2.4.1 Water
Essential to life, the environment, and all economic activities, renewable fresh water is very unequally distributed within and between countries around the Pacifi c Rim.
Southeast Asia includes most of the countries in the top decile of annual rainfall and surface water per capita, yet China has 20 percent of global population and only
2005
Oth SE Asia 9.4%
Hi Inc Asia 52.5%
Hi Inc Asia 52.5%
Oth SE Asia 1.7%
Lao PDR 0.1%Viet Nam
1.4% Thailand 3.2%
S. Asia 10.5 %
China 21.1%
China 53.5%
2020
Oth SE Asia 11.2%
Cambodia 0.3%
Oth Asia 0.8%
Lao PDR 0.0%
VietNam 0.9%
S.Asia 7.4%
Thailand 2.3%
Cambodia 0.2%
2005 Total Agrifood Imports Increase 70% (billions of 2005 USD) 1,500
1,000 500 -
2020
FIGURE 2.10 Asian Regional Food Imports, 2005 and 2020
Source: Jha et al.: 2011.
CLIMATE RISK AND RESPONSE 71
5 percent of the planet’s renewable fresh water sources. Weather patterns distribute fresh water via storm systems, particularly in long monsoon and Pacifi c circulation cycles, while aquifers, snow, and ice reserve water for dry season use. Th e latter have been complemented by large investments in artifi cial storage and conveyance sys- tems, distributing water across time and space to compensate for supply-demand mismatches. Climate change will profoundly aff ect all this, and necessitate signifi - cant regional adaptation. We review water challenges for the Pacifi c Rim from three perspectives, according to the source of water.
2.4.1.1 Water from the Sky
Most climate models agree that global warming will increase precipitation in temperate latitudes and reduce it in tropical ones. It is also expected that seasonality of rainfall will intensify, meaning shorter, more intense rain and longer dry periods. Subject to exist- ing storage capacity, these trends would lead to a steady decline in total water availabil- ity, moderate increases in annual variability, and sharp increases in seasonal variability, meaning longer and deeper droughts. Th ese trends will be aggravated by reductions
0
–5
–10
–15
–20
–25
1945 1955 1965 1975 1985 1995 2005
Cumulative global mean specific mass balance (m w.e.)
Mean of all glaciers Mean of “reference” glaciers
FIGURE 2.11 Global Average Glacier Mass Balances
Average of All Glaciers/Average of “Reference” Glaciers
Ref: GRIDA (2013), High Mountain Glaciers and Climate Change: An Interactive E-book, http://www.grida.no/publications/high-mountain-glaciers/e-book.aspx.
Source: UNEP/GRID-Arendal.
in storage capacity, as aquifers are more aggressively exploited in dry spells, and snow packs shrink with global warming.
Demographic pressures will also affect the sustainable water supply. Clean and consistently available water has been one of the blessings of modernization, and most of the Pacific Rim’s people have seen substantial improvements in water qual- ity and availability over their lifetimes. This has happened primarily in cities and townships, however, where populations have been steadily migrating and per capita water use is much higher (2–3 times) than in rural areas. Thus we see water quality improving, but water availability is becoming less certain as urban use escalates. In many rural areas, the response to this has been increased groundwater exploitation, using more carbon fuel energy to extract an ever-receding resource. This combina- tion is unsustainable and threatens both public health and food security. In popu- lous Asian and smaller island economies in the region, determined initiatives for water efficiency, recycling, and scarcity pricing will be needed to avert more serious problems.
2.4.1.2 Water from the Mountains
Meanwhile, capacity of the world’s second-largest fresh water storage facility, ice and snow, is expected to decline sharply as climate change progresses (Figure 2.11). So-called mid-latitude mountain ranges are very important to water supplies for Pacifi c Rim economies, including the Himalayas, Alps, Rocky Mountains, Cascade Range, and southern Andes. Glaciers in these ranges are showing the largest proportionate snow and ice losses as global temperatures have risen. Th e Himalayan plateau, for example,
FIGURE 2.12 Historical Extent of the Gangotri Glacier
Source of 70 percent of Ganges River Summer Flow
Source: Earth Observatory, NASA.
Karachi Chennai Colombo Jakarta Bangkok Ho Chi Minh City Kuala Lumpur Singapore
Kolkata
ChittagongTaipei
Tokyo
Seoul
SapporoNon LECZ 0.0 – 5.0 5.1 – 10.0 10.0 –15.0 15.1 – 20.0 20.1 – 25.0 Small Intermediate Big Population of cities Small: 100–500 thousand Intermediate: 500 thousand – 1 million Big: More than 1 million> 25.0
PercentofNational Population Vulnerable CitySize
Ha Noi FIGURE 2.13 Population at Risk from Sea-Level Rise—Asia
Casablanca Conakry Monrovia Freetown AbidjanAccra Pointe-Noire Luanda Kayamnanadi Port ElizabethDurban
Maputo
Qucimane St. DenisConcepcion
Vina del Mar
Arica
Lima Mombasa Dar-es-Salaam
Mogadishu
Guayaquil
Panama CityOjibouti
Bur Sudan
Culiacan
Reynosa
Tijuana Alexandria
Tunis Tarabulus
Algiers MenidaNassau San Juan Paramaribo Belem Fortaleza Trunca Salvador Itaquari Rio de Janeiro Porte Alegre Buenos Aires
Port-au- Prince Lagos Douala Libre- ville FIGURE 2.14 Africa and Latin America Will Be More Aff ected by Reduced Rainfall
CLIMATE RISK AND RESPONSE 75
with combined drainage basins serving some 3 billion people (almost half of the Earth’s population) in 18 countries, is seeing about 90 percent of glaciers retreat (Figure 2.12).
Even if total annual rainfall changes little, seasonal variation will escalate without mon- tane water storage, and this could sharply curtail growing seasons and induce much more severe droughts in dry seasons.
2.4.1.3 Water from the Sea
Sea-level rise is one of the hallmark challenges of climate change, and for the Pacifi c Rim it will have special signifi cance. Th e sea has been a catalyst for the region’s collec- tive prosperity, linking high-income markets to lower-income economies in globaliza- tion’s continuing cycle of growth spillovers. In the case of sea-level rise, we shall again see shared destiny. Most of the defensive investments needed to protect people will be in export-oriented East and Southeast Asia.
Asia is home to 90 percent of the world’s population at risk from rising sea level and, as Figure 2.13 suggests, this regional risk is concentrated in Pacifi c Rim Asian mega-cities (compare to, e.g. Africa and South America in Figure 2.14). By contrast, Canada and the United States, as well as countries in the Eastern Pacifi c and in western Central and South America, are signifi cantly insulated by tectonic subduction, as the Pacifi c Plate has driven itself under both continents, raising extensive cliff s along most of their coast- lines. In any case, these Pacifi c Rim countries have much lower coastal population den- sities than their Asian counterparts.
It must also be recognized that sea level is not a static object nor even a smooth trend.
Th is kind of “bathtub” perspective greatly understates climate-induced sea level risk, both in terms of severity and timing. In fact, sea level is constantly subjected to variance from wave action, tides, and storm activity. Moreover, storm severity and frequency both appear to be escalating as a result of climate change. Taken together, these facts imply sea-level risk will become apparent sooner and more dramatically than simply average melting trends might suggest.