Impact 2 - Management
Severe erosion in southern Hawkes Bay following a major storm in 2011. Image - Les Basher
Opportunities and threats to land resources and ecosystem services are recognised and balanced to maintain or enhance the provision of ecosystem services.
Land use change and ecosystem services
A decade of accelerating land-use change and intensification has benefitted the economy but the consequences for ecosystem services are poorly understood. Land use intensification is a complex process to model as it involves manipulation of stock, plant species, disturbance, nutrients, and water. Worldwide, there is no agreed terminology, with many different definitions and surprisingly diverse metrics to describe land use. In addition, these components are integrated in complex ways along gradients of land use intensification.
To ensure greater objectivity and robustness, we first reviewed published information then developed a new framework and standardised terminology for land use intensification. This framework will enable consistent quantification of current land-use intensity, and enable comparisons of the effects of ongoing intensification on ecosystem services across land-cover classes. More generally, this research underpins the ability to report on status and trends of land resources and ecosystem services by developing comparable measurements across sectors and land uses.
We then developed a holistic model that assesses the impacts of land use change on all ecosystem services for all sections of the community. As such, it could be used to assess sustainable development and equity in resource use. Detail is provided at the level that policy and management decisions are made. Spatially explicit indicators cover important services for New Zealand − regulation of climate, control of soil erosion, regulation of water flow (quantity), provision of clean water (quality), provision of food and fibre, and provision of natural habitat.
In one scenario, we used the model to assess potential trade-offs between biodiversity and the non-biodiversity goals (e.g. reduced soil erosion, nitrogen retention, and fewer greenhouse gas emissions) derived from restoration projects. If restoration projects are prioritised based on non-biodiversity or multi-objective goals, biodiversity gains are likely to be compromised (especially compared with projects prioritised on biodiversity goals only).
This research is part of the Understanding Ecosystem Services and Limits portfolio, and was supported by Core funding.
A Land Use Management Support System
Sustainable land management depends on a deep understanding of the spatial variability of ecosystem properties and processes, and how they are affected by human activities. We developed the Land-Use Management Support System (LUMASS) to help planners assess the environmental impact of land use and decide where a particular land use might best occur (or should not occur) and identify appropriate new opportunities to provide greatest benefit to the well-being of people and the environment. In situations where there are multiple and possibly conflicting stakeholder objectives and constraints, LUMASS can identify optimal land use and critically assess the environmental limits within which compromises or trade-offs need to be found.
In case studies in the Waitaki catchment (South Island), the central North Island, and Hawke’s Bay, we used LUMASS to demonstrate how optimised land use could improve ecosystem services while maintaining agricultural production.
This research is part of both the Enhancing Policy Development and Characterising Land Resources portfolios, and was supported by Core and Envirolink funding.
Improving policies to protect groundwater
Where land–water policy reforms dictate significant changes to existing agricultural practices, regional councils and industry groups need to demonstrate that the changes are based on robust scientific evidence. We are providing key components of the evidence base. In the first project, we continued working with ECan to review modelled values of nutrient losses, and application of these values in setting nutrient discharge allowances and in estimating total loads in a catchment. We assessed the suitability of the Land Use Capability Classification (LUC) as a proxy for setting nutrient limits according to the natural capital of the land (as described in Horizons Regional Council’s One Plan). We suggested some modifications to the One Plan approach to better allow for irrigation in the drier Canterbury conditions. We also developed a new, spatially more accurate, model of LUC that is suitable for the flatter parts of Canterbury, based on S-map information.
In a second project, we showed how different ways of entering soils information affected results from the OVERSEER® Nutrient Budgets model. This highlighted some issues for the OVERSEER® development team to consider, and marks the beginning of a new collaboration between S-map and OVERSEER®.
This research is part of the Characterising Land Resources portfolio, and was supported by Core funding and ECan.
Reducing farm runoff into Lake Taupō
Water quality is deteriorating in the once pristine Lake Taupō (Taupō-nui-a-Tia). Each year, the lake receives about 1250 tonnes of nitrogen (N), 30−40% of which is leached from pastoral farmland. The Waikato Regional Council aims to reduce manageable N entering the lake by 20%. This target is challenging and farmers are now looking for economically viable, low-N-loss alternative land use options. The Lake Taupō Protection Trust commissioned a 3-year field research project to quantify N-leaching under cut-and-carry lucerne and other land management regimes. Our large-scale soil lysimeter array near Lake Taupō is pivotal to this work.
This research is part of both the Understanding Ecosystem Services and Limits and Realising Land’s Potential portfolios, and was supported by the Lake Taupō Protection Trust.
Irrigation proposals in Tasman District
The results of two complex modelling projects will be used by Tasman District Council to guide water allocation. In the first project (with GNS Science), we showed that proposed increases in irrigation for the upper Motueka River catchment could be feasible. We modelled interactions between groundwater and river water levels across six development scenarios. This indicated that new groundwater abstraction in the lower reaches could occur, in addition to existing abstraction, without breaching the river’s low-flow limits during the irrigation season.
The second project (with Plant & Food Research and the Cawthron Institute) assessed nutrient contamination risks to groundwater from the proposed Waimea Water Augmentation Project. Full irrigation across the Waimea Plains could potentially increase nitrogen (N)-concentrations entering groundwater by 23%, and hypothetically by up to 50% if the entire plains were irrigated for market gardening.
However, the increased irrigation would dilute and disperse N within the multiple aquifers so at most, only about half the total load would reach sensitive down-gradient receiving waters such as springs and the lower river. When the augmentation scheme is operating with water being released from the dam, river water quality is likely to improve.
Both projects made several recommendations for best-practice land and water management to further protect the various water bodies.
This research is part of both the Understanding Ecosystem Services and Limits and Realising Land’s Potential portfolios. The first project was supported by MBIE and Tasman District Council, and the second one by MPI and the Waimea Water Augmentation Committee.
Managing future erosion risk
We identified areas of New Zealand that would be most susceptible to erosion under future climate change, and the potential impacts of climate on erosion control. Annual rainfall is predicted to increase in the west and south of the country and decrease in the east and north (with more frequent extreme events). By 2080–2099, most places are projected to experience nearly twice as many 24-hour extreme rainfall events with a 100-year return period than occurs at present. Increased windiness and incidence of drought are predicted, particularly in the east. This project was collaborative with NIWA, GNS Science, AgResearch, Plant & Food Research and Scion.
Ongoing work with Scion investigated how trees and forests affect erosion and how forest management can minimise or mitigate erosion. Around 45% of New Zealand’s 1.8 million ha forest estate is first-rotation Pinus radiata, much of which was planted on steep terrain for erosion control. During harvesting of these forests, now and over the next 10–15 years, forest owners must manage landslide risk and the offsite movement of logging debris. Logged areas will need to be replanted, with consideration given to non-timber benefits such as ‘erosion mitigation’.
This research is part of the Realising Land’s Potential portfolio, and was supported by MBIE contestable funding and MPI funding via subcontracts from Scion and Future Forests.