Progress report for GS23-276
Project Information
The South Florida agricultural sector in Homestead, Florida is vital to the U.S fruit and vegetable market, providing specialty crops such as tomatoes, squash, and eggplant. These crop species are already being grown during the winter months at their maximum temperatures. Climate change and heat stress have the potential to greatly damage this important industry. This study examines how changing climates may impact these crop-pollinator systems by studying the plant and pollinator response to heat stress, their interactions, and grower perceptions in relation to changing climates and environments.
My research seeks to understand the various management practices and tools which vegetable growers in South Florida use to successfully grow annual crops in the face of climate change, as well as their perceptions of climate change and valuation of pollinators. Many growers and agricultural workers in South Florida are migrants from different countries, stakeholders who carry generational knowledge from different growing environments. Learning management practices to combat heat, drought, and other environmental stressors from those who are most vulnerable can help Florida continue to produce stable, quality vegetables in changing climates.
The objectives of this project are focused on linking natural and human systems to determine how climate change may impact plants, pollinators, and people in agriculture. With support of the FIU Agroecology program, the Miami-Dade County Extension Office, and local farming community organizations, this project will be shared as part of a collaborative effort to promote alternative management practices to sustainable farming.
The goal of this research is to understand these cropping systems in Homestead, FL, and how climactic factors impact them to understand vulnerabilities. Additionally, to propose growing solutions that benefit crop and pollinating insect sustainability, as well as learn growers' perspectives around heat stress to give advice for future farming practices
Objective 1: Tomato growers in South Florida are competing with Mexico and South America for the U.S wintertime market. They are vulnerable to temperature rise as they are already growing crops during the coolest months. Additionally, hand pollination for large-scale greenhouse production is not feasible ($18 million for the hand pollination of 1600 ha), which has led to adoption of buzz-pollinating bumblebees (Wurz and Tscharntke, 2021). To examine heat stress, an experiment on tomatoes and their bumblebee pollinators (Bombus terrestris) will be conducted. Plants and insects will be heated using growth chambers at optimal growing temperatures, moderate, and extreme predicted higher temperatures to understand how heat stress affect this cropping system.
Objective 2: An additional experiment will be conducted using open top chambers (OTC) to simulate warming of eggplants in the field. These chambers will be placed around eggplants in the ground to cause excess heating and simulate a heat wave, which will be compared to control plants without OTC, as well as a pollinator exclusion treatment where plants within and outside OTC’s are restricted from pollinators. This will allow understanding of how eggplants, a specialty crop grown in South Florida, are impacted by rising temperatures and extreme heat. In addition, it will increase understanding of the importance of wild pollinators, and how their presence may affect production in heat stressed crops. Further, it allows insight into the synergy between how lack of pollinators and heat stress may exacerbate crop loss, an increasing threat to the world's agriculture.
Objective 3: A final field experiment will be conducted looking at how weather and chemical use affects wild squash pollinators. Squash flower visitors' diversity and abundance will be observed and identified across four different farms in South Florida-two organic and two conventional-for two growing seasons. The aim is to determine A) natural squash pollinators in South Florida, B) how weather variation affects these pollinators, C) if organic versus conventional farming affect pollinators, and D) how squash plant biology and morphology is affected by weather variability and farm landscape. During this study, potential heat waves or cold fronts may occur, in which the response of pollinators and plants will be evaluated, as well as pollinators overall response to varying temperatures.
Farmers and the farm workers collaborating in this project will be interviewed to gather their observations before, during, and after the field experiment. Farmer perceptions of climate change and heat stress will be assessed, including their methods of mitigation and farming practices in response to heat stress. Surveys will be repeated during the experiment, as well as following the conclusion to see how perceptions change following sharing the results of the study.
Research
Objective 1: Tomatoes and their Bombus terrestris (Natupol; Koppert Products, Michigan, U.S.A) pollinators will be heated using growth chambers at optimal growing temperatures, moderate, and extreme predicted higher temperatures of climate change induced heat stress. This growth chamber experiment compares an optimal growing temperature, a 1.5°C, and 3°C rise in the day/night temperature of the average tomato growing season in South Florida. Temperature treatments in growth chamber begin 12 days before flower differentiation to ensure flowers are exposed to heat stress during development (Firon et al. 2006). Growth chambers will be accessed at Florida International University and the University of Miami.
In addition to measuring tomato yield, physiological, morphological, chemical and behavioral changes in bees and tomatoes between different temperature treatments, there will be three pollination treatments using flight cages. Tomatoes and bees will be placed together for 48 hours to see interactions of A) normal pollination of tomatoes and bees, B) heated tomatoes and bees, and C) a pollinator exclusion cage with only tomatoes from the three temperature treatments. Flight cage interactions will be repeated weekly for 10 weeks (the longevity of the experimental bumblebee hive).
Bumblebee colony activity and resource consumption under temperature treatments will be compared using EthoVision XT software (Noldus), as well as the temperature within hives. Bumblebee hives will be tested throughout the treatment for morphological and behavioral changes, as well as dissected at the conclusion for population (larvae and adults) and chemical sampling.
Objective 2: Open Top Chambers (OTC) will be used to warm eggplants grown in the field. Chambers will be placed around eggplants in the ground to cause excess heating, which will be compared to plants without OTC. Temperature, humidity, and rainfall within the OTC will be measured and compared to ambient conditions. Weather will be recorded daily at one-hour intervals using an automatic temperature and humidity recorder placed inside and outside the OTCs. Natural wild pollinator diversity and abundance of visitors to heated and non-heated plants will be observed and collected for identification, with OTCs removed prior to observations to avoid any possible bias in visitation rates among treatments. In addition, a pollinator exclusion treatment will be used to enclose the eggplants both inside the OTC and outside to see how the absence of wild pollinators affects heated and non-heated plants.
Objective 3: A field experiment will be conducted examining how farming practices and weather affect wild squash pollination. Squash flower visitors' diversity and abundance will be observed and identified across four different farms in Homestead, FL-two organic and two conventional-for two growing seasons. Each farm will have weather data collected over time, including temperature, humidity, rainfall, and wind. The aim is to determine A) natural squash pollinators in South Florida, B) how weather variation affects these pollinators, C) if organic versus conventional farming affect pollinators, and D) how squash plant biology and morphology is affected by weather variability and farm landscape. A pollinator exclusion treatment will be applied to a subset of plants on each farm, to see how lapses in pollination affect production. Squash production per farm will be quantified and compared based on insect visitor abundance and diversity, as well as weather variation.
Farmers and the farm workers collaborating in this project will be interviewed to gather their observations before, during, and after the field experiment (Objective 3). Farmer perceptions of climate change and heat stress will be assessed, including their methods of mitigation in response to heat stress. Surveys will be repeated during the experiment, as well as following the conclusion to see how perceptions change following the results of the study. The research will be a mixed methods approach, using aspects of both qualitative and quantitative methods (Creswell 2018). This design was chosen as it allows a reflexive, practical approach to develop case studies in understanding minority farmers. This approach begins with exploration of the subject (case-studies, interviews of farmers), which builds further surveys (different methods of farming, production values, ecosystem service of pollinator valuation). Similarly, farmer surveys and socioeconomic data will link different results (such as pollinator visitation rates/species diversity on farm) to how growers manage their fields, which may include methods for mitigating heat/drought.
The goal is to synthesize information on different growing practices to best grow vegetables in changing environments. The type of data collection will be interview and focus group based, using open ended questions and surveys. Additionally, preliminary farm visits and demonstrations will be used to gain knowledge as well as trust. Group sessions, interview circles, and collaborative talking circles of all the farmers, as well as shared farm tours will also be a way to encourage ideas and collaborative learning. Studies on farm scale pollinator biodiversity, abiotic factors (weather, soil quality), and comparisons of yield quantity and quality, will also provide evidence to support management practices of farmers. A multivariate analysis of variance statistical analysis can be one tool to support this.
Plant- pollinator interactions for all three objectives will examine foraging behavior of pollinators via observational studies of interactions with flowers. Pollinator effectiveness and efficiency will be examined, as well as the number of visits to flowers, handling time (amount of time spent on one plant), and type of reward collected (pollen, nectar, or both). This will determine how exactly pollination may be affected by temperature increases (Objective 1, 2 and 3), as well as which wild pollinator species are most effective for crop pollination (Objective 2 and 3).
Temperature consequences for pollination will be analyzed by comparing flower morphology among treatments. In addition, floral volatiles and nutrition (pollen nutrients, antioxidants, and germination rates) will be analyzed to see temperature effects on pollinator attraction, nutrition, and subsequent fruit quality.
Fruit abundance and quality will be examined for all three objectives, including fruit timing, yield, weight, seed mass, number, and germination rate. Economic valuation of yields will be calculated for all three crops to determine the economic value of pollinators and sustainable temperatures. Additional plant characteristics will be compared, including morphology and nutritional elements of the plants and soil (Carbon/Nitrogen/Phosphorous).
Educational & Outreach Activities
Participation Summary:
Multiple students assisted in the completion of this project, specifically two undergraduate student mentees from the University of Miami: Ella Bussy and Sidney Blumenfeld. This project was assisted with lab space at the Kampong and International Center for Tropical Botany, allowing outreach to the public and fellow researchers to view the arena flight trials of the bumblebees, including outreach talks given to fieldtrips given at the Kampong.
A field study was implemented at the FIU Organic Garden, with undergraduate student support and used as a teaching tool for outreach of this SSARE funded research. Multiple students assisted in the creation and maintenance of these OTC’s, including Alexis Quiroz in the mechanical construction.
A core group of field assistants was vital to the execution and data collection in these farms, assisted consistently by undergraduate Agroecology interns and mentees: Sarah Tillem, Sophie Ramos, Fabiana Moran, and Natalie Valdes. Others assisted on a semi-regular basis in field/lab work as well.
Project Outcomes
Successful completion of this trial with two rounds of bees per heat treatment and data collection on plant/bee responses to heat stress.
Successful prototype deployment and preliminary assessment of zucchini growth in chambers. A fully fledged trial will be conducted at the FIU Organic Garden in Spring 2025.
Squash plants with floral plantings close by (<50 meters) had higher yields compared to control plants, weighing almost twice as much. Farmer participation and enthusiasm to conduct surveys and implement floral plantings, with the farmer implementing on his own a wildflower planting across multiple other 40 acre farms. Determination of the best flower species for floral plantings in south Florida squash farms.
Objective 1
Activities: Preliminary trials were conducted Summer 2024 using growth chambers at the University of Miami. Issues with conducting the mesh arena trials to allow pollination of squash in outdoor arenas arose (Miami experienced extreme heat days in Summer 2024- killing 2 hives). Repetition of the trial using new hives was conducted Fall 2024, with arena trials being done indoors at the Kampong Botanical Garden/International Center For Tropical Botany in Coconut Grove.
Outcomes: Successful completion of this trial with two rounds of bees per heat treatment and data collection on plant/bee responses to heat stress.
Students Mentored: Multiple students assisted in the completion of this project, specifically two undergraduate student mentees from the University of Miami: Ella Bussy and Sidney Blumenfeld. This project was assisted with lab space at the Kampong and International Center for Tropical Botany, allowing outreach to the public and fellow researchers to view the arena flight trials of the bumblebees, including outreach talks given to fieldtrips given at the Kampong.
Objective 2
Activities: Preliminary trials were conducted to create and test prototype OTC’s and determine the range of heating they create in consultation with Dr. Steve Oberbauer and colleagues. Different chamber heights were constructed to find the correct range of heating needed (3 degrees Celsius).
Outcomes: Successful prototype deployment and preliminary assessment of zucchini growth in chambers. A fully fledged trial will be conducted at the FIU Organic Garden in Spring 2025.
Students Mentored: This project was implemented at the FIU Organic Garden, with undergraduate student support and used as a teaching tool for outreach of this SSARE funded research. Multiple students assisted in the creation and maintenance of these OTC’s, including Alexis Quiroz in the mechanical construction.
Objective 3
Activities: Two replicates of flower planting were conducted in Fall 2023 and Spring 2024 in Sam S. Accursio and Sons squash farms in Homestead, Florida. Pollinator activity and behavior was assessed to determine the natural squash pollinators in South Florida. Weather stations were deployed to determine how weather variation affects these pollinators and how squash plant biology and morphology is affected by weather variability and farm landscape. Replication on two additional Accursio family farms will be repeated in Spring 2025.
Outcomes: Squash plants with floral plantings close by (<50 meters) had higher yields compared to control plants, weighing almost twice as much. Farmer participation and enthusiasm to conduct surveys and implement floral plantings, with the farmer implementing on his own a wildflower planting across multiple other 40 acre farms. Determination of the best flower species for floral plantings in south Florida squash farms.
Students Mentored: A core group of field assistants was vital to the execution and data collection in these farms, assisted consistently by undergraduate Agroecology interns and mentees: Sarah Tillem, Sophie Ramos, Fabiana Moran, and Natalie Valdes. Others assisted on a semi-regular basis in field/lab work as well.