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Incorporating disaster resilience in MPA networks – impacts of sea-level changes on the Kaikōura coast in Aotearoa New Zealand
By Shane Orchard, Oceania Regional Chair, Commission on Ecosystem Management, International Union for the Conservation of Nature (IUCN) and Adjunct Research Fellow, University of Canterbury | Te Whare Wananga o Waitaha
Context and challenge
The 2016 Kaikōura Earthquake caused uplift of the intertidal zone by as much as six meters along a substantial section (c. 130 km) of the South Island’s east coast in Aotearoa New Zealand. The associated sea-level changes caused massive mortality of intertidal communities, even in areas that experienced relatively little uplift (e.g., 0.5 m) (Orchard et al., 2021). The primary connectivity challenge for affected ecosystems involved a process of reassembly in the new intertidal zone which was located a variable distance to seaward of its previous position (Figure 1). Recovery from this displacement relied heavily on recruitment processes and dispersal from remnant populations yet was further hampered by further post-earthquake changes in the new intertidal zone, leading to a slow and patchy reassembly process (Schiel et al., 2019). These included much accelerated rates of reef erosion and sediment movement that was partly influenced by a severe reduction in the stabilisation and sheltering services of the formerly dominant kelp forests (Orchard et al., 2021; Schiel et al., 2021). Additional stressors of particular note include a series of marine heatwaves (Thomsen et al., 2021) and ongoing sediment influx and turbidity effects associated with erosion processes in the earthquake ravaged hill-country (Tait et al., 2021) – illustrating an important element of land-sea connectivity. This case study provides a summary of some of the key ecological impacts and transferable principles for investigating and managing the connectivity effects of sea-level change in nearshore environments.
Figure 1. Displacement of coastal ecosystems by the 7.8 Mw Kaikōura earthquake. A) Severe mortality of bull kelp (Durvillaea spp.) at a high uplift site with the location of the previous low tide mark indicated for scale. B) Horizontal displacement of the intertidal zone to seaward. The area between the new and old high tide marks has generated new coastal land. C) Example of the diverse low intertidal zone seaweed communities that are characteristic of the Kaikōura coastline. This image is from a study site at Oaro that was not affected by vertical displacement, providing valuable information as a nearby comparative control. D). Example of the former low tide zone at an uplifted site with the terrestrial vegetation succession now underway and the new intertidal zone visible in the distance.
Figure 2. Overview of MPA networks the vicinity of the township of Kaikōura, a major wildlife and marine tourism destination. The area shown is only a portion of the coastline that was uplifted by the 7.8 Mw Kaikoura earthquake, with further areas of coastal displacement extending northwards into the region of Marlborough. The southern limit of the uplift was located near Oaro.
Approach
Following the earthquake, a series of government funded research programmes were initiated to quantify change and track the recovery trajectory (Schiel et al., 2024). Primary objectives included identifying intervention points that might assisted the recovery of key ecosystems and their services. These included providing decision support for policy and management decisions on recreational fishery regulations, new arrangements for coastal access, and area-based protections for important species and habitats in the post-earthquake environment. The wide diversity of affected ecosystems (e.g., kelp-dominated rocky shores, gravel and sandy beaches) necessitated the use of a variety of techniques to understand the extent of initial impacts and track the post-disaster recovery processes as they unfolded. Over a 6-year period some of the methodologies used included remote sensing at a variety of spatial scales (e.g., satellite imagery analysis, airborne LiDAR and UAV surveys), extensive field surveys of the littoral environment, and community-based monitoring with local groups. Aside from this investment in research and information exchange, some of the early management interventions included closure of the commercial pāua / abalone (Haliotis iris and H. australis) fishery, worth around $2M annually, and closure of culturally-important shellfish and seaweed harvesting on the earthquake affected coast (Gerrity et al., 2020; Orchard et al., 2024; Schiel et al., 2023).
Results
Findings from spatial ecology research on the displacement of key habitats included changes in the location of juvenile pāua rearing habitat in the intertidal zone, spawning grounds for diadromous fish at river mouths, and threatened dune vegetation and shorebird nesting grounds on uplifted beaches along the coast (Gerrity et al., 2020; Orchard et al., 2022; Orchard & Schiel, 2021). These changes were additional to the expected seaward shift in the major intertidal communities that was associated with the contraction of suitable habitat in some locations, and expansion in others, reflecting interactions between the degree of uplift and the cross-shore topography of the coast (Figure 2). At many other sites where brown algal taxa have remained dominant there has been a pronounced shift from Durvillaea spp. to Carpophyllum maschalocarpum as the dominant canopy species, leading to intense interest in the prospects for Durvillaea recovery (Thomsen et al., 2021).
The MPA network in the affected area includes a no-take marine reserve (Hikurangi Marine Reserve) established under the Marine Reserves Act 1971 and several other marine management areas including two types of customary protected area (mātaitai and taiāpure) established under the Kaikōura (Te Tai o Marokura) Marine Management Act 2014 (Figure 2). The landward limit of these MPAs is generally defined by the Mean High Water Springs (MHWS) line with the exception of the Ōhau New Zealand Fur Seal Sanctuary which straddles the high tide line to include seal haul-out areas. With the ecosystem displacements being almost exclusively in a seaward direction (consistent with uplift), the recovering nearshore marine habitats remain within the footprint of the pre-existing MPAs. However, the combination of high mortality followed by patchy and potentially altered patterns of recovery suggest that new areas may become important that are outside of the focus of the current MPAs or may be effectively unknown. Ongoing research needs include evaluating the fit between the emerging new distribution of key species and ecosystems and the current MPA network. Aside from the lengthy and non-linear nature of recovery processes this task remains challenging due to the size of the affected area and multitude of ecologically important scales.
To date identification of displacement effects has primarily been completed for coastal intertidal and terrestrial areas which are readily surveyed, and the results have informed protected area management in numerous ways. Examples include changes to significant natural areas identified for statutory protection under New Zealand’s Resource Management Act, and the creation of a new bylaw under the Local Government Act and Land Transport Act to control motorised vehicle impacts on previously remote beaches that were made more accessible by the landscape changes. In addition, the new coastal land generated by the uplift presents new opportunities for improving land-sea connectivity that could include improved buffering functions for existing MPAs (Orchard & Schiel, 2022).
Takeaway messages for managing the connectivity changes that may be generated by natural disaster events include the importance of capacity to assess the initial impacts at multiple scales, which is turn facilitated by a high degree of preparedness for mobilising the necessary responses. This can be assisted by drawing on learning from past events, particularly those that featured methodological developments or refinements were made to improve the feasibility and/or cost-effectiveness of disaster impact assessments and longer-term monitoring programmes. This case also illustrated the importance of interactions with additional stressors following an initial major disturbance event. They had a strong bearing on the speed and direction of ecosystem structure and functional recovery (e.g., dominance of desirable habitat types, primary productivity) which in turn affected the nature of long-term shifts in distribution patterns. These aspects have also influenced ecosystem service provision with examples including the recommencement of sustainable harvesting activities for shellfish and seaweed, with considerable economic implications. In looking for solutions and intervention points, a focus on identifying and tackling ‘manageable’ stressors provides a strategy that can assist with the attainment of desirable outcomes by helping to accelerate the recovery process while guarding against the potential establishment of undesirable stable states (e.g., caused by invasive species). This strategy can also improve resilience to future disturbances which must be kept in mind in dynamic coastal environments that are expected to undergo further changes.
Learn more: RECOVER Kaikoura Earthquake
References
Gerrity, S., Alestra, T., Fischman, H. S., & Schiel, D. R. (2020). Earthquake effects on abalone habitats and populations in southern New Zealand. Marine Ecology Progress Series, 656, 153-161.
Orchard, S., Fischman, H. S., Gerrity, S., Alestra, T., Dunmore, R., & Schiel, D. R. (2021). Threshold effects of relative sea-level change in intertidal ecosystems: empirical evidence from earthquake-induced uplift on a rocky coast. GeoHazards, 2(4), 302-320. doi:10.3390/geohazards2040016
Orchard, S., Fischman, H. S., & Schiel, D. R. (2022). Managing beach access and vehicle impacts following reconfiguration of the landscape by a natural hazard event. Ocean & Coastal Management, 220. doi:10.1016/j.ocecoaman.2022.106101
Orchard, S., Gerrity, S., & Schiel, D. R. (2024). Re-thinking recreational fishing – how a natural disaster presents insights and opportunities for achieving sustainability and equity objectives. Marine Policy, 159, 105916. doi:10.1016/j.marpol.2023.105916
Orchard, S., & Schiel, D. R. (2021). Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and environmental controls on īnanga (Galaxias maculatus) spawning grounds. Pacific Conservation Biology, 28(2), 140-153. doi:10.1071/PC21004
Orchard, S., & Schiel, D. R. (2022). Natural disaster recovery as resilience-building opportunity: lessons from an uplifted coast. Proceedings of Australasian Coasts and Ports Conference (2021), 738-744.
Schiel, D. R., Alestra, T., Gerrity, S., Orchard, S., Dunmore, R., Pirker, J., . . . Thomsen, M. (2019). The Kaikōura earthquake in southern New Zealand: loss of connectivity of marine communities and the necessity of a cross‐ecosystem perspective. Aquatic Conservation: Marine and Freshwater Ecosystems, 29(9), 1520-1534. doi:10.1002/aqc.3122
Schiel, D. R., Falconer, T. R. L., Gerrity, S., Dunmore, R. A., Crossett, D., Virgin, S. D. S., . . . Orchard, S. (2024). Recovery of rocky intertidal and subtidal communities affected by the 2016 Kaikōura earthquake and coastal uplift: 6-year assessment. New Zealand Aquatic Environment and Biodiversity Report No. 328. 84pp.
Schiel, D. R., Gerrity, S., & Orchard, S. (2023). Allocations, quota and abalone fishery management: the Tragedy of the commons revisited. New Zealand Journal of Marine and Freshwater Research, 1-18. doi:10.1080/00288330.2023.2273468
Schiel, D. R., Gerrity, S., Orchard, S., Alestra, T., Dunmore, R. A., Falconer, T., . . . Tait, L. W. (2021). Cataclysmic disturbances to an intertidal ecosystem: loss of ecological infrastructure slows recovery of biogenic habitats and diversity. Frontiers in Ecology and Evolution, 9(827). doi:10.3389/fevo.2021.767548
Tait, L. W., Orchard, S., & Schiel, D. R. (2021). Missing the forest and the trees: utility, limits and caveats for drone imaging of coastal marine ecosystems. REMOTE SENSING, 13(16), 3136. doi:10.3390/rs13163136
Thomsen, M. S., Mondardini, L., Thoral, F., Gerber, D., Montie, S., South, P. M., . . . Schiel, D. R. (2021). Cascading impacts of earthquakes and extreme heatwaves have destroyed populations of an iconic marine foundation species. Diversity and Distributions, 27(12), 2369-2383. doi:10.1111/ddi.13407