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Linking land and sea to inform ahupua‘a (ridge-to-reef) management in Hawai‘i – NSF Coastal SEES

Posted March 19, 2018 | Categories: Blog, Project Environment

A community member from Haʻēna, located on the windward side of Kauaʻi (see Fig 1A), said “come” as she offered her hand inviting me in. I stepped into the forming circle of the pule (prayer), and we stood together silently listening to an oli chanted by a local kupuna (elder) (see Photo 1A). This moment blessed the opening of a public hearing which eventually led to the passage of rule package of Haʻēna Community Based Subsistence Fisheries Management Area (CBSFA) in mid-2015. The significance of this event cannot be understated. This was the first time in the U.S. state of Hawaiʻi that local-level fisheries management rules based on indigenous Hawaiian practices were recognized. Among these rules, a marine refuge (Makua Pu‘uhonua) was designated in the sheltered lagoon of Makua reef to protect a key fish nursery area (see Fig 1B). That same year, the community of Kaʻūpūlehu, located on the leeward side of Hawaiʻi Island (see Fig 1A), initiated a law implementing a 10-year fishing rest period known as ‘Try Wait’ (see Photo 1B). This resulted in the protection of the entire coral reef fringing reef area (see Fig 1C).

Figure 1. Hā‘ena and Ka‘ūpūlehu ahupua‘a location. (A) Location of Hā‘ena and Ka‘ūpūlehu ahupua‘a on Kauaʻi and Hawaiʻi along the main Hawaiian Island chain, with island age and the direction of the prevailing north-east tradewinds and ocean swell indicated. Land use/cover and marine closure/fishing rest area are shown for (B) Hā‘ena and (C) Ka‘ūpūlehu.

Photo 1. (A) Pule at Haʻēna prior to the public hearing for the CBSFA package rules, (B) Gathering at Kaʻūpūlehu prior to the public hearing for the ‘Try Wait’ fishing rest area.

These two communities embody a cultural renaissance that seeks to revive customary management approaches, such as pono fishing practices, kapu (traditional closures), and the ahupua‘a (ridge-to-reef) approach in Hawai‘i to protect terrestrial, freshwater, and marine resources. Both communities initiated these marine closures to protect fish species that feed on algae (herbivorous fish). Without these herbivorous species, algae blooms can cover the reef when excess nutrients flow into the sea from the land. By eating the algae, these protected fish create space for new corals to settle and ensure the persistence or resilience of the reefs. Resilience has been defined as the capacity of an ecosystem to cope with disturbances without shifting to an alternative state, while maintaining its functions and supporting human uses. These local communities are also interested in a better understanding of how land-based sources of pollutants from golf courses, lawns and cesspools affect their marine ecosystems. Even with healthy herbivorous fish populations, these pollutants take a toll on coral reefs, especially with increases in ocean temperature and acidity as a result of climate change. It is important to these communities, and the health of all marine ecosystems, to ensure that future planning takes these impacts into account to promote coral reef resilience to climate change.

Ridge-to-reef management has been widely advocated to foster coral reef resilience, though the degree to which managing land-based pollutants can benefit coral reefs varies among places. In an effort to promote coral reef resilience to climate change, we adopted the traditional ahupua‘a framework to study the effect of existing coastal development on coral reefs and support the restoration of community-based management in Hawai‘i and other Pacific islands. In addition to their engaged communities, we focused on these two locations because they are very different in terms of human coastal development and natural coral reef structure. Hā‘ena is mostly rural with a number of private residences along the coast (see Fig 1B). Kaʻūpūlehu is both commercially and residentially more developed than Hāʻena, with two large luxury resorts, a golf course, and several private residences along the southern end of the coast (see Fig 1C). The powerful waves in Hā‘ena have over time carved wider and shallower reef flats and produced shallow lagoons protected from the swell by well-developed reef crests. In comparison, the coral reefs of Ka‘ūpūlehu are younger and form a relatively narrow fringe on the steep slope of that island.

Effective ridge-to-reef management requires improved understanding of land-sea linkages and tools to evaluate the effects of land (e.g. nutrients carried through groundwater) and marine drivers (e.g. wave power and reef topography) on coral reefs. To accomplish this, we developed a framework to link land to sea through groundwater and identify areas on land to manage human-derived nutrients and promote coral reef resilience (see Fig 2). We applied this framework in Hā‘ena and Ka‘ūpūlehu ahupua‘a, to compare outcomes from these different places and inform place-based ridge-to-reef management.

Fig 2. Linked land-sea modeling framework. Based on (A) climate, groundwater, and nutrient concentration data, (B) groundwater flow and nutrient concentrations were modeled. (C) Nutrient flux from anthropogenic drivers were added to the background nutrient flux. (D) A land-sea link was created by sub-dividing the groundwater model domain into ‘flow tubes’ ending at pour points along the shoreline. (E) The coastal discharge models used the groundwater flow and nutrient flux and GIS distance-based models to generate the land-based driver grid data. (F) The wave model and bathymetry data were coupled with (G) GIS-based models to generate the marine driver grid data. (H) The coral reef predictive models were calibrated on coral reef survey data. (I) Outputs were: (1) response curves, (2) maps of benthic and fish indicators, and (3) a linked land-sea decision-support tool.

Geologically older and exposed to the trade winds, Hā‘ena receives high rainfall, resulting in steeply eroded cliffs, with high surface and groundwater flow (see Fig 3A). Geologically younger and located in the rain shadows of Mauna Loa and Mauna Kea mountains, Ka‘ūpūlehu is very dry and barely eroded, resulting in low surface flow and high groundwater flow (see Fig 3B). More rain in Hā‘ena means that nutrients are more diluted (less concentrated) than Ka‘ūpūlehu which is much drier. Our groundwater models showed that groundwater in Ka‘ūpūlehu has high levels of nitrogen from natural sources. At Hā‘ena, most nutrients come from natural processes due to abundant rainfall and groundwater flow. The key sources of human-derived nutrients were wastewater from houses on cesspools at Hā‘ena and the golf course and wastewater from the injection well at Kaʻūpūlehu.

Fig 3. Illustration of the groundwater system at Hā‘ena and Kaʻūpūlehu. (A) Hā‘ena is located on old, wet, wave exposed coast of Kauai, (B) Kaʻūpūlehu is young, dry, and wave sheltered.

To measure the resilience of the coral reefs at each location, we looked at four benthic groups and four fish groups based on their ecological roles and cultural importance to the communities. The benthic groups were crustose coralline algae (CCA), hard corals, turf, and macroalgae. CCA and corals are active reef builders which provide habitat for reef fishes. CCA also stabilize the reef in high-wave environments. Abundant benthic algae can be a sign of high nutrients or low numbers of herbivorous fish, which can harm coral health through competition for space. Algae-eating fish identified as important by the communities (e.g., surgeonfishes and parrotfishes) were modeled based on their feeding modes and ecological role: (1) browsers, (2) grazers, and (3) scrapers.

Our coral reef models showed that high wave power at Hā‘ena has shaped the living community of the reefs which are dominated by CCA and turf algae with many grazers and less scrapers (see Fig 4A). Makua lagoon area is an exception where corals are able to grow, sheltered from powerful waves by a well-developed reef crest. In contrast, low wave power in Ka‘ūpūlehu has resulted in coral dominated reefs with high turf and many grazers and scrapers (see Fig 4B). Our coral reef models also showed that land-based nutrients from groundwater can increase benthic algae, suppress coral and CCA, and decrease numbers of locally important fish at both sites.

Fig 4. Illustrations of the coral reefs. Coral reef community in (A) Hā‘ena and (B) Kaʻūpūlehu.

Coral reefs in Hā‘ena seem less susceptible to nutrient inputs from coastal development because they benefit from dilution and mixing, due to high freshwater and wave power. Hā‘ena is rural with limited development or agriculture, so most of the nutrients come from natural processes, with the exception of land areas to the east of the ahupua‘a where nutrients are largely human-derived (see Fig 1B). These areas that contribute high human nutrients lie upstream from the protected reef fish nursery at Makua. We identified this reef as vulnerable to algae blooms and coral bleaching due to the nearness of human-derived nutrient sources, limited mixing from shallow depth and low wave power, and abundant corals and turf algae (marked in red in Fig 5A). To promote coral reef resilience to climate change, Hā‘ena community can focus on upgrading cesspools in the priority areas that we identified, located upstream from Makua (located in blue zone in Fig 5A).

On the other hand, Ka‘ūpūlehu coral reefs seem more vulnerable to nutrient inputs from coastal development due to high levels of background nitrogen in the groundwater and limited dilution and mixing from low rainfall and wave power. Additionally, Ka‘ūpūlehu’s plentiful coral cover is prone to coral bleaching. Based on our findings, the community can focus on not increasing phosphorus inputs from the wastewater injection well (located in the pink zone in Fig 5B) to reduce the vulnerability of coral reefs located downstream (marked in green tea in Fig 5B). In addition, the community can help foster resilience of their coral reefs (marked in red in Fig 5B) by ensuring that environmentally sound practices are continued when fertilizing the golf course, particularly in the land areas located upstream from Uluweuweu bay and Kahuwai bay (located in blue zone in Fig 5B). This will also help to protect the water quality of a culturally important groundwater spring (Wai a Kāne) that was identified by the Ka‘ūpūlehu community in Kahuwai bay (Fig 1C).

Fig 5. Coral reef areas vulnerable to land-based nutrients and priority land areas at Hā‘ena and Ka‘ūpūlehu. (A) Hā‘ena and (B) Ka‘ūpūlehu coral reef areas vulnerable to nutrients (nitrogen and phosphorus) combined with the priority land areas with the highest human derived nutrients and therefore, where management action should focus on managing wastewater and fertilizers practices.

This research shows that place matters! Different environmental conditions make place-based solutions essential. Second, protecting herbivorous fish is key for coral growth and recovery. Last but not least, efforts to protect coral reefs need to address nutrient inputs from golf courses and cesspools. Using this framework, we located coral reefs vulnerable to land-based nutrients and linked them to areas on land where limiting sources of human-derived nutrients could prevent increases in benthic algae and promote chances of coral recovery from bleaching. Following on this research, we used this framework to assess the three human factors most relevant to these communities and across Hawai‘i more broadly: coastal development, fishing and climate change. More to come!

Note: This work was funded by the NSF Coastal SEES and formed a chapter of my PhD dissertation at the Department of Natural Resources and Environmental Management (refer to the published article at https://doi.org/10.1371/journal.pone.0193230). The NSF Coastal SEES project Principal Investigators were: Tamara Ticktin (UHM Botany), Kim Burnett (UHERO), Stacy Jupiter (Wildlife Conservation Society, Melanesia), Alan Friedlander (UHM Biology and National Geographic), Tom Giambelluca (UHM Geography), Mehana Vaughan (UHM NREM), Kawika Winter (National Tropical Botanical Garden), Lisa Mandle (Natural Capital Project, Stanford), and Heather McMillen (NREM). Special thanks to the researchers who contributed to this work, in particular Robert Whittier, Kostantinos Stamoulis, Leah Bremer, Natalie Kurashima, and Cheryl Geslani. Many thanks to a collaborating artist, Sophie Eugène, for the illustrations and the Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/symbols/) for the marine symbols. I would like to also thank Tamara Smith for editing this piece. Finally, we are grateful to our community and landowner partners in Kaʻūpūlehu and Haʻēna who inspired this research and made this project possible.

- Jade Delevaux
Geospatial scientist in the Department of Geology & Geophysics. School of Ocean and Earth Science and Technology

UHERO BLOGS ARE CIRCULATED TO STIMULATE DISCUSSION AND CRITICAL COMMENT. THE VIEWS EXPRESSED ARE THOSE OF THE INDIVIDUAL AUTHORS.


Makena Coffman appointed to Climate Change Commission

UHERO congratulates Makena Coffman on her appointment to Honolulu's Climate Change Commission. The goal of the commission is to assess potential impacts of climate change on Hawaii, and to provide policy makers with recommendations to address these impacts.

Makena Coffman is the co-director of Project Environment, UHERO Research Fellow, and Professor of Urban and Regional Planning.


Cost-Effectiveness of Herbicide Ballistic Technology to Control Miconia in Hawaii

UHERO is working with Dr. James Leary (CTAHR) to assess cost effectiveness of Herbicide Ballistic Technology (HBT) operations to control invasive miconia (Miconia calvescens) plants before reaching maturity. Based on studies in Costa Rica, Tahiti and Australia, we can interpret spatial and temporal implications of management driven by miconia’s fecundity, dispersal, seed bank longevity and recruitment. We find that the dispersal kernel of miconia in the East Maui Watershed is closely matched to a similar probability density function developed from miconia naturalized in North Queensland, Australia (Fletcher and Westcott 2013). In this spatial model, 99% of recruitment was within 609 m with rare stochastic events (i.e., 1%) extending out to 1644 m. Based on these biological features, one autogamous, mature plant can impact up to 850 ha (i.e., 2100 acres) of forested watershed with hundreds to thousands of dispersed progeny germinating asynchronously over several decades (Fig. 1).

Figure 1. The dispersal kernel displays as a raster layer creating an 850-ha area calculation with corresponding probability density function (color shades).

Effective management is achieved when target mortality outpaces biological recruitment. Cacho et al. (2007) coined the term ‘‘mortality factor’’ described by the simple equation: m=Pd x Pk, where the probabilities of detection (Pd ) and kill (Pk)are equal determinants of the “mortality” product. Our current Pk is 0.98 for all HBT treatments. With this effective and reliable treatment technique, management outcomes largely depend on detection (Leary et al. 2013; Lodge et al. 2006). Koopman (1946) introduced the mathematical framework for estimating the probability of detection: Pd=1-e-c, where the probability of detection asymptotically approaches 1.0 with increasing coverage (Fig. 2). In operations, imperfect detection can be compensated by frequent interventions compounding coverage levels over time, but with obvious diminishing returns (Leary et al. 2014).

Figure 2. Probability of detection (blue) and the inverse for the equally important confirmation of no targets (orange). Note gray dash connotation of a theoretically “perfect” sensor, where coverage is equal to detection and confirmation.

The variable costs for HBT operations (e.g., flight time and projectiles) are driven by target density (Leary et al 2013, Leary et al. 2014). With that knowledge, we estimate the cost to manage the area (i.e., 850 ha) impacted by the dispersal of new progeny created by a mature plant. A new mature miconia with two panicles may produce ~300-400 progeny. With a single, incipient target being such a high risk, intensive efforts should be matched to comprehensively search the entire impact area over the several decades with a level probability of detection (and equal confirmation of no targets) of all progeny recruits. For instance, with 320 propagules dispersed, Pd would need to exceed 0.9968 with coverage at 5.77 s per 100 m2 pixel totaling ~136 hours of effort over the entire impact area over four decades (Fig. 3A). Any level of coverage less than that (including 99%) would be prone to missing a target that ultimately reaches maturity and newly replenishes the seed bank (Fig. 3B). Furthermore, an overwhelming majority of search effort would actually be dedicated to the confirmation of no targets, where, for instance 87% of effort is invested in looking for 1% of the targets dispersed out to the perimeter.

Figure 3. (A) Search effort (EFT; hours) over a 43-year period to match the level of coverage with the probability of detection from a random search effort. (B) is the reproduction of 2nd generation progeny by undetected targets of the 1st generation shown as Base 10 log scale.

Based on this model, we estimate accrual of future management costs ranging from $169,000-337,000 for every mature target detected, with the increase from the base cost dependent on increasing propagule loads and the static cost to treat each those individuals detected.

- James Leary, Kimberly Burnett and Christopher Wada


 

References

Cacho, O.J., Hester, S. and Spring, D., 2007. Applying search theory to determine the feasibility of eradicating an invasive population in natural environments. Australian Journal of Agricultural and Resource Economics, 51(4), pp.425-443. 


Fletcher C. S. and Westcott D. A.. 2013. Dispersal and the design of effective management strategies for plant invasions: matching scales for success. Ecological Applications 23:1881–1892. 


Koopman, B.O. (1946). Search and Screening. Operations Evaluations Group Report no. 56, Center for Naval Analyses, Alexandria, VA. 


Leary, J.J., Gooding, J., Chapman, J., Radford, A., Mahnken, B. and Cox, L.J., 2013. Calibration of an Herbicide Ballistic Technology (HBT) helicopter platform targeting Miconia calvescens in Hawaii. Invasive Plant Science and Management, 6(2), pp.292-303. 


Leary, J., Mahnken, B.V., Cox, L.J., Radford, A., Yanagida, J., Penniman, T., Duffy, D.C. and Gooding, J., 2014. Reducing nascent miconia (Miconia calvescens) patches with an accelerated intervention strategy utilizing herbicide ballistic technology.

Lodge, D.M., Williams, S., MacIsaac, H.J., Hayes, K.R., Leung, B., Reichard, S., Mack, R.N., Moyle, P.B., Smith, M., Andow, D.A. and Carlton, J.T., 2006. Biological invasions: recommendations for US policy and management. Ecological Applications, 16(6), pp.2035- 2054. 



Science and Community Engagement to Improve Water Management in Hawaii

‘Ike Wai (from the Hawaiian ‘ike, meaning knowledge, and wai, meaning water) is a five-year National Science Foundation project. The multidisciplinary research team from UH Manoa and Hilo will collect new geophysical and groundwater data, integrate these data into detailed groundwater models, and generate an improved understanding of subsurface water location, volume and flow paths. Data and outputs from ‘Ike Wai will be used to develop decision making tools to address challenges to fresh water scarcity from climate variability, increasing population demands, and water contamination.

UHERO Project Environment researchers will work with stakeholders to develop land-use scenarios, with a particular emphasis on potential areas for watershed restoration. Recharge values and restoration costs will be estimated for these scenarios and used as inputs to the groundwater model. Assumptions about development and population growth will be used to project consumption on the demand side, and the groundwater model will then allocate pumping spatially to minimize declines in water levels and deterioration in water quality due to seawater intrusion (SWI). Results from the pumping simulations can then be compared with current estimates of sustainable yield. We will also estimate the return on investment in watershed restoration for each of the scenarios.

The new field data and groundwater modeling efforts will help to improve current sustainable yield estimates. With recharge likely to change in the future due to climate change and land use decisions (e.g. watershed restoration), sustainable yield should also be variable. Although, current estimates of sustainable yield do not account for ecological and customary uses, several stakeholders have shown interest in developing a framework to do so. We will therefore look at how submarine groundwater discharge (SGD) along the coast varies with pumping and simulate the effects of different SGD constraints. We will also estimate the costs, in terms of restricting groundwater pumping, of enforcing those constraints. That is, we will: (1) compare projected groundwater consumption under each scenario to new sustainable yield estimates that account for both SWI and SGD, and (2) estimate the potential costs of maintaining pumping below sustainable yield.


Informing Water Policy in Hawaii with Transformative Interdisciplinary Research: UHERO’s Role in ʻIke Wai

UHERO's Project Environment will be leading the economic analysis for a new National Science Foundation project addressing critical gaps in the understanding of Hawaii’s fresh water supply that limit decision making, planning and crisis responses. ‘Ike Wai (from the Hawaiian ‘ike, (knowledge), and wai, (water) spans geophysics, microbiology, cyberinfrastructure, data modeling, indigenous knowledge and economics and connects university scientists to state and federal agencies and community groups.

Diversity in volcano age, eruption types, structural history, and hydrological features generate a complex subsurface water system that provides most of Hawaii’s potable water supply. While many hydrological studies have been carried out in Hawaii, relatively little is known about the exact structure of the many groundwater (GW) aquifers that are present throughout the state. Existing models are able to approximate the structure, but the accuracy of predicted water flows and sustainable yields for Hawaiian watersheds is limited by the availability of existing data, which is used to calibrate the models. Accordingly, ʻIke Wai will use new technology to measure the volume and interconnectivity of aquifers within Hawaiian volcanoes. Geophysical imaging will provide new high-resolution 3D maps of geologic structures. Real-time monitoring will support analysis of aquifer volume and hydraulic conductivity estimations. Flow and aquifer connectivity measurements will integrate three approaches: submarine GW Discharge (SGD) analysis, geochemistry and the innovative use of microbial diversity as a GW tracer.

Data and outputs from ʻIke Wai will provide decision-making tools to address challenges related to water availability and sustainability. Recent research on the West Hawaii coast has shown that we do not fully understand the size, flow rates, and boundaries of our groundwater aquifers. Without a clear understanding of how much water is available, we cannot properly plan future water use and management. There is currently significant debate over whether there is enough water to meet planned development while ensuring the biological and ecological integrity of surrounding nearshore habitats. ʻIke Wai will provide crucial geophysical data that will allow us to assess how much water is available to support both humans and nearshore environments.

Once we know the size, volume, and flow rates of groundwater aquifers, we can match these water supply estimates with current and projected demands for water. These demands come in the form of human demand — for domestic, commercial, agricultural, and municipal use — as well as biological and ecological demands — for example the dependency of nearshore organisms on freshwater discharge to the ocean, which is driven by the size and flow rate of up-gradient aquifers. The research from ʻIke Wai will help resource managers, policy makers, and the general public understand how scarce groundwater is in these areas, and how these resources should be priced, pumped, and managed to achieve the objectives that will be determined as part of our stakeholder engagement process. These objectives could be related to development, ecological integrity, and/or cultural integrity — we won’t know exactly what we are aiming for until we engage the stakeholders in our research.

The ʻIke Wai Initiative will give us a better sense of where the water is, how much is there, how much and where we can pump for what uses, and how we should best manage (price, restrict, require permits for, etc.) this resource. Stakeholder engagement and policy evaluation are also key components of the project, so we believe that the research results will not only be transformative from a scientific perspective but also useful for planning and management. Providing user friendly access to data and research results is an important objective of the project. Software engineers will work collaboratively with other members of the research team and stakeholders to create web and mobile applications for data dissemination, interaction and visualization.

For more information on the project, visit EPSCoR.

--Kimberly Burnett and Christopher Wada


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