Oral history as a citizen science tool to understand biodiversity loss and environmental changes: on firefly extirpation in Morelia, Michoacán, Mexico

Nocturnal fireflies are insects easily recognizable by their notable bioluminescence. They are also bioindicators of ecosystem health due to their sensitivity to environmental changes. In this study we employ oral history regarding fireflies and their habitats to compile the collective memory of the inhabitants of Morelia, in central-western Mexico, to analyze changes in biodiversity associated with urbanization.

The main tools we used were interviews and surveys, in addition to data from scientific literature, entomological collections and citizen science platforms. We explored fireflies as useful elements both to collect oral histories from volunteers (experts or non-experts on the topic) and to serve as a source of biological data (e.g., current and past distribution of fireflies in the city, estimates of biodiversity loss, and threat factors), and even to analyze the potential loss of local ecological knowledge among human generations.

A total of 112 surveys and interviews were conducted with people of three different generations and from different parts of Morelia to collect human demographic data, and spatial, temporal, abundance, and perception data on fireflies. We found local recognition of fireflies by most Morelians, as well as reports of a decrease in both the frequency and abundance of fireflies, and even identified sites of extirpation, i.e., the disappearance of these insects from the environments where people used to see them. Morelians associated these phenomena with increased anthropogenic activities in the city, such as urban growth and a notable increase in pollution and deforestation. Most Morelians believe that the current conditions of the city are unsuitable for the existence of fireflies, and that it is important to conserve these insects because they play an important role in ecosystems and are of high environmental and aesthetic value. In contrast, the younger generation of Morelians showed lower interaction and recognition of these insects in nature, which could be related to the loss of collective memory over generations and the shifting baseline syndrome.

In contexts where historical scientific data are not available, we suggest that fireflies can be used to assess the history of natural environments and changes in the populations of these insects. Moreover, fireflies can be beneficial in terms of engaging people in conservation strategies, citizen science, and science communication.