News release

From: PLOS

Tropical flowers are blooming weeks later than they used to through climate change

Study of museum specimens across decades raises concerns for delicately balanced ecosystems given shifts in flowering timings

Climate change has caused some tropical plants to flower earlier or later than they used to, in some cases by a matter of weeks or even months, according to a study of 8,000 flowers across more than two centuries, published February 25, 2026 in the open-access journal PLOS One by Skylar Graves and Erin Manzitto-Tripp of the University of Colorado-Boulder, U.S.

Among the documented impacts of recent climate change are the shifting flowering times of some plant species. Such changes to plant reproductive behaviors can have wide-ranging ecological consequences, particularly for pollinators and herbivores. This issue has generally been considered to be less of a concern in tropical regions where temperatures fluctuate less over the course of a year so may not be key drivers of flowering timing, but this hypothesis has not been rigorously tested.

In this study, the researchers compiled museum collections data for more than 8,000 flowers collected between 1794 and 2024, representing 33 tropical species with distinct annual flowering periods. Comparing the collection dates for each flower revealed that the flowering periods of these species have shifted over time by an average of two days per decade. The most extreme examples include Ghanan rattlepod shrubs whose flowering period shifted 17 days earlier between the 1950s and 1990s, and Brazilian amaranth trees which now flower 80 days later than they did in the 1950s.

Changes of a similar magnitude have been reported for temperate and boreal species of flowers, contradicting the hypothesis that tropical flowers are less susceptible to climate-induced changes to their reproductive habits. The ecological impacts of this are not fully clear, but these changes to flowering times may threaten the dependent relationships between plants, pollinators, and fruit-eating seed-dispersing animals, therefore raising the likelihood that shifts to flowering periods impact the wider tropical ecosystems.

Graves adds: “We have found tropical plants are not insulated from the impacts of climate change.”

“I hope our work can support conservation initiatives by providing more data on the impacts of climate change on these ecosystems.”

“Tropical latitudes are the most biodiverse ecosystems on earth, and yet they are the most understudied.”

“This work highlights herbarium specimens as more than taxonomic tools. Herbarium specimens make up a massive source of data, far greater in both geographic and temporal scale than any one researcher can hope to achieve in their lifetime. I hope studies like mine can be persuasive for increased funding of herbaria and their digitization worldwide.”