Effects of Global Household Proliferation on Ecosystem Services - Landscape Ecology for Sustainable Environment and Culture - page 108

Fig. 6.6 Percentages of fuelwood collection sites in three decades (1970s, 1980s, and 1990s)
falling in four types of habitat (He et al. 2009 )
based model indicated that household numbers varied very differently than pop-
ulation sizes (An and Liu 2010 ). Fertility-related factors (e.g., fertility rate, spacing
between births, and upper child-bearing age) caused almost instant changes in
population size. All the factors except age at the first marriage had time lags of
approximately 20 years before they affected household numbers. Age at the first
marriage changed household numbers most quickly. A reduction of age at the first
marriage from 38 to 18 could lead to a difference of 90 households at year 5, 150
households at year 10, and approximately 220 households at year 20. This is
largely because of the household lifecycle: delayed marriage usually postpones the
formation of new households and births of babies. It takes more time for other
factors to take effect in changing household numbers. For example, increasing
fertility rate increases the number of children, but the children still stay with their
parents until they establish their own households. This is why there is a time lag of
approximately 20 years.
Changing household numbers through age at the first marriage is the most
effective and fastest way to lower panda habitat loss. Panda habitat is more
influenced by household numbers than population size. This is partly due to how
fuelwood is consumed. A major proportion of fuelwood is used for heating, which
changes little when an existing household has one more or one fewer person. In
terms of cooking, adding or removing one person does not change fuelwood use
much (An et al. 2001 ).
6.3.2.2 Impacts of Household Proliferation on Food Production
Household proliferation also has substantial impacts on other ecosystem services,
such as food production (Table 6.1 ). Because household proliferation requires
more areas for housing and associated infrastructures (e.g., roads and sewer ser-
vices), much agricultural land has been converted into residential areas around the
world. Although there are no accurate statistics at the global level, there are