Scientists Pioneer Evidence on How Trees Could Help Tanzania Farmers Beat Heat Stress

By Adonis Byemelwa

Dar es Salaam – The closing session of the 12th Tanzania Health Summit carried a rare sense of urgency and hope. With more than 1,700 participants and over 400 scientific presentations from across the world, the gathering was a showcase of ideas and solutions. As Arnold Kaihula, General Manager of the Summit, put it, it was a moment when “science came home to the people who need it most.” On October 3rd, amid the final round of discussions, one presentation captured the room’s attention—because it touched not just statistics, but lives.

The study unveiled that day showed fresh, compelling evidence that an age-old companion to Tanzanian farmers—trees—could be one of their most powerful defenses against extreme heat. For years, farmers have endured the sun’s punishing rise, with working hours cut short and health put at risk. Now, scientists are proving what many farmers had long suspected: fields shaded by trees are not only cooler, they are safer, and they open a path to resilience in the face of climate change.

The Kisiki Hai Sustainable Heat Adaptation Development (KISHADE) project, led by the LEAD Foundation in partnership with the London School of Hygiene and Tropical Medicine, the University of Dar es Salaam, the University of Dodoma, Muhimbili National Hospital, and Meta, is the first of its kind to demonstrate with hard data how trees in croplands can directly improve farmers’ health. Funded by the Wellcome Trust, the project marks a significant step beyond anecdotal wisdom toward actionable, evidence-based climate solutions.

“Our focus is on finding out if growing crops alongside trees can make a difference in farmers’ health by changing the local environment around them,” explained Dr. Faranja Chiwanga, an Internal Medicine specialist at Muhimbili National Hospital and Director of Curative Services, who leads the project for LEAD Foundation. “For too long, farmers have endured dangerous heat without protection. This study is showing us that nature itself might provide the answer.”

The findings were unveiled during the KISHADE Forum, held as part of the 12th Tanzania Health Summit at the Julius Nyerere International Convention Centre in Dar es Salaam. With more than 70% of Tanzania’s workforce laboring outdoors in agriculture, the implications of this research could not be more urgent.

For years, farmers under the Kisiki Hai (“Live Stump”) program—through which more than 30 million trees have been restored across 260,000 households—have shared their belief that trees keep fields cooler and more comfortable. What was once dismissed as anecdote is now being rigorously tested.

“The risks are no longer abstract,” Dr. Chiwanga emphasized. “Farmers are facing serious heat-related illnesses, from dehydration to kidney disease and cardiovascular strain. And with little access to shade or cooling, the threat is growing by the day. Trees may be the most accessible and sustainable way to fight this crisis.”

To explore this, researchers observed farmers in their daily routines, measuring their body temperature and heart rate in real time using wearable sensors. They collected urine and blood samples to track potential heat-related damage, while simultaneously recording microclimate conditions in agroforestry versus non-agroforestry fields. The early data is compelling.

Dr. Richard Sambaiga, Head of Sociology and Anthropology at the University of Dar es Salaam and a study co-investigator, reflected on the human side of the project: “The response from farmers has been remarkable. They not only welcomed us into their fields but also embraced wearable technology to track their health. This level of trust shows how urgently they want solutions—and how committed they are to being part of the answer.”

Global health leaders are also paying attention. Dr. Ivan Ivanov, an Occupational and Workplace Health expert at the World Health Organization, underscored the project’s significance: “We know globally that climate change is reshaping the risks of work, especially in agriculture. What this project demonstrates is that adaptation is possible with the resources communities already have.

Encouraging farmers to combine trees with crops is a win-win—protecting health while sustaining livelihoods. Alongside that, simple measures like ensuring access to safe drinking water on farms are vital. But it is this kind of locally driven research that gives us hope.”

Meteorologists also see the study as transformative. A scientist from the Tanzania Meteorological Authority (TMA) stressed, “Data is power. Farmers need to know when it will be dry, when rain will come, and how local microclimates are shifting.

 By combining weather forecasts with agroforestry practices, we can help them make smarter choices—whether it is which crops to plant or how to prepare for extreme weather. This study helps bridge the gap between climate science and everyday farming decisions.”

Beyond research findings, the KISHADE project is also nurturing the next generation of Tanzanian scientists. Young researchers are being trained in cutting-edge data collection and analysis techniques, ensuring that the skills and knowledge generated stay rooted in the country long after the study ends.

 Dr. Peninah Murage, Assistant Professor in Environmental Epidemiology at the London School of Hygiene and Tropical Medicine, shared that the first round of results from the Bahi district already indicate the measurable cooling effect of trees. “Fields managed under Kisiki Hai were cooler, with significantly lower heat indices than those without trees,” she said. “The question now is how strongly this cooling translates into better health outcomes—and the early signs are promising.”

For smallholder farmers, those benefits are not abstract—they are felt in their daily struggles. Henry Mubi, a farmer in Bahi, recalled how the heat once dictated his every move. “Before, I used to suffer a lot. I could only work for two hours, then I would feel dizzy and so tired I had to stop,” he said.

“I noticed that farms without trees were the hardest. But when I worked in fields with shade, I could stay six hours or more. Trees gave me the strength to keep going.” He explained that the lack of shade had even reduced his working hours and cut into his income. “It meant I was earning less,” he admitted. “Now, with Kisiki Hai, things have changed. I can work longer, I feel safer, and I see my revenue improving.”

Policy leaders are equally engaged. Dr. Otilia Gowelle, Director of Preventive Services at Tanzania’s Ministry of Health, noted: “We cannot ignore extreme heat—it is already a public health and occupational safety issue. That’s why we are integrating heat-related risks into our preventive services agenda. We are finalizing the new National Adaptation Plan (2025–2030), which builds on recent climate assessments and will guide our national response. Studies like KISHADE give us the evidence we need to act decisively.”

As the project progresses, the benefits are expected to ripple far beyond Tanzania. Local farmers like Mubi are already experiencing relief, but the evidence will also inform regional and global strategies for climate resilience. International NGOs, policymakers, and donors are watching closely, as the data offers a model for how simple, nature-based solutions can safeguard health in an era of rising heat.

For Henry Mubi, the difference is deeply personal. “I praise this project,” he said with quiet certainty. “It has given us back our strength and our dignity in the fields. Trees are not just shade—they are life.”