Elephants’ Shoes in Maintaining Biodiversity Are Too Big to be Filled by Other Species
Elephants don’t wear shoes, of course. But if they did it would be the shoes of the biggest gardeners on earth.
Elephants and other megaherbivores are the “gardeners” of humid tropical forests, particularly of South East Asia. This is according to Ahimsa Campos-Arceiz, researcher at the School of Geography of the University of Nottingham, Malaysia and lead author of Asian Tapirs Are No Elephants When It Comes To Seed Dispersal. The study was published in Biotropica earlier this year.
According to the study, megafauna like elephants and rhinoceros play a special role in maintaining biodiversity in these forests that other species don’t have the capability to fill. The abundant diversity of plant species found in humid, tropical forests usually translates to barely enough space for most tree species. Tree seeds’ dispersion are further limited by the little light and wind that penetrate the thick forests. Both are crucial agents for dispersion and seed germination. Tree seeds are therefore largely dependent on pulp-eating animals for their scattering and dispersion. Animals deposit seeds by dropping, regurgitating, or passing out seeds after they’ve eaten them with the fruits.
But fruit seeds that are a little larger than average present a difficulty. Mango seeds from ripe, full grown fruits for example are difficult to swallow and digest whole. When eaten by average sized animals, they are either destroyed and fragmented in the digestion process or are left where they are found, usually near the mother tree. This limits their dispersion and decreases their chances for survival and growth.
This is where megafauna like elephants and rhinoceros step in. By being able not only to swallow but to digest fruits with large seeds whole, their contribution to the seeds’ dispersal are critical. Elephants and other megaherbivores are capable of transporting large amounts of seeds in good conditions because they digest them slowly and the seeds survive the gut passage.
Researchers tried to find other species that play the same role in large seed dispersion as the megafauna. They tested the Asian tapir, a large herbivore found in the same forests and weighs up to 300 kilos. Their findings showed that the Asian tapir passed only 8% of tamarind seeds fed to it, in contrast to the 75% that the elephants defecated. Also, none of the seeds passed by the tapirs germinated, whereas 65% of those which came from the elephants did.
According to Campos-Arceiz, the Asian tapirs cannot play the role of elephants when it comes to large seeds’ dispersal. Yet they are the next largest herbivores to megafauna in tropical East Asia.
With no other species capable of dispersing large seeds, elephants and rhinoceros are particularly important in maintaining the biodiversity in the region. Without their contribution, tree species with large seeds will be severely affected in terms of dispersion and survival. The decrease of these trees’ numbers will change the composition and structure in humid tropical forests, Campos-Arceiz states.
According to Science Daily, the Asian elephant has suffered a 95% loss in numbers due to habitat loss and poaching among other factors, and only 50 Java rhinoceroses (Rhinoceros sondaicus) and 200 Sumatra rhinoceroses (Dicerorhinus sumatrensis) remain.
Some argue that nature will always be able to compensate for every loss in species and biodiversity it suffers, and that humans can only cause so much damage. But, resourceful though nature is, there will always be some shoes that are hard if not impossible to fill. Each species is important and should be treated as an irreplaceable part of nature and our world.
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