Dr Jianguo Jack Liu of Michigan State University
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Dr. Jianguo (Jack) Liu of Michigan State University

June 2, 2010
Dr. Jianguo (Jack) Liu of Michigan State University points out a few stray panda hairs left on a tree trunk in Wolong's mountain forest. Pandas habitually mark trees by rubbing their hind ends against them. [One of six images taken at the Wolong Nature Reserve during a research study on world population dynamics. See Next Image.]

More about this Image Scientists from Michigan State (MSU) and Stanford universities, in a fresh look at world population dynamics, have revealed evidence that increased numbers of households, even where populations are declining, are having a vast impact on the world's biodiversity and environment.

Reduction in household size has led to a rapid rise in household numbers around the world and has posed serious challenges to biodiversity conservation, writes Jianguo (Jack) Liu of MSU and Stanford colleagues Gretchen C. Daily, Paul R. Ehrlich and Gary W. Luck in the January 12, 2003 advance online publication of the journal Nature. Biodiversity is threatened severely not only by increased numbers of households, but also by less efficient per capita consumption of natural resources, the researchers say.

A systems ecologist, Liu received his NSF Faculty Early Career Development (CAREER) award in 1997. He already had acquired significant background on the impact of household dynamics on giant pandas in southwest China's mountainous Wolong Nature Reserve when he approached Stanford's Paul Ehrlich, renowned for his population studies, with an idea: Expand the probe into a worldwide look at the impact of households on global biodiversity and environment.

"The numbers of households increased much faster than the size of the population at Wolong," Liu said. "This has important implications because given the same population size, more households mean a need to consume more resources, and therefore, a greater impact on the environment. What was discovered from the panda reserve helped me to conclude that considering population size and growth alone is not enough, and made me want to find out whether other areas in the world have similar phenomena."

In China's Wolong, a reduced average household size was tied directly to an increase in household numbers and a rise in the amount of fuel wood consumed by the local populace for cooking and heating, which has contributed to deforestation and loss and fragmentation of habitat for giant pandas.

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