Lampoon, Kolkata (Calcutta), India A woman selling flower garlands from a street stall, G.M.B. Akash, Panos Pictures
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Chromatic Shifts: the impact of climate change on flower pigmentation and pollination

The science behind the silent transformation of flora due to climate change. Pigment changes could make plants less attractive to pollinators

Floral color change – flowers’ adaptations to cope with climate change

In response to the changing climate, plants and animals have displayed adaptability, expanded their territories and adjusted their breeding patterns. Recent research indicates that flowers, too, have undergone adaptations to cope with rising temperatures and the decline of ozone. These adaptations involve modifications to their ultraviolet (UV) pigments, which are imperceptible to the human eye. Among the most mesmerizing adaptations is the subtle yet captivating evolution of flower colors.

In the realm of nature, where beauty thrives in delicate petals and blooms, a silent transformation is unfolding. Where hues shift and morph, painting a vivid portrait of resilience and adaptation as our planet grapples with the profound effects of climate change, the flora that graces our landscapes is adapting in many ways.

Floral color change: the evolution of flower pigments

In the intricate language of flowers, colors have long played a key role in attracting pollinators and the floral kingdom is compelled to rewrite its palette. Gone are the days of static hues; instead, a myriad of pigments unfolds as flowers adapt to their changing world. 

A phenomenon observed in response to climate change, flowers are exhibiting an increased production of pigments. These pigments, such as anthocyanins, lend a touch of vibrancy to petals, creating a fanciful display that entices pollinators.

While these changes in pigment may go unnoticed by the human eye, they act as a conspicuous signal for pollinators like hummingbirds and bees. Most pollinators are drawn to flowers exhibiting a distinctive ‘bull’s-eye’ pattern, with petal tips reflecting UV light and UV-absorbing pigments concentrated towards the center of the flower. Although scientists have yet to fully comprehend the exact reasons behind this pattern’s appeal, they speculate that it aids in distinguishing flowers from the UV-absorbing backdrop of surrounding plants

This ability to distinguish between flowers is essential for pollinators, as it enables them to efficiently locate and collect nectar and pollen, which they use as food. Without this ability, pollinators may struggle to find flowers, leading to a reduction in pollination rates and a decline in plant populations.

Lampoon, Hanoi, Vietnam A flower seller plies her trade in the old quarter prior to the _Tet_ (New Year) holiday,Jeremy Horner,Panos Pictures
Hanoi, Vietnam A flower seller plies her trade in the old quarter prior to the _Tet_ (New Year) holiday,Jeremy Horner,Panos Pictures

A study: the chameleons of blossoms – Floral color change

According to Matthew Koski, a plant ecologist at Clemson University, flowers employ UV pigments to attract pollinators and shield themselves from the sun’s harmful rays. Just as UV radiation can be detrimental to humans, it can also pose a threat to a flower’s pollen. By incorporating higher levels of UV-absorbing pigments into their petals, flowers can limit the amount of damaging radiation that reaches their cells.

Koski and his colleagues previously discovered that flowers growing at higher elevations or closer to the equator, where UV radiation is more intense, possessed greater amounts of UV pigments. Building upon this finding, Koski wondered whether two human-influenced factors—ozone layer depletion and temperature fluctuations—also had an impact on these UV pigments.

To investigate further, Koski and his colleagues conducted a comprehensive analysis of plant collections spanning North America, Europe, and Australia, dating all the way back to 1941. Their study encompassed 1238 flowers from 42 distinct species.

Floral color change: an overall increase in pigment within flowers across all locations

Employing a UV-sensitive camera, they captured photographs of flower petals of the same species collected at various points across their natural range. These images allowed them to observe changes in UV pigment. The researchers then correlated these changes with data on local ozone levels and temperature.

Their findings, published in Current Biology, revealed an overall increase in pigment within flowers across all locations—an average rise of 2% per year from 1941 to 2017. However, the extent of these changes varied depending on the structure of the flowers.

For instance, flowers with exposed pollen and saucer-shaped petals, such as buttercups, experienced an increase in UV-absorbing pigment when ozone levels declined. Conversely, these flowers exhibited a decrease in UV pigment in areas where ozone levels rose. In contrast, flowers with concealed pollen, like the common bladderwort, exhibited a reduction in UV pigment as temperatures increased, regardless of any fluctuations in ozone levels.

Floral color change – A natural sunscreen

Flowers with concealed pollen are naturally shielded from UV exposure by their petals. UV-absorbing pigments in flowers act as a protective shield, safeguarding the sensitive cells and pollen from harmful radiation.

 However, this protective shielding can also act as a greenhouse, trapping heat. When these flowers are exposed to higher temperatures, there is a risk of the pollen being subjected to excessive heat. By reducing UV pigments in their petals, the flowers absorb less solar radiation, thereby lowering temperatures and mitigating the potential harm to their pollen.

The research sheds light on the intricate relationship between flower structure, UV pigments, ozone levels, and temperature. It unravels how flowers employ subtle adaptations to safeguard their reproductive mechanisms in the face of changing environmental conditions. These findings not only deepen our understanding of the resilience of flora but also emphasizes the intricate balance of nature’s mechanisms in response to a transforming world.

Floral color change – food security is under threat

Pollination is a key process for the reproduction of many plant species, including those that provide the foundation for global food production. Wild pollinators, including bees, butterflies, moths, and birds, are essential for ensuring successful pollination in natural ecosystems. However, human activities, including air pollution, have resulted in the decline of wild pollinators, which has led to concerns about the security of our food supply.

According to the UN, it is estimated that pollination is at least partially dependent on 75% of all food crops worldwide. The change in flower coloration could impact the ability of pollinators to locate and identify flowers, leading to a reduction in pollination rates. This reduction could translate into lower crop yields, which would have implications for global food production and supply.

Floral color change – Human activities’ impact and pollution

While the precise impact of this change in flower coloration on pollination rates is not yet fully understood, it highlights the complex and interconnected nature of the natural systems that support life on Earth.

Human activities, such as burning fossil fuels and deforestation, are driving climate change and air pollution, which are already impacting the health and survival of wild pollinators. The added stress of changes in flower pigmentation could further exacerbate the crisis facing pollinators and the vital role they play in global food production.

Given the critical value of pollinators for food security, there is a growing need for conservation efforts to protect these essential species. This includes reducing air pollution, preserving natural habitats, and promoting sustainable farming practices that support pollinator populations.

Alterations in floral coloration

As climate change continues to escalate, these alterations in floral coloration can disrupt plant-pollinator interactions, impacting the crucial ecological relationships between plants and their pollinators. As they colonize uncharted territories, these intrepid blooms herald a new chapter in the ever-evolving story of Earth’s botanical tapestry.

Farah Hassan

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