5.1 Introduction and Definition
| 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. |
| 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. |
| 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. |
| 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. |
| 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. |
