Heat Stress and Its Influence on Subtropical Annual Crops and Their Pollinators: Implications for agriculture in an era of climate change

Commodities

• Vegetables: cucurbits, eggplant, tomatoes

Practices

• Crop Production: pollinator health

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.