Online version: PDF - DTIE
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UNIT 1: WHERE DO WE STAND? THE STATE OF THE GLOBAL ENVIRONMENT<br />
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major ODSs and set a timetable for their phasing-out through the development of<br />
substitutes, changes in manufacturing processes, and recycling, reclamation and<br />
recovery. The Protocol came into force in 1989.<br />
The Montreal Protocol first established control measures for eight ODSs, known as<br />
‘controlled substances’: five CFCs and three halons. At further meetings (London<br />
1990 and Copenhagen 1992) these controls were extended to require developed<br />
countries to phase out fifteen CFCs, three halons, 34 HBFCs, carbon tetrachloride,<br />
and methyl chloroform. In 1995 a longer-term reduction schedule leading to the<br />
complete phasing-out of forty HCFCs was agreed, and methyl bromide was added<br />
to the control list. Recognising the need for economic development in developing<br />
countries, the Montreal Protocol gave them an extra 10 years to implement the<br />
reduction and phasing-out measures. These countries are known as ‘Article Five<br />
Countries’.<br />
Despite these impressive international efforts the ozone layer continues to be<br />
depleted, with record losses observed in the Antarctic and the northern hemisphere<br />
in 1997-98. Spring 1998 also saw a sharp increase in UVB radiation in the northern<br />
hemisphere’s middle and high latitudes. This was mainly due to the long life of<br />
ODSs already present in the atmosphere – the average lifespan of a CFC molecule<br />
in the atmosphere is 50-100 years. The hole in the ozone layer will therefore<br />
continue to expand until all atmospheric concentrations of ODSs are eliminated.<br />
1.3 Water Scarcities and Pollution<br />
Water is a renewable but finite resource that is naturally recycled in the earth’s<br />
hydrological cycle. Despite being renewable, it is considered a finite resource<br />
because human patterns of water use rarely correspond with natural patterns of<br />
water availability. For example, in temperate regions, most rain falls in winter, while<br />
the greatest demand is in summer. Likewise, many regions of high population and<br />
intensive industry and agriculture are situated in low-rainfall areas. These demand<br />
patterns require water to be stored, treated and supplied for industrial, irrigation<br />
and domestic uses. Water is also required for such ‘in-stream’ uses as tourism and<br />
recreation, transport, and power generation.<br />
Despite the fact that 70% of the earth’s surface is covered with water, only 3% of<br />
that is freshwater; most of it sealed in glaciers. In addition to surface freshwater,<br />
ground and marine water are also major sources of water supply. Over 1,500<br />
million people currently depend on groundwater for their drinking water needs.<br />
Marine water is important both for direct use after desalination and for fisheries<br />
and geological resources.<br />
Despite being<br />
renewable, water<br />
is considered a<br />
finite resource<br />
because human<br />
patterns of water<br />
use rarely<br />
correspond<br />
with natural<br />
patterns of water<br />
availability.<br />
Water Scarcity<br />
Growing worldwide urbanisation and industrialisation are increasing the demand<br />
for water. Many issues are involved, including:<br />
• Pollution of water sources through poor wastewater treatment;<br />
• Interruptions to natural water flows by dams and barrages intended to<br />
facilitate water supplies and storage;<br />
• Inefficiencies in the distribution of water from storage areas.<br />
Countries that extract over 20% of their available water supply (both aquifer<br />
and surface waters) are referred to as ‘waterstressed’. Two thirds of the world’s<br />
population are expected to be waterstressed by 2025.