Temperature thresholds induce abrupt shifts in biodiversity and ecosystem services in montane ecosystems worldwide

Abstract

Montane ecosystems are crucial for maintaining global biodiversity and function that sustain life on our planet. Yet, these ecosystems are highly vulnerable to changing temperatures and may undergo critical transitions under ongoing climate change. What we do not know is to what extent montane biodiversity and ecosystem services will respond to local temperature variations in a gradual versus abrupt manner across global environments. To fill this knowledge gap, we conducted a global synthesis, including 4,462 observations from 290 elevation gradients, to investigate how biodiversity (spanning animals and plants) and ecosystem services (including plant production, soil carbon, and fertility) respond to local temperature variations along elevation gradients. We found that nearly one-third of these gradients exhibited abrupt shifts in multiple biodiversity and ecosystem services in response to local variations in temperature along elevation gradients. More specifically, we showed that once a particular local temperature level (~10 °C for mean annual temperature) was reached, even small increases in temperature resulted in dramatic variations in biodiversity and ecosystem services. We further showed that those abrupt shifts in response to local temperature increases were commonly positive for plant and animal diversity, as well as plant production, while soil carbon and fertility more commonly exhibit negative abrupt trends. Our work, based on the most comprehensive empirical evidence available so far, reveals the pervasive abrupt responses of biodiversity and ecosystem services to local temperature variations in montane ecosystems worldwide, highlighting the highly sensitive nature of montane ecosystems in the context of climate change.

Keywords: climatic change; elevation gradient; local temperature; non-linear responses; thresholds.

Fig. 1.

Global geographical distribution of the sampling sites in this study. The sites are colored based on the Köppen–Geiger climate classification. A total of 4,462 observations were collected from 290 elevation gradients (each with at least seven sampling points) across 270 studies.

Fig. 2.

Abrupt shifts in biodiversity and ecosystem services along elevation gradients in montane ecosystems worldwide. The pie chart illustrates the percentage of neutral (green), positive (blue), and negative (red) trends for biodiversity and ecosystem services in response to variations in elevation. The ring around the pie chart indicates the percentage of linear, curvilinear, and abrupt patterns for each trend. “n” represents the number of elevation gradients.

Fig. 3.

Abrupt shifts in biodiversity and ecosystem services along temperature gradients in montane ecosystems worldwide. (A) Percentage of different response patterns, including linear, curvilinear, and abrupt patterns within neutral (green), positive (blue), and negative (red) trends for biodiversity and ecosystem services in response to local variations in temperature; (B) Comparison of response patterns of biodiversity and ecosystem services along corresponding elevation and temperature gradients. This analysis aimed to evaluate whether elevation gradients with abrupt shifts in biodiversity and ecosystem services also exhibited similarly abrupt responses to local temperature variations and whether these abrupt shifts showed opposite trends (negative vs. positive) along corresponding elevation and MAT gradients. MAT. “n” represents the number of elevation gradients.

Fig. 4.

Temperature thresholds linked to abrupt shifts in biodiversity and ecosystem services along elevation gradients worldwide. Numbers on the boxplot indicate the average values of temperature thresholds identified.