The flowering times for many plant species have shifted due to climate change, with most of the change occurring in temperate zones. Researchers assumed the tropics, which are largely the same temperature year-round, would be insulated from such climate change-driven changes to flowering times. However, a new study challenges that assumption.
Researchers examined more than 200 years of flowering plant data from herbarium collections of tropical plants across Africa, Asia and South America. They identified 33 plant species with distinct annual flowering times, and recorded data from 8,000 individual plant specimens collected between 1794 and 2024. They found that the flowering times shifted by an average of two days per decade; approximately one-third of the species flowered earlier and two-thirds shifted later.
However, there were some anomalies. Brazilian amaranth trees (Peltogyne recifensis), for example, now flower 80 days later than they did in the 1950s. By 1995, the Ghanaian rattlepod shrub (Crotalaria mortonii) flowered 17 days earlier than it did in the 1950s.
Study lead author Skylar Graves, from the University of Colorado Boulder in the U.S., said the findings show that herbarium specimens can be used to examine the climate impacts on plants over time.
“Herbarium specimens are functionally a global and multigenerational dataset of plants,” she told Mongabay by email. “These specimens can be used for countless purposes, and with enough collections taken … you can use them to compare anything you want at any scale.”
The shifts observed in tropical plant flowering times is comparable to those for temperate and boreal plants, the researchers note. Such disruptions can threaten the finely tuned pollinator-plant relationship and the feeding behavior of fruit-eating species, including primates that evolved in sync with the fruiting and flowering times of their food plants.
Emma Bush from the Royal Botanic Garden Edinburgh, in the U.K., who wasn’t involved in the study, told The Guardian, “When plants, insects and other animals are out of sync they could all lose out — and the risk is that we lose biodiversity that benefits people, too.”
Banner image: A flowering forest in Brazil. Image by Rhett A. Butler/Mongabay.
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