The gradual disappearance of large mammals seed dispersers, such as elephants and rhinos, threatening the structural integrity and biodiversity of the tropical forests of Southeast Asia. An international team of researchers, with Spanish participation, confirms that even other herbivores like tapirs can replace them.
"The megaherbivores are" gardeners "of tropical rainforests: promote forest regeneration and maintain its structure and biodiversity," says the agency SINC Ahimsa Campos-Arceiz, lead author of a study published in Biotropica and researcher in School of Geography, University of Nottingham in Malaysia. In these forests of eastern Asia, the great diversity of plant species prevents sufficient for all the trees germinate and grow space. In addition to the low light, seed dispersal is complicated by the lack of wind when dealing with trees up to 90 meters high. The vegetation is therefore limited to scattering by animals consuming the pulp and spread the seed to drop it, or regurgitate defecarla after a few hours.
In the case of large seeds, "plants need a large animal that is able to eat, transport and defecate the seeds in good condition," according to Luis Santamaria, co-author and researcher at the Mediterranean Institute for Advanced Studies, CSIC. This is where elephants and rhinos enter digesting some food and disperse large quantities of seeds over long distances due to their slow digestion game.
However, loss of habitat, human-elephant conflict and poaching have reduced by 95% the historic range of the Asian elephant and rhinoceros have left one step away from extinction: there are fewer than 50 individuals Javan and Sumatran 200. According to the Red List of the International Union for Conservation of Nature, the elephants are "endangered" and the two rhino species "critically endangered".
In this situation, the research team assessed the capacity as seed disperser of another large herbivore of 300 kg, which for cultural reasons it is not hunted and having a digestive system similar to elephants and rhinoceroses: the Asian tapir. The study allowed us to analyze the effect of dispersion by tapirs in the survival of seeds from nine different plants, including some large, like mangoes and durians, and smaller, as the "elephant apple." The results show, among others, that tapirs defecated 8% of the 224 tamarind seeds ingested, compared to 75% of the 2,390 seeds ingested by the elephant. In short, there are good dispersers for plants with large fruits and seeds.
According to the authors, if megaherbivores disappear from the ecosystem, their contribution to ecological processes is lost and ecological trajectories of ecosystem change irreversibly, so that "the most probable consequences would be the change in the structure of the forest and undergrowth, and the loss of certain species. " Elephants and rhinos have unique ecological functions and other species can not replace them. In this sense, species that depend on large animals will become increasingly rare, while those that rely on wind or animals and abundant smaller increase in density and importance.
To avoid this scenario, researchers suggest protect megafauna, and in some cases reintroduce species megaherbivores previously missing.