Designing grazing systems that enhance the health of New Zealand high-country grasslands : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

Grazing management enabling pastoral livestock-production systems to deliver multiple ecosystem services is key to assure the long-term health and stability of grasslands. In the context of designing multi-functional grazing systems to enhance grassland health, systems thinking emerges as a useful tool to understand, modulate and enhance the resilience of those systems. The objective of the outlined research was to apply systems thinking and design theory to design alternative grazing systems that enhance grassland health using high-country stations in New Zealand as a model and Lincoln University Mount Grand Station (LUMGS) as the case study. This was conducted over five modelling exercises described as the design method to design scenarios representing distinct grazing management that enhance grassland health in different ways. The first design step applied spatial analysis to create a modern rich picture for grassland health diagnostic which determined that 97.7% of LUMGS grassland has a moderate health condition. Then, a geospatial modelling approach was used to assess the current capability of LUMGS in delivering ecosystem services. It was determined that LUMGS has a spatially variable potential for agriculture productivity, a high flood mitigation capacity, a high capacity of C sequestration, an extreme risk of erosion, a capacity to reduce sediment delivery to streams, and overall, a low to moderate nitrogen and phosphorus accumulation. Those ecosystem services were negatively affected by farming activities. Next, a geospatial modelling approach was used to understand the spatiotemporal impacts of different stock densities, grazing occupation periods, and stock types on soil susceptibility to erosion. Increases in the occupation period were more detrimental to soil loss than increases in stock density, and losses were greater for cattle than for sheep and deer. Those effects were spatially and temporally variable. In the following chapter, we applied a spatial-chemical analysis to grassland ecosystems for the illustration of chemoscapes and the creation of healthscapes. We created maps that show an extra perspective of plant nutritional value by illustrating their distribution over LUMGS according to their medicinal effects. Finally, by integrating all those design tools, three alternative grazing system scenarios were created and evaluated, from which a multi-criteria evaluation defined that the ‘best-compromise’ scenario to enhance grassland health is the scenario with lower soil erosion, the lower total emission of greenhouse gases, and greater profitability compared to the parsimonious approach of the ‘status quo’. The design methodology proposed in this thesis demonstrates that grasslands need to be managed as context-adjusted, adaptive, and complex systems to be multifunctional and continually deliver multiple ecosystem services to enhance grassland health.