# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"From Elton to Mathematics and Back Again," by Dave Raffaelli. *Science,* 10 May 2002, pages 1035-1036.

Raffaelli writes of work in ecology by Neutel *et al* ("Stability in RealFood Webs: Weak Links in Long Loops," page 1120 of the same issue) that blendsnew mathematical models with traditional ideas like food webs. The researchersused a concept called trophic loops--"closed chains representing interactionstrengths between adjacent species in a food chain"-- to explain stability insome complex soil ecosystems. Interaction strengths are numbers between 0 and 1that represent effects of a predator on prey or prey on a predator. Theconclusion of the study is that stable systems have long loops of weakinteraction strengths.

*--- Mike Breen*