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