Featured Research

from universities, journals, and other organizations

Overgrazed grasslands tied to locust outbreaks

Date:
January 27, 2012
Source:
Arizona State University
Summary:
Scientists have shown that insect nutrition and agricultural land management practices may partially explain modern day locust outbreaks.

Two juvenile Oedaleus asiaticus.
Credit: Image courtesy of Arizona State University

While residents of the United States and much of Europe think of locust plagues as biblical references, locust swarms still have devastating effects on agriculture today, especially in developing countries in Asia and Africa. In a study to be released in the journal Science on Jan. 27, scientists from Arizona State University and the Chinese Academy of Sciences show that insect nutrition and agricultural land management practices may partially explain modern day locust outbreaks.

During an outbreak year, locusts can populate over 20 percent of Earth's land surface, negatively affecting more than 60 countries and the livelihood of one out of every 10 people. In this study undertaken at the Inner Mongolia Grassland Ecosystem Research Station in China, researchers examined Oedaleus asiaticus, one of the two swarming locusts of Asia. A closely related species, Oedaleus senegalensis, is a major pest in Africa.

Led by Arianne Cease, a doctoral student, in concert with scientists Jon Harrison and James Elser, and undergraduate student Colleen Ford from the School of Life Sciences in ASU's College of Liberal Arts and Sciences, the collaborative team also included Chinese researchers Shuguang Hao and Le Kang. Funding for their work was provided by the National Science Foundation.

The team's initial experiments were designed to test the hypothesis that locusts form swarms partly to escape deteriorating conditions or to seek out better food sources. Most herbivores, including insects, are thought to be limited by obtaining sufficient protein. The researchers began, therefore, by fertilizing grassland plots with nitrogen. Their expectation was that the added nitrogen would raise the plants' protein levels, enhance locusts' survival and growth and stop locusts from swarming.

They couldn't have been more wrong. Locusts fed on nitrogen-fertilized plots either died or grew more slowly. Puzzled, the scientists took a step back, examining which host plants these locusts preferred. The results showed that these locusts ate plants lower in nitrogen; not higher.

It had been known for some time that overgrazing in Inner Mongolia caused soil erosion, leading to nitrogen depletion from the soil, and reductions in the protein levels in plants. The team's surveys had showed that heavily grazed plots were populated by much higher numbers of locusts, so the scientists compared the preferences and performances of locusts for plants from grazed versus ungrazed plots. Remarkably, the locusts preferred to consume the low-nitrogen plants from the heavily grazed plots.

Moving the study into the laboratory and using chemically-defined diets, the scientists next tested the effect of different protein and carbohydrate levels on the locusts' growth rates. These experiments confirmed their field studies: Oedaleus locusts strongly preferred low protein, high carbohydrate diets. This ratio was about one part protein to two parts carbohydrate -- lower than any grasshopper previously studied. "These experiments confirmed that consuming foods with too much protein is deleterious for this locust, explaining why heavy grazing promotes populations of Oedaleus," said Harrison.

"Our results fit with an emerging paradigm that animal species can vary dramatically in their nutritional responses," said Cease. "The particularly low protein: carbohydrate preference of Oedaleus may explain their success in a heavily-grazed world."

Besides revealing new understanding about an age-old plaguing question, the authors' findings offer new possibilities for improving land management strategies. "Our study also showed that nitrogen fertilizer may be an inexpensive, environmentally less-damaging alternative pest control solution for this species," noted Cease, with a sidenote from Elser, who added, "Who knows? With the large global increases in atmospheric nitrogen from air pollution, we might find, at least in this limited way, some 'good news.' That is, that the airborne nitrogen deposited on grasslands may interfere with future locust outbreaks."

The scientist's work on the grasslands was also groundbreaking in one other way. Ford, Cease's undergraduate co-author, who is now a Phoenix Teaching Fellow at Yuma High School, said of her experience: "Being in the field surrounded by nothing but hoppers, grass, and fellow scientists made me realize the amount of patience, dedication, and passion research pulled out of me. At the end of the experiment, when questions became answers that led to further research, the days in the sun and rain were worth it. Not only did I enjoy the field research, but the collaboration between Chinese and U.S. citizens made me more deeply understand the ability of individuals to work together towards one goal that may have the potential to bring about 'real world' impacts throughout the globe."


Story Source:

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


Journal Reference:

  1. A. J. Cease, J. J. Elser, C. F. Ford, S. Hao, L. Kang, J. F. Harrison. Heavy Livestock Grazing Promotes Locust Outbreaks by Lowering Plant Nitrogen Content. Science, 2012; 335 (6067): 467 DOI: 10.1126/science.1214433

Cite This Page:

Arizona State University. "Overgrazed grasslands tied to locust outbreaks." ScienceDaily. ScienceDaily, 27 January 2012. <www.sciencedaily.com/releases/2012/01/120126152127.htm>.
Arizona State University. (2012, January 27). Overgrazed grasslands tied to locust outbreaks. ScienceDaily. Retrieved September 3, 2014 from www.sciencedaily.com/releases/2012/01/120126152127.htm
Arizona State University. "Overgrazed grasslands tied to locust outbreaks." ScienceDaily. www.sciencedaily.com/releases/2012/01/120126152127.htm (accessed September 3, 2014).

Share This



More Plants & Animals News

Wednesday, September 3, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Snack Attack: Study Says Action Movies Make You Snack More

Snack Attack: Study Says Action Movies Make You Snack More

Newsy (Sep. 2, 2014) You're more likely to gain weight while watching action flicks than you are watching other types of programming, says a new study published in JAMA. Video provided by Newsy
Powered by NewsLook.com
Get A Mortgage, Receive A Cat — Only In Russia

Get A Mortgage, Receive A Cat — Only In Russia

Newsy (Sep. 2, 2014) The incentive is in keeping with a Russian superstition that it's good luck for a cat to be the first to cross the threshold of a new home. Video provided by Newsy
Powered by NewsLook.com
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

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