Researchers use lava flow analysis on Reunion Island to determine the ecological impact that humans had on species extinction and biodiversity loss.

For millennia, Reunion Island, a remote island off the eastern coast of Madagascar, thrived with a variety of native and endemic wildlife undisturbed by humans. The island was home to populations of fruit adoring fauna including tortoises, flying foxes, and birds like Bulbuls and Hoopoes. All these species adapted to the islands challenging conditions including the presence of active volcanoes such as, Piton de la Fournaise, a volcano on the eastern side of the island which is among the most active in the world. Species thrived, that is until human contact in 1655 sparked the downfall of Reunion’s ecological integrity. The decline of biodiversity of Reunion has long been known, but new research utilized lava flow analysis to identify the turning point and specific time periods.

Utilizing carbon dating and historical records, scientists have been able to date lava flows and determine Reunion’s ecology at specific times in history. Researchers discovered the specific points before humans arrived, when the ecosystem started to unravel, and when harm to the island’s wildlife became crystal clear. When people arrived they both intentionally an unintentionally brought animals with them, leading to the spread of feral cats and invasive rats. According to the analysis of lava from Piton de la Fournaise, invasive species swiftly reduced plant and animal populations.

After each eruption, large amounts of forest surrounding Piton de la Fournaise were destroyed. However, the island remained a lush landscape due to its frugivorous or fruit-eating species. These species would fly, hop, slither, or stomp around the island depositing seeds, via their scat. The seeds would sprout and eventually grow tall, allowing the island to become lush again. That is until humans docked their ships and destroyed around 98.5% of the lowland forests on Reunion.

In less than 200 years humans caused the extinction of giant tortoises, flying foxes, parrots, hoopoes, fruit pigeons, and skinks on Reunion. This is, unfortunately, a phenomenon that occurs on islands all over the world, “the largest vertebrates disappear first” according to Sébastien Albert, an ecologist at the Université de la Réunion and lead author of the study. Now more then ever science is able to determine the extent to which humans are negatively impacting the world’s ecosystems, demonstrating the urgent need for conservation and restoration.

Source: Atlas Obscura
Feature photo: Inactive volcanic mountain on Reunion Island named Piton des Neiges. Credit: bilderkombinat berlin