1. The Environmental Space Concept

"If 7 billion people were to consume as much energy and resources as we do in the West today we would need 10 worlds, not one, to satisfy all our needs"

- Gro Harlem Brundtland

1.1 Background

1.1.1 Definition of the concept

The term "environmental space" - or more precisely the Dutch milieugebruiks-ruimte (literally: "environmental utilisation space"), is commonly credited to J.B. Opschoor (1987), although Opschoor himself has pointed to an earlier source (Siebert 1982). In the words of Opschoor and F. Weterings (1994 a, b), the concept "reflects that at any given point in time, there are limits to the amount of environmental pressure that the Earth's ecosystems can handle without irreversible damage to these systems or to the life support processes that they enable". The services provided by the Earth's ecosystems, and for which there is a limited space, include both stocks (of renewable, semi-renewable and non-renewable resources) and sinks (i.e. capacities to absorb waste, pollution and encroachment).

The "society" for which the biosphere provides services is of course global. As defined by Weterings and Opschoor, environmental space similarly means the space available to humanity as a whole for utilisation of stocks and sinks. At least, this applies to stocks that are globally tradeable, and sinks that are global in extent. However, the same authors point out that the recognition of global limits forces us to face the issue of how environmental space is to be allocated between nations and regions.

Following its introduction by Opschoor, the concept of environmental space became the subject not only of considerable academic discussion, but also of political interest in his native country (Netherlands Council for the Environment 1994; Milieu 1994). The term gained much broader international currency with the publication in English of the Action Plan for a Sustainable Netherlands (Buitenkamp et al. 1993) by Friends of the Earth (FoE) Netherlands.

The Action Plan is an effort to actually quantify the amount of environmental space for some major resources, that will be available to each Dutchman in 2010. In so doing, the authors impart a new meaning to the term "environmental space" itself. It is used not only of the space available to all of humanity, but also of the share in this space that will accrue to the Netherlands (or to the average Dutchman), if the global space is to be distributed on what the authors regard as a fair basis.1

"Sustainable Netherlands" gave the cue to similar efforts in other countries, and most significantly to a study with a pan-European perspective, "Towards sustainable Europe" (Spangenberg 1994), carried out by the Wuppertal Institute in co-operation with Friends of the Earth Europe.

In "Towards Sustainable Europe" (TSE), environmental space is defined as "the quantity of energy, water, land, non-renewable raw materials and wood that we can use in a sustainable fashion". It is furthermore made clear that "sustain-ability", at least with respect to energy and materials resources, is intended to include global equity. In other words, we are exceeding our environmental space for these resources if our use-rates cannot be reconciled with ecological sustainability and equity. (The understanding of "equity" in TSE, as well as some alternative interpretations, are discussed in section 1.2 below. Suffice it for the moment to say that equity is not regarded as compatible with the present great North-South disparity in per capita access to resources).

The definition given in TSE thus departs from Opschoor's usage on at least two points. The first is that the distributive aspect is incorporated into the concept as such. The other is that environmental space is defined in terms of resources - Opschoor's "stocks" - only, i.e. of inputs to the human economy. Further, TSE introduces the notion of a minimum sustainable use-rate of resources, so that environmental space has a "floor" as well as a "ceiling".

In the present paper, "environmental space" will be used in a sense that accords fairly closely with the usage in TSE, namely: The maximum amounts of natural resources that we can use sustainably and without violating global equity. ("We" may, depending on the context, refer to the population of a country or of a group of countries, such as the EU).

However, the possible existence of minimum sustainable use-rates of natural resources will not be considered in this paper.

1.1.2 Why an input-oriented concept of environmental space?

Clearly, the concept of environmental space, as just defined, becomes of most immediate importance if we believe

  • that the present global use-rate of some resources at least is unsustainable, or
  • that the present share-out of some resources at least is inequitable, and that sustainability combined with equitable distribution will mean that some people at least must reduce their resource consumption.

Equally clearly, the evolution of the (resource-oriented) environmental space concept in the 1990's reflects growing concern on both scores. At first glance, this concern may appear to hark back to the formative years of the modern environmental movement - those which led up to the Stockholm Conference in 1972. The classic "Limits to Growth", published in the same year, saw the exhaustion of energy or mineral resources or the insufficiency of agricultural resources as likely causes of a global catastrophe in the next century - much more so than overpollution.

In the late 70s and early 80s, however, the question of resource consumption lost ground in the Northern public awareness to those of pollution and other forms of environmental disturb-ance. This was also reflected in political priorities as Departments of Environ-ment and the like were established: "cleaning up" - often at the end of the pipe - took precedence over reducing the level of inputs to the economy. To the extent that energy consumption was of major concern, this was as much on account of price increases and worries about short-term security of supply, as for ecological reasons.

The reasons for this shift of emphasis are complex and beyond the scope of this paper. However, it is fair to suggest that some of the more alarmist literature of a quarter-century ago may actually have contributed to it. The case for resource scarcity was often based on rather simplistic interpretations of fact.

The new focus on resource consumption in the nineties does not, however, simply mean that the debate over the human ecological predicament has come full circle. An upward spiral turn would definitely be a better image.

There are at least two important differences between the thinking that underlies the environmental space concept, and that which was common in the early 1970s.

The first is that we have moved beyond the static notions concerning resource limits. It is generally recognised that improved technology can increase the exploitable potential of most resources (geological, geophysical or biotic) and even on occasion "invent" entirely new resources. However, these possibilities are not infinite. The fact that some people in the 1970's mistook mineral reserves for ultimately exploitable resources, and falsely predicted the exhaustion of the latter within decades, does not mean that we can go on extracting any amounts of minerals forever. And the fact that 6 billion people today are eating, on average, slightly better than 4 billion were in the 1970's, does not necessarily mean that it will ever be physically possible to feed 10 billion an American diet. In fact, an increasing number of leading agronomists appear strongly to doubt it.

At the same time, there is a much greater awareness today that the environmental effects of exploiting resources set limits to the acceptable rate of exploitation, which may be more stringent than those which physical availability alone would impose. This applies both to energy (with impacts such as CO2 emissions and radioactive waste), to non-fuel minerals (destructive effects of extraction as well as processing and eventual disposal or dissipation) and to biotic resources (negative impacts of intensive agriculture and forestry on biodiversity, erosion, physical hydrology, CH4, N20 and NH3 emissions, nutrient loss to water etc.) Some of these effects are impossible to delink from the rate of resource exploitation, while in other cases this is possible only to a limited extent and with difficulty.

Now, if negative environmental effects (e.g. exceedance of sink capacities) are major reasons for limiting resource consumption, we may ask why environ-mental space should be defined in terms of resource consumption only. The first reason is that it simplifies matters. The major inputs to a modern economy, each of which is associated with a host of environmental problems, can be considered under relatively few headings. If indeed many of the environmental problems are difficult to delink from the rate of resource exploitation, or if reducing the latter is simply the surest and most cost-efficient way of reducing the former, then a concept which focuses on inputs is in itself cost-efficient.

The other reason is linked to the global equity aspect of the environmental space concept. Most sinks are in fact regional or local in extent (major exceptions being those for greenhouse gases, ozone depleting substances and persistent toxins which can be globally distributed through ocean waters or food chains). By contrast, most resources are globally tradeable. The disturbances to which their extraction, harnessing and/or processing give rise consume sink capacities where these processes take place, not (necessarily) where the resources are ultimately consumed. In other words, our consumption of sink capacities is largely mediated via our consumption of resources.

If we are to talk of a globally fair distribution of rights to put pressures on the environment, then we must begin by talking about the distribution of resource consumption.2

The second important point about the environmental space concept, compared to much previous thinking about resource limits, is - precisely - the emphasis it places on global equity. "Limits to Growth", for instance, skirted the issue of distribution entirely, and other major futures studies of the seventies assumed that a large consumption gap between North and South would persist for as long as it was worthwhile thinking about. Even the Brundtland Commission envisaged, in its favoured energy scenario, that the North after 40 years would still be consuming three times more per capita than the South.

By contrast, the environmental space concept, as defined above, involves the principle that access to resources should (as a rule with some unavoidable exceptions) be equitably shared among people in all countries. This is of course an ethical ideal, which will become a political and ecological reality only when people in the now-poor countries have the purchasing power to actually claim their fair share of environmental space.

However, there is much to suggest that it may not merely be just, but also wise to plan for such a situation within the first half of the next century. If, for instance, the countries of East Asia sustain their recent growth rates of around 10% p.a., the whole region will in one generation have about the same per capita GDP as the OECD today - and twice the population of the OECD and CEE countries taken together. It is difficult enough to imagine that one billion people might sustainably consume resources at the present European rate, but quite another thing to imagine that 10-12 billion may be doing so in 2050.

1.2 Quantification of environmental space - The example of "Towards Sustainable Europe"

It follows from the discussion above that the amount of environmental space for any given resource that is available to the citizens of a country or region, will depend on

  • the amount that one estimates can be sustainably exploited at the global level, if the resource is considered globally tradeable, or at some lower geographical level if not;
  • the understanding one has of "equity", and the particular consequences this may have for the country or region in question.

In this section, we shall first see how these two sets of problems have been addressed in the "Towards Sustainable Europe" study, and what conclusions it yields regarding environmental space for European countries. TSE is the most ambitious effort so far at roughly quantifying the environmental space for most major inputs to the European eco-nomy, and therefore a natural point of departure. Afterwards, we shall consider how the conclusions of that study might be modified through other possible approaches to questions (a) and (b).

1.2.1 Equity principles in "Towards Sustainable Europe"

The main premise in TSE is that a country's environmental space, or fair share in the resources which can be sustainably exploited globally, should be determined by its share in global population. There are, however, some important modifications.

The first is that changes in population shares after the year 2010 should not affect countries' environmental space. In other words, countries whose population goes on growing after that date will see their per capita environmental space decreas-ing, whereas it will remain constant in countries whose population is constant and increase if population declines.

Apart from this modification, TSE upholds the principle of equal per capita shares for all countries in the cases of energy and non-fuel minerals, which (with some qualifications in the case of renewable energy sources and low value-to-weight minerals) may be regarded as globally tradeable.

In the cases of timber and agricultural land, however, TSE defines environmental space on the basis of continental resources. The premise is that Europe should be self-sufficient, not in an absolute sense, but in the sense that the amount of land used in other continents to produce for export to Europe should not exceed the amount used in Europe to produce for others. On this point, the modification of the environmental space concept accords with the thinking behind the concept of the "ecological footprint" (Wackernagel 1993).

In TSE, water is for obvious reasons defined as a regional resource. It is impracticable (and can be ecologically undesirable) to transport very large quantities of it over very long distances. Therefore, people's environmental space for water use will depend on what can be sustainably extracted in the region or drainage basin they live in.

Similarly, the sustainable use-rate of land for construction and other non-agricultural purposes must be determined at a sub-continental level, depending inter alia on population density. However, TSE suggests an approximate guideline value for the EU as a whole.

TSE contains no explicit judgements on how environmental space should be distributed within countries, beyond the "floor" principle: that everyone's basic needs should be satisfied. The reason given for not discussing intra-national distribution is that people's judgements regarding distributive justice vary as between countries; therefore, these issues must be left to the political process within each country.

1.2.2 Limits to resource exploitation in "Towards Sustainable Europe"

To quantify the sustainable use-rate of resources, knowledge is needed both of their physical availability and the environmental effects of exploiting them. If precise and complete know-ledge is not available, estimates must be made.

In addition to scientific facts or estimates, however, such quantification must necessarily incorporate value judgements about the degree of environmental degradation or risk that we are willing to accept, and also about obligations towards future generations.

In TSE, the sustainable use-rate of major resources is estimated as follows:

Energy: The space for fossil fuel consumption is limited by the need to reduce CO2 emissions enough to avoid a global temperature increase of more than 0.1 degree per decade, or an ultimate increase of more than 2 degrees. Based on IPCC estimates, this means halving global emissions by 2050, to a per capita level 77% lower than the present European average. The reduction in fossil energy use could be slightly less, as indicated in Table 1 below, if some coal is replaced by gas. However, nuclear energy is ruled out as being associated with unacceptable risks. The availability of renewable energy is based on an assessment of European resources. In principle, solar energy could be globally traded as hydrogen or possibly super-conducted electricity.

However, the main constraint on solar energy development according to TSE is not absolute physical availability - be it at the European or the global level - but the amounts of materials required to construct solar energy systems.


The concept of "material input" (MI) is a conceptually radical way of simplifying the problem of material-resource consumption.

The concept reflects the idea that the sum of problems associated with materials consumption (physical disturb-ance, pollution through dissipation, waste disposal and so on) can be roughly related to the total amount of materials moved in the course of economic activity. If this amount can be reduced, then so will the overall impact of materials consumption. In other words, the assumption is that, in practice, shifts as between the kinds of materials moved are likely to mean less than changes in the total quantity.

Materials moved not only include those actually extracted with a view to making products out of them (e.g. limestone extrac-ted to make cement and then buildings, or bauxite extracted to make aluminium pro-ducts). They also include the earth or rock overburden that must be removed (albeit only a short distance) in order to get at the economically valuable material. Also, they include the economically worthless mate-rials that have to be moved in the course of construction activities, and materials unintentionally moved in the course of economic activity, e.g. by accelerated erosion.

Associated with the concept of MI is that of "rucksacks". The rucksack is the amount of "invisible" MI - moved materials - behind our consumption of a specific material, e.g. aluminium.

To make one ton of aluminium takes about 4.8 tons of bauxite. In order to extract one ton of bauxite, however, some 0.6 tons of topsoil must typically be removed. So far, this makes for a "rucksack" of (4.8 x 1.6) -1 = 6.8 tons of moved material per ton of aluminium. To make the aluminium, however, various other materials are also required as auxiliary inputs. The total "rucksack", counting these materials but not the materials moved to provide energy for the processes, has been estimated by at Wuppertal Institute researchers at some 8.6 tons per ton of aluminium.

Virgin steel has a smaller relative "rucksack" (requires less MI per ton), partly because iron ore grades are typically around 50-60%, so less ore is moved per ton of metal. Copper, on the other hand, has a very large "rucksack", because the average ore grade today is only 0.7%. Therefore, 140 tons of rock must be blasted to make one ton of copper.

Non-fuel minerals: TSE takes an unconventional approach to the question of non-renewable raw materials. The problem is not seen as one of limits to the amounts of specific raw materials that may be consumed. Instead, it is seen as one of limits to the aggregate "material input" to the economy, defined as the total amount of materials moved in the course of economic activity (see box). According to assessments by Prof. F. Schmidt-Bleek and co-workers at the Wuppertal Institute, the total material input to the world economy must be halved if the environmental impacts of movement, extraction, processing and dissipation of materials are to be reduced to acceptable levels.

Timber: It is a requirement in TSE that 10 per cent of total land area, and the same proportion of forest land, must be set aside for conservation. This is in accordance with IUCN recommendations, as the minimum necessary to preserve or re-establish natural eco-systems of sufficient diversity (IUCN 1991). In remaining forest areas, forestry must be based on endemic species, with natural regeneration and selective felling. This will limit annual increment. If the whole of the increment is harvested, it is estimated that annual yield in Europe will nevertheless be about equal to current production. At present, harvest is much less than increment in most countries in Europe.

Agricultural products: The availability of land for agriculture is limited by the requirement that 10% of total land area be set aside for nature conservation. Availability of agricultural products will be further limited by the requirement that agriculture should be on organic principles, and that there should be no net appropriation of foreign land to supply Europe. Calculations in TSE nevertheless suggest that it will be possible to provide Europeans with an acceptable diet from only 70% of the present agricultural land area. However, this presupposes a drastic two-thirds reduction in meat consumption.

Land for construction: The environ-mental space for built-up land is not analysed in detail and per region. As a first approximation, the space is assumed equal to present consumption (the size of which is itself uncertain in some countries).

Water: As a regional resource, per capita environmental space for water consumption will vary widely.

Marine resources are not explicitly discussed in the TSE study. However, it is quite clear that the environmental space for these is also limited and that, for many of them, current rates of exploitation already exceed the environ-mental space.

Table 1 shows the reductions in per capita resource consumption that will be required for compliance with environ-mental space in the EU, according to TSE. The study suggests that these goals should be reached by the year 2050. The table also shows goals for the year 2010, by which year TSE suggests as a main rule that 25% of the necessary reductions should be achieved. Exceptions are nuclear energy (to be phased out by 2010) and targets for land use, which should also be achieved faster.

Table 1: Per capita environmental space for major resources in the EU and required reductions in consumption from 1990 levels, according to "Towards Sustainable Europe"

Resource Environmental space per capita (2050) Reduction required from 1990 Suggested reduction goal for 2010
Total primary energy 60 GJ/a 50% 12.5%
-fossil energy 25 GJ/a 75% 19%
-nuclear energy 0 100% 100%
Timber* 0.56 m3/a 15% 4%
Cement 80 kg/a 85% 21%
Iron 36 kg/a 87% 22%
Aluminium 1.2 kg/a 90% 22.5%
Copper 0.75 kg/a 88% 22%
Lead 0.39 kg/a 83% 21%
Chlorine** 0 100%
N, P, K fertilizer** 0 100%
Built-up land 0.0513 ha 3.2% 3.2%
Agricultural land*** 0.281 ha 30% 30%
"Imported" land (net) 0 100% 50%

* Based on self-sufficiency in Western and Central Europe. Environmental space increases to 1.0 m3/a if the resource base is extended to include the European part of the former Soviet Union.
** Based on the premise that the use of chlorine and chemical fertilizers is to be phased out. Sustainable Europe also gives other figures based on resource limitations only.
***Estimated amount required to cover nutritional requirements with organic agriculture. If agricultural area were limited only by the requirement that 10% should be set aside for conservation, availability would be 0.36 ha/capita.

Source: Spangenberg 1994.

1.2.3 Discussion

"Towards Sustainable Europe" represents one approach to the quantification of environmental space, and so far the internationally most prominent one. This attempt clearly rests on a number of judgements and assumptions which can be contested. The question is not whether other approaches are possible, but whether other at least equally reasonable approaches might yield very different results.

Let us first consider the question of inter-national equity. A copious literature already exists, if not exactly on the subject of equity in access to all natural resources, then certainly on rights to GHG emissions, which are closely linked to fossil energy consumption. The main ethical viewpoints advanced in this debate may be transferable to consumption of other resources as well.

The simplest possible viewpoint is that equitable distribution is the same as equal per capita distribution. Important modifications to this principle that have been proposed in the GHG debate are :

  1. That national quotas should be distributed on a "once-off" basis, taking no account of differences in population growth after they have been distributed;
  2. That national quotas should be adjusted to compensate for historical emissions (e.g. Agarwal and Narain 1991);
  3. That quotas should take account of natural conditions which affect objective "needs" for fossil energy (such as climate, population density or availability of renewable energy sources) (e.g. Benestad 1994).

The first modification is adopted by TSE in the cases of energy resources and non-renewable raw materials. Its ethical justification rests on the idea that the citizens of states can be held collectively responsible for their reproductive behaviour. The obvious counter-argument is that yet unborn children can neither be held responsible for their place of birth, nor for the reproductive behaviour of their own or their neighbours' parents.

If one assumes that world population will grow to 10-11 billion by 2050 - in accordance with UN mid-range estimates - and also holds that environmental space should at all times be distributed on the basis of current population, then per capita availability of global resources, in Europe as elsewhere, will be reduced by one-third from the figures one arrives at by applying the principles in TSE.

The idea that rights to (non-renewable) resources should be adjusted to take account of countries' historical consumption, may also be read as "visiting the sins of the fathers upon the sons". In this case, however, it is possible to argue that countries which have consumed large amounts of resources in the past have not only gained an economic head start by doing so, but also built up physical stocks of recyclable materials, including in-place infrastructure. Allowing less developed countries greater per capita rights to virgin raw materials and/or fossil energy, may therefore be seen as a compensatory mechanism. However, it would obviously not be easy to decide the appropriate rates of compensation. What is certain, is that any scheme of "historical compensation" would allow Europeans less and not more environmental space.

The idea that differences in natural conditions create different objective needs for particular resources is most obviously relevant to energy. It has been discussed elsewhere by the author (Hille 1995) with specific reference to Norway, a country which on several counts (climate, topography, population density) might appear at first glance to have greater energy needs - for heating as well as transport - than most others. The conclusion, however, is that while objective differences do exist, they are minor in relation to total energy consumption in a modern industrial society. If this is true of the relationship between world-average conditions and those of an "extreme case" such as Norway, then it is all the more likely to be true of the relationship between world-average and European-average conditions.

So far, the suggestion is that applying alternative principles of equity would, if anything, give Europeans less environ-mental space than suggested in TSE.

With regard to agricultural land and timber, TSE departs from the principle of global equity, giving priority to that of continental self-sufficiency. In the case of agricultural land, this has very important consequences. At present Europe (including European Russia, Belarus and Ukraine) has some 0.4 hectares of agricultural land per capita, compared to a global average of only 0.24. Excluding the three countries mentioned, Europe has only 0.27 ha/cap., but these are, on average, more productive than the world average. By 2050, Europe (broadly defined) is likely to have almost three times more arable land per capita than the world average. (Given a world population of 10 billion, and assuming that 10% of presently cultivated area is to be set aside for conservation, while losses to built-up land will be roughly balanced by new cultivation, global per capita availability of arable land in 2050 will be only 0.13 ha.)

In other words, continental self-sufficiency means allowing Europeans a very much better diet than Africans or Asians. Conversely, an equitable global share-out of agricultural resources would put Europe in the position of a net exporter, with much less meat left on the table for home consumption.

With regard to timber, it is a moot point whether a global share-out would leave Europeans with more or less per head than would self-sufficiency. On a global average, annual gross increment in presently standing forests (uncertainly estimated at 7-8 bn m3 ) is probably slightly higher per head of population than it is in Europe. However, this relationship is likely to be reversed by 2050. With more intensive management of tropical forests and some allowance for plantation forestry, global-average per capita timber yield could still be somewhat greater than the European. To what extent logging of presently virgin tropical forests and/or short-rotation plantations can be made sustainable in the long term, however, are still matters open to debate.

Alternative interpretations of equity, then, could make environmental space for some or all resources in Europe significantly smaller than TSE suggests; none of those mentioned would make it much larger.

The other set of questions that may be raised, concern the global (or continental) limits to resource exploitation. Space does not permit anything like a thorough discussion of all the data and judgements underlying the conclusions on these limits in TSE, only a few comments on major points.

Global space for energy. The view taken of fossil fuels in TSE is only moderately "precautionary", in that the study accepts consumption levels which are likely to lead to global warming by 0.1 degree per decade, and could lead to more rapid warming. To increase the space for fossil fuels significantly through the second half of next century, however, we would in fact have to accept much greater environmental risks than this. At present rates of world consumption (never mind present European per capita rates!) oil and gas resources would be largely exhausted by 2100. If the world's population were to go on consuming fossil fuels at much more than the rate suggested in TSE, it would by that time be relying heavily on coal. Unless we are willing to face such a scenario, the only possible question is whether the reduction in fossil fuel consumption that TSE advocates should be advanced, or could be delayed, by some decades.

By contrast, the view TSE takes of nuclear energy is strongly precautionary, and a straight matter of judgement about acceptable risks. Some EU countries concur with this judgement as a matter of policy; others do not.

The area in which differences in purely scientific opinion could make a substantial difference to the sums, is that of renewable energy. If one compares avail-able estimates of the potentials of renewable energy sources at the global level, it seems probable that they would suffice to provide a population of not just 7, but even 10 billion with the 35 GJ/capita that TSE suggests for Europe.

This is true even after one applies substantial reduction factors on account of the negative environmental effects of utilising these energy sources. The question remains of whether we might achieve significantly more - the main "joker" in the picture being solar energy, whose purely theoretical potential is vastly greater than that of all other renewable sources combined.

Table 2. Some estimates of potential availability of renewable energy in the 21st century

Source Global renewable energy potential*


Greenpeace/Stockholm Environment Institute (Lazarus et al. 1993) 239 (2030)

987 (2100)

Worldwatch Institute

(Flavin and Lenssen 1994)

c. 300 (2050)**

c. 500 (2100)**

van Ettinger (1994) 248 (2050)
IPCC (Biomass- intensive LESS scenario, 1995) c. 300 (2050)** c. 600 (2100)**
Shell Oil ("Sustained growth"scenario, 1995) c. 1000 (2060)**

* None of the estimates pretend to represent the absolute technical potential of renewable energy sources; in general, both environmental and economic limitations have been taken into account. However, the nature, strength and relative weight given to requirements for profitability and for environmental compatibility vary considerably between the sources.
** Figures are approximate because the sources present estimates in diagram form only.

As TSE points out, the long-term physical constraint on solar energy utilisation will be the amounts of materials required to construct the systems. Any conclusions on this point therefore depend on one's view of the sustainable use-rate of materials (below). But they also depend on the extent to which one believes that future technolo-gies will be able to improve the efficiency of materials utilisation in solar-energy conversion. Because the technologies are still young and strongly evolving, the plausible range of conjecture about what will be achieved in the next 50 years is broad. However, it is also worth noting that if renewable energy is to substitute entirely for fossil fuels (as it ultimately must), then we shall need not 35, but 60 GJ each from these sources to fill the overall energy "allowance" of TSE. This would mean 600 EJ annually for a global population of 10 billion, which is already in the optimistic part of the range of estimated potentials, cf. Table 2; and to provide everyone with the present European per capita consumption, 1200 EJ would be needed.

Global space for materials. TSE makes two basic and controversial assumptions about the environmental space for non-renewable materials. The first is that it is relevant to consider all humanly induced movement of materials ("material input") under one heading - and, by implication, that the size of this aggregate (in tons) is likely to be roughly correlated with the overall ecological impacts. The other is that the permissible global level of MI is 0.5 (rather than 0.1, or 1, or 5) times the present (1990) level.

One possible objection to the MI approach is obviously that not all movement of materials has equal ecological impact. The movement of one ton of common soil or rock in connection with construction activity is not the same as the movement of one ton of an ore with a high sulphur and heavy metal content, capable of polluting water and atmosphere. Nor is the extraction of one ton of mercury ore, combined with the use and eventual dissipation of the mercury, necessarily equivalent to the extraction of one ton of iron ore, combined with use and dissipation of the iron content.

TSE makes some allowance for this by presenting the 50% global reduction of material input as a minimum require-ment, which will need to be supple-mented by a "systematic detoxifi-cation of production", i.e. greater reductions in forms of MI that involve especially serious pollution or health risks. If indeed some kinds of MI need to be reduced more than others, however, the question remains of whether one ought not to specify a separate environmental space for each.

It is also important to note that MI is an entirely flow-based concept, taking no account of the scarcity of non-renewable materials. In this, TSE differs from the approach taken by Weterings and Opschoor (1994 b) and also from the "Action Plan for a Sustainable Netherlands". A main reason why TSE avoids incorporating stock depletion as a factor limiting environmental space, is that this is regarded as an economic, rather than a strictly environmental problem.

However, the depletion of non-renewable resources is certainly a potential sustainability problem, and thus falls within our (and TSE's) initial definition of environmental space. If one does choose to take account of scarcity in quantifying environmental space, then clearly this may lead to the conclusion that environmental space for some resources is less than environmental considerations alone would dictate. The reverse does not apply (if the flow of a resource needs to be limited on environmental grounds, abundant stocks will not alter the fact).

In practice, stock-depletion considera-tions would be little likely to affect the environmental space for geochemically abundant metals, such as iron and aluminium. On the other hand, their environmental effects are certainly severe enough to warrant reductions in consumption. For instance, Wuppertal institute researchers estimate that tailings from iron ore mining alone release as much sulphur dioxide into the atmosphere as all combustion of fossil fuels.

Most other metals are geochemically scarce, which means that there are quite clear limits to the amounts present in ore mineral form in the Earth's upper crust, and that these would in most cases be exhausted in centuries or a few millenia at current rates of extraction.

For these metals, a case could certainly be made that extraction should be restricted on the grounds of scarcity. On the environmental side, many scarce metals are toxic in themselves. Coupled with the fact that, as elements, they are non-degradeable, this is a strong argument for approaching closed-loop recycling, i.e. minimising new input and throughput.

Many non-metal minerals occur only in surficial deposits which would also be exhausted in centuries at current rates of extraction. Some of these are being regenerated under present geophysical conditions - usually at rates well below those of current extraction - while others are not. Where they are, one might suggest that the sustainable use-rate at most equals the rate of regeneration. Where they are not, a similar problem arises as in the case of scarce metals - though with the added complication that most non-metal minerals are difficult or impossible to recycle.

As in the case of metals, the purely environmental case for reducing throughput of non-metal minerals in the global economy is strong. For instance, three of the four minerals that are used in highest volume (excepting aggregates) are limestone, phosphate rock and common salt. The first is used to make cement and lime, which inevitably leads to large CO2 emissions; all major uses of the second contribute to eutrophication; and the most important uses of the third include deicing and chlorine production, both of which entail severe environ-mental problems.

In short, there is a lot to support the postulate in TSE that overall consumption of non-renewable raw materials at the global level should be reduced, be it by 50% or more or less. A more refined approach, whereby environ-mental space is defined separately for individual (classes of) materials, taking account of their specific toxicity and/or scarcity, may be desirable.

However, this would not alter the directional con-clusion. Rather, it would raise the possibility that the ceiling on consump-tion of some materials should be set at considerably less than half the current rate.

Environmental space for land use. TSE proposes three main kinds of limits to the use-"rate" of land for economic purposes: that 10% should be set aside for conservation, that built-up area (in Europe) should be frozen, and that agricultural as well as forest land should be subject to certain management practices.

The requirements concerning the percentage of land which should be set aside for conservation and the limits to built-up land will not be discussed further here. Clearly, it would be possible to argue for higher or lower figures in each case (meaning, in the case of built-up land, that one could opine that there is too much of it already - be it from the point of view of landscape aesthetics, biodiversity or conservation of agricultural resources).

The requirement that agriculture should be "organic" raises more problems of definition and principle. In the popular conception, organic agriculture is negatively defined: no pesticides, no chemical fertilisers. This is most obviously a pair of restrictions on materials consumption, rather than on the use of land as an input.

However, agriculture does in fact consume land in two senses or dimen-sions. It consumes land-in-depth, i.e. soil, by accelerating erosion; and it consumes land area, or land-scape, by converting it into (increasingly homo-genised) cropland or pasture. TSE would limit the latter kind of land consumption by putting 10% of land area altogether out of bounds for agriculture (and the latter by retiring "severely degraded" land from produc-tion, which is a very small fraction of land in Europe). However, there are strong grounds for also limiting the degree to which the remaining agricultural landscape may be "monocultured"; that is, for preserving or re-establishing such features as hedgerows, shelterbelts, open water-courses and other natural boundaries between fields, as well as for more diversified crop rotations and the (re-)integration of cropping and animal hubandry. A claim could be made that agriculture is exceeding its environmental space, if either the rate of ero-sion exceeds that of soil formation, or the landscape is homogenised beyond a certain point.

Many practitioners of organic farming would concur that considerations such as these are as much a part of the concept as the avoidance of chemical fertilisers and pesticides. Practitioners of so-called "integrated" farming might claim that limited use of fertilisers and pesticides, combined with other measures to conserve soil, landscape and biodiversity, is getting closer to sustainability than 100% avoidance of the former and nothing of the latter.

- Defining environmental space for land use in their terms might make food availability somewhat larger than if the requirement is 100% organic agriculture as conventionally defined. On the other hand, one should note that TSE makes an optimistic estimate of food availability from organic agriculture; while quoting research that suggests it will reduce yields by 10-30% from current levels, the study uses the minimum figure (10%) as a basis for calculations3. So a slightly more "liberal" definition of the environmental space for exploitation of agricultural land, might not lead to very different conclusions regarding food availability from those drawn in TSE.

1.2.4 Quantification of environmental space - concluding remarks

Environmental space is a young concept. "Towards Sustainable Europe" is the first systematic effort to quantify it at the European level. It is quite possible to contest the conclusions of TSE on the grounds that other principles of equity should have been applied; that there is a need to differentiate more between categories of resources; and/or that the estimates of sustainable availability for some resources are off the mark. In this author's view, alternative approaches, if motivated by a genuine concern for sustainability, would be at least as likely to make the environmental space for most resources smaller than TSE suggests, as to make it larger.

The point of departure for the remainder of this paper is therefore that the level of inputs to the European econonomy, including both energy, materials and land, must be significantly reduced. Reference will sometimes be made to the reductions proposed in "Towards Sustainable Europe". As the reader will have gathered, this does not mean that the study should be regarded as the last word on quantification of environmental space, but that its conclusions may be indicative of the order of magnitude of necessary reductions in resource con-sumption (which is all they claim to be).

1.3 Environmental space, efficiency and economic growth

The environmental space concept as such implies no judgements about the possibilities for continued growth in the GDP in now-rich countries. The message for Europe is simply that the levels of inputs to the economy must be reduced, in some cases drastically so. If it is possible to increase GDP while staying within these limits - which according to "Towards Sustainable Europe" means reducing energy intensity by a factor of more than 50%, the intensity of many primary materials by more than 90%, and delinking growth entirely from the expansion of built-up area - then such growth may be sustainable.

Achieving sustainable growth, however, presents a formidable challenge at best. Although materials as well as energy efficiency has in fact improved greatly in the EU in the past quarter-century, this has not been sufficient, at average GDP growth rates of just over 2%, to prevent an absolute increase in consumption of many resources. Since 1970, energy consumption in Western Europe has increased by 40%. Although steel consumption has stabilised or even declined slightly, copper consumption has grown by 20% and aluminium consumption by over 100%. Many industrial minerals have also shown strong growth rates. And the extent of built-up land in some countries has virtually doubled.

The corollary is that we must either drastically increase the rate of improvement in the resource efficiency of the economy, or reduce or even stop growth in final consumption of goods and services. ("Resource efficiency" is a function both of technology and of the mix of goods and services that are consumed).

The size of the challenge may also be expressed in these terms: If we need to reduce consumption of virgin raw materials by 90 per cent, then at constant rates of final consumption, this means increasing the efficiency with which they are used by a factor of 10. At 2% annual growth, however, we would need to improve efficiency by a factor of 80 by the end of next century; and at 3% annual growth, by a factor of 200!

However, it is important to note that there are ways of getting more welfare out of a given level as well as mix of consumption (or the same welfare out of less consumption, of goods in particular). This can be done, for example, by increasing the lifetime of goods or by more people's sharing goods which are otherwise used for only a few hours per day, week or year. To take account of such possibilities, it has been suggested that consumption of goods should be measured in terms of "service units", i.e. the amount of utility or want satisfaction they actually provide, rather than simply in terms of money (Bringezu 1994a).

1.4 Implications for policy-making and reporting

Taken seriously, it is clear that a commitment to observe environmental space must affect policy-making at all institutional levels (EU, national, regional, local) and in all sectors, though in some more than others.

Besides authorities with general responsibility for environment (at the EU level: DG XI), both the EU (DG XVII) and most national governments have ministries and/or agencies with special responsibility for energy policy. Land use strongly involves authorities responsible for agriculture and forestry (EU: DG VI). Also, local authorities in most countries have an important statutory role in land-use planning. By contrast, neither the EU nor many national governments have created authorities with particular responsibility for management (as opposed to extraction) of materials resources. Waste management (at the national or local level) is only a partial exception.

While the creation of authorities with special responsibility for resource policy, or the empowerment and "rebriefing" of existing ones, may be a necessary step on the way to policy-making for sustainability, it will not be enough. Others needing to be involved include the authorities responsible for economic sectors that create pressures on environ-mental space (including transport, industry, construction, tourism and once again agriculture). Equally important will be those responsible for cross-sectoral instruments, including finance, science and technology and consumer policy. Since it is very probable that neither technology alone, nor such changes in the pattern of consumption as may be induced by financial or other (dis)incentives, will be enough to bring the economy within its environmental space, the question may arise of restructuring the economy to cope with less or no overall growth. This of course involves macroeconomics policy-making at the highest level and questions such as employment, with shorter working hours and changes in the organisation of work being possible parts of the solution.

Just as the observance of environmental space has wide-ranging implications for policy-making, a wide range of indicators will be required to measure progress in the various fields and a wide range of planning tools adapted to give better guidance as to which options are more sustainable.

This paper discusses a selection only of these issues. Chapter 2 discusses implications for policy-making within two sectors, namely transport and agriculture. Chapter 3 concerns implications for what is currently termed environmental reporting (but should perhaps be called sustainability reporting) at the EU and national levels. Finally, Chapter 4 discusses the implications of the environmental space concept for environmental assessments.

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1: This author has suggested elsewhere (Hille 1995) that ambiguity might be avoided by using the term "environmental share" for the fraction of environmental space accruing to a nation, region or individual. However, the present paper follows the more widespread usage whereby "environmental space" may refer either to the whole or the part.
2: A similar point is made by Weterings and Opschoor (1994 c): "...a country's performance in terms of sustainability depends on the environmental pressure it generates through what is consumed, irrespective of where the environmental impacts occur, and hence access should be established on the basis of consumption rather than production".
3: This optimism is motivated by the view that a reorientation of plant breeding, towards the development of varieties suited to organic agriculture, would be likely to improve "organic" yields. (Joachim Spangenberg, personal communication).



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