| dc.description.abstract | Abstract. The effectiveness of population policy in reducing
the combined impacts of population change and climate
change on water resources is explored. One no-policy scenario
and two scenarios with population policy assumptions
are employed in combination with water availability under
the SRES scenarios A1b, B1 and A2 for the impact analysis.
The population data used are from theWorld Bank. The river
discharges per grid of horizontal resolution 0.5 are obtained
from the Total Runoff Integrating Pathways (TRIP) of the
University of Tokyo, Japan. Unlike the population scenarios
utilized in the SRES emission scenarios and the newest representative
concentration pathways, the scenarios employed
in this research are based, even after 2050, on country-level
rather than regional-level growth assumptions.
Our analysis implies that the heterogeneous pattern of population
changes across the world is the dominant driver of
water stress, irrespective of future greenhouse gas emissions,
with highest impacts occurring in the already water-stressed
low latitudes. In 2100, Africa, Middle East and parts of Asia
are under extreme water stress under all scenarios. The sensitivity
analysis reveals that a small reduction in populations
over the region could relieve a large number of people
from high water stress, while a further increase in population
from the assumed levels (SC1) might not increase the number
of people under high water stress considerably. Most of
the population increase towards 2100 occurs in the already
water-stressed lower latitudes. Therefore, population reduction
policies are recommended for this region as a method
of adaptation to the future water stress conditions. Population
reduction policies will facilitate more control over their
future development pathways, even if these countries were
not able to contribute significantly to greenhouse gas (GHG)
emission cuts due to economic constraints. However, for the
European region, the population living in water-stressed regions
is almost 20 times lower than that in the lower latitudes.
For countries with high population momentum, the population
policy scenario with fertility-reduction assumptions
gained a maximum of 6.1 times the water availability in
Niger and 5.3 times that in Uganda compared with the nopolicy
scenario. Most of these countries are in sub-Saharan
Africa. These countries represent 24.5% of the global population
in the no-policy scenario, and the scenario with
fertility-reduction assumptions reduces it to 8.7% by 2100.
This scenario is also effective in reducing the area under extreme
water stress in these countries. However, the policy
scenario with assumptions of population stabilization at the
replacement fertility rate increases the water stress in highlatitude
countries. Nevertheless, the impact is low due to the
high per capita water availability in the region. This research
is expected to widen the understanding of the combined impacts
of climate change in the future and of the strategies
needed to enhance the space for adaptation. | en_US |
