Trade-offs between environmental and economic factors in conversion from exotic pine production to natural regeneration on erosion prone land

Background: Some of New Zealand’s exotic pine (Pinus radiata D.Don) forests were planted for erosion mitigation but cultural, legislative, environmental, and profitability limitations in some parts of the landscape have led to reassessment of their suitability. There is limited information to support landowner decisions on the viability of natural regeneration of native forest post-pine-harvest. Methods: We evaluated scenarios of post-harvest natural regeneration, compared to remaining in pine production, using erosion susceptibility determined from historical occurrence of landslides, gullies and earthflows, biophysical growth modelling of mānuka–kānuka (Leptospermum scoparium-Kunzea ericoides (A.Rich) Joy Thomps.) shrubland using the process-based CenW model, and cost-benefit analyses using NZFARM with two land use change scenarios, at two levels of erosion mitigation ± honey profits. Results: In our study area, the Gisborne Region (North Island of New Zealand), ~27% of the land has moderate–very high susceptibility to landslides, 14–22% a high probability of contributing material to waterways, and 19% moderate–very high gully erosion susceptibility. Pines grow 10 times faster than naturally regenerating mānuka–kānuka shrubland, but mānuka–kānuka is used for honey not wood production. Natural regeneration resulted in losses of $150–250 ha-1 yr-1 compared to the current profitability of pine production. Honey production offset some reduction in pine revenue, but not fully. Thus, the viability of shifting from pines to native forest is highly dependent on landowner impetus and value for non-market ecosystem services (such as cultural and biodiversity values) provided by native forest. Conclusions: A mosaic of land uses within a property may sufficiently offset income losses with other benefits, whereby highly erosion-prone land is shifted from rotational pine forest production to permanent native forest cover with honey production where possible. At the regional scale in Gisborne, the conversion of the most highly susceptible land under production forestry (315–556 ha) to natural regeneration has the potential for wider benefits for soil conservation reducing erosion by 1–2.5 t yr–1 of sediment facilitating achievement of cleaner water aspirations and habitat provision.

Flood inundation and broader ecosystem service modelling in a data-sparse catchment; application of LUCI to Marokopa, NZ

<p>Event magnitude, societal vulnerability, and exposure define hazard impact. In New Zealand, flooding is the most common and damaging hazard at the decadal scale. Residents within the Marokopa catchment (west coast of the Waikato region) identify flood and erosion as significant local hazards. Flooding is influenced by a diverse range in factors, from environmental factors in the catchment, such as hydrology and climate, to socio-political policies and community awareness. Each of these factors is themselves influenced by climate change, and therefore requires study at the local and national scales. A mixed-methods approach was used to analyse flood and erosion through application of the Land Use and Capability Indicator (LUCI). Qualitative analysis along with rainfall-runoff, inundation, and holistic ecosystem service (ES) modelling are used to evaluate both flood and erosion extent, but also influencing factors. This research used a unique, mixed-methods approach to research a traditionally quantitative topic, improve on the understanding of karstic rainfall-runoff modelling and support LUCI development through application in a geomorphologically distinct location. Local knowledge facilitated both temporal and spatial outlining of flood and erosion extent at macro and catchment-scales. Bespoke rainfall-runoff modelling of the Marokopa upper catchment defined localised rainfall, seasonality and the karstic system as significant influences on runoff, with poor to excellent model-fit. Preliminary inundation findings outlined tidal, upper catchment bank-overflow, and overland flow as significant mechanisms of flooding. Finally, flood and erosion mitigation ecosystem services were modelled, with synergistic comparisons also analysed. Priority areas for future land management and hazard mitigation investment include the Marokopa floodplains ~5 km inland from the coast. Novel integration of physical and social observations outlines current flood risk extent and evaluates factors which contribute to flooding, providing a thorough knowledge base for future flood modelling within the Marokopa catchment.</p>

Flood inundation and broader ecosystem service modelling in a data-sparse catchment; application of LUCI to Marokopa, NZ

<p>Event magnitude, societal vulnerability, and exposure define hazard impact. In New Zealand, flooding is the most common and damaging hazard at the decadal scale. Residents within the Marokopa catchment (west coast of the Waikato region) identify flood and erosion as significant local hazards. Flooding is influenced by a diverse range in factors, from environmental factors in the catchment, such as hydrology and climate, to socio-political policies and community awareness. Each of these factors is themselves influenced by climate change, and therefore requires study at the local and national scales. A mixed-methods approach was used to analyse flood and erosion through application of the Land Use and Capability Indicator (LUCI). Qualitative analysis along with rainfall-runoff, inundation, and holistic ecosystem service (ES) modelling are used to evaluate both flood and erosion extent, but also influencing factors. This research used a unique, mixed-methods approach to research a traditionally quantitative topic, improve on the understanding of karstic rainfall-runoff modelling and support LUCI development through application in a geomorphologically distinct location. Local knowledge facilitated both temporal and spatial outlining of flood and erosion extent at macro and catchment-scales. Bespoke rainfall-runoff modelling of the Marokopa upper catchment defined localised rainfall, seasonality and the karstic system as significant influences on runoff, with poor to excellent model-fit. Preliminary inundation findings outlined tidal, upper catchment bank-overflow, and overland flow as significant mechanisms of flooding. Finally, flood and erosion mitigation ecosystem services were modelled, with synergistic comparisons also analysed. Priority areas for future land management and hazard mitigation investment include the Marokopa floodplains ~5 km inland from the coast. Novel integration of physical and social observations outlines current flood risk extent and evaluates factors which contribute to flooding, providing a thorough knowledge base for future flood modelling within the Marokopa catchment.</p>

Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico

Coral reefs are increasingly recognized for their shoreline protection services. The hydrodynamic performance of this ecosystem is comparable to artificial low-crested structures often used in coastal protection, whose objective is to emulate the former. Coral reefs also provide other important environmental services (e.g., food production, habitat provision, maintenance of biodiversity and social and cultural services) and leave almost no ecological footprint when conservation and restoration actions are conducted to maintain their coastal protection service. However, studies have focused on their flood protection service, but few have evaluated the morphological effects of coral reefs through their ability to avoid or mitigate coastal erosion. In this paper, we investigate the relation between shoreline change, reefs’ geometry and hydrodynamic parameters to elucidate the physics related to how the Mesoamerican Reef in Mexico protects sandy coastlines from erosion. Using numerical wave propagation and historical shoreline change calculated from satellite imagery, a direct correlation was found between shoreline movement, the depths and widths of reef flats, changes in the wave energy flux, and the radiation stresses of breaking waves. The findings indicate that the most remarkable efficacy in preventing beach erosion is due to reefs with shallow crests, wide reef flats, a dissipative lagoon seabed, located at ∼300 m from the coastline. The results provide essential insights for reef restoration projects focused on erosion mitigation and designing artificial reefs in microtidal sandy beaches. Results are limited to wave-dominated coasts.

The Impact of Soil-Improving Cropping Practices on Erosion Rates: A Stakeholder-Oriented Field Experiment Assessment

The risk of erosion is particularly high in Mediterranean areas, especially in areas that are subject to a not so effective agricultural management–or with some omissions–, land abandonment or wildfires. Soils on Crete are under imminent threat of desertification, characterized by loss of vegetation, water erosion, and subsequently, loss of soil. Several large-scale studies have estimated average soil erosion on the island between 6 and 8 Mg/ha/year, but more localized investigations assess soil losses one order of magnitude higher. An experiment initiated in 2017, under the framework of the SoilCare H2020 EU project, aimed to evaluate the effect of different management practices on the soil erosion. The experiment was set up in control versus treatment experimental design including different sets of treatments, targeting the most important cultivations on Crete (olive orchards, vineyards, fruit orchards). The minimum-to-no tillage practice was adopted as an erosion mitigation practice for the olive orchard study site, while for the vineyard site, the cover crop practice was used. For the fruit orchard field, the crop-type change procedure (orange to avocado) was used. The experiment demonstrated that soil-improving cropping techniques have an important impact on soil erosion, and as a result, on soil water conservation that is of primary importance, especially for the Mediterranean dry regions. The demonstration of the findings is of practical use to most stakeholders, especially those that live and work with the local land.

Assessing the Impact of a Winter Storm on the Beach and Dune Systems and Erosion Mitigation by Plants

The impact of storms on coastal dunes and beaches and the effects they induce in topography and plant communities are natural processes that contribute to maintaining natural coastal dynamics. However, because coasts are often densely populated, these phenomena are perceived as major threats to human property. To protect human assets sustainably, nature-based defenses have emerged as an option. Coastal dunes act as natural buffers that mitigate the extent of erosion and inland flooding, and their resistance depends on the biogeomorphological feedback between the plants and the dunes. This study aimed to evaluate the effect of one winter storm on beach and dune topography and the plant communities, and to explore the effect of plants in mitigating erosion on beaches with different geomorphological features. The effects on plant communities were evaluated by comparing diversity and plant cover before and after the storm. Later, the role of plants in conferring dune resistance against erosion was examined by measuring erosion on the exposed face of the dunes considering plant cover and plant richness. The results did not show significant differences in plant diversity and plant cover between pre-and post-storm conditions, but turnover of species was recorded. The dune building species were not affected but inland species disappeared. Erosion was reduced when the dunes were higher and, furthermore, plant cover was negatively correlated with erosion on these dunes. The results showed a reduced impact of the storm on the plant communities, which is important as it facilitates the recovery of dunes by the dune-building species and protects them in a subsequent storm. The novelty of this study is that: (a) it demonstrates the species-specific role of plants in mitigating dune erosion in field conditions; (b) it shows the interaction between plant-related features and geomorphological variables in promoting dune resistance to erosion, and (c) it explores the immediate effect of a winter storm on the plant community and dune-building species.

Exploring Relationship between Perception Indicators and Mitigation Behaviors of Soil Erosion in Undergraduate Students in Sonora, Mexico

Soil erosion represents a critical socio-economic and environmental hazard for Mexico and the world. Given that soil erosion is a phenomenon influenced by human activities, it is essential to know the level of cultural perspectives on this matter. An instrument with eight scales was applied to 275 university students from a northwestern Mexican city, which measured the knowledge about soil erosion, self-efficacy in solving the problem, future perspectives, perceived consequences, obstacles to addressing soil erosion, and mitigation intentions and behaviors. To analyze the relationship between the scales and the intentions and behaviors of soil erosion mitigation, a model of structural equations was tested. In summary, the participants know the problem of soil erosion, its impacts, and recognize risks to human and environmental health. They also know their important role within soil conservation; however, they identified significant obstacles to action. This study determined that each indicator has a correlation with soil erosion mitigation intentions except for the obstacles. The indicators that had the greatest positive relationship in mitigation intentions were knowledge, self-efficacy, and the perspective of the future. The implications of these results open the landscape to the creation of efficient strategies to mitigate soil erosion in this region and Mexico.

Numerical Analysis of Elbow Erosion Mitigation Using Swirl Pipes in Gas-Particle Two-Phase Flows

In the oil and gas industry, sand particle erosion damage to elbows is a common problem. The ability to predict erosion patterns is of great importance for sizing lines, analyzing failures, and limiting production rates. Computational fluid dynamics (CFD) can be utilized to study the erosion behavior and mitigate the erosion problem for safety purposes and greater equipment longevity. In order to alleviate the adverse results of sand erosion in elbows, the current study investigated the potential of the geometrically induced swirl flow generated from flow passing through a four-lobed twisted pipe upstream of an elbow. To this end, first, the airflow in a standard elbow equipped with different swirl pipes was simulated using the SIMPLE method, then an Eulerian-Lagrangian approach was employed to track the particles, and finally, the erosion rate was computed. The simulation results indicated that the elbow’s maximum erosion rate with twisted pipes placed upstream of the elbow is lower than the one obtained for the standard pipe. In addition, as the twisted pipe position gets closer to the bend, the erosion rate further reduces. Thus, swirling flows provide a promising prospect as a mechanism to control the erosion rate in elbows.

The effect of natural infrastructure on water erosion mitigation in the Andes

Soil erosion by water is affecting natural and anthropogenic environments through its impacts on water quality and availability, loss of soil nutrients, flood risk, sedimentation in rivers and streams, and damage to civil infrastructure. Sustainable management aims to avoid, reduce and reverse soil erosion and can provide multiple benefits for the environment, population, and livelihoods. We conducted a systematic review of 121 case studies from the Andes to answer the following questions: (1) Which erosion indicators allow us to assess the effectiveness of natural infrastructure? (2) What is the overall impact of working with natural infrastructure on on-site and off-site erosion mitigation? and (3) Which locations and types of studies are needed to fill critical gaps in knowledge and research? Three major categories of natural infrastructure were considered: protective vegetation, soil and water conservation measures, and adaptation measures that regulate the flow and transport of water. From the suite of physical, chemical and biological indicators commonly used in soil erosion research, two indicators were particularly relevant: soil organic carbon (SOC) of topsoil, and soil loss rates at the plot scale. In areas with protective vegetation and/or soil and water conservation measures, the SOC of topsoil is –on average– 1.3 to 2.8 times higher than in areas under traditional agriculture. Soil loss rates in areas with natural infrastructure were reported to be 38 % to 54 % lower than rates measured in untreated croplands. Further research is needed to evaluate whether the reported effectiveness holds during extreme events related to, for example, El Niño–Southern Oscillation.