Guam’s ecosystem is in serious danger, thanks to an invasive species of snake that is decimating the native animal population and threatening the growth of new trees.
By the 1980s, the snake Boiga irregularis, introduced to the island of Guam in the 1940s, had already decimated 10 of the 12 bird species on the 544 square kilometer island sitting between Australia and Japan. However, this very special ecosystem is based on plant species that disseminate their seeds by ornithocory. The seeds indeed transit along the digestive system of the birds by resisting the juices and are disseminated intact in the droppings of the animal. Without birds, the forest can therefore no longer regenerate and the situation is worrying.
the boiga irregularis, which also feeds on lizards, small birds, bats and rodents, therefore threatens the sustainability of the island’s forests. A recent study published in the journal Nature Communication quantifies the observation: during an in situ experiment, the dispersal of seeds from two types of trees studied was reduced by 61 and 92%, which in the long term severely limits the ability new trees to grow.
» The overall impact of the boiga irregularis invasion, and the decline of the birds, is yet to be determined, but our results clearly suggest that the indirect effects are going to be important and will potentially damage the structure and composition of the forests. “Said Joshua Tewksbury, co-author of the study and member of the organization Future Earth. » Huge drop shows how crucial birds are to forest life “, underlines in a press release Haldre Rogers, a researcher who participated in the study.
The scientist from the University of Iowa says that on the island of Guam » everything is silent « while on that of Saipan, close, but preserved from the boiga irregularis, » birdsong is constant « . The researchers conclude that while the consequences of bird decline are not yet fully understood, the study nevertheless shows the potential for invasive species to reshape entire ecosystems. The island of Guam has become the only place in the world where all native fruit-eaters have disappeared without being replaced.