Geospatial Assessment of Smallholder Maize Farm Distribution, Heatwave Exposure and Farmer Adaptation in Thulamela Local Municipality, Limpopo Province, South Africa

In the rural landscapes of South Africa, maize is more than just a crop; it is the backbone of daily life and the primary source of food for countless households. For small-scale farmers, who grow this grain on modest plots of land without the vast resources of industrial agriculture, the margin for error is slim. Their success depends entirely on the rhythm of the seasons and the reliability of the rain. However, the climate is shifting. Rising global temperatures are bringing more frequent and intense periods of extreme heat, known as heatwaves. These are not merely hot days, but sustained spells where temperatures climb well above the normal average for several days in a row, drying out the soil and stressing plants. For a crop like maize, which is sensitive to temperature changes during its growth, such heat can be devastating, turning a potential harvest into a failure. Understanding exactly where these farms are located and how they are being affected by these rising temperatures is crucial for protecting the food security of entire communities.

Researchers from the University of Venda set out to map this invisible threat in the Thulamela Local Municipality, a region in the Limpopo Province known for its smallholder farming. They wanted to answer two fundamental questions: where are these maize farms located, and how much heat stress are they actually facing? To do this, they combined two very different types of information. First, they looked at the land from space using high-resolution satellite images. These images act like a detailed photograph of the Earth's surface, allowing scientists to distinguish between different types of land cover, such as forests, water, buildings, and the specific green signature of maize fields. Second, they gathered historical weather data from ground stations and computer models to track how often and how intensely the region has experienced heatwaves over the last three decades. By layering the map of the farms directly over the map of the heat, they could see exactly which fields are in the most danger.

The team used advanced computer programs to analyze the satellite images, teaching the software to recognize the difference between a maize field and other types of land. They tested two different methods to see which one was more accurate. One method, which works by building many decision trees to classify the land, proved to be the superior tool, correctly identifying the crops in 91 percent of the test cases. The other method was less precise. Using the better method, the researchers calculated that there are approximately 73,400 hectares of smallholder maize farms scattered across the municipality. This is a significant area of land, representing a vital economic and food-producing zone.

Once the farms were mapped, the researchers overlaid them with data on heat stress. They defined heat stress in three levels based on temperature thresholds that are known to harm maize. The first level, where temperatures exceed 30 degrees Celsius, is considered stressful for the crop. The second, above 35 degrees, is high stress, and the third, above 40 degrees, is extreme. The results revealed a worrying picture. Nearly three-quarters of the mapped maize farms, specifically 74.5 percent, are located in areas that experience high heat stress, where temperatures regularly climb above 30 degrees. This means that for the vast majority of these farmers, the growing season is frequently interrupted by temperatures that can reduce pollen viability and shorten the time the grain has to fill, ultimately lowering the harvest. While fewer farms face the extreme heat of 40 degrees, the study found that even these rare, intense spikes are a real threat, with isolated hotspots capable of causing severe damage.

To understand how farmers are coping with these conditions, the researchers spoke directly with 60 smallholder producers in the area. The survey painted a clear picture of the struggle. Most farmers reported that heatwaves are becoming more severe and lasting longer, often exceeding ten days. They described visible damage to their crops, including wilting leaves, drying plants, and poor grain development. Despite these challenges, the farmers are not sitting idle. The most common strategy they use to adapt is crop rotation, a traditional practice where different crops are grown in a field in sequence to maintain soil health. More than half of the farmers reported using this method. Others are trying to time their planting to match the first rains or are switching to drought-resistant varieties of maize. However, the study also highlighted a significant gap in support. Nearly three-quarters of the farmers said they receive no agricultural support from the government or other organizations. Many lack access to irrigation systems, which could help them survive dry spells, and few have the financial resources to invest in new technologies or inputs like fertilizer.

The study concludes that the smallholder maize farms in Thulamela are under increasing pressure from a warming climate. The combination of satellite mapping and on-the-ground surveys shows that while the farmers are resilient and actively trying to adapt, the tools and resources they need to succeed are often out of reach. The data suggests that without better access to water storage, affordable irrigation, and targeted support for the women and older farmers who make up the majority of this workforce, the threat of heatwaves will continue to undermine household food security. The research provides a clear, evidence-based map of the problem, showing exactly where the risk is highest and offering a foundation for future efforts to help these communities build a more secure future.