THE PRECAUTIONARY PRINCIPLE

Assimilative capacity

Economic instruments are based on the idea that the environment has a certain capacity to absorb waste materials without long-term damage: in other words, that the environment has an assimilative capacity.

The philosophy behind tradeable pollution rights is based on the assumption that the environment can take a certain amount of pollution and that trading can ensure efficient allocation of that capacity to firms that need to utilise it. Tradeable pollution rights are a way of allocating ownership to the assimilative capacity of the air or water through rights to pollute it.

Assimilative capacity is based on three premises (NENT 1998: 116):

• A certain level of pollution causes no harm to the environment, or at least no irreversible harm - this is referred to as the self-healing poten­tial of environment.

• Environments can only absorb a certain amount of pollution/wastes before there are unacceptable adverse consequences; these are then cumulative and irreversible.

• The assimilative capacity of an environment can be quantified, appor­tioned and utilised.

Some business groups even argue that the capacity of the environment to absorb wastes and pollution is not a scientific fact but 'will depend heavily on the level of community wealth and living standards', because people place more value on clean air and water as they become more wealthy (BCA1991). In other words, the assimilative capacity of the envi­ronment depends on value judgments about how much pollution a com­munity is willing to put up with.

The unspoken assumption behind all such models is that the capacity of the environment to tolerate a certain number of renegades is some­thing that we ought, collectively, take advantage of. We ought to make sure that all those slots are taken, we ought to allow just as many renegades as nature itself will tolerate. (Goodin 1992: 16)

The Business Council of Australia claims that Australia has excess assim­ilative capacity because it is not as polluted as other industrialised coun­tries and that therefore environmental standards do not need to be so high. It argues that Australia could do the world a favour by carrying out polluting activities here 'to relieve the burden on countries already at environmental capacity' (BCA 1991: 7-8).

The assimilative capacity approach is not a precautionary approach. It assumes that a certain level of pollution is safe until proven harmful. For this reason critics of the assimilative capacity approach sometimes label it the 'permissive principle'. The precautionary principle, on the other hand, requires that if a substance is likely to harm the environment - and we can't be sure how much will do harm - we should do some­thing about even small quantities of it.

The assimilative capacity approach is highly dependent on the ability of scientists to assess the impact of pollutants on the environment and to determine a safe level that will not irreversibly or severely damage the environment. But with some 300 000 chemicals being invented each year, and 70 000 in daily use, scientists cannot possibly keep up. Even where chemicals are tested they are only tested for toxicity, persistence and bioaccumulation, although they can have other damaging impacts, including altering salinity, physical smothering and thermal pollution. What is more, plants and animals and ecosystems interact with chemi­cals in such complex ways that assumptions about assimilative capacity and 'safe levels' of pollution or exposure bear little relation to reality.

The US-based Center for Progressive Regulation (CPR 2005) points out:

So-called 'cross-pollutant' (one chemical for another) and 'cross­media' (air emissions for water discharges) trades should not occur in the absence of reliable scientific evidence that they will not worsen environmental conditions, or cause and exacerbate hot spot prob­lems. These expansions of traditional trading can result in exchanges of markedly more benign chemicals for their far more toxic cousins, as well as the substitution of poorly characterized pollution in one medium for pollution in another medium the effects of which are better understood.

A precautionary approach would require pollutants to be progressively removed from the environment altogether through clean production techniques.

Carbon sinks

Carbon offsets are little more than a way of temporarily expanding assimilative capacity. The capacity of the planet to absorb carbon dioxide, rather than release it into the atmosphere to form the blanketing layer that causes global warming, is aided by forests. By planting trees, people hope to increase the assimilative capacity of the atmosphere to absorb carbon dioxide. The capacity of plantations to act in this way is highly uncertain, however.

Scientists are unable to accurately assess how much carbon a group of trees will store during their growth. This is, firstly, because 'Scientific understanding of the complex interactions between the biosphere (trees, ocean, and so on) and the troposphere (the lowermost part of the atmos­phere) is limited' (Bachram 2004: 6). The carbon stored by growing trees varies across different species and different soil types, as well as varying with the amount of soil litter and below-ground biomass.

Recent research in the US suggests that the flux of carbon into forests is uncertain by a factor of two or three and annual variability as high as 100 per cent. For the continental US, sink estimates range between 0.2 and 1.3 billion tonnes per year and for Europe, between 0.2 and 0.4 billion tonnes.

In some cases, most notably in plantations located in wet areas of Finland, the loss of carbon from the soil and the draining of peatlands outweigh the gain from the growing trees. Other factors that may coun­teract the gains from planting trees include the removal of groundcover and the effect of plantations on erosion and soils downstream. Even preparing an area for planting of trees can release large quantities of CO2 from the soil, and CO2 can also be generated by the manufacture of the agrichemicals used on the plantation, and by the machinery used to clear the site (Lohmann 1999; 2001: 37).

Uncertainty of continued absorption

Another problem recognised in the 1990s by the UN's Intergovernmental Panel on Climate Change (IPCC) is that Earth's natural carbon sinks may well be at the point of saturation already. Before industrialisation, there was equilibrium in the transfer of carbon dioxide between forests and the atmosphere. The amount absorbed by photosynthesis was equal to the amount released during respiration when the plant matter broke down. When levels of CO2 in the atmos­phere increased as a result of industrialisation, the rate of photosyn­thesis increased and forest growth accelerated. The question is whether this can continue indefinitely.

Some experts, such as Bob Scholes from South Africa's government research agency, argue that a turning point may already have been reached, so that respiration is now increasing as a result of warmer tem­peratures and thus the ability of trees to absorb more CO2 than they emit may be decreasing. In this scenario planting more trees will not help but may even hinder efforts to prevent global warming (Pearce 1999).

Sten Nilsson from the International Institute for Applied Systems Analysis (IIASA) claims that it may take 50 years to find out whether plantations and afforestation actually act as carbon sinks and to what extent.

Uncertain life of trees

The second problem is that the life of those trees that are supposed to absorb carbon is uncertain. Carbon stored in oil and coal deep below the Earth's surface is locked in permanently until humans intervene. Carbon in trees is stored temporarily, while they are growing, and can be easily released through 'fire, natural decay and timber harvesting'. Plantations are fragile and monocultures are particularly vulnerable to disease and insect infestation, as well as to the usual threats of accidental fires, extreme weather events and illegal logging. In addition, global warming itself will affect the growth rate of the trees, their rate of respiration, and the likelihood of fire (Bachram 2004: 6; Kill amp; Pearson 2003: 2-7).

These events are often beyond the control of governments. More than half the timber exported from countries like Brazil and Indonesia comes from illegal logging. Similarly, forest fires are beyond the control of the most technically advanced nations, as can be seen in the USA and Australia. And in the event of such fires, who is liable for the lost carbon which returns to the atmosphere?

The length of time for which the carbon is stored in trees is therefore very uncertain. At best it delays for a few years a fraction of the warming that will result from greenhouse gases. Carbon offsets are thus an attempt to compensate for permanent emissions of carbon into the atmosphere by means of temporary and uncertain storage. One tonne of carbon stored in trees is not the same as one tonne of carbon stored in coal deep under the ground.

The European Commission has decided to exclude carbon sinks from Europe's emissions trading scheme (ETS) because 'they do not bring technology transfer, they are inherently temporary and reversible, and uncertainty remains about the effects of emission removal by carbon sinks' (quoted in Kill amp; Pearson 2003: 10). This has not prevented European companies from being involved in such projects, however.

The precautionary principle says that uncertainty should not be used as an excuse not to act to protect health and the environment. By the same token, if the actions taken are of highly uncertain effectiveness, those actions are likely to allow the original threat to health and the environ­ment to remain. They should be subject to the precautionary principle in the same way as the original activities that pose the threat. Carbon offsets are not an adequate response to the threat posed by burning fossil fuels.

Ability to respond to new information

Economic instruments also lack the flexibility that a precautionary approach would require. Because pollution rights have economic value, once they have been allocated it is difficult to withdraw them. Thus, if new knowledge is gained about the dangers of a pollutant, to either the environment or human health, after pollution rights have been allocated, the ability of regu­lators to respond to, and act upon, the new knowledge will be limited.

If the established baseline level for emissions trading is found not to be the ideal ultimate level, or if new information comes to hand that means the regulator has to tighten environmental standards, the baseline level will have to be reduced. How would that affect a firm's 'banked' credits? Would the government have to buy them back? Otherwise, according to Robert Hahn and Gordon Hester, 'reductions that were once surplus would then be required, thereby effectively confiscating the property right held by the firm'. Proponents of emissions trading schemes are very much against such changes, as they add to the uncer­tainty of firms that may not be inclined to get involved for fear of having their banked credits devalued (Hahn amp; Hester 1989: 117).

A regulatory agency may want to reduce total pollutant loadings allowed in a waterway in the light of how well a trading system is working, which means reducing the value of credits or reclaiming them. This in turn means that the security and certainty of trade is compromised, and the market will not work very well unless the government promises compensation to those affected. The Golden Gate Audubon Society noted:

Once a trading system is established it will be very difficult to go back to the polluting entities (corporations, local governments, etc.) who have been given credits and tell them those credits must be withdrawn because society is ready to go the next step to pollution- free waters. (quoted in Caton 2002)

The ability to respond to new scientific findings is a key part of the pre­cautionary principle, which requires that measures taken to avoid or mit­igate harm be provisional. This means they should be reviewed periodically so that consideration can be given to relevant new scientific information which may change the assessment of potential harm.