Purposive interventions into life processes (PILs)

Purposive interventions in natural ecosystems are historically the oldest form of modification of the environment for economic purposes. They characterize the beginnings of agriculture and animal breeding. This exchange with the environment is quite different from simple "input" - for example, the intake of plants or meat as nutrition and it is specifically human, at least as specifically as the use of tools.

There are many indications that PILs will gain even more importance in the future. As Moscovici (1990) and Oechsle (1988) state, emissions are a typical problem caused by a `'mechanical" mode of economic production (and a corresponding mechanical paradigm of nature). The necessity of reducing emissions is now broadly accepted, and in the long run their importance will certainly diminish in relative terms. On the other hand, a new, "cybernetic" mode of economic production (and paradigm of nature) is arising, which is characterized by qualitatively new and enhanced possibilities of human control over nature.

There are many examples of this new tendency. The application of analytical-chemical methods yields new possibilities for directing and utilizing natural processes in order to meet human demands (Korab, 1991); new biological technologies are developing rapidly and are being strongly promoted - not least because it is hoped that they will lead to "clean technologies." This tendency can be described as replacing EMIs with PILs, for example, by using biological instead of chemical techniques (Fischer-Kowalski et al., 1991b).

Module of indicators

We developed the following module of indicators in order to mirror relevant processes by which the socio-economic system intervenes in life processes in favour of particular social uses (Fischer-Kowalski et al., 1991a; Haberl, 1991; Wenzl and Zangerl-Weisz, 1991):

1. Interventions into biotopes. Indicators for socio-economic efforts to change the structure of natural ecosystems. The most important efforts of this kind are interventions in water systems, the appropriation of photosynthetically fixed energy (see below), and the input of technically produced substances (fertilizers, pesticides).

2. Violence towards animals. Indicators for social activities that cause suffering and pain to animals. This subset contains two indicators, one for the circumstances in which animals are kept (long-term aspect), and one for short-term aspects: the killing of animals and animal experiments.

3. Interventions in evolution. Indicators for direct (genetic engineering) and indirect (breeding techniques) influences on the gene pool (see Wenzl and Zangerl-Weisz, 1991).

This systematization is based upon the different biological hierarchical levels on which these interventions take place (fig. 6).

Interventions in biotopes: An empirical example

Energy is the "motor" not only for industrial metabolism, but also for natural systems. Ecosystems can be conceptualized as compartment models, in which (more or less closed) materials circles between the compartments are driven by a flow of energy. In fact, the development of ecology as a theoretically integrated discipline in the natural sciences began with the investigation of energy flows by Eugene P. and Howard T. Odum (see Odum, 1983, 1991).

Fig. 6 PlLs according to the level of intervention (Source: Fischer-Kowalski et al., 1991b)

Today, the following concept - described in rather simplified terms - is broadly accepted: Green plants convert the radiant energy of the sun into chemical energy by the process of photosynthesis. The accumulated energy the net primary production (NPP) - is available to all other (heterotrophic) organisms. Consequently, "photosynthetically fixed energy ultimately supports the great diversity of species that inhabit the world's ecosystems" (Wright, 1990).

NPP is the photosynthetically fixed energy accumulated by green plants in a certain period of time (usually one year). It is an important figure for several reasons. First, empirical studies show that "energy flow can be related to numbers of species with species-energy curves" (Wright, 1990). This means that if the amount of energy remaining in the ecosystem is reduced, the number of species living in this ecosystem will diminish (see figure 7). Secondly, there are limits to the fraction of NPP which can be used in a sustainable manner. The human appropriation of NPP is currently estimated at between 20 and 40 per cent of the total terrestrial NPP (Wright, 1990; Max-Neef, 1991). Even if it is not clear at which percentage of human appropriation of NPP the limits of sustainability are reached, the current amount is already considerable, and obviously cannot be increased without further speeding up the extinction of many other species.

Fig. 7 The relationship between number of species and energy flow in biotopes

We therefore propose to use the appropriation of NPP by the socioeconomic system as one of three indicators for purposeful interventions in biotopes (Haberl, 1991). The indicator is formulated as the difference between the hypothetical NPP of the undisturbed ecosystem and the actual NPP.

What does this mean? The hypothetical NPPh (per space unit and year) depends upon morphological and climatic circumstances. Under Austrian conditions it may vary from about 5 TJ/km² in alpine grasslands to 50TJ/km² in flood plains. If man did not intervene, this biological energetic basis would be available to all other species. The socio-economic system may intervene in qualitatively different forms, but they boil down to two strategies: (a) the building of structures (such as highways or buildings) that prevent or drastically reduce the NPP in a certain area (the same road prevents a certain NPPh each year by its very existence); (b) consumption, in that certain amounts of NPP are harvested (or grazed off by cattle) and serve as inputs to the socio-economic system, thereby being no longer available to the ecosystem. What is shown in table 3 as NPPa appropriated by the socio-economic system is therefore the sum of "prevented" NPP and "consumed" NPP.

Table 3 Appropriation of net primary production in Austria, 1988: first estimation

Socio-economic ses	Area concerned (km²)	Photosynthetically fixed energy
		Hypothetical, NPPb(PJ/a)	Appropriated by man, NPPa (PJ/a)	Distribution of approp. NPP (%)
Agricultureb	15,900	370	250	40.4
Grassland, alpine pastures
	21,000	280	180	29.0
Forests (logging)	34,300	580	110	17.7
Gardens	1,700	40	20	3.2
Traffic zones	1,600	40	40	6.5
Buildings	700	20	20	3.2
Other	8,000	40	0	0.0
Total	83,200	1.370	620	100.0

Sources: Bundesamt fur Eich- und Vermessungswesen, 1989; BMLF, 1989a; BMLF' 1989b; ÖSTAT, 1990; own calculations.

a. First estimates based on international literature.

b. Including wine.

c. Including waters and wasteland.

The hypothetical NPP on Austrian territory is estimated to be around 1370 PJ/yr. Thus the socio-economic appropriation of the products of photosynthesis in Austria (620 PJ/yr) amounts to about 45 per cent of the total production.

This means that the socio-economic system produces and reproduces environmental structures that leave more than half of the current photosynthetically fixed energy for all other species apart from human beings. This certainly is highly relevant from the viewpoint of both the natural balances paradigm and the conviviality paradigm.