Investigating the Impact of Landscape Fire Smoke on Migratory Insect Flight

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Smoke emissions from landscape fires contain trace gases and aerosols - some of which not only pose hazards to human health but also have potential ecological impacts. Since insects play an important role in ecosystems, this research focuses on the potential that smoke has to impact insect migration which may be related to insect dispersal and distribution and which has not been much studied thus far. The overall aim is to use laboratory experiments to quantify the potential effects of landscape fire smoke pollution on migratory insect flight, and to explore which smoke components may be contributing to any effect. Comparative laboratory experiments were conducted to explore these impacts, based around Vanessa cardui L. (Painted lady butterfly) as the research target as they are famous for their annual migration between Africa and Europe. A tethered flight mill (TFM) approach was used to quantitively study the flight behaviour of the adult butterflies, including total flight distance (m), average speed (m·s−1), maximum speed (m·s−1), and flight durations (minutes). Adult butterflies were exposed to different smoke conditions and their flight behaviour compared to butterflies being flown in clean-air conditions (as a control group). To ensure the experiments produced smoke with realistic properties, the emissions characteristics of agricultural residue burning and incense burning (as used in the experiments) were measured.

Vanessa cardui L. was found to have a complex response to different smoke condi- tions - as assessed by fine particulate matter (PM2.5) concentration. There is a negative linear relationship between flight speed and PM2.5 concentration when Vanessa cardui L. are exposed to very high PM2.5 concentrations (up to 4000 µg·m−3) for relatively short amounts of time (less than thirty minutes), and other behavioural parameters associated with flight also show a significant decrease. However, the butterflies increased their flight speed by around 50% as when exposed to a lower, stable smoke PM2.5 concentration of 127 µg·m−3 for six hours. The research finds that the emissions from incense burning are similar to that from landscape fire agricultural residue burning, with similar emission factors of CO2, CO, CH4, and PM2.5, and suggests that it is the particulates rather than the trace gas component of the smoke that is the main driver for the flight behaviour impact. We conclude that exposure to smoke from landscape burning significantly affects the flight behaviour of adult Vanessa cardui L, although the exact impacts depend on the smoke concentration and the duration of exposure. There appears to be reasonable evidence that smoke released from landscape fires may thus affect insect migration, especially when periods of widespread and intense agricultural or other burning closely match
migration times.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMartin Wooster (Supervisor) & Robert Francis (Supervisor)

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