Revising the global biogeography of annual and perennial plants

TL;DR

This study maps the global distribution of annual and perennial plants, revealing that annuals are less common than thought, favored in dry regions, and likely to increase due to climate change, impacting ecosystems worldwide.

Contribution

It provides the first comprehensive global biogeography of plant life cycles using extensive species and georeferenced data, highlighting environmental drivers and future trends.

Findings

Annuals constitute only 6% of plant species.

Annuals are favored in hot, dry regions, especially with specific climate conditions.

Climate change may increase annual prevalence in 69% of ecoregions by 2060.

Abstract

There are two main life cycles in plants, annual and perennial. These life cycles are associated with different traits that determine ecosystem function. Although life cycles are textbook examples of plant adaptation to different environments, we lack comprehensive knowledge regarding their global distributional patterns. Here, we assembled an extensive database of plant life cycle assignments of 235,000 plant species coupled with millions of georeferenced data points to map the worldwide biogeography thereof. We found that annuals are half as common as initially thought, accounting for only 6% of plant species. Our analyses indicate annuals are favored in hot and dry regions. However, a more accurate model shows annual species' prevalence is driven by temperature and precipitation in the driest quarter (rather than yearly means), explaining, for example, why some Mediterranean systems have more annuals than deserts. Furthermore, this pattern remains consistent among different families, indicating convergent evolution. Finally, we demonstrate that increasing climate variability and anthropogenic disturbance increase annual favorability. Considering future climate change, we predict an increase in annual prevalence for 69% of the world's ecoregions by 2060. Overall, our analyses raise concerns for ecosystem services provided by perennials, as ongoing changes are leading to a more annuals-dominated world.