Stopping to smell the roses may seem like a purposeless pastime, but for pollinators, it’s their entire lives. Communicating largely through smell and pheromones, insects with limited vision rely heavily on recognizable scent profiles to identify and locate their lunch.
Over millions of years, plants and pollinators have engaged in co–evolution — adapting and evolving in tandem often to benefit each other. One way plants have evolved to attract pollinators is by emitting tantalizing fragrances that are unique from species to species. This relationship has led to millennia of peaceful co-existence between the flora and pollinator communities.
Now, this is threatened by climate change. Like many pollinators, bees rely on familiar scents to locate plants they know to forage. A bee can normally recognize hundreds, if not thousands, of scent profiles, using their antennae and pheromone signatures to find the right plants. However, due to their sensitivity to scent, unfamiliar or disrupted fragrances may trigger alarm bells in pollinators, which causes them to avoid plants entirely. If the scent disruption occurs across all plants of a given species, it poses the threat of possible extinction.
Responsible for 75% of flowering plants and roughly 35% of pollination worldwide, bees affect about two–thirds of the produce you’ve ever eaten. Over the past half a century, bee populations have begun rapidly tanking due to habitat loss, shifting climates and weather patterns, increased pesticide use, disease, and more. Being an “indicator species” (an organism that reflects the environmental conditions of a given ecosystem), the recent decline in bee health has monumental implications for the environmental state of our world.
There are efforts supporting these pollinators, like supplemental pollen, pest treatment, increased care, and more, but bees still visit fewer and fewer plants each season. Extensive research has begun focusing on the relationship between bees and plants, attempting to see where this newfound disconnect comes from.
While analyzing the effect of air pollution on plant and pollinator health, researchers from the UK stumbled onto something startling. Their findings published in 2023 showed that stress from extreme heat and rising ozone levels has caused certain flowering plants to emit defensive odors, modifying their scent profiles. A similar study conducted in Finland found that carbon dioxide and higher temperatures had parallel effects on plants, changing their scents in a way that confused pollinators.
Not only is air pollution affecting plant scent profiles, but it is also impairing pollinators’ abilities to detect scents in the first place. Another study experimented with elevated ozone fumigation’s effect on plant scent and pollinators found that when ozone levels were elevated beyond typical levels, the number of pollinators visiting individual flowers declined by 89%. This steep decline is hypothesized to result from degraded floral odors, which inhibited the ability of pollinators to locate plants.
Then, as air pollution worsens, it deteriorates pollinators’ already–challenged ability to smell. Without one of the major senses they use to locate their food, pollinators become incredibly limited in their nectar supplies and diversity of pollen, leading to weakened populations and possible starvation.
Air pollution and climate change both play a huge part in the war between pollinators and the changing environment, but pollinators don’t have to fight them alone. Understanding the relationship climate change has on pollinators, helps scientists better address these challenges. Without this understanding, we risk facing a future where something as simple and beautiful as flowers may no longer exist. And while stopping to smell the roses might feel like a purposeless pastime for some, it’s actually a wonderful luxury.
