Effects of extreme weather events on the production and marketing of hydroponic lettuce in RS

Climate change is profoundly transforming the global environment and is having a significant impact on vegetable production. Rising average temperatures, changing precipitation patterns and the increased frequency of extreme weather events are creating unprecedented challenges for both farmers and agricultural ecosystems. In this scenario of uncertain climate conditions, challenges lie in adapting and maintaining cultivation structures, as well as developing production techniques that meet high productivity levels associated with vegetable quality parameters.

Rio Grande do Sul (RS) is one of the most important Brazilian states for agricultural production. The catastrophic floods that hit the state between April and May 2024 showed us, in addition to the vulnerability of urban areas, impacts that have not yet been measured in rural areas. Recent studies in the region indicate that events of this category will become more frequent and intense in the future (Clarke, et al., 2024), making it essential to consider more resilient cultivation techniques.

These events, which include intense storms, flooding, prolonged droughts, and heat or cold waves, create adverse conditions that impact the maintenance of cultivation structures, development cycles, and plant quality standards. Throughout this text, we will explore some factors and how they influence hydroponic lettuce production and marketing systems, especially at this time of reconstruction that we are experiencing in the state of RS.

1) Effects of storms and floods on hydroponic structures

Severe storms can have devastating effects on hydroponic vegetable production and greenhouse infrastructure, causing significant losses and challenging producers’ ability to recover. Figure 1 shows a hydroponic cultivation area completely compromised by rising water in the Taquari Valley region.

In addition to the damage to the main structures of the agricultural greenhouse, where damage to the support posts and rupture of the films and covering screens were observed, losses were observed in the entire hydraulic system and the nutrient solution distribution system, as illustrated in figure 2.

2) Effects of extreme temperatures on the production and quality of vegetables

The quality of lettuce can be significantly affected by extreme weather events. Periods of intense heat and cold waves, with high temperature gradients in short periods of time, such as those recorded from May and June (post-floods) create adverse conditions that impact both the growth and quality of the plants.

In relation to extreme cold, the first symptoms in plants are manifested by a reduction in the growth rate, leading to slower development and delayed harvesting. This occurs because low temperatures affect metabolic processes and enzymatic activity, which are essential for growth and the formation of new leaves.

However, when the period of exposure to low temperatures is prolonged, freezing of plant cells may occur, followed by rupture of cell membranes and disintegration of tissues. In the case of leafy vegetables, this process compromises the structural integrity of the leaves and their quality standard for commercialization.

The effects of extreme cold on lettuce leaves can be seen in figure 3, where it was observed that after four nights with temperature records ranging from -1 to -5° in the municipality of Manoel Viana (RS), the plants showed symptoms of freezing of the edges of the leaves (figure 3, A) and wrinkling of the leaves (figure 3, B).

Management strategies such as completely closing the cultivation structure to maintain the temperature and increasing the nutrient levels (such as potassium) in the nutrient solution can delay the effect of low temperatures on the production environment. However, there are records of such extreme conditions, such as those recorded in Argentina, also in July 2024 (Figure 4), where the freezing of the entire structure demonstrates that some regions are prone to climate events in which there is no possibility of containing or reversing the damage.

3) Effects of extreme weather events on marketing

The events recorded in RS during the months of May, June and July created exceptional conditions for the commercialization of vegetables. CEASA/RS (State Supply Company) itself had its headquarters flooded, requiring an emergency plan and temporary headquarters for commercialization operations.

However, the biggest challenges are faced by farmers, who face a scenario of chaos in their cultivation structures, on access roads or in maintaining activities in a scenario of inflation in production costs and little interference from public policies that meet, in the short term, the emergencies that arose in this exceptional period of the year 2024.

Amid the flooding scenario, record prices were recorded for many foods, including lettuce (Figure 5), which reached a maximum price of R$60,00 per dozen (R$5,00 per unit) according to the CEASA/RS quotation during the month of May. These prices are justified first by the scarcity of the product, considering the destruction of many production areas and the logistical restrictions imposed by the destruction of bridges and roads in almost the entire state of RS during this period.

In order to minimize the impacts of intense storms and improve the resilience of agricultural operations, it is crucial to adopt mitigation and recovery strategies, such as:

•Strengthening infrastructure: Investing in greenhouses and hydroponic systems with more robust and resistant structures can help to better withstand storms.

•Emergency plans: Have an emergency plan that includes strategies for dealing with power outages, flooding, and structural damage. This may involve installing power generators, implementing emergency drainage systems, and creating protocols for rapid damage repair.

•Risk management plan: Implementing climate risk management plans, which include crop insurance and rapid response strategies, can help producers recover more quickly and protect their operations against future losses.

•Government support: Public policies and financial support programs are essential to help producers face the consequences of climate disasters and invest in adaptation measures.

In summary, climate change poses a significant threat to vegetable production, with potential impacts ranging from deterioration of crop structures to irreversible changes in plant growth patterns. Addressing these challenges requires a combination of innovation, adaptation and effective policies to protect both agricultural production and global food security.

By Narielen Moreira de Morais, Marcia Xavier Peiter, Adroaldo Dias Robaina e Nicolas Gerotto (Irrigation Engineering Laboratory - UFSM)