Cover Image
close this bookEco-restructuring: Implications for Sustainable Development (UNU, 1998, 417 p.)
close this folder1. Eco-restructuring: The transition to an ecologically sustainable economy
View the document(introduction...)
View the documentIntroduction: On sustainability
View the documentThe need for holistic systems analysis
View the documentEnvironmental threats and (un)sustainability indicators
View the documentSharpening the debate
View the documentNon-controversial issues: Population, resources, and technology
Open this folder and view contentsControversial issues: Pollution, productivity, and biospheric stability
View the documentFinding the least-cost (least-pain) path
View the documentConcluding comments
View the documentNotes
View the documentReferences

Environmental threats and (un)sustainability indicators

There has been a good deal of academic debate in recent years on the exact meaning that should be ascribed to the term "sustainability." For instance, Repetto states that "current decisions should not impair the prospects for maintaining or improving future living standards" (Repetto 1985, p. 16). The WCED paraphrased the same general idea; sustainable development "meets the needs of the present without compromising the ability of future generations to meet their own needs" (Brundtland 1987). Tietenberg phrases it in utility terms, and defines sustainability as non-declining utility (Tietenberg 1984, p. 33). Pezzey goes further and insists that it is the discounted present value of utility that should not decline (Pezzey 1989). Mainstream economists have concerned themselves with replacing depleted natural resource stocks. For instance, Nobel Laureate Robert Solow proposed that "an appropriate stock of capital - including the initial endowment of resources - [be] maintained intact" (Solow 1986). More recently Solow has said: "If 'sustainability' is anything more than a slogan or an expression of emotion, it must amount to an injunction to preserve productive capacity for the indefinite future. That is compatible with the use of non-renewable resources only if society as a whole replaces used-up resources with something else" (Solow 1992).

All of these definitions (and others) essentially agree on a single economic measure of welfare (GNP). They fundamentally assume unlimited substitutability between conventional economic goods and services that are traded in the market-place and unpriced environmental services, from stratospheric ozone to the carbon cycle. However, virtually all environmentalists and an increasing number of economists explicitly reject the unlimited substitutability view as simplistic (e.g. Boulding 1966; Ayres and Kneese 1971; Ayres 1978; Daly 1990). Similar critiques have been articulated by David Pearce and his colleagues (Pearce 1988; Pearce et al. 1989).

The "ecological" criterion for sustainability admits the likelihood that some of the important functions of the natural world cannot be replaced within any realistic time-frame - if ever - by human technology, however sophisticated. The need for arable land, water, and a benign climate for agriculture is an example; the role of reducing bacteria in recycling nutrient elements in the biosphere is another; the ozone layer of the stratosphere is a third. The ecological criterion for long-run sustainability implicitly allows for some technological intervention: for example, methods of artificially accelerating tree growth may compensate for some net decrease in the area devoted to forests. But, absent any plausible technological "fixes," this definition does not admit the acceptability of major climate changes, widespread desertification, deforestation of the tropics, accumulation of toxic heavy metals and non-biodegradable halogenated organics in soils and sediments, or sharp reductions in biodiversity, for instance.

Having said this, it is obviously easier to find indicators of unsustainability than of sustainability. In work for the Advisory Council for Research on Nature and the Environment (Netherlands), preparing for the UNCED Conference in Rio de Janeiro, 1992, Dutch researchers proposed a taxonomy of sustainability indicators (Weterings and Opschoor 1992). Their taxonomy has three dimensions:

1. Pollution of natural systems with xenobiotic substances or natural substances in unnatural concentrations. The results include acidification and "toxification" of the environment.

2. Depletion of natural resources: renewable, non-renewable, and semi-renewable. In fact, biodiversity can be regarded as a depletable resource, though not one that is commonly thought of as such. Of course, it also differs from other depletable resources that are exchanged in (and priced by) well-developed markets. There is no such market for biodiversity, or for its complement, genetic information. Nevertheless, I regard this as a market failure and argue that loss of biodiversity is an aspect of depletion.

3. Encroachment (human intervention) affecting natural systems, e.g. loss of groundwater or soil erosion.

Based on this taxonomy, Weterings and Opschoor prepared the summary table of quantifiable sustainability indicators shown in table 1.1. The notion of "sustainable level" in regard to pollution, toxification, acidification, greenhouse gas build-up, and so on is predicated on the idea that natural processes will compensate for some of the damage. For instance, natural weathering of rocks generates some alkaline materials that can neutralize acid. (Increased acidity will, however, increase the rate of weathering.) Similarly, it is assumed that some of the excess carbon dioxide produced by combustion processes may be absorbed in the oceans or taken up by accelerated photosynthetic activity in northern forests (this process is called "CO2 fertilization").

Regarding depletion, it is assumed that some minerals (such as aluminum) can be mined more or less indefinitely, even though the highest-quality ores will be exhausted first. Other depletable ores could in effect be exhausted, in the sense that recovery from minable ores would be too expensive to be worthwhile except for very specialized and limited uses. Copper might be an example of this kind (though many geologists are more optimistic than Weterings and Opschoor). As regards renewable resources such as fisheries and groundwater, it has long been known that there is a level of exploitation that can be sustained indefinitely by scientific management, but that beyond that level harvesting pressures can drive populations down to the point where recovery may take decades, or may never occur at all. Many fisheries appear to be in this situation at present, notwithstanding the fact that sustainable levels are not very precisely known. Granted some uncertainty, it is nevertheless clear that, in all three dimensions, "sustainability" would require significant reductions in current levels of impact.

In recognition of the fact that both soil erosion and groundwater loss overlap considerably with the "depletion" category, the later version of their work substituted "loss of naturalness," namely loss of integrity, diversity, absence of disturbance (Weterings and Opschoor 1994). What remains in category (3) is the notion of "disturbance of natural systems" as such. Most environmentalists think of "systems" in terms of ecosystems and biomes. The sum total of such disturbances is indeed a significant environmental problem, though individual cases tend to be geographically localized. However there are also global systems that are being dangerously disturbed by anthropogenic activity. Examples of global systems include the hydrological cycle, ocean currents, the climate, the global radiation balance (including the ozone layer that protects the earth's surface from lethal ultraviolet radiation), the carbon/oxygen cycle, the nitrogen cycle, and the sulphur cycle.2 This problem is discussed in detail later.

Table 1.1 Sustainable vs. expected level of environmental impact for selected indicators

Dimension/indicator of environmental impact

Sustainable level

Expected level, 2040

Desired reduction

Scale

Depletion of fossil fuels:





Oil

Stock for 50 years

Stock exhausted

85%

Global

Natural gas

Stock for 50 years

Stock exhausted

70%

Global

Coal

Stock for 50 years

Stock exhausted

20%

Global

Depletion of metals:





Aluminium

Stock for 50 years

Stock for >50 years

None

Global

Copper

Stock for 50 years

Stock exhausted

80%

Global

Uranium

Stock for 50 years

Depends on use of nuclear energy

Not quantifiable

Global

Depletion of renewable resources:





Biomass

20% tern animal biomass

50% tern animal biomass

60%

Global


20% tern primary production

50% tern primary production

60%

Global

Diversity of species

Extinction of 5 species/ year

365-65,000 species/ year

99%

Global

Pollution:





Emission of CO2

2.6 gigatonnes carbon/ year

13.0 gigatonnes carbon/ year

80%

Global

Acid deposition

400 acid eq./hectare/ year

2400-3600 acid eq.

85%

Continental

Deposition of nutrients

P: 30 kg/hectare/year

No quantitative data

Not quantifiable

National


N: 267 kg/hectare/year

No quantitative data

Not quantifiable

National

Deposition of metals:





Cadmium

2 tonnes/year

50 tonnes/year

95%

National

Copper

70 tonnes/year

830 tonnes/year

90%

National

Lead

58 tonnes/year

700 tonnes/year

90%

National

Zinc

215 tonnes/year

5190 tonnes/year

95%

National

Encroachment:





Impairment through dehydration

Reference year 1950

No quantitative data

Not quantifiable

National

Soil loss through erosion

9.3 billion tonnes/year

45-60 million tonnes/ year

85%

Global

Source: Weterings and Opschoor (1992), table 6, p. 25.

Holistic analysis presupposes that it is possible to classify variables by degree of importance and derive significant and defensible results by judicious simplification. A universal measure to estimate and compare the relative environmental impact of different activities, goods, services, 7and regulatory policies would be of great value.

Such a measure should satisfy the following conditions:

- it should be based on measurable quantities;

- it should relate to the most significant environmental impact potentials of human activities;

- it should allow transparent, cost-efficient, and reproducible estimates of the environmental impact potentials of all kinds of plans, processes, goods, and services;

- it must be applicable on the global level as well as regional and local levels.

Choosing a single indicator to compare the environmental impact intensities of all kinds of present and future processes, goods, and services might seem to be a daring step, precisely because it constitutes a vast reduction of complexity. Simplification cannot be proven to be "correct" in scientific terms.3 Only its plausibility in a variety of circumstances can be established.

For several reasons it can be argued that aggregate resource productivity, the ratio of GNP (or a better unit of economic welfare) to an index of total renewable-but-unrenowned or non-renewable resource inputs, in physical units, might be a plausible measure of sustainability. At least the two are correlated: the greater the resource productivity, the nearer to long-term sustainability. Obviously, the inverse of resource productivity - non-renewable or non-renewed resource use per unit of welfare output - is a measure of unsustainability.

Regrettably, neither this measure nor anything similar is currently computed at the national level by statistical agencies, and the required data are not readily available even to them, still less to non government organizations. However, note that the corresponding measure can be computed in principle for a sector (industry), a firm, a region with well-defined boundaries, or even a single product. Something like the inverse of resource productivity, materials intensity per unit service (MIPS), has been calculated for a number of specific cases at the Wuppertal Institute.4