- Firefly populations along the banks of the Rembau River in Malaysia have declined drastically in the past decade due to habitat loss, a new study has found.
- Researchers, who used satellite imagery to monitor changes in land use, found that conversion of Rembau’s mangroves to oil palm plantations and dryland forests were the top two factors behind the loss.
- Remote-sensing technology could help locals better understand the impact of various land use types on mangrove ecosystems and more efficiently prioritize areas for conservation.
Every evening, along the banks of the Rembau River in Malaysia, fireflies put on a spectacular display. Against the dark silhouette of the berembang mangroves (Sonneratia caseolaris) they dance, synchronizing their flashing in a bioluminescent performance that draws thousands of tourists every year.
In the past decade, however, the light show has somewhat dimmed. As early as 2008, studies on firefly populations in Rembau have revealed significant declines. A confluence of factors has converged to put fireflies at risk of local extinction, and chief among them is habitat loss, a new study has found.
Researchers, whose work was published this month in Global Ecology and Conservation, used satellite imagery to monitor changes in land use around Rembau’s mangroves. They found that, between 2002 and 2017, overall mangrove areas had decreased by 17.8% — a loss of 93 hectares (230 acres) of key firefly habitat.
According to the study, the top two driving factors behind mangrove loss in Rembau were replacement with oil palm plantations and dryland forests, each of which accounted for a third of mangrove areas lost. (The latter arises when mangroves are cleared to make way for planned agricultural activities, which later fail to materialize.) Mangrove areas were also variously transformed into settlements, barren land, rubber plantations, and roads, though at smaller scales.
Beyond these direct conversions, human activities also affected the mangroves in more insidious ways, the study found. Even in instances where mangrove areas were not directly replaced with plantations and settlements, the presence of these activities as far as hundreds of meters away had negative impacts: they reduced vegetation cover and density. Along the river, motorboats chugging up and down carrying fishermen and firefly tourists alike have also created water swells that, over the years, have eroded the banks and toppled trees.
Fireflies (family Lampyridae) are some of the world’s most charismatic insects. Across the world, an estimated 1 million people travel each year to witness dazzling displays from some two dozen species, according to a March 2021 study. Firefly habitats range from mountainous river valleys, such as the Great Smoky Mountains in the U.S., to the forests and shrublands of Southeast Asia, including the Rembau mangroves.
While the researchers’ remote-sensing technology has highlighted a dim future for firefly habitat and populations in Rembau, it also offers glimmers of hope, said corresponding author Muzzneena Ahmad Mustapha, an associate professor at Universiti Kebangsaan Malaysia.
“Remote sensing offers advantages in monitoring a large coverage area, over a long period of time,” Ahmad Mustapha said. This makes it suitable for mangrove ecosystems, which not only “cover a very wide area” but also “take years and years” to reflect change, she said.
Instead of constantly going into the field to monitor mangroves, which can be time-consuming, researchers can now use satellite data to efficiently determine changes in land use, forest cover and ecosystem health, she added. “That will help with conservation strategy planning. You can prioritize the areas that need immediate action, or those that will have a larger impact, which saves time and money.”
To differentiate between the various land use types visible in their satellite images, the researchers ran the images through software that picked out 12 distinct classes: mangroves, swamps, forests, oil palm plantations, settlements, roads, and more. The team then validated the accuracy of the classification model with field surveys, before using it to identify and track how land use around the Rembau River had changed over the years, and the effect on its mangroves.
Some land use types reduced the adverse effects of others, the team found. For instance, settlements impacted mangrove areas, but if there were forests between the settlement and the mangroves, their negative impact was reduced — with conservation implications, Ahmad Mustapha said.
“[Rembau] is an important firefly ecotourism site. And the fireflies depend on the mangrove ecosystem. We need to better monitor and manage their habitats if we want them to continue existing in future,” she added.
“Fireflies hold a special fascination for people, and their fading lights make an obvious and visible case for conservation,” Sara Lewis, lead author of the March study on firefly tourism, said in a statement. “[But] there is also a larger opportunity here.
“Fireflies can also be a gateway bug to get tourists interested in conserving many other insects, which might not be so charismatic.”
Banner image of fireflies illuminating a forest. Image by Roberto Marchegiani via Flickr (CC BY-NC-ND 2.0).
Editor’s note: This story was supported by XPRIZE Rainforest as part of their five-year competition to enhance understanding of the rainforest ecosystem. In respect to Mongabay’s policy on editorial independence, XPRIZE Rainforest does not have any right to assign, review, or edit any content published with their support.
Idris, N. S., Ahmad Mustapha, M., Sulaiman, N., Khamis, S., Husin, S. M. & Darbis, N. D. A. (2021) The dynamics of landscape changes surrounding a firefly ecotourism area. Global Ecology and Conservation, 29. doi:10.1016/j.gecco.2021.e01741
Lewis, S. M., Thancharoen, A., Wong, C. H., López‐Palafox, T., Santos, P. V., Wu, C., … Reed, J. M. (2021) Firefly tourism: Advancing a global phenomenon toward a brighter future. Conservation Science and Practice, 3. doi:10.1111/csp2.391
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