The progressive disappearance of seed-dispersing animals like elephants and rhinoceroses（犀牛） puts the structural integrity and biodiversity of the tropical forest of South-East Asia at risk. With the help of Spanish researchers, an international team of experts has confirmed that not even herbivores（食草动物） like tapirs can replace them. "Megaherbivores act as the 'gardeners' of humid tropical forests: They are vital to forest regeneration and maintain its structure and biodiversity," as was explained by Ahimsa Campos-Arceiz, the lead author of the study that was published in the 'Biotropica' journal and researcher at the School of Geography of the University of Nottingham in Malaysia.

In these forests in East Asia, the large diversity of plant species means that there is not enough space for all the trees to germinate（发芽，生长） and grow. As well as the scarce light, seed dispersion is made more complicated by the lack of wind due to the trees that are up to 90 metres high. Plant life is then limited to seeds dispersed by those animals that eat pulp（纸浆，果肉） . 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," as outlined by Luis Santamaría, 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% 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).

According to the red list of the International Union for Conservation of Nature (IUCN), elephants are in 'danger of extinction' and the two rhinoceros species are 'critically endangered'.