Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Restoration ecology wikipedia , lookup
Biogeography wikipedia , lookup
Biological Dynamics of Forest Fragments Project wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Habitat conservation wikipedia , lookup
Overexploitation wikipedia , lookup
Sustainable agriculture wikipedia , lookup
Reconciliation ecology wikipedia , lookup
Human impact on the nitrogen cycle wikipedia , lookup
Helmut Haberl Human Appropriation of Net Primary Production as An Environmentallndicator: The human appropriation of net primary production (NPP) significantly alters the energy flow of ecosystems. The NPP-appropriation, defined as the difference between the NPP of the hypothetical undisturbed vegetation and the amount of biomass currently available in ecological cycles, is investigated for the 99 political districts of Austria (1990). Calculations are based on data for land-use, forestry, yield, and climate. Total aboveground NPP of the actual vegetation was found to be 7% less than that of the potential natural vegetation. Additionally, 34% of potential production is harvested, resulting in a total reduction of ecologically available aboveground NPP of 41%. SinGethis could have significant ecological effects, e.g. on biodiversity, it is of potential interest for strategies of sustainable development, indicators for stresses on the environment, and the environmental effects of increased utilization of biomass. This article relies on a spatially highly resolved study on the societal NPP appropriation in Austria. Austria is an industrialized country with medium population density (area 83 000 km2, population 7.8 million). Forests cover about 45% of its area. This is a rather high percentage for Central European standards due to the mountainous landscape. MATERIALS AND METHODS In this article, NPP appropriation is defmed as the difference between the NPP of the potential natural vegetation (NPPo, i.e. the vegetation that would prevail if human interference were absent) and the amount of biomass currently available in ecological cycles (NPPJ. Two processes contribute to NPP appropriation (NPP.): i) changes in the averageproductivity (NPP per unit area and year) of ecosystems, e.g. the construction of a road in a forested ecosystem; and ii) harvest. 1f the NPP of the actual veg- etationis denotedas NPPact and harvestas NPPh,total NPP appropriation can be calculated with the formula: NPP. = NPPo - NPP, withNPP, INTRODUCTION The production of biomass by green plants is the main energetic basis of lire on earth and provides the primary input für most food chains of all types (herbivory, carnivory, detritivory). While hunters and gatherers dwelled upon the products of photosynthesis much like any other kind of animal species, thus, reaching only very small densities, the cultural evolution of humanity has seena tremendous intensification ofbiomass use (1). This could only be achieved by a transformation of natural ecosystems into managed Olles with an increasing number of ecosystem variables hefig controlled. While agriculture allowed the harvest of more biomass per unit area, it did not generally increase the average productivity in terms of total energy or carbon fIXation. Additionally, ever-increasing areas are used für the construction of buildings, loads, etc. and thus their primary productivity is reduced. While ecologists were concerned about the possible ex.haustion of the world's biomass resources already very early (2), it was the seminal paper of Vitousek et al. (3) that opened the dOOf für a broader discussion of the problem. In the meantime, it is estimated that the human appropriation of the products of photosynthesis amounts to between 25 and 39% of the global terrestrial net primary production (NPP) (3, 4). This result inspired Meadows et al. to worry about the possible consequencesof the human world biomass use, which can be expected as a result of the projected doubling of the world population and economy within the next 20 or 30 years (5) and was broadly noticed in the discussion on sustainable development (6, 7). This discussion revealed that NPP is an important limiting resource für the future development of humanity and current levels of NPP appropriation already appeal to be considerable (3). Moreover, current strategies of sustainable development in the energy sector partly rely on the substitution of fossil fuels by biomass in order to reduce CO2 emissions-a strategy that would further increase NPP-appropriation. Ambio Vol. 26 No. 3, May 1997 = NPPact- NPPh All calculations were perfonned on the spatiallevel of communities (Austria consists of approximately 2350 communities). Since there are few reliable data on the subterraneanprimary production of forest ecosystem~(it was significantly underestimated in previous research (8-10)), this article focuses on aboveground net primary production (ANPP) which can be assessed with greater accuracy. (see Haberl (11) für an in-depth description of all applied methods). The ANPP of the potential natural vegetation in Austria was estimated with two independent methods: i) The average productivity of different types of natural vegetation was assessed on the basis of the literature available (11), applying regression analyses on the relation between mean annual temperature, precipitation and net productivity in forest ecosystems using data compi1ed by Cannel (12) and the climate data of Walter and Lieth (13); ii) The so-called Miami modell ofLieth (14) was used with a correction für Lieth's assumption on subterranean NPP. Data on mean annual precipitation and lang-tenn temperature averages were obtained from the Austrian association of meteorology (15) and modified to reflect elevation. The area of each community was distributed over six elevation classes (less than 600 m, 600-1300 m, 1300-1700 m, 1700-2200 m, 2200-2600 m, more than 2600 m) assessedby a geographic infonnation system (Loibl, pers. comm.) which served to detennine the potential natural vegetation. The data used für the calculation of ANPPoand ANPPact in natural ecosystems(and actual forests, as described below) are given in Table 1. The productivity of the actual vegetation was calculated by using land-use data as assessedby the Austrian Central Statistical Office (16). The productivity of agricultural areas (crops and meadows) was estimated by using harvest factors of the fonn NPP = H x F, where H is the commercial harvest and F an appropriate factor für total or aboveground productivity. Harvest @RoyalSwedishAcademyofSciences1997 143 factors were taken from the literature (14, 17-20).The productivityof grazingland was I calculated from averageproductivity estimates,dependingon elevation,basedon the literature. The productivity of forests was: j estimatedby two independentmethods,fIrSt' by harvestfactors from the literature (11), usingthe Austrianforestinventory(21), and secondby assumingthe averageproductivity by forest type, modified by elevation class(Table 1). Harvestwascalculatedfrom Austrian agricultural and forestry statistics(22, 23). Subterraneanparts of cropslike potatoes(about 1% of total harvest)were countedas "above-ground".Agricultura1biomasswasconvertedto dry mass and calorific value using standardtables on nutritive value of the materialsunderconsideration(24, 25), wood was treatedin the samewar on the basisof tableson species-specific dry-matter contentand calorific value. RESULTS Both calculation methods für the ANPPo of the hypothetical undisturbed vegetation of Austria led to almost the same result. While Lieth's Miami model predicts the ANPP to be 1445 PI yr-1 (74 mill. t yr-l dry matter, DM), the assumption of average productivities dependent on elevation gave an estimate of 1501 PI yr-1 (77.6 mill. t yr-1 DM). Since Lieth's model is based on rather old productivity data which tended to underestimate productivity (26), the higher value is believed to be more reliahle and taken as a reference point. The average productivity of the Austrian vegetation is 0.93 kg m-2 yr-1 or 17.9 MI m-2 yr-l. Human activities, above all agriculture and construction, have significantly lowered the productivity of the vegetation in Austria. ANPPaclwas estimated to be 1396 PI yr-1 which is 105 PI yr-1 (7.6%) lower than the ANPPo. In terms of dry matter, the difference is smaller (ANPP acl= 74.2 mill. t yr-1 DM), since the calorific value of forest biomass is higher than that of most cultivated herbaceous plants. About 50 PI yr-1 of this reduction is due to construction. The difference between the two independent methods used to estimate primary production of forests (elevation classes and forest inventory) was only about 2%, with forest inventories giving a slightly higher value. The value reported above is based on elevation classes. It should be mentioned that these estimates are conservative, since the statistical data on land-use für construction are believed to be lower than actual values and many of the underlying assumptions (11) were made with great caution to avoid a possible overestimation of NPP appropriation. Together with a straightforward estimation of harvest (512 PI yr-1 or 27.6 mill. t yr-1 DM) ANPP appropriation (ANPP.) can be assessedto amount to 617 PI yr-1 or 41.1 % of potential aboveground production in Austria (Fig. 1). My tentative calculations on total NPP and its appropriation show that the difference betweenNPPoand NPPact should be much higher than that für aboveground NPP, because the belowground productivity of forests is considerably higher than that of annual crops; even in cases where aboveground productivity is similar or crops are more productive. Total NPP appropriation, however, is smal1er,since mainly aboveground biomass is harvested. As these results are rather uncertain, they will not be discussed hefe in detail (11). As Figure 2 shows, there is more NPP appropriation in districts with high ANPPo than in districts with low ANPPo. Obviously, fertile regions are more intensively cultivated and a higher share of their net primary production is harvested. Settlements and roads are also preferably situated in low, fertile regions. Thus, thehigher the level of ANPPo, the higher the proportion of appropriated ANPP. Natural fertility explains 50% of the variance of ANPPjANPPo, this relation being significant at p < 0.001 (chi square). DISCUSSION The reliability of the results can be assumed to be high für aboveground NPP. A previous study (27), which used much simpler calculation methods and a much narrower data base, yielded rather similar results. The results on average productivity of ANPPoand ANPPacl are weIl in line with the comparabledata in recent large-scale productivity studies (14, 28-30). The appropriation of ANPP in Austria is higher than the estimates für global NPP appropriation, ranging from 25 to 39% (3,4). Nevertheless, it can be assumed that values für other highly industrialized western and Central European countries may be even higher: They typically have less than the Austrian 45% of forests with rather low NPP appropriation per m2. Furthermore, 20 -'>. 'I E 15 ~ 10 00Z c( : I 5 ~:::::~~~~ EE -ANPPact ANPPO -ANPPt Regional subdivision of Auslria (99 polilical dislricls) ANPPo Figure 2. NPP appropriation greatly reduces the spatial differences between the energy input of different terrestrial ecosystem types. While ANPPact Figure 1. Appropriation of aboveground net primary production (AN PP) in Austria 1990. Of the 1501 PJ yr-1 which would be available in natural ecosystems if human interference were absent, only 884 PJ yr-1 can actually serve as energy input of all heterotrophic food chains. 144 ANPPo and ANPPact fall within a range between 8 and 22 MJ m-2 yr-', the amount of energy actually remaining serving as input for the heterotrophic food chains is much more evenly distributed and ranges from about 7 to 15 MJ m-2 yr-l. ANPPoand ANPPactare the aboveground NPP of the potential vegetation and the actual vegetation, respectively. @RoyalSwedishAcademyof Sciences1997 Arnbio Vol. 26 No. 3. Mav 1997 12.6%of the Austrianterritory is above1800m elevation,where no NPP appropriationwas assumedto occur. In other countries agriculturalareas,roadsandbuildingsarelikely to covera much higher percentageof the surface. Theseresultsraise the questionof which effectshumanNPP appropriationmay haveon naturalecosystems. Obviously,it significantly altersthe energyflow of natural ecosystemsand thus may be seenasan indicator für the intensity of humaninterventions into natural ecosystemprocesses(27). But what do we know aboutits likely effectson the structureand functioning of ecosystems? If we follow the argumentsof Hutchinsonin bis famouspaper "Homageto SantaRosalia,or why are there so many kinds of animals?" (31), we may suspectthat areduction of energy flow is likely to causeareduction of the length of food chains. His argumentwas that sincelessthan 10% of the energyavailahle at the level n of a food chain can be gatheredat the level n + 1, food chainscannotbe very lang. Although it appearsto be clear that the length of food chains is ultimately constrainedby the amountof energy available,it may weIl be that in many casesother factors-body size,stability of food chains,etc.-may be more important. Until now, empirical studiesfailed to produceunequivocalresults on this matter.While Briand and Cohenfound no correlationbetween energyflow andfood chainlengthin an analysisof 38 food wehs (32), Yodzis could show that ectothermfood chainsare significantly longerthanendothermfood chains(33). Sinceectotherms convertfood to secondaryproductionmuchmoreefficiently than endothermsthis result supportsthe energytheory of food chain length regulation. In addition, only recently an experimental study hagshownthe importanceof energyavailability on food chain length (34). In model calculations,Oksanenshowedthat the amountof energyavailableper unit areagreatly influences food chain structure,as rar as vertebralesare concemed:According to the resultsof his models,big grazerswill dominate ecosystemswith an averageabovegroundproductivity below approximately 12 MJ m-2yr-l, while complex food chains in wbich the herbivoresareregulatedby carnivores,andhavemuch lower populationdensity,prevail in richer habitats(35). If it is true that a reductionof energyflow reducesthe length of food chains,then a secondassertionof Hutchinson(31) may also prove correct,namely that the amountof energyavailable exertsan importantinfluenceon speciesdiversity.In the last two decadesthis ideaexperienceda renaissance asthe so-calledspecies-energytheory of biodiversity (4, 36-38). In short, the species-energytheorypredictsthat the numberof specieswhich can inhabit a certain environmentincreaseswith the amountof energy available;conversely,the numberof specieswill decrease, if energy flow is reduced (Fig. 3). The rationale behind this E2 E1 E energy flow (e.g. NPP) Figure 3. Species-energy curves demonstrate the relation between energy flow (E) and species richness (N). If energy flow is reduced, species-energy theory predicts a reduction of species richness. Ambio Val. 26 No. 3. May 1997 theory is that in habitats with abundant resources rivaling species will be ahle to specialize with respect to more gradients and thus can avoid extinction due to Gauses principle of competition exclusion (36). While in poor habitats there are few, generalistic species, in resource-rich habitats many specialists prevail. ODe reason für this are the "costs of cpmmonness", i.e. negative effects of high population densities, e.g. parasitism, pests, specialized predators (38). The species-energy theory has been shown to be an extension of species-areatheory (37), which relies on the theory of islandbiogeography by MacArthur and Wilson (39). The core of this theory is that the number of species on an island is a steady state between immigration (and speciation) and extinction, and the bigger the island, the greater a number of species it is ahle to support. Species-energy theory claims that this assertion can be explained by the fact that ceteris paribus bigger islands provide more energy, and predicts that among islands of the same size more productive ones will support a higher number of species (4). The species-energy theory is not only ahle to explain the gradient of species diversity from the poles to the equator, hut has also been empirically tested and verified (38, 40--42). Even if the species-energy theory may be an innovative approach in biodiversity research, it is currently not generally accepted. For example, it cannot explain the "paradox of enrichment" (43); i.e. the observation that nutrient-rich (and thus more productive) habitats may have lower species diversity than less fertilized ones, a phenomenon Tilman has explained with a microeconomic model (44). Since such a model fails to explain the big biogeographical biodiversity gradient from the poles to the equator, however, it cannot claim to be the unique theory of biodiversity. In general, it is likely that the explanation of biodiversity patterns requires more than ODescientific approach. As rar as the Austrian data are concerned, my results are consistent with the species-energy theory. If the properties of the species-energy curve ofWright (4) are assumed, species-energy theory predicts that in Austria between 5 and 13% of the species should have gone extinct up to now. Actual surveys show that 8% of the bird species, 7-14% of the reptiles (but no amphibians) have gone extinct in Austria (45, 46). However, since this may just be coincidental, it is not a very strong argument in favor of the species-energy theory. But it does ascertain that the theory does not contradict the data. Further research, based on the data now available, which have a high spatial resolution, will be directed towards an attempt to explain biodiversity patterns with variations of available energy (ANPPJ. CONCLUSIONS REGARDING SUST AINABLE DEVELOPMENT Even if the effect of NPP appropriationon biodiversity is yet unproven,it is obviousthat the currentlevel of NPP appropriation constitutesa significantinterventioninto the naturalenergy flow of ecosystems.The potential effects this interferencemay have,and which arecurrentlynot weIl understood,demandthat NPP appropriationshould be regardedas an important indicator für pressureson the environment.Sincethe NPP of a natural ecosystemappearsto be an insurmountablelimit (globally asweIl asat the locallevel), this indicator shouldbe considered asa coreparameterfür sustainabledevelopment(47). Many strategiesfür sustainabledevelopmentin the energysector seekto promotethe substitutionof fossil fuels with biomass (48). Most of these strategies,however, imply an increaseof biomassharvestand thus are likely to contributeto an increase of NPP appropriation,e.g. an increaseof firewood combustion für heatingpurposes,and thus could threatenbiodiversity.As a consequence, target conflicts may exist betweenCO2-reduction and the conservationof biodiversity, which are both important aspectsof sustainabledevelopment.Moreover,the calculations @RoyalSwedishAcademyofSciences1997 145 presentedabove show that the idea of a simple substitutionof fossil fuels with biomasswould not work, at least in Austria, simply becausethe total energyinput of 1680PI yr-1(including biomass für nutrition) of Austria already is higher than the ANPPact (1396PI yr-1 (49). Which strategiesmay be envisagedto avoidthis potentialconflict? One possible part of a solution is the cascadeuse of biomass.This meansthat wastebiomassshouldbe usedfür energy generationinsteadof harvestingmore biomass.This would permit an increaseof biomassuse für energygenerationwithout augmentingNPP appropriation.Oneexampleis the production of biogas from wet biomass waste, e.g. animal manure. Potentials für the generationof additional energy from used biomassshouldbe systematicallyinvestigated. Anotherstrategy,which hasthe advantageof alleviatingother ecologicalproblemsasweIl, is basedon the observationthat the References and Notes I. Fischer-Kowaiski,M. and Haberl, H. 1993.Metabolism and colonization. Modes of production and the physical exchangebetweensocietiesand nature.Innov. SOG.Sci. Res.6, 415-442. 2. Whittaker, R.H. and Likens, G.E. 1973.Primary Production:The Biosphereand Man. Human Ecol. I, 357-369. 3. Vitousek, P.M., Ehrlich, P.R., Ehrlich, A.H. and Matson, P.A. 1986. Human appropriaton of the producls of photosynthesis. BioScience 36, 368-373. 4. Wright, D.H., 1990. Human impacts on energy flow through natural ecosystems, and implications für species endangerment. Ambio 19,189-194. 5. Meadows,D., Meadows,D. andRanders,J. 1992.BeyondtheLimits. Global Collapse or a SustainableFuture. Earthscan,London. Germanedition: Die neuenGrenzendes Wachstums.Die Lage der Menschheit:Bedrohung und Zukunftschancen.Deutsche Verlags-Anstalt,Stuttgart. 6. Daly, H.E. 1992. Vom Wirtschaftenin einer leeren Welt zum Wirtschaften in einer vollen Welt. In: Nach demBrundtlandbericht:NachhaltigeEntwicklung,R. Good1and, H.E. Daly; S.E. Serafy;Droste, B.(eds).DeutschesMAß-Nationalkomitee,Bonn, pp. 29--40. 7. Gore, A. 1992.Earth in the Balance: Ecology and the Human Spirit. Plume Books, New York. GermanEdition: Wegezum Gleichgewicht.Ein MarshallplanJür die Erde. S. Fischer,Frankfurt/Main. 8. Vogt, K.A., Grier, C.C., Meier, C.E. and Edmonds,R.L., 1982.Mycorrhizal role in net primary production and nutrient cycling in Abies amabilis ecosystemsin Western Washington.Ecology63,370-380. 9. Vogt, K.A., Grier, C.C. and Vogt, D.J. 1986. Production,tumover, and nutrient dynamicsof above-and belowgrounddetritus ofworld foresls.Adv. Ecol. Res.15, 303377. 10. Melillo, J.M. and Gosz,J.R. 1983.Interactionsofbiogeochemicalcyclesin forest ecosystems.In: The Major BiogeochemicalCyclesand Their Interactions. Bolin, B. and Cook (eds).SCOPE21, JohnWiley & Sons,Chichester,pp. 177-222. 11. Haberl, H. 1995. Menschliche Eingriffe in den natürlichen Energiefluß von Ökosyste1!1en, Sozio-ökonomischeAneignung von Nettoprimärproduktion in den BezirkenOsterreichs.IFF-Social EcologyPapersNo. 43, Vienna. 12. Cannell,M.G.R. 1982.World ForestBiomassand Primary ProductionData. Academic Press,London. 13. Waller, H. andLieth, H. 1973.Klimadiagramm-Weltatlas.VEB Fischer,Jena. 14. Lieth, H. andWhittaker,R.H. (eds).1975.Primary Productivity olthe Biosphere.EcoI.\,gicalstudies14, Springer,Berlin, Heidelberg,New York. .. 15. OsterreichischeGesellschaftfür Meteorologie (ed.) 1988.Klimadaten in Osterreich 1951-1980.PublicationNo. 326, Vienna. 16. Various sources,including specialassessmenls by the StatisticalOffice were used.For referencesee(li). 17. Hall, D.O., Scurlock, J.M.O., Bolhar-Nordenkampf,H.R., Leegood,R.C. and Long, S.P.(eds).1993.Photosynthesis and Productionin a ChangingEnvironment.Chapman & Hall, London. 18. Lieth, H. (ed.). 1978.Patterns 01Primary Production in the Biosphere.Benchmark Papersin Ecology 8. Dowden,Hutchinson& Ross,Stroudsburg. 19. Loomis,R.S. andGerakis,P.A. 1975.Productivity of agriculturalecosystems.In: Phatosynthesisand Productivity in Different Environments.Cooper,H.P. (ed.).Cambridge Univ. Press,Cambridge,pp. 145-172. 20. Loomis,R.S. 1983.Productivityof Agricultural Systems.In: PhysiologicalPlant Ecology IV, EcosystemProcesses:Mineral Cycling, Productivity and Man's Influence. Lange,O.L., Nobel, P.S., Osmond,C.B. and Ziegler, H. (eds).Encyclopedia01Plant Physiology,New SeriesVol. 12D, 151-172. 21. Forstliche Bundesversuchsanstalt,1993. Österreichische Forstinventur 1986/90. ForstlicheBundesversuchsanstalt, Wien. 22. ÖsterreichischesStatistischesZentralamt, 1992. Ergebnisseder landwirtschaftlichen Statistik im Jahre1991.Beiträgezur österreichischenStatistik Val. 1062.Wien. 23. Gerhold,S. 1992.Stoffstromrechnung: Holzbilanz 1955-1991.StatistischeNachrichten 47,651-656. 24. Souci, S.W, Fachmann,W.; Kraut, H. 1989.Die Zusammensetzung der Lebensmittel -Nährwerttabellen 1989{90.WissenschaftlicheVerlags-GmbH,Stuttgart. 25. DeutscheLandwirtschaftsgesellschaft. 1991.DLG-FutterwerttabellenJürWiederkäuer. DLG- Verlag, Frankfurt. 26. Long, S.P,Jones,M.B. and Roberts,M.J. (eds). 1992.Primary Productivity 01Grass Ecosystemsolthe Tropicsand Sub-tropics.ChapmannandHall, London. 27. Fischer-Kowaiski,M., Haberl,H. andPayer,H.P. 1993.A piethoraof paradigms,out1iningan information systemon physicalexchangesbetweenthe economyand nature. In: Industrial Metabolism.Ayres, R. and Simonis,U.E. (eds).United NationsUniversity Press,Tokyo, New York, Paris,pp. 337-360. 28. Ajtay, G.L., Keiner, P. and Duvigneaud,P. 1979.Terrestrialprimary production and phytomass.In: The Global Carbon Cycle. Bolin, B., Degens,E.T., Kempe, S. and Keiner P. (eds).SCOPE13,Wiley & Sons,Chichester,New York, Brisbane,Toronto. 29. Cooper,H.P. (ed.). 1975.Photosynthesisand Productivity in Different Environments. InternationalBiological Programme3, CambridgeUniversity Press,Cambridge,London, New York, Melboume. 146 currentenvironmentalproblemsarea consequence of the quantity and quality of man-madematerialand energyflows. From this perspective,a reductionof the overall energyand materials throughputof industrial societiesshouldbe the core of sustainable development.Ratherthan replacingOllematerial with another, this conceptfocuseson the delinking of material and energy flows from economicperformanceand the quality of lire (1,27,49). On the operationallevel,then,energyconservation should have priority over an increaseof biomassuse as a climateprotectionstrategy(50). 30. Reichle,D.E., Franklin,J.E.andGoodall,D.W. (eds).1975.ProductivityolWorld Ecosystems.Proceedingsof an IBP Symposium,31.8-1.9.1972in Seattle,National Academy of Sciences,WashingtonDC. 31. Hutchinson,G.E., 1959.Homageto SantaRosalia,or why arethereso many kinds of animals?Am. Nat. 93,145-159. 32. Briand, F. and Cohen,J.E. 1987.Environmentalcorrelatesof food chain length. Science238, 956-960. This study hasbeencriticisedby Moore et aI. becauseaccording to them Briand and Cohenbad useduncosistentlydefineddata (Moore, J.C., Walter, D.E. andHunt, H.W. 1989.Habitatcompartmentation andenvironmentalcorrelatesof food chain length,Science243,238-239),an objectionwhich Briand and Cohencould not clearly reject (Briand,F. andCohen,J.E., 1989.Response.Science243, 239-240). 33. Yodzis, P. 1984.Energyflow andthe vertical structureofreal ecosystems.Dekologia 65,86-88. 34. Jenkins,B., Kitching, R.L. and Pinun, S.L. 1992.Productivity, disturbance,and food web structureat a local spatialscalein experimentalcontainerhabitats.Dikos 65, 249255. 35. Oksanen,L. 1990.Predation,herbivory,andplant strategiesalonggradientsof primary productivity. In: Perspectiveson Plant Competition.Grace,J.B. and Tilman, D. (eds). AcademicPress,SanDiego,pp. 445-473. 36. Brown, J.H. 1991.Speciesdiversity. In: Analytical Biogeography,Myers, A.A. and Giller, P.S.(eds).Chapman& Hall, London(3rd. edition),pp.57-89. 37. Wright, D.H. 1983.Species-energy theory,an extensionof species-area theory. Dikos 41,495-506. 38. Wright, D.H. 1987.Estimatinghumaneffectson global extinction.Int. J. Biometeor. 31,293-299. 39. MacArthur,R.H. andWilson,E.O. 1967.TheTheoryollsland Biogeography.Princeton University Press,Princeton. 40. Currie,D.J. andPaquin,V., 1987.Large-scalebiogeographicalpatternsof speciesrichnessof trees.Nature 329,326-327. 41. Turner, J.R.G., Gatehouse, C.M. and Corey, C.A. 1987. Does solar energy control organic diversity? Butterflies, moths and the British clin1ate. Dikos 48, 195-205. 42. Turner, J.R.G.,Lennon,J.J. and Lawrenson,J.A. 1988.British bird speciesdistributions andthe energytheory.Nature335, 539-541. 43. Rosenzweig, M.L. 1971. Paradox of enrichment, destabilization of exploitation systems in ecological time. Science 171, 385-387 eco- 44. Tilman, D. 1980.Resources,a graphical-mechanistic approachto competitionand predation.Am. Nat.166, 362-393. 45. Bittermann, W. 1990. NaturvorratsrechnungFauna,Amphibien- und Reptilienarten Österreichs.StatistischeNachrichten45,543-549. 46. Bittermann, W. 1991. NaturvorratsrechnungFauna, die Vogelarten Österreichs. StatistischeNachrichten46, 69-72. 47. Munasinghe,M. and Shearer,W. (eds).Defining and MeasuringSustainabi/ity,The BiogeophysicalFoundations.The United Nations University and The World Bank, WashingtonDC. 48. Johansson,T.B., Kelly, H., Reddy, A.K.N. and Williams, R.H. (eds). 1993.Renewahle Energy,Sourceslor Fuelsand Electricity. IslandPress,WashingtonDC. 49. Haberl, H. 1996.Metabolismand colonization:Conceptsfür sustainabilityindicators. In: Econometrics 01 the environment and transdisciplinarity. Baranzini, A. and Carlevaro,F. (eds).Lf' InternationalConferenceof the Applied EconometricsAssociation (AEA), ConferenceProceedings,Lisbon,Geneve,51-67. 50. Für help, advice,anddiscussions1amindebtedto W. Bittermann,M. Fischer-Kowaiski, B. Hammer,W. Hüttler, W. Loibl, H. Payer,H. Schandl,V. Winiwarter, H. ZangerlWeisz,andtwo anonymousreferees. 51. First submitted28 November 1995.Acceptedfür publication after revision 19 June 1996. Helmut Haberl, PhD, is currently with the Austrian Institute of Applied Ecological Research and at the Interdisciplinary Institute of Research and Continuing Education (IFF), Department of Social Ecology. He works on energy and the environment, environmental indicators, societal metabolism and the colonization of nature, and sustainable development. His address: IFF, Social Ecology, P.O. Box 232, Seidengasse 13, A-1070 Vienna, Austria, e-mail: [email protected] @ Royal Swedish Academy of Sciences 1997 Arnbio Vol. 26 No. 3. May 1997