Global warming and pollution are stripping vibrant colours from nature, PgII

Key Highlights:

• Over the past 20 years, more than half of the world's oceans have become greener, and forests are browning prematurely due to climate change and pollution.
• A study in the Amazon revealed that deforestation is causing butterflies to lose their bright colors, impacting their survival.
• Insects in the northern hemisphere, including ladybirds and dragonflies, are turning lighter due to frequent heatwaves, as reported in a 2024 study.
• In February 2025, coral bleaching was reported in the Gulf of Mannar, Palk Bay, Lakshadweep, Andaman and Nicobar Islands, and the Gulf of Kachchh, threatening marine ecosystems.

Detailed Insights:

• Ecological discoloration is a consequence of climate change, affecting the survival and reproduction of various species.
• Rising deforestation leads to butterflies with less diverse palettes, as they camouflage to escape predators and adapt to the loss of natural vegetation.
• The Industrial Revolution saw a similar change with darker peppered moths becoming more common due to engine smoke darkening tree barks.
• A reduction in melanin pigments is observed in animals as an adaptive response to global warming, causing them to become lighter.
• Bogert’s rule states that animals in colder regions will be darker, while those in warmer regions will be lighter, mainly applicable to cold-blooded animals.
• Gloger’s rule applies to warm-blooded creatures, indicating animals are darker in areas with high humidity and rainfall and lighter in colder, drier regions.
• Urbanization and pollution cause birds in cities to become darker and duller, potentially due to heavy metals like lead binding with melanin.
• Changes in plant pigments affect animals, with urban plants producing less carotenoids, impacting their attractiveness to pollinators.
• Coral bleaching occurs when corals expel symbiotic algae due to heat stress, increasing their risk of starvation and disease.
• Algal blooms reduce water clarity and lower oxygen levels, harming fish and other marine life, further disrupting marine ecosystems.
• Preserving microhabitats and regulating coastal development can help minimize the adverse effects of climate change on natural colors.

Scientific/Technical Concepts Involved:

• Melanin: Pigments that produce dark brown/black (eumelanin) and yellow/red (pheomelanin) shades in animals.
• Bogert’s Rule: Animals in colder regions will be darker, and those in warmer regions will be lighter, mainly applicable to cold-blooded animals.
• Gloger’s Rule: Warm-blooded animals are darker in areas with high humidity and rainfall and lighter in colder, drier regions.
• Carotenoids: Pigments that afford plants red, yellow, and orange hues, attracting animals to consume them.