Topography and human pressure in mountain ranges alter expected species responses to climate change - PubMed (original) (raw)

Topography and human pressure in mountain ranges alter expected species responses to climate change

Paul R Elsen et al. Nat Commun. 2020.

Abstract

Climate change is leading to widespread elevational shifts thought to increase species extinction risk in mountains. We integrate digital elevation models with a metric of human pressure to examine changes in the amount of intact land area available for species undergoing elevational range shifts in all major mountain ranges globally (n = 1010). Nearly 60% of mountainous area is under intense human pressure, predominantly at low elevations and mountain bases. Consequently, upslope range shifts generally resulted in modeled species at lower elevations expanding into areas of lower human pressure and, due to complex topography, encountering more intact land area relative to their starting position. Such gains were often attenuated at high elevations as land-use constraints diminished and topographic constraints increased. Integrating patterns of topography and human pressure is essential for accurate species vulnerability assessments under climate change, as priorities for protecting, connecting, and restoring mountain landscapes may otherwise be misguided.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1

Fig. 1. The global distribution of topographic classes within mountain ranges.

The distribution of classes when considering all land a and intact land b. Inset donut plot in a shows the proportion of mountain ranges per mountain class considering total land area. Inset donut plots in b show the proportion of ranges from their original classification in each mountain class (denoted by donut labels) that were then reclassified considering only intact land area. Mountain ranges classified as intensified have no intact land area remaining when removing all land under intense human pressure. c Comparisons of area-elevation distributions considering total land area (left column) and intact land area (right column) for four example mountain ranges, colored by mountain classification. Black rectangles with alphanumeric symbols in a and b indicate the geographical location of each mountain range in c.

Fig. 2

Fig. 2. Comparing projected area from modeled elevational range shifts with and without accounting for human pressure.

Map of global mountain ranges shows the proportion of the elevational gradient for each range where percentage of change in intact area equals or exceeds the percentage of change in total area following range shifts for a suite of modeled hypothetical montane species. Range shifts are calculated using mountain range-specific rates of mean annual temperature change averaged across 17 GCMs for RCP 8.5 in 2070, mountain range-specific adiabatic lapse rates, and varying elevational range sizes for hypothetical species (see “Methods” section and Supplementary Fig. 9 for descriptive and schematic overviews of the modeling procedure). Insets for select mountain ranges show mean and standard error percentage of changes in area across all modeled species in two cases, one where species are allowed to occupy all land area (blue lines ΔAreatotal), and one where species only occupy intact land area (red lines ΔAreaintact). Values of –100% signify that the species have no available total or intact land area remaining and face local extinction. The _x_-axis elevation represents the lower boundary of elevation prior to the range shift. See the plot for Cordillera Occidental for a detailed legend to other insets. Therefore, the global map depicts the proportion of each mountain range’s elevational gradient where the change in area in the second case equals or exceeds the change in area in the first case (i.e., the proportion of elevation where the red curve equals or exceeds the blue curve). See also Supplementary Data 1 for analogous inset plots for all mountain ranges (n = 1010) and Supplementary Fig. 7a for the analogous global map using RCP 4.5.

Fig. 3

Fig. 3. Average projected area changes for species undergoing elevational range shifts.

a Mean (lines) and standard error (shaded regions) percentage of change in projected total (gray lines) and intact (red lines) land area across all modeled species and all mountain ranges by mountain classification. b Elevation bin-wise comparison of percentage of change in projected total and intact area. Dashed line is 1:1 line. Cells are colored by the total number of elevation bands (50 m) across modeled species and all mountain ranges, with panels arranged by mountain classification based on total area availability. See text and “Methods” section for details of modeled range shifts and Supplementary Fig. 6 for analogous results using RCP 8.5 for panel a.

Fig. 4

Fig. 4. The influence of species’ elevational range sizes on projected area changes following modeled elevational range shifts.

a Mean and standard error percentage of change in projected total (gray) and intact (red) land area across all modeled species (within elevational range size classes, _x_-axis) and all mountain ranges by mountain classification. b Proportion of mountain ranges where percentage of change in intact land area equals or exceeds percentage of change in total land area following elevational range shifts across the elevational gradient by mountain classification. Blue lines indicate proportions for each elevational range size class considered in modeling (100–4000 m, in 100-m increments); red line indicates the mean response across all range class sizes. See text and “Methods” section for details of modeled range shifts.

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