Human appropriation of net primary production in South Africa, 1961 - 2006

Die Republik Südafrika unterlag fundamentalem sozial-politischen Wandel im 20.Jahrhundert. Das Apartheidregime intensivierte die ernsten sozial-politischen Probleme die Südafrika auch heute noch spürt und weite Teile des Landes wurden durch Kultivierung von natürlichen Ökosystemen transformiert. Im 19. Jh. verdreifachte sich und die Fläche des Ackerlandes und die Fläche von Holzplantagen wuchs um das 10-fache. Die vorliegende Studie analysiert anthropogen verursachte Änderungen in Kohlenstoffflüssen indem sie den sozial-ökologischen Indikator HANPP (Human Appropriation of Net Primary Production) anwendet. HANPP wird einerseits durch menschliche Ernte verursacht und andererseits durch menschliche Änderungen von ökologischer Biomasseproduktion (NPP), beispielsweise durch Landtransformation, Landnutzungsänderungen oder Bodendegradation. HANPP dient als integrierter Indikator für die Intensität von Landnutzung, da er nicht nur Änderungen in Biomasseflüssen durch menschliche Aktivitäten aufzeigt, sondern auch in Beziehung zu Faktoren wie sozialem Wohlstand, Biodiversität, nachhaltiger Nutzung von natürlichen Ressourcen und zukünftiger Entwicklung von Landnutzungssystemen gesetzt werden kann. Diese Studie quantifiziert HANPP in Südafrika von 1961 bis 2006. Der Trend in HANPP blieb relativ konstant in diesem Zeitraum und bewegte auf einem jährlichen Level von etwa 24% der potenziell verfügbaren Biomasse (NPP0). Erst unter genauerer Betrachtung der unterschiedlichen Ströme von HANPP werden Auffälligkeiten deutlich. HANPP auf Ackerland verkleinerte sich zusehends nach 1986 und gleichzeitig stieg HANPP verursacht durch Weidewirtschaft und Feuerholzentnahme an. Diese Ergebnisse können einerseits in Bezug zur grünen Revolution, welche bis in die 1970ger eine Steigerung agrarischer Produktivität bewirkte, gestellt werden und andererseits zur finanziellen Krise ab den 1980ern bis zum Ende der Apartheid (1994), welche eine Stagnation landwirtschaftlicher Modernisierung mit sich brachte. Die wachsenden Bevölkerungszahlen und die schwache agrarische Produktivität bewirkten ein Sinken der HANPP pro Kopf über den gesamten Zeitraum hinweg. Da aber der Bedarf an Biomasse pro Kopf nicht zurückging, wurde Südafrika zu einem immer größeren Nettoimportland von Biomasse, was bedeutet, dass sich HANPP auch auf andere Länder verlagert und die Aneignung von Biomasse nicht mehr auf die Landesfläche von Südafrika beschränkt ist.During the 20th century the Republic of South Africa experienced fundamental social, political and ecological transitions. The Apartheid regime intensified the severe socio-economical problems with which South Africa is still struggling today and humans transformed natural ecosystems to a wide extent. From 1900 until today, the area under crop production more than tripled and the area under forest plantations grew more than 10-fold. This thesis applies the socio-ecological indicator Human Appropriation of Net Primary Production (HANPP) that aims at measuring human-induced changes in biomass flows resulting from two processes: Anthropogenic harvest and human-induced land conversion (such as land cover change, land use change and human induced soil degradation). HANPP is useful as an integrated indicator of land-use intensity, because it does not only measure changes of biomass flows in ecosystems from land use, but can also be related to the main social and economical driving forces for long-term changes in land cover and land use. HANPP data allow for drawing conclusions on the degree of transformation of natural ecosystems and its implications for factors such as social wealth, biodiversity, sustainable use of natural resources and prospects for a future development of land use. This study quantifies HANPP in South Africa over the period from 1961 to 2006. Despite the rapid changes that South Africa underwent in the observed period, HANPP remained approximately constant, suggesting that over the whole period under investigation humans appropriated around 24% of the total biomass potentially available in each year. However, shifts in patterns of biomass appropriation can be discerned when analyzing pathways of aHANPP separately. HANPP on cropland steadily declined after 1986 and simultaneously aHANPP caused by grazing, harvest of roundwood and fuelwood increased. These results can be interpreted either in context of the green revolution, which initially brought a rise in productivity on agricultural land, or in the background of the economic and political crisis in the 1980ies, which triggered a stagnation in agricultural modernization until 1994, when the country finally had its democratic opening. Rising population numbers and weak agricultural productivity in the past decades resulted in a decreasing aHANPP per head. However, per person demand for agricultural biomass did not decline. As a consequence South Africa became a net-import country of biomass, which means that South African aHANPP is distributed among other countries as well

From the past to the present, from census to the grid : a socio-ecological analysis of land-use intensity across multiple spatial and temporal scales

Supplying sufficient amounts of biomass to a growing and prospering world population, while avoiding natural depletion, is a key challenge of the 21st century. From a production side perspective this will likely entail the intensification of current agricultural lands. However, many uncertainties relate to potentials of harvest increases and associated environmental trade-offs, particularly at the global scale. In this thesis I apply a consistent socio-ecological perspective on land systems that allows addressing three interrelated and virulent knowledge gaps: (a) Detecting current global patterns of land-use intensity through integrating socio-economic costs and benefits with changes at the land system level; (b) identifying regions with the highest (sustainable) intensification potentials and (c) tracing past land system trajectories in order to identify socio-economic and natural framework conditions under which changes in land-use intensity occur. Results on long term land system trends in Europe reveal surprising similarities between the most heterogeneous political and biophysical regions over the past 150 years. Land-use intensification was a somewhat universal trajectory on croplands in Europe, whereas trends on grasslands and forests were highly diverse, owing to economic and natural particularities. However, in a global perspective, cropland use intensity around 2000 differed substantially in terms of associated costs and benefits across biophysical regions. Improving global input efficiency could substantially reduce environmental burdens in high-input regions, such as many European countries and Eastern Asia, and raise biomass outputs by ca. 30% in the one quarter of croplands that are under low land-use intensity. This thesis contributes to land-use intensity research, both in a conceptual and empirical way. The holistic perspective on land use across various spatial and temporal dimensions allowed for insights into archetypical patterns of intensification, including related costs, benefits and future potentials, both, for societies and ecosystems.Keine Zusammenfassung vorhandenMag.a Maria NiedertscheiderAlpen Adria Universität Klagenfurt, Dissertation, 2016OeBB(VLID)241351

Mapping and analysing cropland use intensity from a NPP perspective

Meeting expected surges in global biomass demand while protecting pristine ecosystems likely requires intensification of current croplands. Yet many uncertainties relate to the potentials for cropland intensification, mainly because conceptualizing and measuring land use intensity is intricate, particularly at the global scale. We present a spatially explicit analysis of global cropland use intensity, following an ecological energy flow perspective. We analyze (a) changes of net primary production (NPP) from the potential system (i.e. assuming undisturbed vegetation) to croplands around 2000 and relate these changes to (b) inputs of (N) fertilizer and irrigation and (c) to biomass outputs, allowing for a three dimensional focus on intensification. Globally the actual NPP of croplands, expressed as per cent of their potential NPP (NPP _act% ), amounts to 77%. A mix of socio-economic and natural factors explains the high spatial variation which ranges from 22.6% to 416.0% within the inner 95 percentiles. NPP _act% is well below NPP _pot in many developing, (Sub-) Tropical regions, while it massively surpasses NPP _pot on irrigated drylands and in many industrialized temperate regions. The interrelations of NPP losses (i.e. the difference between NPP _act and NPP _pot ), agricultural inputs and biomass harvest differ substantially between biogeographical regions. Maintaining NPP _pot was particularly N-intensive in forest biomes, as compared to cropland in natural grassland biomes. However, much higher levels of biomass harvest occur in forest biomes. We show that fertilization loads correlate with NPP _act% linearly, but the relation gets increasingly blurred beyond a level of 125 kgN ha ^−1 . Thus, large potentials exist to improve N-efficiency at the global scale, as only 10% of global croplands are above this level. Reallocating surplus N could substantially reduce NPP losses by up to 80% below current levels and at the same time increase biomass harvest by almost 30%. However, we also show that eradicating NPP losses globally might not be feasible due to the high input costs and associated sustainability implications. Our analysis emphasizes the necessity to avoid mono-dimensional perspectives with respect to research on sustainable intensification pathways and the potential of integrated socio-ecological approaches for consistently contrasting environmental trade-offs and societal benefits of land use intensification

Transitions in European land-management regimes between 1800 and 2010

Land use is a cornerstone of human civilization, but also intrinsically linked to many global sustainability challenges-from climate change to food security to the ongoing biodiversity crisis. Understanding the underlying technological, institutional and economic drivers of land-use change, and how they play out in different environmental, socio-economic and cultural contexts, is therefore important for identifying effective policies to successfully address these challenges. In this regard, much can be learned from studying long-term land-use change. We examined the evolution of European land management over the past 200 years with the aim of identifying (1) key episodes of changes in land management, and (2) their underlying technological, institutional and economic drivers. To do so, we generated narratives elaborating on the drivers of land use-change at the country level for 28 countries in Europe. We qualitatively grouped drivers into land-management regimes, and compared changes in management regimes across Europe. Our results allowed discerning seven land-management regimes, and highlighted marked heterogeneity regarding the types of management regimes occurring in a particular country, the timing and prevalence of regimes, and the conditions that result in observed bifurcations. However, we also found strong similarities across countries in the timing of certain land-management regime shifts, often in relation to institutional reforms (e.g., changes in EU agrarian policies or the emergence and collapse of the Soviet land management paradigm) or to technological innovations (e.g., drainage pipes, tillage and harvesting machinery, motorization, and synthetic fertilizers). Land reforms frequently triggered changes in land management, and the location and timing of reforms had substantial impacts on land-use outcomes. Finally, forest protection policies and voluntary cooperatives were important drivers of land-management changes. Overall, our results demonstrate that land-system changes should not be conceived as unidirectional developments following predefined trajectories, but rather as path-dependent processes that may be affected by various drivers, including sudden events.</p