Environment
Nature
Threatened by Shrinking Households
Deforestation, greenhouse gases linked to smaller household size
nimals and their habitats are getting pushed aside as households decrease in size
and increase in number, according to scientists at Michigan State University (MSU) and
Stanford University.
Smaller numbers of people per household on average use more energy and
goods per person. Greater numbers of households--resulting from a rise in divorces and
"empty nesters," plus fewer multigenerational homes worldwide--require more
natural resources for construction. The potential result of this twofold problem may
ultimately be insufficient natural resources to meet consumer demand without endangering
habitats crucial to biodiversity.
"Personal freedom and social choice may come at a huge
environmental cost," says MSU scientist Jianguo (Jack) Liu. Direct costs include
visible damage to animal habitats and plant life. Indirect costs include the release of
more greenhouse gases.
The impacts of such "personal freedom and social choice" have
already surfaced in southwest China's Wolong Nature Reserve, where Liu studied panda
habitat under a grant from the National Science Foundation. In Wolong, Liu found that a
reduced average household size was directly tied to an increase in homes, and thus an
increase in the amount of firewood consumed for cooking and heating. The rise in wood fuel
use has contributed to deforestation and to the loss and fragmentation of habitat for
giant pandas, Liu says.
Curious about whether other parts of the world were experiencing similar
phenomena, Liu enlisted a team of researchers including Stanford's Paul Ehrlich, renowned
for his population studies, to evaluate the household dynamics in 141 countries between
1985 and 2000. Their study confirmed that the Wolong dilemma is part of a global trend.
In the 76 countries considered biodiversity "hotspots," such
as the United States, Brazil, Australia, and Kenya, the number of households grew annually
by 3.1%, while the population increased just 1.8%. Meanwhile, the number of people per
home dropped from 4.7 to 4.0. The decline in household size has resulted in 155 million
additional households in hot-spot countries, invariably straining biodiversity, according
to the research team.
In the 65 non-hot-spot countries--those without high-density areas of
animal and plant species--similar results were found, though on a lesser scale. Even in
countries experiencing population decline, such as New Zealand, the number of households still
increased because of a reduction in household size.
"While there is still a need to reduce pollution and ecological
destruction caused by factories and companies, this study provides a wake-up call and
suggests that efforts at the individual and household levels are also needed to reduce
impacts on the environment," Liu says. He suggests that governments could help curb
the trend via tax incentives for sharing housing and resources. --Hope Cristol
Source: National Science Foundation, 4201 Wilson Boulevard,
Arlington, Virginia 22230. Telephone 1-703-292-5111; Web site www.nsf.gov.
