Climate extremes are putting species in sync – and in danger

Shifts in coastal weather systems could make the West’s species less resilient.

 

Every few winters, a high-pressure climate system called the North Pacific High flares up on California’s coast. For several months, northerly winds blow harder than usual down the continent’s West Coast, pushing coastal waters out to sea. The sea level drops, and a soup of nutrient-rich waters rises toward the surface from the depths. Thanks to this coastal upwelling, when the system is strong, everything from phytoplankton to seabirds thrives.

But the same climate feature pushes rain northward, parching the Interior West. In winters when the coast feasts, the Interior West’s land- and river-based systems starve. Alternatively, in winters when the North Pacific High is weak, the coast dries out, while the Interior West flourishes under heavy precipitation. Many Western ecosystems — from coastal ecosystems to landlocked forests and snow-dependent rivers — are in sync with the oscillating nature of the North Pacific High. That means that, even if they are nowhere near each other, scattered populations of the same species of trees will all seed at the same time, or butterflies of the same species will find food and flourish, using cues from this erratic climate phenomenon. 

Now, by studying growth rings in the ear stones of long-lived fish and the trunks of ancient trees, researchers have found that the North Pacific High may be becoming more variable and driving a bigger swath of Western ecosystems to biological synchrony — a deceptively nice-sounding situation wherein disparate populations operate on the same clock despite being separated by distance. Unfortunately, synchrony could harm the West’s biodiversity, because it eliminates the natural variation that makes species resilient. And it is only expected to increase with continued human-caused climate change.

The study’s lead author, University of Texas marine biologist Bryan A. Black, began his research career as a forest ecologist. As he was finishing his graduate studies in tree-ring research, Black came across an advertisement for a postdoctoral position at the Hatfield Marine Science Center in Oregon, where he could study the growth rings that form in the ear stones, or otoliths, of fish that can live for more than a century. “I thought, well, maybe it’s possible that these techniques that had been so well developed by tree-ring scientists could be applied to growth increments of long-lived fish,” he said.

An otolith, magnified 80 times, from a splitnose rockfish that was born in the early 1930s and lived approximately 56 years.
Bryan A. Black

Otolith organs, which evolved long ago in vertebrates, aid balance and motion, and, in bony fish, assist hearing. Fish otoliths grow from calcium carbonate, the same material that forms shells, with layers of material accumulating each day. The growth of a fish’s otoliths depends on how much food that fish is getting. Otoliths, like trees, develop growth rings over time, so biologists can count them to learn a fish’s age as well as to measure its food intake. 

Black examined the oval, pea-sized otoliths of splitnose rockfish, a species that can live longer than 80 years. Once full-grown, the spiny, solitary creatures – which have the approximate size and energy level of cinderblocks – dwell on the floor of the continental shelf from the Gulf of Alaska to Baja California, resting either near sheltering rocks or in shallow depressions that they excavate in soft sediments, feeding on shrimp and krill and sporting dour expressions that inspired one aquarium to call them the “grumpy cats of the deep blue sea.” All the while, their ear stones grow rings that record years of upwelling and years of hunger. 

Researcher Bryan A. Black measures a tree core.
University of Texas Marine Science Institute

Black found that rockfish growth rings correlate with the variability in the winter North Pacific High: Rockfish grow more when the pressure system is strong, because it means better food supplies. And this is true of rockfish throughout the region, even if they live in separate populations. Other coastal animals show similar patterns. Seabirds, for example, rear more young successfully in strong North Pacific High winters, and the small marine invertebrates called copepods explode in population, providing an important food source for other ocean dwellers. “The winter can really be boom or bust in the marine system,” Black said, so more nutrients brought up by coastal upwelling have a sweeping effect on the ecosystem. The North Pacific High’s extremes create similarly intense environmental conditions throughout the California Current System, triggering similar responses from the region’s organisms. That pushes species to biological synchrony.

For the West’s wild organisms, scientists predict, that’s a gamble akin to investing all your money in a single stock. 

Ecological stability requires having a “diverse portfolio of responses or behaviors,” Black said. The idea is that if one population gets wiped out by a local event — if a wildflower goes locally extinct because of drought, for example — nearby populations might be able to recolonize the community, perhaps by sprouting at a lusher time in future. But with increasing synchrony, “there’s less and less of a diverse portfolio that helps spread the risk,” Black said. “Everyone is tied to the same fate.”

And the synchrony created by the North Pacific High doesn’t end at the water’s edge. Dan Griffin, a tree-ring researcher at the University of Minnesota, examined growth patterns of old-growth blue oak trees in California and concluded that the West’s landlocked life is growing more synchronized, too. Blue oaks, which Griffin calls “Halloween trees” because of their gnarled, twisted shapes, are long-lived and deciduous, growing in open, parklike savannas between the forest and grasslands. Their growth is closely tied to water availability, so their tree rings are excellent record-keepers of drought. By coring old-growth blue oaks, Griffin could follow drought patterns in California going back hundreds of years. “You can look at a plant and just tell it has weathered centuries,” said Griffin, with trees whittled down to a few heavy craggy limbs, or missing their crowns because of windstorms or lightning. “Sometimes we’ll even see the root collar from centuries of erosion.” His team sampled living trees as much as three centuries old growing in 16 sites, and found that in years when rockfish feasted and their otoliths grew wide rings, the trees’ trunk rings grew only narrowly as the oaks suffered through drought. The tree rings extended the timeline for what Black has found with fish ear stones: Winter rains have become increasingly variable over the past 100 years, with drier dry years and wetter wet years. The result was that blue oaks’ growth became increasingly synchronized, with tree-ring patterns across the state more closely resembling each other over time.

An old growth blue oak tree. “You can look at a plant and just tell it has weathered centuries,” says tree ring researcher Daniel Griffin.
Daniel Griffin

The North Pacific High is also influencing the Interior West’s aquatic systems. Black looked at river discharge records from the West’s least disturbed watersheds from 1920 on. He found that in unusually strong North Pacific High years, rivers ran low across the region, while in unusually weak years, they ran high. “As (the North Pacific High) varies over time, it’s imprinting patterns in the marine, terrestrial and freshwater systems,” Black said. While the study did not look for a connection between increasing wobbliness in the North Pacific High’s extremes and climate change, more climate variability overall is predicted by climate change models.

Connie Woodhouse, a geographer and tree-ring researcher at the University of Arizona who was not part of the study, said a connection between the North Pacific High and increasing synchrony across the Interior West added up. “The fact that they’re finding that (the North Pacific High) is connected to stream flow, tree growth and precipitation in Western North America makes sense,” she said.

It’s not yet clear what the researchers’ findings mean for biodiversity. But other studies have confirmed that increasing variability and synchrony may be devastating, because species need population diversity to survive a constantly changing landscape. One study from 2002 found a connection between rising variability in winter rains and the extinction of two populations of the bay checkerspot, a protected butterfly. Researchers linked the insects’ disappearance to the increasingly variable October-through-April winter rainy season, which affected the growth of the local vegetation that the butterflies needed. Over the seven decades leading to their extinction, extremely wet and extremely dry years became more frequent, and the difference in rainfall from year to year grew. The seasonal appearance of the plants that the butterflies ate as larvae, including purple owl’s clover and dwarf plantain, became synchronous, following the rain’s fluctuations. Eventually, this meant that very hungry caterpillars showed up when food was not available.

Woodhouse cautioned that more research is needed before researchers know whether the same fate awaits other Western species. Most of the increased variability that Black and Griffin documented in the North Pacific High occurred over the last 50 years, which is not a very long time in the life of an old-growth tree. More information is needed to understand what increasing climate variance means for the West’s biodiversity. To that end, Black hopes to head to the Gulf of Alaska next, coring old-growth conifers and measuring growth patterns of centenarian bivalves called geoducks, searching for similar patterns connecting climate variability to synchrony — and possibly, to species survival — in another part of the West.

Note: This story has been updated to show that the North Pacific High causes northerly, not southerly, winds.

Maya L. Kapoor is an associate editor for NewTowncarShare News. 

NewTowncarShare News Classifieds
  • Assistant Editor, NewTowncarShare News, Telecommute. Edit, write and help shape digital strategy for one of the best magazines in the country. Committed to inclusivity....
  • Associate Editor, West-north Desk, NewTowncarShare News, Telecommute. Dream job. Write, edit and contribute to the vision and strategy of one of the best magazines...
  • Take over the reins of a dynamic grassroots social justice group that protects Montana's water quality, family farms and ranches, & unique quality of life....
  • EXECUTIVE DIRECTOR - Winter Wildlands Alliance seeks an experienced and highly motivated individual to lead and manage the organization as Executive Director. Visit https://winterwildlands.org/executive-director-search/ for...
  • Background: The Birds of Prey NCA Partnership is a non-profit 501(c)(3) organization based in Boise, Idaho, which was established in 2015 after in-depth stakeholder input...
  • Southwest Borderlands Initiative Professor of Native Americans and the News Media The Walter Cronkite School of Journalism and Mass Communication at Arizona State University is...
  • AWF seeks an energetic Marketing and Communications Director. Please see the full job description at https://azwildlife.org/jobs
  • The Southwest Communications Director will be responsible for working with field staff in Arizona, Colorado and New Mexico to develop and execute detailed communication plans...
  • An intentional community designed for aging in place. Green built with Pumice-crete construction (R32), bamboo flooring, pine doors, T&G ceiling with fans, and maintenance free...
  • (CFROG) is a Ventura County, CA based watch-dog and advocacy non-profit organization. cfrog.org
  • Take your journalism skills to the next level and deepen your understanding of environmental issues by applying for the 2019-2020 Ted Scripps Fellowships in Environmental...
  • The San Juan Mountains Association is seeking a visionary leader to spearhead its public lands stewardship program in southwest Colorado. For a detailed job description...
  • The Cascade Forest Conservancy seeks a passionate ED to lead our forest protection, conservation, education, and advocacy programs.
  • Mountain Pursuit is a new, bold, innovative, western states, hunting advocacy nonprofit headquartered in Jackson, Wyoming. We need a courageous, hard working, passionate Executive Director...
  • The Draper Natural History Museum (DNHM) at the Buffalo Bill Historical Center of the West in Cody, WY, invites applications for the Willis McDonald, IV...
  • Couple seeks quiet, private, off-grid acreage in area with no/low cell phone service and no/low snowfall. Conservation/bordering public lands a plus. CA, OR, WA, ID,...
  • Former northern Sierra winery, with 2208 sq.ft. commercial building, big lot, room to expand.
  • The dZi Foundation is seeking a FT Communications Associate with a passion for Nepal to join our team in Ridgway, Colorado. Visit dzi.org/careers.
  • Available now for site conservator, property manager. View resume at http://skills.ojaidigital.net.
  • Stellar seed-saving NGO is available to serious partner. Package must include financial support. Details: http://seeds.ojaidigital.net.
У нашей компании авторитетный веб портал на тематику ситроен пикассо https://citroen.niko.ua