Upward shifts in elevational limits of forest and grassland for Mexican volcanoes over three decades

Abstract

Global climates have been warming over the past four decades, with many implications and effects on species and natural communities, in terms of shifts in geographic and elevational ranges. Nonetheless, major knowledge gaps exist, particularly for tropical regions, as regards the timescale and rate of range shifts. We used Landsat imagery to characterize the upper limits of forest and of bunch grassland on the 15 highest (>3500 m) volcanoes of central Mexico over three decades (1986–2018), and documented upward vegetation shifts averaging >490 m in elevation over this period. Treelines showed upward shifts averaging 17.3 m/year over 1986–2018; for one eastern Mexican volcano (Sierra Negra), the NDVI-based rate (35.7 m/year) contrasts dramatically with a rate of 4.5 m/year measured over the preceding century for that volcano based on comparisons of photographs. These upward elevational shifts imply areal reductions for high-elevation habitats, and particularly for the bunch grassland that is the focus of considerable local endemism. Abstract in Spanish is available with online material.