Smaller households=Greater consumption

a trend towards smaller households is threatening biodiversity around the world, a new study finds. Both in developed and developing countries, multi-generational living arrangements are disintegrating, with couples moving out. Rising divorce rates mean families that used to live in one dwelling now occupy two.

Even where the human population is declining, number of households continues to increase, concludes the study by scientists from the us-based Michigan State University (msu) and Stanford University. The researchers examined household dynamics and population changes in 141 countries worldwide. In particular, they scrutinised data pertaining to seven countries -- Australia, India, Kenya, Brazil, China, Italy and the us -- having biodiversity hotspots. They found that in 1985, the average household size was 4.7 persons in countries having hotspots and 3.7 in other nations. By 2015, this is expected to reduce to 3.4 in the former and 3.6 in the latter.

The result is inefficient use of resources. Among numerous other things, each household takes up space, requires materials to construct a dwelling and fuel to heat and cool. For example, a refrigerator uses the same amount of energy irrelevant of whether it belongs to a family of four or two. Rising energy consumption increases the emission of greenhouse gases. Even wildlife is affected. For instance, in the Wolong province of China, the researchers observed that a reduced average household size was linked to a rise in the amount of fuelwood consumed by the local populace. This has degraded the habitat of the giant pandas.

While households may be shrinking in numbers, most are growing in terms of area. For instance, in Indian river county of Florida, usa, the average area of a one story-single family house has increased by 33 per cent in the last three decades -- from an average of about 200 square yards in 1970 to 266.6 square yards in 2000.

"This study suggests that efforts at household levels are also needed to reduce adverse impacts on the environment," says Jianguo 'Jack' Liu, an associate professor at msu.