Flowers Across The World Have Changed Color In The Face Of Climate Change

Alpine Cinquefoil (Potentilla crantzii) was one of the plant species studied in this new research. COULANGES/Shutterstock

In the face of climate change and other environmental shake-ups, many lifeforms on Earth are faced with either adapting or perishing. In a desperate bid to keep up with the changing planet, it now appears that flowers across the world are changing their colors. This rapid revamp, however, could come at a huge cost to the plants.

New research has shown how flowers have adapted rapidly over the past 75 years in response to rising temperatures and declining ozone by altering ultraviolet (UV) pigments in their petals. Reported in the journal Current Biology, scientists led by Clemson University closely looked at over 1,200 preserved plant specimens, accounting for 42 different species from three continents dating between 1941 and 2017, analyzing their levels of floral pigmentation using a UV-sensitive camera. 

Their findings show that UV-absorbing pigmentation of flowers increased throughout the latter half of the 20th century. In fact, levels of petal UV pigmentation increased globally by an average of 2 percent each year for the past seven decades. By no coincidence, the increasing levels of pigment over the decades were also closely reflected by rising temperatures and declining ozone in the atmosphere. 

Ozone is a gas found in Earth’s stratosphere that strongly absorbs incoming UV radiation from the Sun. Considering the total amount of ozone in Earth's atmosphere has been steadily decreasing since the 1970s, plants and other lifeforms are being exposed to more UV radiationClimate change is also causing more intense UV radiation. Plants need sunlight to grow, but just like human skin, too much UV radiation from the Sun can damage them. 

Two species of flower (A-C, and D-F) show the variation in UV floral pigmentation. The darker areas indicate higher UV-absorbing compounds. Koski et al., 2020, Current Biology

These pigments are not visible to humans like the red of a rose petal or the yellow of a daffodil. Many pigments, including UV pigments, are invisible to the human eye, but are used by the flower to attract pollinators and shield against UV radiation, like sunscreen. So, while the flowers might not look too different to us, they have undergone a pretty significant change in a remarkably rapid space of time in a bid to adapt to their shifting environments.

Not all the flower petals were affected equally. First of all, plants that experienced larger ozone declines displayed larger increases in pigmentation. Secondly, plants with exposed pollen were also more likely to have increased pigmentation because this part of the plant is especially sensitive to UV and high-temperature stress can render pollen infertile. 

It might sound like good news that some flowering plants are trying to adapt to the changes that are facing their environments, however, the researchers warn this change in pigment could come at a hefty cost to the plants' reproductive performance since coloration is one of the main tools to attract pollinators. In particular, the contrast between UV-absorbing and UV-reflecting portions of petals might become dampened down after this adaptation, making it harder for the plant to impress any passing pollinators. 

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