Too Hot to Bloom on Time? Climate Change Disrupts Tropical Flowering

Climate change is not only affecting winter and spring in the Northern Hemisphere, but is also significantly altering the timing of flowering in tropical forests worldwide. An analysis of thousands of flower specimens collected over more than two centuries shows that some tropical plants now bloom earlier or later than they did in the past — a shift experts warn could disrupt fragile ecosystems.

Skylar Graves, an ecologist at University of Colorado Boulder and the study’s lead author, described the findings as a slow-moving change unfolding at the heart of global biodiversity. “We found that tropical plants are not immune to climate change as previously assumed,” she said, emphasizing the importance of herbarium records as long-term evidence of ecological shifts.

Measurable Shifts in Flowering Time

The research, published Feb. 25, 2026 in the journal PLOS ONE, analyzed more than 8,000 flower specimens from museums and scientific collections gathered between 1794 and 2024. From those collections, researchers selected 33 tropical plant species with clearly defined annual flowering periods, allowing them to quantify changes in blooming time and compare them with patterns observed in other regions.

Overall, flowering time shifted by an average of about 2.04 days per decade over the past 200 years. However, the changes were not uniform. Some species shifted by less than a day per decade, while others showed changes of more than 14 days per decade.

Graves said the direction of change also varied. Some plants now bloom earlier in the year compared with historical records, while others bloom later. “This is not a simple trend in one direction. There is substantial variation among species, reflecting how each responds differently to environmental factors,” she said.

Broad Ecological Impacts

Scientists warn that shifts in flowering time could affect critical relationships between tropical plants and other organisms, including pollinators such as insects and animals that disperse seeds. Many species have evolved to synchronize their life cycles with specific flowering periods. When blooming times change, that synchronization can break down.

“When flowers bloom outside the time pollinators expect them, it’s like breaking a rhythm that has lasted for thousands of years,” said Dr. Erin A. Manzitto-Tripp, a co-author of the study who is also affiliated with University of Colorado Boulder. She added that such changes could trigger ecological mismatches that ripple through tropical food webs.

According to Manzitto-Tripp, the complexity of plant–animal interactions in the tropics makes the consequences difficult to predict. “Tropical systems have often been considered more stable. Our study suggests that assumption is no longer entirely accurate,” she said.

Why the Tropics Flower Matter

Tropical regions harbor the majority of the world’s biodiversity, including more than half of all vascular plant species and most vertebrate species. Yet they have been relatively understudied in the context of climate change compared with temperate and boreal regions.

This study helps close that gap by demonstrating that fundamental biological processes — such as flowering time — are also shifting in the tropics. It further highlights the value of herbarium collections as long-term ecological archives that allow scientists to track changes across centuries.

Graves said she hopes the findings will encourage greater investment in digitizing herbarium collections worldwide, enabling researchers to use historical data to better understand ecosystem responses to global climate change.

The Current State of Tropical Flowers

Today, shifts in flowering time across tropical regions are increasingly documented and monitored. Some species show particularly dramatic changes. In Brazil, for example, certain plants now bloom roughly 80 days later than they did in the mid-20th century. In Ghana, other species are flowering several weeks earlier than they did just decades ago.

While the average change may appear modest when measured in days per decade, the cumulative effect over many decades can result in substantial differences in seasonal timing. Ecologically, these patterns signal that tropical systems are not as buffered from climate pressures as once believed.

Such changes may accelerate mismatches between plants and the animals that depend on them. Pollinators may no longer find nectar at the expected time, while plants risk losing pollination opportunities if their biological partners have not yet emerged — or have already disappeared.

Researchers say understanding these phenological shifts in tropical flowers is essential for developing adaptive conservation strategies. Without careful monitoring and mitigation efforts, small but persistent changes could ultimately alter the structure and functioning of tropical forest ecosystems in the decades to come. (Sulung Prasetyo)

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