Research ArticleECOLOGY

Climate warming drives local extinction: Evidence from observation and experimentation

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Science Advances  21 Feb 2018:
Vol. 4, no. 2, eaaq1819
DOI: 10.1126/sciadv.aaq1819
  • Fig. 1 A. septentrionalis and the Warming Meadow.

    (A) A. septentrionalis, also known as Northern rock jasmine and Northern fairy candelabra, grows along wide global and local climate gradients. Here, it is pictured growing on the rocky summit of Treasury Mountain in the Elk Range of the Colorado Rocky Mountains (elevation, 4103 m). (B) The Warming Meadow, indicated by the red star, is located at the Rocky Mountain Biological Laboratory (Gunnison County, CO; elevation, 2929 m). (C) In the Warming Meadow, suspended infrared radiators have actively warmed five heated plots night-, day-, and year-round since 1 January 1991. Photo credit: A. M. Panetta, University of Colorado, Boulder.

  • Fig. 2 Experimental warming accelerates advancing spring snowmelt.

    (A) In early spring, bare ground appears in heated plots when adjacent control plots remain blanketed with snow. Photo credit: A. M. Panetta, University of Colorado, Boulder. (B) Experimental warming accelerates rates of advancing spring snowmelt caused by contemporary climate change (treatment × year: F = 15.19, P < 0.001). Over the past 2.5 decades, spring snowmelt in control plots has advanced by ~0.5 days per year (F = 11.88, P < 0.001), whereas spring snowmelt in heated plots has advanced by ~1.3 days per year (F = 92.30, P < 0.001). Experimental warming also simulates the timing of spring snowmelt in warmer, drier A. septentrionalis populations that occur naturally at lower elevations. Means indicate average yearly snowmelt date (ncontrol = 5, nheated = 5, nlow-elevation populations = 2), and error bars indicate ±1 SE.

  • Fig. 3 Experimental warming reduces the abundance of seedlings and established plants, driving population sizes toward zero.

    (A) Relative to neighboring control plots, heated plots have ~90% fewer seedlings (C = 93.3 ± 30.8, H = 9.0 ± 3.4) and ~92% fewer established plants (C = 32.0 ± 9.8, H = 2.5 ± 1.2). Data indicate average yearly abundance per plot from 2013 to 2016 (ncontrol = 5, nheated = 5). Photo credit: J. B. Curtis, University of Colorado, Boulder. (B) After 25 years of experimental warming, heated-plot population sizes are either at or near absolute local extinction (indicated by dotted black line). Earlier snowmelt, across all meadow plots and both treatments, is strongly associated with lower population size (χ2 = 21.76, P < 0.001). Means indicate average abundance in each of the ten warming meadow plots from 2013 to 2016 (n = 4 per plot). Error bars indicate ±1 SE.

  • Fig. 4 Experimental warming affects performance across multiple life stages.

    (A) The life cycle of A. septentrionalis. Emergence (E) from seed occurs from late summer to early fall in late-season monsoonal moisture. Emergent individuals are highly susceptible to drought stress, thus their survival (LE) to become fall seedlings depends on the timing and amount of rainfall. Fall seedlings that survive under winter’s snowpack and through their first growing season (L1) become established plants at age 1. Established plants may survive a second (L2), third (L3), and in rare cases fourth (L4) year. Individuals typically become reproductive (R) in their second year of life, producing white flowers, each of which develops into a small fruit containing seeds (S). Red arrows indicate life stages significantly affected by experimental warming (tables S5 to S9). Photo credit: J. B. Curtis, University of Colorado, Boulder. (B) The effects of experimental warming on emergence and survival throughout the life cycle of A. septentrionalis. Experimental seed introductions demonstrate that warming increases seedling emergence (E) but decreases fall survival of those that emerge (LE). Longitudinal plant surveys reveal that although warming has no significant effect on the survival of fall seedlings to age one, it substantially reduces the survival of established plants to age two (L2) and beyond. Data indicate average percent emergence (LE) and average percent survival L(1-5). Treatment sample sizes vary by transition (see table S6), and error bars indicate ±1 SE.

  • Fig. 5 Experimental warming depletes A. septentrionalis seed banks by reducing deposits and increasing withdrawals.

    (A) Warming reduces annual seed deposits into belowground seed reservoirs by ~98% (C = 4732.0 ± 1153.9, H = 83.4 ± 50.9). Data represent the average number of seeds produced per plot from 2013 to 2016 (ncontrol = 5, nheated = 5). (B) Warming decreases seed dormancy, stimulating emergence by ~41% (C = 30.0 ± 2.8, H = 42.2 ± 3.0). Data indicate average percent emergence from experimental seed banks introduced into each Warming Meadow plot (ncontrol = 5, nheated = 5). Photo credit: (A) A. M. Panetta and (B) J. B. Curtis, University of Colorado, Boulder.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/2/eaaq1819/DC1

    fig. S1. The initial distribution of A. septentrionalis across Warming Meadow heated and control plots.

    fig. S2. The initial distribution of A. septentrionalis across Warming Meadow control plots with respect to snowmelt date.

    table S1. The effects of experimental warming on snowpack and soil temperature.

    table S2. The effects of experimental warming and contemporary climate change on snowmelt date in the Warming Meadow.

    table S3. The effects of experimental and contemporary warming on the abundance and distribution of A. septentrionalis in Warming Meadow.

    table S4. Mean abundance (±1 SE) of A. septentrionalis in control and heated plots from 2013 to 2016.

    table S5. The effects of experimental warming on emergence and post-emergence survival of A. septentrionalis.

    table S6. The emergence and post-emergence survival of A. septentrionalis in control and heated plots.

    table S7. Mean number of seeds produced per plant (±1 SE) by age in control and heated control plots.

    table S8. Components of A. septentrionalis mean reproductive success (±1 SE) in control and heated plots.

    table S9. The effects of experimental warming on the reproductive success of A. septentrionalis in the Warming Meadow.

    table S10. The ghosts of reproduction past: Relationships between seedling abundance in yeart and the number of flowering stalks in yeart−1 and yeart−2.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. The initial distribution of A. septentrionalis across Warming Meadow heated and control plots.
    • fig. S2. The initial distribution of A. septentrionalis across Warming Meadow control plots with respect to snowmelt date.
    • table S1. The effects of experimental warming on snowpack and soil temperature.
    • table S2. The effects of experimental warming and contemporary climate change on snowmelt date in the Warming Meadow.
    • table S3. The effects of experimental and contemporary warming on the abundance and distribution of A. septentrionalis in Warming Meadow.
    • table S4. Mean abundance (±1 SE) of A. septentrionalis in control and heated plots from 2013 to 2016.
    • table S5. The effects of experimental warming on emergence and post-emergence survival of A. septentrionalis.
    • table S6. The emergence and post-emergence survival of A. septentrionalis in control and heated plots.
    • table S7. Mean number of seeds produced per plant (±1 SE) by age in control and heated control plots.
    • table S8. Components of A. septentrionalis mean reproductive success (±1 SE) in control and heated plots.
    • table S9. The effects of experimental warming on the reproductive success of A. septentrionalis in the Warming Meadow.
    • table S10. The ghosts of reproduction past: Relationships between seedling abundance in yeart and the number of flowering stalks in yeart−1 and yeart−2.

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