New research from the University of Ottawa indicates that monarch butterflies face a new challenge during their migration: declining nectar quality due to warming temperatures. Monarchs typically fly thousands of kilometers from Canadian fields to Mexico's mountain forests for overwintering.
A team of scientists, led by Associate Professor Heather Kharouba, conducted an experiment focusing on plants that monarchs utilize during migration. They observed that a temperature increase of just 0.6 degrees Celsius was sufficient to reduce the quality of nectar produced by these plants.
Butterflies that fed on these "warmed" blooms accumulated approximately 25% less body fat than those feeding on nectar from plants at regular temperatures. Professor Kharouba clarified that the heat did not directly harm the butterflies; instead, it made the nectar less nutritious, even if the butterflies consumed as much as they wanted.
The experiment, carried out by Katherine Peel, ensured only the plants were warmed, while butterflies experienced normal outdoor temperatures. Results consistently showed that as temperatures rose, late-season flowers produced less nectar, and the nectar contained lower sugar levels.
This study identifies a subtle but significant risk, highlighting how climate change can indirectly affect pollinators by diminishing the quality of their essential food resources. Professor Kharouba emphasized that these findings serve as a reminder for individuals involved in butterfly conservation and environmental management as the planet warms.
The research also inspired an art exhibition, 'Flutterings: Monarchs and Climate Change,' aimed at fostering public understanding of complex environmental issues through art-science collaboration.
The study, titled "Warming-mediated decreases in nectar quality translate into lower energy reserves of the monarch butterfly (Danaus plexippus)", was published in Global Change Biology Communications.