Featured Research

from universities, journals, and other organizations

Absence of elephants and rhinoceroses reduces biodiversity in tropical forests

Date:
May 11, 2012
Source:
Plataforma SINC
Summary:
The progressive disappearance of seed-dispersing animals like elephants and rhinoceroses puts the structural integrity and biodiversity of the tropical forest of South-East Asia at risk. Experts have confirmed that not even herbivores 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, researchers say.

Habitat loss, poaching, and the conflict between elephant and man has caused a 95% loss in Asian elephant (Elephas maximus) historical distribution range.
Credit: Ahimsa Campos-Arceiz

The progressive disappearance of seed-dispersing animals like elephants and rhinoceroses 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 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 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. 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'.

Asian tapirs are no elephants

In light of the situation, the research team evaluated the seed-dispersing capacity of another large herbivore weighing 300 kg. For cultural reasons it is not hunted and has a similar digestive system to that of elephants and rhinoceroses: the Asian tapir (Tapirus indicus).

The study allowed researchers to analyze the effect of dispersion by tapirs on the seed survival of nine different plants. This included some large plant species such as the mango tree and durian, as well as other smaller species like the 'elephant apple' (Dillenia indica).

Among other outcomes, the results show that tapirs defecated 8% of the tamarind seeds ingested (none of which germinated) compared to elephants, who defecated 75% of the 2,390 ingested seeds (65% of which germinated).

"The Asian tapirs spit, chew or digest the majority of large seeds. This either destroys them or leaves them in the same place. As a result, they are not good dispersers for plants with large fruits and seeds," confirms Campos-Arceiz. In this sense, "given the role that they play they belong to a different group to elephants and rhinoceroses."

Stopping illegal hunting is the priority

"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," explains 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." Elephants and rhinoceroses play a unique ecological role that cannot be replaced by other species.

Without large herbivores, new large seed plants will always grow in close proximity to the mother plant and are therefore "unable to colonise available space in other forest areas," warns the IMEDEA researcher.

In this respect, those species that depend on large animals will become increasingly rare whereas those that depend on the wind and smaller, abundant animals will increase in terms of density and dominance. Campos-Arceiz asserts that "at the end of the day, the composition and structure of the forest changes and ends up becoming less complex on a structural and functional level: this translates as a loss of biodiversity."

To avoid such a scenario, researchers suggest that megafauna should be protected and in some cases megaherbivores should be reintroduced into areas from where they had previously disappeared. "In the south-east of Asia, the priority is to stop illegal hunting and mitigate the impact of habitat loss," indicates the expert, criticising the "absurd" motivation to kill in order to sell their horns and tusks for traditional medicine ("with no therapeutic benefits") or to make ornamental products. This also highlights the need to combat illegal trade in a "much more determined way."


Story Source:

The above story is based on materials provided by Plataforma SINC. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ahimsa Campos-Arceiz, Carl Traeholt, Razak Jaffar, Luis Santamaria, Richard T. Corlett. Asian Tapirs Are No Elephants When It Comes To Seed Dispersal. Biotropica, 2012; 44 (2): 220 DOI: 10.1111/j.1744-7429.2011.00784.x

Cite This Page:

Plataforma SINC. "Absence of elephants and rhinoceroses reduces biodiversity in tropical forests." ScienceDaily. ScienceDaily, 11 May 2012. <www.sciencedaily.com/releases/2012/05/120511101347.htm>.
Plataforma SINC. (2012, May 11). Absence of elephants and rhinoceroses reduces biodiversity in tropical forests. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2012/05/120511101347.htm
Plataforma SINC. "Absence of elephants and rhinoceroses reduces biodiversity in tropical forests." ScienceDaily. www.sciencedaily.com/releases/2012/05/120511101347.htm (accessed September 2, 2014).

Share This




More Plants & Animals News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

Newsy (Sep. 2, 2014) — The U.N. says the problem is two-fold — quarantine zones and travel restrictions are limiting the movement of both people and food. Video provided by Newsy
Powered by NewsLook.com
Sharks Off the Menu and on the Tourist Trail in Palau

Sharks Off the Menu and on the Tourist Trail in Palau

AFP (Sep. 2, 2014) — Tourists in Palau clamour to dive with sharks thanks to a pioneering conservation initiative -- as the island nation plans to completely ban commercial fishing in its vast ocean territory. 01:15 Video provided by AFP
Powered by NewsLook.com
We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) — A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Coffee Then Napping: The (New) Key To Alertness

Coffee Then Napping: The (New) Key To Alertness

Newsy (Aug. 30, 2014) — Researchers say having a cup of coffee then taking a nap is more effective than a nap or coffee alone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins