Climate change is unraveling natural cycles in the West

Spring’s early arrival creates more mismatches in ecosystems.

 

Across the West, spring has come early this year — by as much as three weeks in some places. But what does that mean, exactly?

From an astronomical perspective, the first day of spring is the spring equinox, the day when the sun passes directly above the equator, occurring around March 21 each year. From a biological perspective, spring arrives when plants and animals respond to an accumulation of seasonal signals, such as growing warmth or longer days. Plants bud, birds fly north and insects emerge from tree holes and leaf litter. This seasonal timing of plant and animal life stages is called phenology.  

This spring, wildflowers filled California's Carrizo Plain National Monument, a grassland in the Central Valley.
Beth Pearson King/BLM

For many plants, warming days are one of the main signals that it’s time to wake up from their winter slumber. As climate change has caused the West to warm earlier in the year, “biological” spring has shifted, too. In many parts of the West, it has crept early across the landscape.

The USA-National Phenology Network (USA-NPN) studies just how much the start of spring is changing using extended spring index models, computer simulations based on a historic data set of lilac and honeysuckle phenology begun in the 1950s. The models also help scientists predict future spring arrivals. Scientists update spring index maps each day on the USA-NPN website, as well as spring leaf anomaly maps, which compare the current year’s spring to 30-year averages.

As the May 9, 2017 spring leaf anomaly map shows, in most of the West spring has come 12 to 20 days early this year, relative to the long-term average. The exceptions are high-elevation Western mountains (in green on the map), where spring is expected to arrive on time, and the Pacific Northwest and parts of the Pacific coast (in blue), where gusts of cold Arctic air have delayed spring.

This follows a growing trend. According to the 2014 National Climate Assessment, from 1950 to 2005, spring shifted about eight days earlier in the Western United States, due to climate change. “This trend matters because of what it means for a lot of ecosystem processes and interactions between organisms,” says Kathy Gerst, research scientist with the USA-NPN. “Plants may flower earlier, but other organisms may respond to different cues, or to the same cues in different ways.”

For example, the 2014 National Climate Assessment notes that some migratory birds now arrive at their breeding grounds after food is most abundant. That’s because temperatures at their wintering grounds, which tell the birds it’s time to head north, are changing more slowly than at spring breeding grounds, which signal to their food plants that it’s time to start making nectar and fruit. On the mammalian side, the earlier spring in Alaska means that caribou have a harder time finding good forage while they breed.

For humans, phenological mismatches can affect harvests by changing when crop pollinators arrive, how dense herbivorous insects are on crops, or even when animals that eat crop pests appear. And allergy sufferers, take note: Ragweed has begun producing pollen later into the fall, thanks to a lengthening growing season.

All of these mismatches embody an idea that ecologists call asynchrony. Ecological systems exist because many different species have evolved to follow the same seasonal schedule, behaving in synchrony, relying on one another for the resources they need. Now, with climate change, some of those systems are unraveling — and this spring’s early arrival is a sign of more asynchrony to come.

Note: This article has been updated to clarify the history of USA-NPN.

Maya L. Kapoor is an associate editor with High Country News.

High Country News Classifieds
  • WATERSHED PROGRAMS COORDINATOR
    Are you looking for a positive and success oriented work environment, the opportunity to join a (small but) dynamic group of people supporting watershed activities...
  • BACKCOUNTRY FILM FESTIVAL MANAGER
    Boise-based Winter Wildlands Alliance is looking for an experienced and highly motivated individual to organize our annual Backcountry Film Festival and Tour and coordinate additional...
  • LAND CONSERVATION MANAGER
    SUMMARY Leads, administers and manages the land conservation, conservation easement stewardship, and property management activities of the City of Fort Collins Natural Areas Department within...
  • CLEAN ENERGY PROGRAM ATTORNEY, NEVADA
    Position Summary: Western Resource Advocates (WRA) is seeking a Staff Attorney who is passionate about Western communities and the protection of the natural environment to...
  • EXECUTIVE DIRECTOR
    Deschutes River Conservancy in Bend, Oregon
  • WATER POLICY ANALYST WITH WRA (BOULDER)
    Position Summary: Western Resource Advocates seeks a passionate Water Policy Analyst with knowledge of western water issues to join our Healthy Rivers Team to strengthen...
  • GILA NATIONAL FOREST
    9+ acre inholding. Passive solar strawbale off the grid and next to the Continental Divide Trail in ponderosa pine/doug fir forest at 7400.
  • HIRING BEARS EARS EDUCATION CENTER DIRECTOR
    Conservation nonprofit Friends of Cedar Mesa in Bluff, Utah is hiring an Education Center Director to oversee the operation of the Bears Ears Education Center....
  • PROGRAM MANAGER, SUSTAINING FLOWS
    Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • PROGRAM ASSOCIATE - VERDE RIVER EXCHANGE
    Verde River Exchange - Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • CODE COMPLIANCE OFFICER
    Teton County Planning & Building is hiring! Our ideal candidate is a team-player, a problem-solver, pays attention to detail, and can clearly communicate technical material...
  • ARCHITECTURE DRAFTSPERSON/PROJECT MANAGER
    Studio Architects is seeking a full time Architectural drafts-person/project manager with1-3 years of experience to join our firm. At Studio Architects our mission is to...
  • ASSISTANT MANAGER/TRAINEE, COLORADO RANCH
    needed for 16,000+ acre conservation property in south central Colorado. Qualified candidate would have experience working on a ranch or wilderness property, general forestry/fire management...
  • FARM HAND &/OR NANNY IN ESCALANTE
    Nanny for 18-mnth-old. Yearly salary, vacation, health insurance. Spanish/other foreign-language native spkr prefrrd.
  • EXECUTIVE DIRECTOR
    Washington Association of Land Trusts seeks an ED to build on WALTs significant success & to lead the association to new levels of achievement. See...
  • BEAUTIFUL CUSTOM STRAWBALE HOME IN WESTERN COLORADO!
    Secluded, energy efficient Southwestern home on 40 wooded acres. Broker - Rand Porter - United Country Real Colorado Properties. 970-261-1248, $425K
  • FORMER RETREAT CENTER/CONSERVATION PROPERTY FOR SALE
    57 acres in Skull Valley, AZ, 17 miles from Prescott, year-round creek, swimming holes, secluded canyon, hiking/meditation trails, oaks, pines, garden, greenhouse. House, office building,...
  • HISTORIC RANCH HOME W/ 20 ACRES
    Historic 1893 Ranch Headquarters. 4 Bdrm, 3.5 Ba, 4000 ft2. Remodeled 2002. Includes 2 studio apts, stables, arena, workshop, 5 RV hookups. Chirachua & Peloncillo...
  • VICE PRESIDENT OF RETAIL OPERATIONS
    The Vice President of Retail Operations will provide overall leadership and accountability for purchasing, product development, merchandising planning, visual merchandising, retail operational excellence, oversight and...
  • ASSOCIATE DIRECTOR
    Grand Staircase Escalante Partners seeks an experienced fundraiser with excellent communication and organizational skills.