Research ArticleECOLOGY

The past and future human impact on mammalian diversity

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Science Advances  04 Sep 2020:
Vol. 6, no. 36, eabb2313
DOI: 10.1126/sciadv.abb2313
  • Fig. 1 Different time periods of diversity decline and extinction rate increases between areas and orders.

    The plots show the declining diversity (black lines, 100 modeled extinction dates for each species) and the magnitude of extinction rate increases relative to the starting rate (red lines, mean values) through time, for all spatial (A to H) and two examples of taxonomic subsets (I to J) analyzed in this study. Extinction rates were estimated with a Bayesian rate-shift model, inferring the timing, number, and magnitude of shifts in extinction rates from the extinction dates of each subset. We calculated the mean marginal rates (harmonic mean) separately for all shift number models, which were supported by more than 10% posterior probability (table S3). The rate-shift model that was best supported by the data is shown in solid red, while the transparent red lines show the second-best model, if present. All rate estimates are transformed and plotted as the magnitude of extinction rate increase relative to the base value 126 ka ago. Note that the extinction rate axis (right, in red) is plotted in logarithmic space for better visibility. The time axis to the left of the solid vertical black line (0 CE) is plotted in units of ka before present (BP), while the time axis to the right of 0 CE is plotted in years CE in logarithmic space for better visibility of recent rate changes. Vertical columns shaded in green mark the times of first human arrival (if applicable).

  • Fig. 2 Higher model adequacy for human correlation model compared to climate model.

    The displayed models can be grouped into correlation models (A to C) in which extinction rates are estimated as a function of time continuous predictors and a rate-shift model (D) with a distinct and limited number of rate changes, estimated solely from the extinction dates dataset. The applied correlation variables were global human population density (A) and global mean temperature (B), as well as the interaction of the two in a mixed model (C). Shown for each model are the time-continuous predictor trajectories (black, top; only for correlation models), the estimated rates through time (red, middle; mean values and 95% HPD) and the simulated mammal species diversity based on the estimated rates (green, bottom). The accuracy scores in the bottom of the lower panels reflect how accurately the respective model predicted past extinctions and was calculated from the MAPE scores of each model (see. fig. S4). The input for the mixed model (C) included the product of human population density and global temperature, as well as each of these variables individually. See fig. S5 for further correlation models. The time axis is scaled in ka before present (BP).

  • Fig. 3 Substantial species losses predicted by year 2100 CE.

    The subplots show the estimates of mammalian species diversity globally (A) and for all spatial (B to H) and taxonomic subsets (I to T) analyzed in this study. The colored violin plots represent density plots of the 95% CI of diversity predictions based on the simulation scenarios “IUCN threat status prediction” (IUCN, red), “present extinction rate prediction” (PR, yellow), and “human population model prediction” (HU, green). In the first scenario (IUCN), we simulated extinctions based on the current threat statuses of species, applying extinction probabilities associated with these statuses. In the second scenario (PR), we applied current extinction rates as estimated from past extinction data. In the third scenario [only for spatial data subsets (A to H)], we simulated future extinction based on the correlation factor estimated for human population density combined with future human population predictions for different areas. The horizontal dashed lines show the current species diversity of each group. Note that the y axes only show a subsection of possible diversity values and do not include 0.

  • Fig. 4 Expected increases in extinction rates for most orders and areas.

    In structure equivalent to Fig. 3, the violin plots (A to T) show the 95% HPD interval density of estimated extinction rates in the year 2100 based on the different diversity prediction scenarios. The IUCN rates (red) were estimated from simulated future extinctions based on the IUCN threat status of species in each subset. These extinction rate predictions are consistently higher than the present rates (PR) estimated from recent extinctions (yellow). For several spatial subsets (B,C,E,F, and H) we predict rate increases based solely on human population size increases (HU, green). Rates were estimated applying a shift model as implemented in PyRate. The multimodality of some rate distributions reflects the model uncertainty of the applied shift model.

  • Table 1 Timing of inferred shifts in extinction rates.

    The table shows the timing of the inferred extinction rate shifts (95% HPD range) for all data subsets analyzed in this study. For several subsets, there were multiple supported shift models, which differ in their inferred number of rate increases. All shift models that were supported by more than 5% posterior probability are shown here for each subset (see table S3 for overview of posterior probabilities for different models).

    SubsetFirst shiftSecondThirdFourth
    Global (1)32,150–63,7929514–16,003600–2292117–182
    Global (2)26,476–56,6505030–14,474143–732
    Africa (1)
    Africa (2)5501-36,342
    Eurasia (1)31–33,733
    Eurasia (2)
    Australia (1)122–357
    Australia (2)43,514–65,035124–216
    North America10,594–20,916
    South America7797–34,810
    Cetartiodactyla (1)8689–19,826
    Cetartiodactyla (2)11,308–38,44122–10,400
    Diprotodontia (1)70–8090
    Diprotodontia (2)41,621–62,62474–685
    Peramelemorphia (1)
    Peramelemorphia (2)62–7214
    Perissodactyla (1)
    Perissodactyla (2)11,668–33,558
  • Table 2 Diversity, extinction rates, and magnitude of rate increase at different time points.

    The displayed extinction rate estimates are based on the shift model [reversible jump Markov Chain Monte Carlo (RJMCMC)], averaging across the complete posterior distribution (excluding 10% burn-in), and scaled in extinctions per species year (E/SY). The last two columns show the magnitude of extinction rate increase relative to the base value at 126 ka ago. Future diversity and rates are estimated from our “IUCN continuing trends” simulations.

    126 ka ago
    2100 CE
    126 ka ago
    2100 CE
    Rate increase
    Rate increase
    2100 CE
    Global6065571451563.894 × 10−86.195 × 10−51.178 × 10−3159130,260
    Africa102710129291.249 × 10−71.249 × 10−79.690 × 10−417758
    Eurasia1268123711341.194 × 10−71.468 × 10−51.005 × 10−31238416
    Australia5134514116.597 × 10−72.678 × 10−41.114 × 10−34061688
    North America5955555045.097 × 10−84.688 × 10−61.104 × 10−39221,657
    South America105510019081.086 × 10−72.386 × 10−61.116 × 10−32210,270
    Caribbean9245373.873 × 10−75.298 × 10−42.568 × 10−313686631
    Madagascar2121911547.842 × 10−84.627 × 10−52.697 × 10−359034,398
    Carnivora2772552359.495 × 10−85.112 × 10−69.230 × 10−4549725
    Cetartiodactyla3022322045.607 × 10−71.601 × 10−51.611 × 10−3292874
    Chiroptera1153114010562.661 × 10−88.216 × 10−68.680 × 10−430932,611
    Cingulata3920191.319 × 10−63.264 × 10−51.473 × 10−3251117
    Diprotodontia1831391181.673 × 10−62.999 × 10−42.054 × 10−31791227
    Eulipotyphla4614514043.582 × 10−85.267 × 10−61.285 × 10−314735,865
    Peramelemorphia2419171.981 × 10−61.981 × 10−62.356 × 10−311189
    Perissodactyla2916134.205 × 10−64.205 × 10−63.663 × 10−31871
    Pilosa341091.095 × 10−69.465 × 10−52.282 × 10−3862084
    Primates4304073371.238 × 10−71.499 × 10−52.366 × 10−312119,101
    Proboscidea17222.566 × 10−61.253 × 10−41.017 × 10−2493961
    Rodentia2271219719981.838 × 10−82.944 × 10−51.101 × 10−3160259,905

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