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Thursday, May 9, 2013

Early warning signs of population collapse

Climate change, a photo by jeancliclac on Flickr.

Boston MA (SPX) Apr 15, 2013, 2013 Many factors - including climate change, overfishing or loss of food supply - can push a wild animal population to the brink of collapse. Ecologists have long sought ways to measure the risk of such a collapse, which could help wildlife and fishery managers take steps to protect endangered populations.
Last year, MIT physicists demonstrated that they could measure a population's risk of collapse by monitoring how fast it recovers from small disturbances, such as a food shortage or overcrowding. However, this strategy would likely require many years of data collection - by which time it could be too late to save the population.
In a paper appearing in the April 10 online edition of Nature, the same research team describes a new way to predict the risk of collapse, based on variations in population density in neighboring regions. Such information is easier to obtain than data on population fluctuations over time, making it potentially more useful, according to the researchers.
"Spatial data are more accessible," says Lei Dai, an MIT graduate student in physics and lead author of the study. "You can get them by satellite images, or you could just go out and do a survey."
Led by Jeff Gore, an assistant professor of physics, Dai and Kirill Korolev, a Pappalardo Postdoctoral Fellow, grew yeast in test tubes and tracked the populations as they approached collapse. Yeast cells cooperate with other members of the population: Each of the organisms secretes an enzyme that breaks down sucrose in the environment into smaller sugars that it can use as a food source. All of the yeast benefit from this process, so a population is most successful when it maintains a certain density - neither too low nor too high.
In last year's study, the researchers found that in populations of yeast that are subjected to increasingly stressful conditions, populations become less and less resilient to new disturbances until they reach a tipping point at which any small disruption could wipe out a population.
This phenomenon can be spotted quickly in yeast, which produces about 10 new generations per day, but measuring these population fluctuations for species such as fish or deer would take much more time. In hopes of finding more useful signals, the researchers turned their attention to spatial information.
There goes the neighborhood
In their new study, the researchers theorized a new type of indicator that they call "recovery length" - the spatial counterpart to recovery time. This idea is based on the observation that populations living near the boundary of a less hospitable habitat are affected, because the neighboring habitats are connected by migration.
Populations further away from the bad region gradually recover to equilibrium, and the spatial scale of this recovery can reveal a population's susceptibility to collapse, according to the researchers.
To test this idea, the researchers first established several linked yeast populations in a state of equilibrium. At the end of each day, a certain percentage of each population was transferred to adjacent test tubes, representing migration to adjacent regions.
The researchers then introduced a "bad" habitat, where only one in every 2,500 yeast survives from one day to the next. This reduction in population mimics what might happen in a natural population plagued by overfishing, or by a drastic reduction in its food supply.
The MIT team found that populations closest to the bad habitat had the hardest time maintaining an equilibrium state. Populations farther away maintained their equilibrium more easily.
"There's some distance you have to go away from the bad region in order to get recovery of the population density," Gore says. "How far you have to go before you reach equilibrium is the recovery length, and that tells you how close these populations are to collapse."
The recovery length varies based on how much stress the populations are already under.
To apply this finding to a natural population, population density would need to be measured in a range of adjacent areas at increasing distances from a good/bad boundary. This information could then be mapped to reveal the recovery length. "What's great about the recovery length is you don't need a long time series. You could just measure it at one moment in time," Gore says.
The MIT researchers are hoping to expand their studies to natural populations such as honeybees, fisheries or forests. They are also studying more complex experimental ecosystems involving several microbial species.
The research was funded by a Whitaker Health Sciences Fund Fellowship, a Pappalardo Fellowship, a National Institutes of Health Pathways to Independence Award and New Innovator Award, a National Science Foundation CAREER Award, a Sloan Research Fellowship, the Pew Scholars Program and the Allen Investigator Program.
by Anne Trafton for MIT News
Source Citation (MLA 7th Edition)
"Early warning signs of population collapse." Space Daily 23 Apr. 2013. General OneFile. Web. 9 May 2013.
Document URL
http://go.galegroup.com/ps/i.do?id=GALE%7CA327268858&v=2.1&u=22054_acld&it=r&p=GPS&sw=w

Gale Document Number: GALE|A327268858

Monday, January 5, 2009

Write Book

Writing a novel for personal or monetary income, has been around over centuries; which people used writing for self-satisfaction.

1) Write every day - schedule time - the more you do it, the better you get.

2) Write a bad- book first, makes a bad story is easier to write; then a good one. Thus, instead of getting frustrated and quiting; a bad novel gives confidence.

3) A bad-book gives the idea of finishing a whole novel. Upon writing a book for 5 months, put the book aside after 5 months. Consequently, a critical eye and human nature will give a different impression.

4) Start writing a good book, while the bad book is in storage for 5 months.

5) Upon proofreading the book set aside for storage; know where weak, and correct errors.

6) Finish the good-book and edit the 1 pages, before publication

As a result, building your muscles effects the exercise of your mind; by practice and leaving the comfort zone to by building on areas you are really, terrible. Thus, find the weak spots, and attack them

Write for the reader, not to hear yourself talk. The whole process takes time, patience.

http://writers2008.googlepages.com/