Valuing Avoided Soil Erosion by Considering Private and Public Net Benefits

The population in New Zealand is expected to increase to over five million by the mid 2020’s from the current level of 4.3 million (Statistics New Zealand, 2009). An increasing demand for primary produce as a result may put pressure on marginal land to be farmed. Understanding the economic value of avoided erosion in New Zealand is therefore an important factor in policy making to optimise the soil related activities in the economy. Establishing a methodology for estimating the economic value of avoided soil erosion is the first step in assessing the problem. This study uses the future forest scenarios developed by Scion to identify potential afforestation areas and thereby compare the current erosion/sedimentation status under current land-use (non woody vegetation) with potential future afforestation. The study aims to quantify the incremental public and private net benefits from the change in scenario. The notion has come under different headings in the literature, such as on-site and off-site erosion effects or sediment and soil erosion effects, all of which recognize the importance of separation of effects to avoid double-counting. The separation into public and private benefits and costs in this case, while avoiding double-counting, will also help identify appropriate policy instruments to avoid soil erosion damage using the private and public net benefit framework (Pannell, 2008).Environmental Economics and Policy, Land Economics/Use,

Assessing drivers of plantation forest productivity on eroded versus non-eroded soils on hilly and steep land in eastern North Island, New Zealand: From catchment to regional scale

The impacts of soil erosion on forest productivity in a Pinus radiata plantation forest were assessed to determine the effects of key soil properties on tree volume. Fifteen plots on soils markedly eroded (truncated) by landsliding were established in a plantation forested atchment (Pakuratahi) comprising mainly hilly and steepland in a dominantly mudstone/sandstone terrain overlain in places with a mantle of pumiceous tephras in Hawke’s Bay, eastern North Island, New Zealand. Fifteen control plots were established on noneroded soils alongside the eroded soils on landslide scars for comparison. Soils within these eroded and non-eroded sites were analysed and associated trees were measured for height and volume. The analyses of 0.1 m of the soil profile within eroded sites, compared with those of non-eroded sites, revealed that soil properties in eroded sites had significantly lower values: total nitrogen (N) 52%, total carbon (C) 47%, total phosphorus (P) 43% and soil organic matter 36% (SOM) (at 99% confidence interval). The C:N ratio, soil pH, and mean soil depth in eroded plots were also significantly reduced (at 95% confidence interval). Trees on the eroded sites had 14% less volume compared with those growing in soils at the non-eroded sites. Regression analysis revealed a significant relationship between tree volume and total C, total N, and SOM at 99% confidence interval and total P at 95% confidence interval. Total recoverable volume was less in trees from eroded plots. Log quality and value was assessed using Atlas Forecaster. High-quality pruned logs and large unpruned structural grade sawlogs returned smaller volumes from the eroded plots than from the non-eroded plots. Lower-grade sawlogs returned a higher volume in the eroded plots. Total recoverable volume for a 25-year rotation growing on eroded sites was valued at $68,494 (2013 value) - 9$75,989). Eroded plots yielded 16% less volume from high quality pruned logs which accounted for a reduction in revenue of around $4,000 per hectare at eroded sites. A reduction in total recoverable revenue was estimated at$7,500 per hectare on eroded sites. Erosion scars were measured and the average soil loss was estimated and reported at 0.1 m depth. On average, an eroded plot lost around 277 m³ of soil. In total, around 415 tonnes of soil had been displaced from all measured eroded sites. Using digital layers orthorectified from aerial photographs, it was estimated that Pakuratahi catchment has erosion scars covering around 12 hectares of a total area of 774 ha. Extrapolating the soil data from the plots to the catchment, it was estimated that 2385 t of the soil profile, 271 t of C, 20 t of N, and 3 t of P have been displaced from the slopes of Pakuratahi catchment in the last 100 years. Using a non-linear regression model the potential soil loss following an 80-year and a 100-year extreme rainfall event was predicted. Total soil loss in Pakuratahi catchment was estimated to be 2630 t and 7890 t for an 80-year and 100-year event, respectively. To gain perspective of the value of avoided erosion or erosion mitigation, at a regional scale in Hawke’s Bay, areas with terrain attributes comparable to those of Pakuratahi catchment were identified. The area currently under plantation forestry in such landscapes is around 65 km². The conservative estimate of soil loss on unforested land following an extreme rainfall event for this area is up to 1.69 x 10⁵ t. Based on the estimated soil loss calculated from Pakuratahi eroded sites, the value of afforestation of these potentially erodible soils is around NZ$288 per tonne of soil. Afforestation of erodible land provides a valuable ecosystem service through land stabilisation but this service is currently not recognised financially in New Zealand

Shallow landslides and vegetation at the catchment scale: A perspective

Shallow, rainfall-triggered landslides are an important catchment process that affect the rate and calibre of sediment within river networks and create a significant hazard, particularly when shallow landslides transform into rapidly moving debris flows. Forests and trees modify the magnitude and rate of shallow landsliding and have been used by land managers for centuries to mitigate their effects. We understand that at the tree and slope scale root reinforcement provides a significant role in stabilising slopes, but at the catchment scale root reinforcement models only partially explain where shallow landslides are likely to occur due to the complexity of subsurface material properties and hydrology. The challenge of scaling from slopes to catchments (from 1-D to 2-D) reflects the scale gap between geomorphic process understanding and modelling, and temporal evolution of material properties. Hence, our understanding does not, as yet, provide the necessary tools to allow vegetation to be targeted most effectively for landslide reduction. This paper aims to provide a perspective on the science underpinning the challenges land and catchment managers face in trying to reduce shallow landslide hazard, manage catchment sediment budgets, and develop tools for catchment targeting of vegetation. We use our understanding of rainfall-triggered shallow landslides in New Zealand and how vegetation has been used as a tool to reduce their incidence to demonstrate key points

Quantitative landslide susceptibility assessment of the Waikato region using GIS

Areas that have experienced landslide events in the past and the conditioning factors present at these sites can be used to identify areas of the same or similar susceptibility. This can be achieved through a landslide susceptibility assessment using a landslide inventory, a set of predictor variables and specialised computer software. A quantitative landslide susceptibility assessment was conducted for the Waikato Region using two statistical approaches and eleven predictor variables. A landslide inventory map was constructed from the GNS QMap landslide spatial data and GeoNet landslide catalogue. Parameter maps for slope, elevation, aspect, lithology, land cover, soil order, mean monthly rainfall, maximum monthly rainfall, distance from roads, distance from faults and distance from rivers, were constructed and compiled into a database with the landslide inventory. The compiled data underwent both bivariate (weights of evidence) and multivariate (logistic regression) statistical analysis, and a landslide susceptibility map was derived for each. In the weights of evidence approach, the presence and absence of each class in relation to landslide occurrence and non-occurrence was individually assessed for each predictive factor. Logistic regression involves fitting a generalised non-linear model to the data based on a binary predictor (presence or absence of a past landslide event). For each method, a landslide susceptibility map was derived, and the model fit assessed using the landslide inventory. Both susceptibility maps underwent an evaluation to determine the better predictive model. An independent landslide data set was compiled from observations made in Google Earth, and used to establish a set of prediction rate curves and cumulative area curves. Both susceptibility maps resulted in very similar prediction rate curves. Weights of evidence gave a better prediction rate in the 10, 20 and 30% most susceptible pixels, but not in the 40% most susceptible pixels. Neither susceptibility map could be justified as being better than the other based on the prediction rate curves alone. The cumulative area curves for each susceptibility map resulted in very different outcomes. Logistic regression gave the best result with a large proportion of the landslide area within a small proportion of the total area in the high susceptibility classes. Weights of evidence had a larger proportion of the landslide area in high susceptibility classes than logistic regression, but this was associated with a large proportion of total area. Based on the evaluation, the susceptibility map derived using logistic regression was determined to be superior

Evaluation of empirical approaches to estimate the variability of erosive inputs in river catchments

Die Dissertation erforscht die Unsicherheit, Sensitivität und Grenzen großskaliger Erosionsmodelle. Die Modellierung basiert auf der allgemeinen Bodenabtragsgleichung (ABAG), Sedimenteintragsverhältnissen (SDR) und europäischen Daten. Für mehrere Regionen Europas wird die Bedeutung der Unsicherheit topographischer Modellparameter, ABAG-Faktoren und kritischer Schwebstofffrachten für die Anwendbarkeit empirischer Modelle zur Beschreibung von Sedimentfrachten und SDR von Flusseinzugsgebieten untersucht. Der Vergleich alternativer Modellparameter sowie Kalibrierungs- und Validierungsdaten zeigt, dass schon grundlegende Modellentscheidungen mit großen Unsicherheiten behaftet sind. Zur Vermeidung falscher Modellvorhersagen sind kalibrierte Modelle genau zu dokumentieren. Auch wenn die geschickte Wahl nicht-topographischer Algorithmen die Modellgüte regionaler Anwendungen verbessern kann, so gibt es nicht die generell beste Lösung. Die Ergebnisse zeigen auch, dass SDR-Modelle stets mit Sedimentfrachten und SDR kalibriert und evaluiert werden sollten. Mit diesem Ansatz werden eine neue europäische Bodenabtragskarte und ein verbessertes SDR-Modell für Einzugsgebiete nördlich der Alpen und in Südosteuropa abgeleitet. In anderen Regionen Europas ist das SDR-Modell bedingt nutzbar. Die Studien zur jährlichen Variabilität der Bodenerosion zeigen, dass jahreszeitlich gewichtete Niederschlagsdaten geeigneter als ungewichtete sind. Trotz zufriedenstellender Modellergebnisse überwinden weder sorgfältige Algorithmenwahl noch Modellverbesserungen die Grenzen europaweiter SDR-Modelle. Diese bestehen aus der Diskrepanz zwischen modellierten Bodenabtrags- und maßgeblich zur beobachteten bzw. kritischen Sedimentfracht beitragenden Prozessen sowie der außergewöhnlich hohen Sedimentmobilisierung durch Hochwässer. Die Integration von nicht von der ABAG beschriebenen Prozessen und von Starkregentagen sowie die Disaggregation kritischer Frachten sollte daher weiter erforscht werden.This dissertation thesis addresses the uncertainty, sensitivity and limitations of large-scale erosion models. The modelling framework consists of the universal soil loss equation (USLE), sediment delivery ratios (SDR) and European data. For several European regions, the relevance of the uncertainty in topographic model parameters, USLE factors and critical yields of suspended solids for the applicability of empirical models to predict sediment yields and SDR of river catchments is systematically evaluated. The comparison of alternative model parameters as well as calibration and validation data shows that even basic modelling decisions are associated with great uncertainties. Consequently, calibrated models have to be well-documented to avoid misapplication. Although careful choices of non-topographic algorithms can also be helpful to improve the model quality in regional applications, there is no definitive universal solution. The results also show that SDR models should always be calibrated and evaluated against sediment yields and SDR. With this approach, a new European soil loss map and an improved SDR model for river catchments north of the Alps and in Southeast Europe are derived. For other parts of Europe, the SDR model is of limited use. The studies on the annual variability of soil erosion reveal that seasonally weighted rainfall data is more appropriate than unweighted data. Despite satisfactory model results, neither the careful algorithm choice nor model improvements overcome the limitations of pan-European SDR models. These limitations are related to the mismatch of modelled soil loss processes and the relevant processes contributing to the observed or critical sediment load as well as the extraordinary sediment mobilisation during floods. Therefore, further research on integrating non-USLE processes and heavy-rainfall data as well as on disaggregating critical yields is needed

Erosão Hídrica de Solos Caso de Estudo do Concelho de Tarouca

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Gestão do Território, área de especialização em Detecção Remota e Sistemas de Informação Geográfica.A determinação de áreas susceptíveis à erosão hídrica é fundamental na tomada de decisões que envolvam actividades relacionadas com o uso do solo, nomeadamente actividades agrícolas. Estas decisões passam por medidas que podem ser preventivas, no sentido de se evitar a perda de solo através da implementação de medidas futuras, ou reactivas quando se obtém a perda de solo real, resultados que permitem a actuação imediata sobre o território na minimização dessa perda. Esta avaliação deve contemplar todos os factores que intervêm neste processo (e.g. características do solo, precipitação, uso e coberto do solo). Sendo o Concelho de Tarouca (área de estudo) uma área com elevada dependência agrícola, é fundamental a preservação do solo, evidenciando-se aqui, o reconhecimento das áreas mais susceptíveis à erosão hídrica. Neste sentido, recorreu-se à Equação Universal de Perda de Solo (EUPS) para determinar a erosão potencial e real nesta área, sendo necessário nestes procedimentos, o recurso à Detecção Remota (DR) e aos Sistemas de Informação Geográfica (SIG), por um lado na determinação da ocupação do solo a partir de imagens de satélite e, por outro, no cálculo de todos os factores considerados pela Equação. Das imagens de satélite obteve-se, essencialmente, índices de vegetação por diferença normalizada (NDVI), informação utilizada como complemento da cartografia de ocupação do solo disponível. Analisaram-se dados de precipitação das estações meteorológicas localizadas na área de estudo e no seu redor, na percepção da sua distribuição temporal e espacial. Parte destes dados integraram a avaliação da erosão através da EUPS. Os resultados aqui obtidos permitiram aferir as áreas mais susceptíveis à erosão hídrica, destacando-se a influência de vários factores, como o relevo, precipitação, características químicas e físicas do solo, o seu coberto e práticas nele desenvolvidas, na variação da distribuição da erosão potencial e real

The identification of unproductive hill country for planting carbon farmed vegetation and the economics of doing so : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science, School of Agriculture and Environment, Massey University, Manawatu, New Zealand

The Emissions Trading Scheme (ETS) is New Zealand’s main legislative tool for ensuring the domestic and international greenhouse gas reduction commitments are met. Tradeable ‘Carbon Credits’ (NZUs) are awarded to forestry owners for the carbon storage capabilities of their forests. Afforested areas under 100 hectares in size are subject to carbon storage estimation through the use of default ‘carbon look-up tables’. Recent mass land use change on New Zealand hill country from pastoral production to blanket planted exotic trees is divergent to government policy, which promotes the integration of native trees into the landscape. A pilot study tests whether ‘carbon look-up tables’ for Indigenous Forest are aligned with actual carbon sequestration of Leptospermum Scoparium (Manuka). This work aims to determine whether mass land use change is a consequence of the ETS in its current form. This is achieved through the economic modelling of exotic Pinus radiata (Pines) and Manuka on different slope classes of a typical New Zealand hill country farm. Allometric equations used on Manuka stands identified by random grid sampling showed that carbon sequestration of regenerating bush may be underestimated by over 82%. Economic modelling highlights the large earnings associated with blanket planted fast-growing Pines (peaking at $2,915/ha in Year 7) compared to the existing pastoral system ($242/ha/yr). Net Present Value (NPV) and sensitivity analysis results parallel findings at different inflation rates and market prices. Pines outperform natural regeneration of Manuka in every model from an economic perspective, although preferential income revenues like honey are not accounted for. Targeted plantings are not cost effective due to (a) increased fencing costs and (b) exclusion from the ETS. Recommendations made to align the impacts of the ETS with government policy include: (a) collecting carbon sequestration data for specific native species in different environments; (b) removing spatial constraints associated with the ETS’ definition of a forest; and (c) assigning a monetary incentive to promote certain forest values; such as biodiversity. Silvopastoral systems where pastoral and forest species spatially coexist are a potential solution. Areas requiring research in a New Zealand hill country context are identified using a recently improved framework

"Values that are to be safeguarded" : meeting the challenge of improving the health of waterways on agricultural land : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatū, New Zealand

Aotearoa New Zealand’s waterways are valued for many reasons. However, nationally, their health has been declining. Animal agriculture is a significant contributor to this decline. The country’s largest farm, Molesworth Station, is managed to safeguard its cultural, conservation, recreation, historical and farming values. For this reason, managers of the station’s farming operation sought information on possible impacts of current animal agriculture on the habitat and water quality of Molesworth’s streams and rivers, and recommendations on monitoring and improving the health of its waterways over time. This thesis found the health of streams and rivers on Molesworth to be good. It provides recommendations on monitoring and management, including areas where action could be taken to address the likely impacts of fine deposited sediment on waterways. Given both the scale of Aotearoa New Zealand’s animal agriculture, and its impact on freshwater quality and habitat, improving the health of waterways will require an increase in pro-environmental behaviour from farmers and will need to be sustained. This thesis also looks beyond Molesworth Station to investigate the influence of basic human values on pro- environmental behaviour in Aotearoa New Zealand’s agricultural sector. It suggests that prioritisation and priming of certain basic human values are likely to suppress pro- environmental behaviour and posits that targeted values-sensitive communication could play a role in encouraging and increasing pro-environmental behaviour to meet the challenge of improving the health of waterways on agricultural land