Patterns, dynamics and implications of global HANPP

This project will analyze socio-economic as well as natural drivers and implications of the global human appropriation of net primary production (HANPP). HANPP is a spatially explicit indicator of socio-ecological metabolism that measures to what extent land conversion and biomass harvest alter the availability of trophic energy in ecosystems. The project is a continuation of the FWF project P16692-G05 "Global HANPP 1700-2000" that has generated spatially explicit (10x10 km) global HANPP datasets and a 300 year timeseries. Its aim is to systematically analyse spatial patterns and dynamics of global HANPP in the course of the last 300 years, to explore underlying factors, mechanisms and determinants, and to identify drivers of change. The project aims at examining and quantifying the effects of HANPP on ecosystem patterns and processes, including biodiversity, flows and selected stocks of C and N. The project relies on analytical statistics and modelling techniques. Results will be interpreted in the context of resilience and stability, on global, regional and national scales. The project contributes to sustainability science, land-change science, environ-mental history, ecological economics, industrial ecology and human ecology and aims at improving understanding of humanity`s role in the biosphere.

The human appropriation of net primary production (abbreviated HANPP) is a measure of the changes in ecosystems resulting from agriculture, forestry, settlements, etc. HANPP measures the fraction of the biomass that would result from plant growth in the absence of land use (i.e. in the potential vegetation) which remains available for ecosystem processes at any point in time. HANPP is an indicator of land-use intensity as well as the human domination of ecosystems. Net primary production (NPP) measures the net-production of energy-rich organic substances (biomass) by green plants in the process of photosynthesis - i.e., using solar energy - NPP is hence a central process of ecosystem functioning: it delivers the trophic energy for all food chains or food webs and hence provides the basis for the diversity of all animals, fungi and microorganisms. During photosynthesis, plants absorb CO 2 from the atmosphere and fixed in - more or less long-lived - biomass. NPP is therefore also the ecophysiological basis for the sequestration of carbon in biota and soils (`carbon sink`). This project has shown that global HANPP almost doubled from 1910 to 2005, rising in this period from 13% to 25%. This rise in HANPP was related to increasing pressures on global ecosystems. At the same time, this increase was considerably lower than that of the world population (+274%), global GDP (+1655%) as well as the human harvest of biomass (+169%). This shows that it was possible in the past to `decouple` HANPP from its most prominent drivers. Several factors were decisive for this decoupling, above all the substitution of fossil fuels for biomass as primary energy during industrialisation, increases in NPP of agro-ecosystems related with agricultural intensification as well as increased efficiency of biomass use. For example, if the share of biomass in total global primary energy supply had remained constant, global HANPP would currently be 41%, that is, about two thirds higher than the present value. This result shows how far-reaching effects could be connected to a policy to substitute biomass for fossil fuels at a grand scale. Agricultural intensification was also associated with substantial ecological costs, for example with increased fossil energy inputs of agriculture (tractors, fertilizers, etc.), N leaching, soil degradation, etc. This project analysed HANPP from various angles. The HANPP approach was used to construct a biomass-balance model to analyse future interdependencies between food demand, agricultural technology, land use and bioenergy. This work was used, among others, in the Global Energy Assessment. The project developed a system-dynamic model to simulate long-term (>100 year) changes in HANPP on the national scale. Methods were developed to account for the HANPP related to the production processes of biomass- based products. This indicator (`embodied HANPP`) can also be used to analyse environmental effects of world trade.