Pollinator-plant mismatch spells disaster for both species
Representational photo from iStock Climate change is leading to a significant mismatch in plant cycles and pollinator behaviour, which has multiple impacts on the phenology and other traits of plants. I have observed, for example, significant changes in apple-producing areas of the Himalayan region over the past 25 years. Apples are grown in low- as well as mid-altitude hills and the higher Himalayan ranges. However, with the increase in temperatures, fruit production has seen a reduction. At the same time, warmer weather has resulted in early flowering that coincides with low pollinator availability.
A decrease in pollination hampers fruit production and yield quality, which has been evident in apples and almonds grown in the Himalayan region. Hence, commercial orchard owners now import honeybees and are diversifying pollinators to ensure pollination.
Cross-pollination allows plants to mix genes and add new traits, while self-pollination or selfing can induce inbreeding depression in species, make them more prone to diseases and reduce diversity, which lowers their ability to fight climate change.
The disruption in plant-pollinator interaction also brings other changes in plant traits. A 2020 study in the journal Current Biology indicates that between 1941 and 2017, the species Velleia paradoxa changed the colour of its flowers by increasing an ultraviolet (UV)-absorbing pigment to adapt to the high exposure to UV radiation. But this has made the flowers less favourable to pollinators. The rise in atmospheric carbon dioxide can also increase insect herbivore incidence by altering nutritional quality and plant defence, says another 2020 study in the journal Scientific Reports. The increase in carbon dioxide enables plants to produce more carbohydrates and the high proportion of sugary food attracts herbivores such as fruit flies and grasshoppers, dissuading other pollinators. A long-term study, published in the journal Cell Reports in 2019, demonstrated that such a diet can also reshape the feeding behaviour of fruit flies.
The spread of invasive species also shifts pollinators away from traditional plant species. According to the International Union for Conservation of Nature (IUCN), climate change can increase cover of invasive species. Their presence introduces both risks and opportunities for pollinator nutrition, alters species interactions and influences native pollination dynamics and community stability. In the long term, such changes can result in a feedback loop amplification—a decline in pollinator populations may affect plant reproduction and potentially lead to further declines in both species.
Gaurav Zinta is senior scientist, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh
This was first published in the 16-31 January, 2024 print edition of Down To Earth
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