Quantifying the Environmental Impact of Doubling Hawaii’s Local Food Supply

Final report for GW18-187

Project Type: Graduate Student
Funds awarded in 2018: $21,119.00
Projected End Date: 03/31/2020
Grant Recipient: University of Hawaii at Manoa
Region: Western
State: Hawaii
Graduate Student:
Principal Investigator:
Dr. Kimberly Carlson
University of Hawaii
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Project Information


Hawaii currently imports almost 90% of its food, meaning that this isolated Pacific island archipelago has low food self-sufficiency. To address this vulnerability, support the local economy, and generate jobs, Hawaii’s government has committed to doubling local food production by 2030. While such expansion or intensification of local agriculture coupled with a reduction of imports may have socio-economic benefits, it will also affect local and global environmental services. Producing more local food is likely to increase certain environmental burdens in Hawaii (e.g., fertilizer runoff from farms) and reduce these impacts in other producing regions. Because Hawaii residents depend on the local environment for both sustenance and tourism, such negative impacts associated with additional local agriculture are important to consider in initiatives designed to boost local food production. Additional local food production is also expected to alter environmental effects associated with agricultural imports. Although food that has traveled long distances is often perceived as more energy intensive and greenhouse gas-emitting than local food due to the resources required for transportation, “food miles” ignore differences between different forms of transport and energy use intensity in other stages of the supply chain. Therefore, an assessment that evaluates the on-farm conditions where food is produced as well as the various modes of transport to and within Hawaii is needed to assess the local as well as net global outcomes from boosting local food production.
The objective of this research was to assess the local, distant, and global environmental impacts of increasing food production in Hawai‘i by answering the following questions: 1) How do Hawaii-produced foods compare to imported foods with respect to highly local versus global environmental impacts? 2) How do these environmental impacts differ across food types? and 3) How might doubling production of these food types in Hawaii affect local versus global environments?
To answer these questions, we used a life cycle analysis (LCA) approach to quantify the environmental impacts of several foods grown locally and imported to Hawaii, including banana, lettuce, carrot, and beef. Specifically, we compared environmental burdens incurred globally (climate change) and locally (freshwater eutrophication, marine eutrophication, land use, and water use) from farm to plate for local and imported foods. We elicited Hawaii-specific inputs to the LCA by surveying farmers and ranchers across the state.
Results suggest wide variation in global to local impacts across locally-produced and imported foods and emphasize the dominant role of production rather than transport in driving these impacts. Doubling Hawaii-produced food production would generate a small absolute change in most environmental impact categories because local production currently comprises a very small fraction of total food supply. The single exception may be bananas, for which local production serves and important role in Hawaii’s food system.
These findings can be used to inform farmers of the importance of their management practices for environmental outcomes, and policymakers of the tradeoffs between importing food and producing it within Hawai‘i. The results of this project have the potential to affect the future of Hawaii’s food supply and support a more sustainable food system in Hawaii.

Project Objectives:

The objective of this research was to assess the local, distant, and global environmental impacts of increasing food production in Hawai‘i by answering the following questions: 1) How do Hawaii-produced foods compare to imported foods with respect to highly local versus global environmental impacts? 2) How do these environmental impacts differ across food types? and 3) How might doubling production of these food types in Hawaii affect local versus global environments?


Materials and methods:

Life Cycle Analysis. We undertook a comparative LCA approach to derive quantitative estimates of several environmental burdens at every stage of the food product’s lifecycle from “farm to plate” using the SimaPro (www.simapro.com) software package. For imported foods, we used reference values already available in SimaPro. For local foods, we developed inputs that reflect the impact relative to a reference unit of one kg of food product entering the market to be sold for consumption in Hawaii.

Focal Foods. We selected four focal food products - banana, lettuce, carrot, and beef - that contribute to Hawai‘i’s food supply via both local production and imports. These foods represent several USDA food groups (i.e., fruits, vegetables, and, meats). We estimated mass of imports and local food production for banana, carrot, and lettuce from 2008 Hawaii Department of Agriculture reports. Although these 2008 figures are outdated, no more recent information was available. We quantified mass of local beef production and beef imports based on Hawaii Beef Council Industry and UHM CTHAR Cooperative Extension estimates, as well as statistics from the USDA Economic Research Service and World Agricultural Supply and Demand Estimates for the year 2018.

Environmental Indicators. In SimaPro, we quantified the environmental impacts embodied in food imports and local production for each focal food across five impact categories consisting of Climate Change, Freshwater Eutrophication, Marine Eutrophication, Land Use, and Water Resource Depletion. We selected these environmental impacts because they are global or local in nature, and thus provide contrast between the global, local-distant, and local-Hawaii impacts of increasing local food production in Hawai‘i.

Farmer and Rancher Survey. We surveyed farmers and ranchers across the state of Hawaii to elicit management practices and inputs involved with the production of focal foods, as well transportation modes and distances to retail markets. Our survey adapted questions from the USDA Economic Research Service 2018 Soybeans Phase 2 Questionnaire and the 2018 Cow-calf Phase 3 Questionnaire. We piloted this survey with the agricultural extension agents at the University of Hawai‘i at Manoa College of Tropical Agriculture and Human Resources (CTAHR). After revising the survey based on feedback garnered during this pilot, we then administered the survey to farmers and ranchers statewide including the islands of O`ahu, Hawai`i, Maui, Kauai, and Molokai. Surveys were conducted either in person or over the phone from February to June 2019.

Survey Sample. To identify farmers and ranchers of the focal food products, we used a combination of personal networking, word of mouth, internet research, and attending farmers’ markets. In addition, we asked each respondent if they could refer us to other farmers willing to answer to the survey. We contacted 147 farmers and 42 ranchers, of which 54 farmers and 12 ranchers responded to the survey. Of the farmer respondents, 25 grew bananas, 21 grew lettuce, and 10 grew carrots.

Inputs to Agriculture. The survey asked farmers about several aspects of their production activities for the focal food products. These included the land area needed for the crop or beef production, annual crop or beef production, electricity use (e.g., for refrigerators), and inputs including N P and K fertilizers, pesticide use, herbicide use, and fungicide use. In the case of beef, we also asked about live weight sent to slaughter, feed (e.g., grain), drinking water, and on-farm diesel use. We also recorded the geographic location of the farm or ranch. We used this information to calculate inputs needed for SimaPro including yields, annual irrigation water requirements, and dry matter intake (for beef).

Markets and Transportation. For each product, we estimated the transportation methods and routes to market. All survey respondents were asked about the end market retail locations of their products including retail stores, farmer’s markets, and wholesale deliveries. Inter-island transport was assumed to be mainly by barge because of the proximity between islands and the use of barges within the primary interisland shipping transportation service. Road distances from the farm gate to these end markets were determined by averaging route distances from farm addresses to retail addresses in kilometers from Google Maps (www.google.com/maps). For food imports, we conducted a literature review and interviewed individuals in Hawaii familiar with imports to understand typical origins and routes for each focal food. Sea distances were determined using port information from the Hawaii Department of Transportation - A Guide to Port Hawaii Document and the National Oceanic and Atmospheric Association (NOAA)’s 2019 Distances Between United States Ports Report.

Beef Import Scenarios. Beef consumed in Hawaii may be raised in Hawaii, the US mainland, or in a foreign country. To evaluate how the production conditions and transportation influence the environmental footprint of Hawaii’s beef supply, we developed several scenarios of beef production and supply chains. These included Hawaii-raised grass-fed beef, Hawaii-raised grass fed beef grain finished in the mainland US and shipped back to Hawaii, beef raised and grain finished in the mainland US, and grass-fed beef raised in Australia or New Zealand.

Doubling Scenario. To model a doubling of local food production for each focal food, in SimaPro we doubled total local production compared to 2008 or 2018 (the baseline), and subtracted the respective increase from total imports. We then compared the local-Hawaii, local-distant, global, and overall impacts of doubled Hawaii production for banana, carrot, lettuce, and beef to the baseline.

Research results and discussion:

Producer Surveys. We completed interviews with 20 lettuce producers (n = 14 land grown lettuce, 3 hydroponically grown lettuce, 3 produced aquaponically grown lettuce), 25 banana producers, 10 carrot producers, and 12 ranchers. Yields for all products were slightly lower than yields previously reported in Hawaii or in other subtropical environments.

Hawaii Markets. Hawaii lettuce farmers sold their produce to retailers on the islands of Oahu, Maui, Kauai, and Hawaii Island. Hawaii-produced lettuce was consumed both on the islands where it was produced, and transported between islands, to grocery stores, farmers markets, and restaurants. In contrast, carrot and banana production captured in the survey was not transported between islands, and was mainly sold at farmers’ markets (carrots and bananas), grocery stores (bananas), and restaurants (carrots). For beef, around 33% of the cattle born each year were exported to the mainland, which contrasts with about 80% of Hawaii cattle exported according to UHM CTAHR Cooperative Extension. Cattle raised and consumed in Hawaii are transported to a processing facility which may be on another island and then the final product is distributed from that facility all over the state.

Import Origins. All focal food imports are typically shipped to Hawaii via ports in California. Lettuce is usually produced domestically in California and Arizona; banana is imported from Central and South America; most carrot production occurs in California; and beef is sourced from the US mainland, Australia, or New Zealand.

Import versus Local Food Relative Impacts. Here, we compare the relative environmental impact of the food on a per kilogram, or production-scaled, basis (impact per kg production).

Land Use: Every focal Hawaii-grown food except hydroponic lettuce used more land relative to imports (i.e., Hawaii produced food had lower yields than imported foods). Although both aquaponic and hydroponic lettuce are grown vertically and require relatively little land, land is needed to produce fish feed for aquaponic lettuce, which means that total land area for this system is larger than that of hydroponic lettuce.

Climate Change: All Hawaii-grown crops except banana had a larger climate change footprint than imports. Bananas were imported to Hawaii from Central and South America, driving relatively high transportation emissions and a larger carbon footprint than Hawaii-produced bananas. Grass fed beef was associated with greater emissions than grain-fed beef, so that Hawaii-produced beef had more climate change impact than imports from the mainland US (largely grain fed), but lower impact that imports that were grass fed (New Zealand and Australia).

Emissions from the production phase accounted for majority of the gross GHG emissions for most imports and locally produced products. Exceptions were imported carrot and imported and locally produced banana. Hawaii-produced bananas sequester more carbon than they emit via transportation and other production activities, and therefore have negative net emissions. In beef, emissions are driven by enteric fermentation, feed production, and manure management rather than transport.

Freshwater Eutrophication: Hawaii grown crops tend to have higher freshwater eutrophication potential (driven by P inputs to production) than imported crops, except banana, which had slightly lower freshwater eutrophication potential. Beef of all kinds (imported and locally produced) had higher freshwater eutrophication potential than focal crops, but this impact did not differ substantially between Hawaii-produced and imported beef.

Marine Eutrophication: In contrast to freshwater eutrophication results, all Hawaii-grown crops except aquaponic lettuce had lower marine eutrophication potential (driven by N inputs to production and transport) than their imported counterparts. The aquaponic system has a higher N footprint than other crops because it requires fish feed which is produced from soy. Marine eutrophication potential from beef production was substantially higher than for crops, but differed little across imports and locally produced beef, despite differences in feed across systems.

Water Resource Depletion: All Hawaii-produced foods except beef had more water usage than imports, likely because of higher evapotranspirative demand in subtropical Hawaii compared to locations that produced imports. Yet, because Hawaii cattle are grass fed and therefore do not use water in the form of feed production, Hawaii beef used less water than US mainland beef.

Baseline Food Supply. In 2008, imports of focal crops made up majority of Hawaii’s food supply; Hawaii largely consumed imported carrot (2% of supply), banana (27%), and lettuce (2%). The same was true for beef (92%) in 2018. Thus, net environmental impact of Hawaii’s food supply is largely driven by imports under current levels of production.

Doubling Scenario. Doubling Hawaii-produced food production (relative to the baseline supply) with a commensurate reduction in imports would generate relatively small changes in impacts for most foods and impact categories because of the small change in additional local production relative to the total supply (i.e., doubling Hawaii carrot production would increase local carrot production from 2% to 4% of total supply). Because doubling banana production means that bananas would comprise 54% of total supply, meeting Hawaii’s policy goals for bananas has a higher likelihood of generating substantial change in environmental impact. Specially, our models suggest decreases in embodied climate change (-732%), marine eutrophication (-35%), and freshwater eutrophication (-3.7%), and increases in embodied land (+36%) and water use (+48%).

Discussion. Through life cycle analysis informed by producer surveys, we found that Hawaii-produced foods, which have lower yields that their imported counterparts, tend to produce higher production-scaled environmental impacts. Among foods studied, beef production generated the largest impacts, a common result in comparisons of crop and beef environmental footprints. Higher yields produced from the same amount of inputs can mitigate the environmental impacts associated with the production of the agricultural input itself (e.g. fertilizers, infrastructure). Indeed, low yields of Hawaii-produced foods likely drove their relatively higher impacts than imports across most foods and categories. Therefore, sustainable agriculture in Hawaii may depend partly on identifying, addressing, and eliminating any systemic barriers to increased yields and efficiency across the State. Our analysis also emphasizes the small role that transportation has in driving these impacts, which underscores the need to focus on management practices and production of Hawaii’s food, rather than food miles, when advocating for local food systems.

Doubling Hawaii-produced food production would generate a small absolute change in most environmental impact categories because local production currently comprises a very small fraction of total food supply. The single exception may be bananas, for which local production serves an important role in Hawaii’s food system. Though many scenarios of doubled Hawaii-production would likely produce a net decrease in environmental impacts, those environmental benefits are global (climate change) or local-distant (eutrophication) and will not directly benefit Hawaii’s environment.

Participation Summary
66 Producers participating in research

Research Outcomes

No research outcomes

Education and Outreach

11 Consultations
1 Curricula, factsheets or educational tools
4 Webinars / talks / presentations
2 Workshop field days
1 Other educational activities: The student published a master's thesis.

Participation Summary:

66 Farmers participated
6 Ag professionals participated
Education and outreach methods and analyses:


In September 2017, Torres and Carlson consulted with Dr. PingSun Leung, co-author of “Hawai‘i’s food consumption and supply sources: benchmark estimates and measurement issues” to obtain feedback on the goals and scope of the project and also about obtaining the LCA software, of which his lab was familiar with.

In February 2018, Torres consulted with Dr. Matthew Loke, also co-author of “Hawai‘i’s food consumption and supply sources: benchmark estimates and measurement issues”. Dr. Loke further explained the methods taken to achieve the benchmark estimates of his research and provided Torres with insight on the first steps of how to obtain the desired import data.

In February 2018, Torres met with Dr. Monique Mironesco to discuss her work in the Sustainable Community Food Systems program at UH West Oahu. Dr. Mironesco has experience in communicating with local farmers in Hawai‘i. Her strategies and methods of conducting surveys were discussed.

In April 2018, Torres consulted with Dr. Albie Miles, assistant professor of Sustainable Community Food Systems at UH West Oahu. Dr. Miles also agreed to be a member of Torres’ thesis committee at this meeting.

Torres met with Dr. Michael Cooney several times from September 2018 through December of 2019. Dr. Cooney is a professor in the UHM Engineering department who teaches a Life Cycle Analysis course using the SimaPro software. Torres took this course in Spring of 2018. Dr. Cooney has been coaching and guiding the modelling process of this project.

In October 2018, Torres consulted with the UHM CTAHR Interim Associate Dean for Extension, Kelvin Sewake, for help with contacting farmers across the state. Sewake provided Torres with contacts for all agricultural extension agents in the state.

In November 2018, Torres consulted with fellow UHM (Dept. of Geography and Environment) graduate student, Hunter Heavilin, on his efforts of gathering Hawaii’s agricultural import data.

In December 2018, Torres briefly consulted with the Kokua Hawai‘i Foundation ʻĀINA In Schools Program Manager Kelly Perry. Perry was excited to incorporate the data and findings of this project into the educational curriculum of her program.

In January 2019, Torres met with Sharon Hurd from the Hawai‘i Department of Agriculture (HDOA) to discuss the project’s relevance to HDOA as well as inquire about more recent import data.

In February 2019, Torres consulted with Janel Yamamoto, Director of GoFarm Hawaii, to go over survey questions and get help with farmer contacts.

In February 2019, Torres consulted with three CTAHR agricultural extension agents to pilot the farmer survey and gain feedback.

Workshop / field days:

In October 2017, Torres attended the Hawaii Farmers Union United (HFUU) State Convention, a three-day event exploring the concepts of Aloha 'Aina and Malama 'Aina to create the regenerative agricultural systems we envision for Hawai'i. 

In May 2018, Carlson traveled to Palo Alto California to participate in the 2018 National Food System Resilience and Equity Workshop, a two-day event that brought together participants from across the United States to draft food resilience plans for their regions. As part of this group, Carlson contributed to planning activities around food resilience for the State of Hawai‘i, including informally presenting the research planned under this Western SARE grant.

Curricula, factsheets or educational tools:

We developed a three-page factsheet summarizing the results of the research, and sent this to all farmers and ranchers interviewed during the study, as well as agricultural professionals in academia and government. The factsheet is posted online at www.carlson-lab.org/hi-food.


Torres T. 2019. “Doubling Hawaii's Local Food Supply.” Department of Natural Resources & Environmental Management Fall 2019 Seminar Series. Honolulu, HI, USA. November 27.

Torres T. 2019. "Quantifying the Environmental Footprint of Doubling Hawaii's Local Food Supply." American Association of Geographers Annual Meeting. Washington D.C., USA. April 3-7.


Torres T and KC Carlson. 2018. "Quantifying the Environmental Footprint of Doubling Hawaii's Local Food Supply." CTAHR Student Research Symposium. Honolulu, HI, USA. April,6.

Torres T and KC Carlson. 2018. "Quantifying the Environmental Footprint of Doubling Hawaii's Local Food Supply." NOAA Symposium on Science in Support of Archipelagic Management. Honolulu, HI, USA. November 19.-20.


Torres T. 2019. "Quantifying the Environmental Footprint of Doubling Hawaii's Local Food Supply." University of Hawaii, Dept. of Natural Resources and Environmental Management, Master of Science Thesis.

Information Products

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.