would average out to about one to one.

“An increase in average temperatures of a few degrees may not seem like much, but it correlates with a noticeable increase in days that are hotter than any in the records, and nights that will remain warmer than we’ve ever experienced in the past,” he said.

“Even with much warmer temperatures on average, we will still have winter and we will still get record cold temperatures,” he went on to explain. “But the numbers of those will be really small compared to record high temperatures.

The 15-to-1 ratio of record highs to lows assumes temperatures across the continental United States increase by slightly more than 5.4 degrees Fahrenheit (3 degrees Celsius) above recent years. That’s the amount of warming expected to occur by 2065 with the current pace of greenhouse gas emissions.

Last week, the World Meteorological Organization reported that it is very likely that 2016 will be the hottest year on record globally.

“Long-term climate change indicators are also record breaking,” the organization said in a press release. “Concentrations of major greenhouse gases in the atmosphere continue to increase to new records. Arctic sea ice remained at very low levels, especially during early 2016 and the October re-freezing period, and there was significant and very early melting of the Greenland ice sheet.”

Can we adapt to higher temperatures? To an extent, yes. Snowmaking was conducted at California’s Boreal Mountain Resort in July even as temperatures rose above 80 degrees. It took a lot of energy to make the snow, but it can be done.

But as was noted in Telluride and Beaver Creek this past week, cold temperatures are needed to make snow with any great volume.

In Park City, National Weather Service hydrologist Brian McInerney, looked through the crystal ball of increasing greenhouse gas emissions to predict even more rapid climate change.

“We’re going to see areas that are (now) 100 percent snow-covered in December, January (and February) and are only going to be 50 percent snow-covered starting in 2035,” he said at an event covered by The Park Record.

“The young people in the audience that are skiers, they’re going to have a hard time getting to the base areas of Park City, Powder Mountain Beaver Mountain, some of these lower-elevation areas,” he added.

That’s in the future. This winter might still be a good one. Ryan Boudreau, a forecaster with aspen-weather.net, predicted plenty of snow in the Northern and Southern Rockies in December and January.

“It’s going to hammer in December. It’s just a little delayed,” he told the Telluride Daily Planet.

But if we continue to dump carbon dioxide, methane and other greenhouse gases into the troposphere the way we have, ski season will get a lot shorter.

Doing a snowdance
Doing a snowdance

#ENSO Wrap-Up: The tropical Pacific Ocean remains El Niño–Southern Oscillation (ENSO) neutral

All models indicate warming of the central Pacific is likely over the coming months.
All models indicate warming of the central Pacific is likely over the coming months.

From the Australian Bureau of Meteorology:

Negative Indian Ocean Dipole ends, while central tropical Pacific Ocean warms

The Indian Ocean Dipole has returned to neutral levels, after being in a negative phase since May. The tropical Pacific Ocean remains El Niño–Southern Oscillation (ENSO) neutral.

In the tropical Pacific, most indicators of ENSO are well within neutral bounds. In the past fortnight, sea surface temperatures in the central tropical Pacific Ocean have warmed once again, further dampening chances of La Niña. The Southern Oscillation Index (SOI) has been negative since late October (La Niña values are typically positive) but remains neutral. Trade winds are currently close to average. Only cloudiness near the Date Line continues to show some La Niña-like characteristics.

Climate models predict the tropical Pacific Ocean will remain cooler than average, but in the ENSO-neutral range, through until the end of the 2016–17 summer. Only one of the eight models surveyed indicates La Niña for the summer months. A La Niña developing this late in the calendar year has only occurred once since 1980.

The Indian Ocean Dipole (IOD) has returned to neutral levels as the monsoon trough transitions to the southern hemisphere. This shift changes the wind patterns over the tropical Indian Ocean, breaking down the typical IOD circulation. The strong negative IOD event helped drive Australia’s wettest May–September period in 117 years of record. The July IOD value was equal-strongest for at least 50 years.

#Drought news:

Colorado Drought Monitor November 15, 2016.
Colorado Drought Monitor November 15, 2016.

From The Prowers Journal (Russ Baldwin):

Colorado experienced above average temperatures in October and the first half of November combined with well below normal precipitation as weak La Niña conditions have developed. October was the third warmest on record and temperatures across the state through November 14 ranged from 4-10 degrees above normal. While the 2016 Water Year ended with nearly average precipitation, the 2017 water year is off to a dry start with all basins in the state recording well below normal precipitation as of November 14 at the mountain SNOTEL sites.

Statewide snowpack as of November 14 is at 6% of average. This is the worst start to the mountain snowpack season since at least 1986, although daily snowpack records only date back to that year. At this point in the water year, Colorado typically receives 2.1 inches of snow water equivalent however the state is currently at 0.1 inches.

Statewide water year to date mountain precipitation is 34% of average. The South Platte & Yampa/White basins have the highest percentage of average at 42% and 47% respectively. The lack of precipitation has negatively affected the winter wheat crop.

Reservoir storage statewide remains strong at 104% of normal. The Southwest and Yampa/White River basins have the highest storage levels in the state at 112 and 114% of average, respectively. The Upper Rio Grande has the lowest storage levels at 87% percent.

Water providers in attendance all reported storage levels ranging from 70 to 123 percent of average. Demand is above average & providers hope colder temperatures will help decrease the demands.

A weak La Niña has developed contributing to the lower than average precipitation in the state this fall. The long term forecast predicts the weak La Niña may be gone by early 2017. CPC forecasts give Colorado equal chances for moisture through late winter with a chance for extra moisture in December. Weak La Niña conditions should favor the northern and central mountains through mid winter, after which it would revert to being a negative factor. The next two weeks promise to bring near normal moisture to the state in a welcome change from dry fall conditions.

The US Drought Monitor shows D2, severe drought, has been introduced into Larimer and Lincoln counties. D1, moderate drought, has been expanded further towards the southeastern part of the state. Only 1.6% of Colorado in the northwest part of the state is currently drought free.

An Ecosystem’s Lifeblood, Flowing Through Gravel — @NYTimes

Photo via GrizzlyTours.com
Photo via GrizzlyTours.com

From The New York Times (Jim Robbins):

In a paper published earlier this year, a team of ecologists sought to outline the essential role of gravel-bed rivers in Western mountain ecosystems — the first time an interdisciplinary team has looked at river systems on such a large scale.

“A river doesn’t just flow down the channel,” said F. Richard Hauer, a professor of stream ecology at the University of Montana and the lead author of the paper. “It flows over and through the entire flood plain system, from valley wall to valley wall, and supports an extraordinary diversity of life.”

Perhaps most surprising of all: “Most of the water in these systems is not in the river — it’s in the gravel.”

These river systems are among the most ecologically important habitats on the continent, Dr. Hauer and his colleagues concluded, supporting a hidden wealth of biodiversity. And not just in the West; the life-sustaining dynamics are at play in the mountains of Europe, the Andes, the Himalayas and New Zealand.

In the West, a dynamic river is not important just to fish or to amphibians, but to grizzly bears and mountain lions descending from mountaintops to the flood plain for important foods. Indeed, two-thirds of the species in a large river valley spend at least part of their lives in its flood plain.

The new study also demonstrates that altering this complex biological machinery with dams and diversions has far-reaching effects, leading to long-term decline of the ecosystem.

“A river is a huge, huge biodiversity engine with multiple parts,” Dr. Hauer said. “If you keep taking out parts, pretty soon the engine stops.”

Until now, scientists had never put together such a comprehensive ecological blueprint of river dynamics.

Melting snow and groundwater flow down the channel; this is what we think of as a “river.” But underground, far more water is moving slowly through a labyrinthine network of cobbles, gravel and sand that make up the entire valley bottom.

This deeply buried habitat is far more important and far more productive than thought. The matrix of gravel and sand cleans the water, filtering organic material and freeing up nitrogen and phosphorous embedded in the gravel.

These natural fertilizers spread across the valley bottom, a shot of adrenaline that nourishes plants in the flood plain such as willows and aspen, which in turn draw birds and beavers, elk and caribou. The plant-eaters attract predators like wolves and grizzly bears.

In the summer, warm water is stored underground. It takes so long for the water to move that it surfaces in winter, moderating water temperatures and creating a refuge for some aquatic species, shielding them from winter’s freeze. In the winter, the opposite happens.

The river also continually rearranges and renews the ecosystem.

During high water, topsoil, gravel and woody debris are washed into new sites downriver and below ground, fostering new habitats and new plant communities. The new habitats blend with existing ones, from mature cottonwood forests to grasslands, to create a patchy mosaic.

On a recent flight over the Bitterroot River, a gravel-bed river near Missoula, Dr. Hauer pointed out the flood plain.

While the river below flowed down a main channel, it was easy to see from the air that over centuries, the Bitterroot had frequently jumped its bounds to create a network of new channels.

The old channels were covered with gravel — an important habitat for the stoneflies and other insects that feed the fish. Everywhere in the valley, water flowing underground through the gravel surfaced to create a diverse assortment of ponds, seeps and springs.

Dr. Hauer also pointed out a number of places where people have sought to tame the river’s unruly habits in order to plow farm fields or build subdivisions.

“There’s no renewal — the river doesn’t move gravel around and doesn’t create new mosaics of habitat,” he said. “Nutrients are not dispersed. Everything gets locked in place and starts getting old and declines.”

The environmental damage is hidden — at first. Channels feeding the underground habitats are sealed off as the river is confined. The species that depend on the hidden flows begin to falter.

These gravel flood plains, Dr. Hauer said, are among the most endangered ecosystems worldwide.

Keeping them intact will help dependent species adapt to the greatest environmental threat of all: climate change. “The implication for conservation is enormous,” Dr. Hauer said.