According to the study, nearly all farmers in the area are experiencing changes in temperature and rainfall that make farming more difficult than it used to be.

They were already struggling to feed their families, the data show. But while most said they expect things to get worse in the future, remarkably few are altering their farming practices to adapt.

That’s according to interviews conducted in 2023 in the villages of Sarahandrano and Mandena, some 50 kilometers apart from each other on the outskirts of Marojejy National Park.

Most people there make a living tending to vanilla beans but also to crops such as rice, bananas and coffee on small plots of land. They use hand tools such as sickles and shovels and water from springs and rivers to care for their crops, some of which they sell in the market. The rest they keep for their own consumption.

But in recent years, locals say they’ve noticed changes in the weather, said senior co-author Charles Nunn of Duke, a professor of evolutionary anthropology and global health who has been working in the area for about a decade.

About three quarters of the survey respondents reported that their water sources were drying up, or said they had to reduce the time spent working their land because of weather extremes such as scorching temperatures or torrential downpours.

The respondents said changing weather brings other problems. Many also reported an uptick in pests such as rodents and mosquitoes in villages and fields or noticed more people getting sick with malaria or diarrhea.

Despite these concerns, only one in five participants said they were taking steps to adapt, such as using fertilizers or mulch to improve soil health or shifting their planting and harvesting calendars for certain crops.

“That is significantly lower than prior studies of climate adaptation among small-scale farmers in other countries,” said Duke Ph.D. student Tyler Barrett, who led the study.

The study revealed that men and people who owned more durable goods, such as a generator or a computer, were more likely to change their practices, suggesting that financial barriers constrain farmers’ ability to take action.

Indeed, some four-fifths of Madagascar’s population lives below the poverty line.

“Many of these alternative farming practices cost the farmers more in labor or materials or both,” said senior co-author Randall Kramer, a professor emeritus of environmental economics and global health at Duke.

Programs and policies aimed at offsetting these costs can help, “particularly for those farmers with less means,” Kramer said. “But we're just not seeing much of that yet in Madagascar.”

Other changes could improve their options, such as adding fruit trees to fields, or raising fish in flooded rice paddies, said study co-author Voahangy Soarimalala, president of Madagascar’s Vahatra Association and curator at the University of Antananarivo.

These methods can improve food security but also “help with fertilization and pest control,” she added.

Farmers in Madagascar already face numerous risks.

Most are no strangers to cyclones and tropical storms, which can bear down on the island several times a year, uprooting plants and flooding fields with their violent winds and punishing rains -- sometimes forcing families to relocate or flee their homes.

During the rainy season, flooded or muddy roads or washed-out bridges can make it harder for people to get their crops to market, Soarimalala said.

Northeast Madagascar isn’t the only region affected.

In the villages around Andringitra, a mountainous national park in southeast Madagascar known for its high peaks and occasional snowfall, elders say they haven’t seen frost in a decade.

Data from 15 weather stations across the country show that average temperatures have grown warmer over the past 50 years, while at the same time average precipitation has decreased.

“It is a serious problem that many farmers worldwide are facing, particularly in tropical areas,” Kramer said.

But small-scale farmers -- who produce a third of the world’s food supply -- are particularly vulnerable, he added.

As a next step, the researchers are expanding their survey to 34 villages across the region, to see if the patterns they’re seeing so far are confirmed across a wider range of habitats, and to study the impacts of some of the farmers’ adjustments.

“This is just the first of our analyses,” Nunn said.

“Climate change means that farmers are going to have to be more flexible, more resourceful, take more risks,” Kramer said. “That's really problematic when the success of your farm in a particular year determines if your family goes hungry or not.”

Funding was provided by the joint NIH-NSF-NIFA Ecology and Evolution of Infectious Disease Program (R01-TW011493).