Earth’s warming climate has caused pulses of forest mortality, associated with hotter-drought stress. Further warming is expected to exacerbate this phenomenon, with maximum temperatures approaching an intensity that is hot enough to kill. A recently assembled global database of climate-induced forest mortality events found that of the 157 species to have experienced rapid pulses of elevated mortality (e.g., die-off events) since 1970, 26 belong to the genus Pinus, in the family Pinaceae. Earth’s oldest living organisms are pine trees, yet Pinus may be one of the most vulnerable tree genera on Earth in the Anthropocene, a proposed geologic epoch characterized by rapid climate warming from human emissions. Gymnosperms broadly, and Pinus especially, have had a high number of species impacted by hotter-drought triggered pulses of forest mortality in recent decades, with massive conifer mortality potential under further anthropogenic warming. However, pine tree mortality events may be more reported due to their typically temperate-to-boreal distribution, occurrence in highly studied areas, economic importance, and dominating relatively large geographic areas, in conditions considered marginal for many other genera of trees. Here, we synthesize global observations of pine mortality events, the reported climatic and biotic drivers, and physiological thresholds known for Pinus species. We present case studies in five regions documenting pine mortality mechanisms and patterns during an ongoing megadrought in the Southwestern USA, at the epicenter of Pinus diversity in Mexico, alongside multiple land-use legacies in the Mediterranean, and in planted pine forests of both Argentina and Israel. Of the 116 pine species, drought was the most frequently reported driver of mortality events, followed by hotter droughts. Of measured survival traits, drought tolerance traits are more widely known, while by contrast, hot thermal limits have been published for few Pinus species, highlighting a major unknown for the response of pines to further warming and hotter droughts. Evidence from manipulative experiments and climate models suggest that the coming decades may become hot enough to kill pine trees across parts of their native ranges, suggesting heat extremes represent an emerging threat to Pinus survival. Understanding the interaction between hydraulic and thermal limits will be critical for predicting the fate of pines in coming decades. We identify critical research questions for understanding pine death in the Anthropocene. While Pinus are likely to persist and remain ecologically, economically, and culturally important across many regions, their distribution and role in Earth’s forests may undergo dramatic reorganization by the end of this century. Every action to further limit anthropogenic warming will likely collectively influence the fate of this iconic genus on our changing planet.

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“Pine Death in the Anthropocene”

  • William M. Hammond,
  • Medelin E. Kant,
  • Marylou Mantova,
  • Gerard Sapes,
  • María Elena Fernández,
  • Javier Gyenge,
  • Gabriel Gatica,
  • Rosana López Rodríguez,
  • Yakir Preisler,
  • Cuauhtémoc Saenz-Romero,
  • Andreas P. Wion,
  • Craig D. Allen

摘要

Earth’s warming climate has caused pulses of forest mortality, associated with hotter-drought stress. Further warming is expected to exacerbate this phenomenon, with maximum temperatures approaching an intensity that is hot enough to kill. A recently assembled global database of climate-induced forest mortality events found that of the 157 species to have experienced rapid pulses of elevated mortality (e.g., die-off events) since 1970, 26 belong to the genus Pinus, in the family Pinaceae. Earth’s oldest living organisms are pine trees, yet Pinus may be one of the most vulnerable tree genera on Earth in the Anthropocene, a proposed geologic epoch characterized by rapid climate warming from human emissions. Gymnosperms broadly, and Pinus especially, have had a high number of species impacted by hotter-drought triggered pulses of forest mortality in recent decades, with massive conifer mortality potential under further anthropogenic warming. However, pine tree mortality events may be more reported due to their typically temperate-to-boreal distribution, occurrence in highly studied areas, economic importance, and dominating relatively large geographic areas, in conditions considered marginal for many other genera of trees. Here, we synthesize global observations of pine mortality events, the reported climatic and biotic drivers, and physiological thresholds known for Pinus species. We present case studies in five regions documenting pine mortality mechanisms and patterns during an ongoing megadrought in the Southwestern USA, at the epicenter of Pinus diversity in Mexico, alongside multiple land-use legacies in the Mediterranean, and in planted pine forests of both Argentina and Israel. Of the 116 pine species, drought was the most frequently reported driver of mortality events, followed by hotter droughts. Of measured survival traits, drought tolerance traits are more widely known, while by contrast, hot thermal limits have been published for few Pinus species, highlighting a major unknown for the response of pines to further warming and hotter droughts. Evidence from manipulative experiments and climate models suggest that the coming decades may become hot enough to kill pine trees across parts of their native ranges, suggesting heat extremes represent an emerging threat to Pinus survival. Understanding the interaction between hydraulic and thermal limits will be critical for predicting the fate of pines in coming decades. We identify critical research questions for understanding pine death in the Anthropocene. While Pinus are likely to persist and remain ecologically, economically, and culturally important across many regions, their distribution and role in Earth’s forests may undergo dramatic reorganization by the end of this century. Every action to further limit anthropogenic warming will likely collectively influence the fate of this iconic genus on our changing planet.