Long-term, gridded standardized precipitation index for Hawai‘i

Spatially explicit, wall-to-wall rainfall data provide foundational climatic information but alone are inadequate for characterizing meteorological, hydrological, agricultural, or ecological drought. The Standardized Precipitation Index (SPI) is one of the most widely used indicators of drought and defines localized conditions of both drought and excess rainfall based on period-specific (e.g., 1-month, 6-month, 12-month) accumulated precipitation relative to multi-year averages. A 93-year (1920–2012), high-resolution (250 m) gridded dataset of monthly rainfall available for the State of Hawai‘i was used to derive gridded, monthly SPI values for 1-, 3-, 6-, 9-, 12-, 24-, 36-, 48-, and 60-month intervals. Gridded SPI data were validated against independent, station-based calculations of SPI provided by the National Weather Service. The gridded SPI product was also compared with the U.S. Drought Monitor during the overlapping period. This SPI product provides several advantages over currently available drought indices for Hawai‘i in that it has statewide coverage over a long historical period at high spatial resolution to capture fine-scale climatic gradients and monitor changes in local drought severity

Local and global pyrogeographic evidence that indigenous fire management creates pyrodiversity

Despite the challenges wildland fire poses to contemporary resource management, many fire-prone ecosystems have adapted over centuries to millennia to intentional landscape burning by people to maintain resources. We combine fieldwork, modeling, and a literature survey to examine the extent and mechanism by which anthropogenic burning alters the spatial grain of habitat mosaics in fire-prone ecosystems. We survey the distribution of Callitris intratropica, a conifer requiring long fire-free intervals for establishment, as an indicator of long-unburned habitat availability under Aboriginal burning in the savannas of Arnhem Land. We then use cellular automata to simulate the effects of burning identical proportions of the landscape under different fire sizes on the emergent patterns of habitat heterogeneity. Finally, we examine the global extent of intentional burning and diversity of objectives using the scientific literature. The current distribution of Callitris across multiple field sites suggested long-unburnt patches are common and occur at fine scales (<0.5 ha), while modeling revealed smaller, patchy disturbances maximize patch age diversity, creating a favorable habitat matrix for Callitris. The literature search provided evidence for intentional landscape burning across multiple ecosystems on six continents, with the number of identified objectives ranging from two to thirteen per study. The fieldwork and modeling results imply that the occurrence of long-unburnt habitat in fire-prone ecosystems may be an emergent property of patch scaling under fire regimes dominated by smaller fires. These findings provide a model for understanding how anthropogenic burning alters spatial and temporal aspects of habitat heterogeneity, which, as the literature survey strongly suggests, warrant consideration across a diversity of geographies and cultures. Our results clarify how traditional fire management shapes fire-prone ecosystems, which despite diverse objectives, has allowed human societies to cope with fire as a recurrent disturbance

Ecosystem carbon balance in the Hawaiian Islands under different scenarios of future climate and land use change

The State of Hawai\u27i passed legislation to be carbon neutral by 2045, a goal that will partly depend on carbon sequestration by terrestrial ecosystems. However, there is considerable uncertainty surrounding the future direction and magnitude of the land carbon sink in the Hawaiian Islands. We used the Land Use and Carbon Scenario Simulator (LUCAS), a spatially explicit stochastic simulation model that integrates landscape change and carbon gain-loss, to assess how projected future changes in climate and land use will influence ecosystem carbon balance in the Hawaiian Islands under all combinations of two radiative forcing scenarios (RCPs 4.5 and 8.5) and two land use scenarios (low and high) over a 90 year timespan from 2010 to 2100. Collectively, terrestrial ecosystems of the Hawaiian Islands acted as a net carbon sink under low radiative forcing (RCP 4.5) for the entire 90 year simulation period, with low land use change further enhancing carbon sink strength. In contrast, Hawaiian terrestrial ecosystems transitioned from a net sink to a net source of CO2 to the atmosphere under high radiative forcing (RCP 8.5), with high land use accelerating this transition and exacerbating net carbon loss. A sensitivity test of the CO2 fertilization effect on plant productivity revealed it to be a major source of uncertainty in projections of ecosystem carbon balance, highlighting the need for greater mechanistic understanding of plant productivity responses to rising atmospheric CO2. Long-term model projections such as ours that incorporate the interactive effects of land use and climate change on regional ecosystem carbon balance will be critical to evaluating the potential of ecosystem-based climate mitigation strategies

A Century of Drought in Hawaiʻi: Geospatial Analysis and Synthesis across Hydrological, Ecological, and Socioeconomic Scales

Drought is a prominent feature of Hawaiʻi’s climate. However, it has been over 30 years since the last comprehensive meteorological drought analysis, and recent drying trends have emphasized the need to better understand drought dynamics and multi-sector effects in Hawaiʻi. Here, we provide a comprehensive synthesis of past drought effects in Hawaiʻi that we integrate with geospatial analysis of drought characteristics using a newly developed 100-year (1920–2019) gridded Standardized Precipitation Index (SPI) dataset. The synthesis examines past droughts classified into five categories: Meteorological, agricultural, hydrological, ecological, and socioeconomic drought. Results show that drought duration and magnitude have increased significantly, consistent with trends found in other Pacific Islands. We found that most droughts were associated with El Niño events, and the two worst droughts of the past century were multi-year events occurring in 1998–2002 and 2007–2014. The former event was most severe on the islands of O’ahu and Kaua’i while the latter event was most severe on Hawaiʻi Island. Within islands, we found different spatial patterns depending on leeward versus windward contrasts. Droughts have resulted in over $80 million in agricultural relief since 1996 and have increased wildfire risk, especially during El Niño years. In addition to providing the historical context needed to better understand future drought projections and to develop effective policies and management strategies to protect natural, cultural, hydrological, and agricultural resources, this work provides a framework for conducting drought analyses in other tropical island systems, especially those with a complex topography and strong climatic gradients

Fire and rain : the legacy of Hurricane Lane in Hawaiʻi

For more about the East-West Center, see http://www.eastwestcenter.org/Hurricane Lane, which struck the Hawaiian islands on 22–25 August 2018, presented a textbook example of the compounding hazards that can be produced by a single storm. Over a four-day period, the island of Hawaiʻi received an average 17 inches of rainfall, while at the same time, three wildfires on the island of Maui and one on Oʻahu burned nearly 3,000 acres of abandoned agricultural land. The rainfall and fire effects of Hurricane Lane may be related to global climate changes that could become more common in the future

Traditional lifestyles, transition, and implications for healthy aging: An Example from the remote island of Pohnpei, Micronesia.

Lifestyle-related, non-communicable diseases, such as diabetes, hypertension, and obesity have become critical concerns in the Pacific islands of Micronesia. We investigated the relationship between the diminution of traditional lifestyle practices and the decline in the health of the population in the State of Pohnpei, Federated States of Micronesia. To assess this, our interdisciplinary team developed two scales, one to rank individuals on how traditional their lifestyles were and one to rank individuals on the healthiness of their lifestyles. Participants' locations were categorized as living on a remote atoll, living on the main island, or as a transitional population. Pohnpeians living in transitional communities (e.g. recently moved from a remote atoll to the main island, or the reverse) ranked lowest on both the tradition and health scales, rather than ranking intermediate between the remote and main island groups as we had hypothesized. As predicted, individuals residing on the remote atolls were living the most traditional lifestyles and also had the healthiest lifestyles, based on our rating system. The higher an individual scored on the tradition scale, e.g. the more traditional life they lived, the higher they scored on the health scale, suggesting the importance of traditional lifestyle practices for maintaining health. These findings have significant implications for promoting health and longevity of Micronesians and other Pacific Island peoples. We suggest the process of transition be recognized as a significant lifestyle and health risk and be given the attention we give to other risk factors that negatively influence our health. Based on our findings, we discuss and recommend the revitalization of particular traditional lifestyle practices, which may advance healthy aging among Pohnpeians

How people, rainfall and vegetation shape tropical island fire regimes across Micronesia

Aim: To provide the first regional analysis of contemporary drivers of Pacific Island fire regimes. Location: Islands of Palau, Yap, Guam, Rota, Tinian, Saipan, Chuuk, Pohnpei, Kosrae. Time Period: 1950-present. Methods: We used land cover, soil maps and contemporary fire histories to (1) describe the relationships among fire activity, vegetation, rainfall and island geography and population; (2) examine the spatial associations of forest and savanna vegetation with respect to fire and soil types; and (3) link fire and savanna distribution to intra-annual and inter-annual rainfall variability. Results: Savanna extent was positively correlated with island age and the range of mean monthly rainfall. The percent of area burned annually reached upwards of 2%–10% of island land areas, correlated positively with rainfall seasonality, and occurred largely within savannas. Savannas were more frequent on acidic soils with higher aluminium than forests but distributed across all soil types. El Niño intensity correlated negatively with dry season rainfall over the entire study region and positively with annual area burned on Guam. Main Conclusions: The contemporary extents of savannas in Micronesia reflect Pacific Islanders\u27 long-term use of fire to shape vegetation and are modulated by inter- and intra-annual rainfall variability. These relationships provide baseline information for ongoing fire management and mitigation projects throughout Micronesia and critical insight for assessing and anticipating fire risk in other insular areas where fire data are limited. © 2023 John Wiley & Sons Ltd

Bringing multiple values to the table: assessing future land-use and climate change in North Kona, Hawaiʻi

As ecosystem service assessments increasingly contribute to decisions about managing Earth's lands and waters, there is a growing need to understand the diverse ways that people use and value landscapes. However, these assessments rarely incorporate the value of landscapes to communities with strong cultural and generational ties to place, precluding inclusion of these values - alongside others - into planning processes. We developed a process to evaluate trade-offs and synergies in ecosystem services across land-use scenarios and under climate change in North Kona, Hawaiʻi, a tropical dry ecosystem where water, fire, biodiversity, and cultural values are all critical considerations for land management decisions. Specifically, we combined participatory deliberative methods, ecosystem service models, vegetation surveys, and document analysis to evaluate how cultural services, regulating services (groundwater recharge, landscape flammability reduction), biodiversity, and revenue: (1) vary across four land-use scenarios (pasture, coffee, agroforestry, and native forest restoration) and (2) are expected to vary with climate change (representative concentration pathway (RCP) 8.5 mid-century scenario). The native forest restoration scenario provided high cultural, biodiversity, and ecosystem service value, whereas coffee's strongest benefit was monetary return. The agroforestry scenario offered the greatest potential in terms of maximizing multiple services. Pasture had relatively low ecological and economic value but, as with native forest and agroforestry, held high value in terms of local knowledge and cultural connection to place. Climate change amplified existing vulnerabilities for groundwater recharge and landscape flammability, but resulted in few shifts in the ranking of land-use scenarios. Our results demonstrate that cultural services need not be sacrificed at the expense of other management objectives if they are deliberately included in land-use planning from the start. Meaningfully representing what matters most to diverse groups of people, now and under a changing climate, requires greater integration of participatory methods into ecosystem service analyses

Assessing Baseline Carbon Stocks for Forest Transitions: A Case Study of Agroforestry Restoration from Hawaiʻi

As the extent of secondary forests continues to expand throughout the tropics, there is a growing need to better understand the ecosystem services, including carbon (C) storage provided by these ecosystems. Despite their spatial extent, there are limited data on how the ecosystem services provided by secondary forest may be enhanced through the restoration of both ecological and agroecological functions in these systems. This study quantifies the above- and below-ground C stocks in a non-native secondary forest in Hawaiʻi where a community-based non-profit seeks to restore a multi-strata agroforestry system for cultural and ecological benefits. For soil C, we use the equivalent soil mass method both to estimate stocks and examine spatial heterogeneity at high resolution (eg. sub 5 m) to define a method and sampling design that can be replicated to track changes in C stocks on-site and elsewhere. The assessed total ecosystem C was ~388.5 Mg C/ha. Carbon stock was highest in trees (~192.4 Mg C/ha; ~50% of total C); followed by soil (~136.4 Mg C/ha; ~35% of total C); roots (~52.7 Mg C/ha; ~14% of total C); and was lowest in coarse woody debris (~4.7 Mg C/ha; ~1% of total C) and litter (~2.3 Mg C/ha; <1% of total C). This work provides a baseline carbon assessment prior to agroforest restoration that will help to better quantify the contributions of secondary forest transitions and restoration efforts to state climate policy. In addition to the role of C sequestration in climate mitigation, we also highlight soil C as a critical metric of hybrid, people-centered restoration success given the role of soil organic matter in the production of a suite of on- and off-site ecosystem services closely linked to local sustainable development goals