The journal Biotropica has published a report which shows thatthe progressive disappearance of seed-dispersing animals like elephants and rhinoceroses is putting the structural integrity and biodiversity of the tropical forest of South-East Asia at risk.
"Megaherbivores act as the "gardeners" of humid tropical forests: They are vital to forest regeneration and maintain its structure and biodiversity," Ahimsa Campos-Arceiz, the lead author of the study, explained. Thick forest growth means little space for trees to germinate and grow and scarce light. Seed dispersion is made more complicated by the lack of wind due to the trees that are up to 90 m high. Plant life is then limited to seeds dispersed by those animals that eat pulp. They either scatter seeds by dropping their food, regurgitating it or by defecating later on.
In the case of large seeds, "plants need a large animal capable of eating, transporting and defecating the seeds in good conditions," said Luis SantamarIa, co-author and researcher at the Mediterranean Institute for Advanced Studies (IMEDEA) of Spain's CSIC Scientific Research Agency. This is where elephants and rhinoceroses come into play because they can scatter large quantities of seeds thanks to the fact that they slowly digest very little of their food.
However, habitat loss, poaching, and the conflict between elephant and man has caused a 95 percent loss in Asian elephant (Elephas maximus) historical distribution range and has left the rhinoceros just a step away from extinction: there are less than 50 Java rhinoceroses (Rhinoceros sondaicus) and 200 Sumatra rhinoceroses (Dicerorhinus sumatrensis).
"If these megaherbivores disappear from the ecosystem, their contribution to ecological processes will too be lost and the path of the ecosystem will change irreversibly," explained the lead author, who goes on to state that "the most probable consequences are the change in the structure of the undergrowth and the forest and the loss of certain species."