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SECTION
5 ASSIMILATIVE CAPACITY CAPITAL STOCK
| 5.1 |
Introduction
and Definition |
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| 5.1.1.1 |
This
section addresses the two related capital
stock functions of natural assimilative
capacity and assimilative capacity enhancers.
Assimilative capacity has been defined for
the purposes of this report as the process
of environmental self-purification or equilibration
and relates to the 'sink' functions of the
capital stock discussed in Section 2.1.
Assimilative capacity enhancers are systems
which provide an anthropogenic response
to past problems of pollution, public health
or resource depletion. These systems are
defined here as man-made environmental infrastructure
that enhances natural processes so as to
reduce or modify pollutant loadings to the
environment. It is important to recognise,
as discussed in Section
2, that assimilative capacity enhancers
may not be perfect substitutes for natural
assimilative capacity functions. Therefore,
while assimilative capacity enhancers can
be important tools for improving environmental
quality and even forestalling pollution
crises, natural assimilative capacity and
source reduction will also play critical
roles in maintaining the natural capital
stock.
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| 5.1.1.2 |
The
section is structured according to the assimilative
capacity of three key natural resource functions:
marine waters, freshwater systems and air.
For each resource, the current status of
the stock is examined in terms of its potential
to provide natural assimilative capacity.
The role of assimilative capacity enhancement
in Hong Kong is then reviewed for each medium.
The residual impacts resulting from any
pollutant input exceeding the combined capacity
of the natural assimilative and the enhanced
assimilative capacities are then examined.
Factors that will act on these assimilative
capacity resources to shape the long-term
sustainability of Hong Kong's environmental
quality are explored as a basis for identifying
possible actions to counteract erosion of
the natural capital stock.
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| 5.1.1.3 |
A
detailed quantitative discussion of assimilative
capacity is not feasible because the scientific
investigations necessary to determine the
pollutant loads that can be accommodated
by marine water bodies, fresh water systems
and air sheds have not yet been conducted
and are beyond the scope of this Study.
Instead, this discussion qualitatively describes
the various system input and absorptive
components and comments on the degree to
which capacity appears to remain or has
been exceeded. Existing tools for evaluating
water and air quality, ie the statutory
objectives for various parameters, are used
as proxies for assimilative capacity figures
to inform this evaluation.
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| 5.1.1.4 |
The
assimilative capacities of these media are
affected by discharges or emissions of pollutants,
and the extent to which the effects of these
pollutants are ameliorated by the absorptive
functions of the environment determines the
observed environmental quality. Therefore,
the environmental quality indicators defined
for the study are directly relevant to the
assimilative capacity resource natural capital
stock. These indicators deal with marine discharges
(water quality and beach quality), freshwater
quality (river quality), and air emissions
(criteria air pollutants, toxic air pollutants,
greenhouse gases, and exposure of the population
to excessive levels of noise). Indicators
developed under the guiding principle for
health are also indirectly relevant since
the natural and enhanced assimilative capacity
will determine public hygiene conditions (relating
to the indicator on the cleanliness of Hong
Kong), and the air quality conditions will
influence the indicator on the incidence of
respiratory diseases. |
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| 5.1.1.5 |
As
discussed in Section 3.1, there are linkages
between assimilative capacity and the stock
of natural resources, since the exploitation
and use of natural resources (see Section
3.2) creates much of the pollution which affects
assimilative capacity. In parallel, the depletion
of some natural resources (eg abstraction
of freshwater) may result in a lowered natural
assimilative capacity. Reduced assimilative
capacity and changes in environmental quality
may also have effects on ecological functions
through pollution of ecosystems and effects
on individual species (see Section 4.3). Air
quality is also known to be a causative factor
in the deterioration of buildings and monuments
through acid rain deposition and aesthetic
impacts (eg dust and soot), and thus relates
to the heritage resources capital stock. Finally,
as discussed in Section
7, a depleted or exhausted assimilative
capacity will impact upon the existence value
(eg connections to environmental stewardship),
the landscape value (eg aesthetics and scenic
resources for tourism), and the recreational
value (eg the health effects and desirability
of swimming at polluted beaches) of the natural
capital stock. |
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