Dressed in a red boubou, a long traditional robe, Diouf cuts a striking figure in an otherwise muted landscape encrusted in white. As the sun sets, casting an orange hue over the salt flats of Fatick, in southwestern Senegal, Diouf stands, hand on hip, surveying a group of sinewy young men chipping away at a hardened, crystallized mound.
"When I saw other men who had their own land I thought, 'why not me?'" Diouf said, gesturing across the expansive plains, dotted with ancient baobab trees. In the distance, tucked away in fields of dry maize, is her village Ndiemou, which means "Salt" in the local Serer language.
When Senegal privatized land in the area in 2000, Diouf became the first woman to invest. It was a bold move in the west African country, where women have limited access to property despite providing the vast majority of agricultural labor. During the high harvesting season, from February to April, the salt flats are scattered with hundreds of women toiling away in over 40 degrees Celsius (100 degree Fahrenheit), scooping the crystalline mineral into baskets later carried aloft on their heads. But they're not necessarily the ones to benefit financially from the production.
It's an inequity that didn't sit well with Diouf.
"When I first started, men were telling me that I wasn't going to last in this business, but I would say to them that every job a man can do, a woman can too."
Today, she employs dozens of women and men -- including her husband -- in her own micro-business, producing about four to five tons of salt daily in peak season by extracting water from a nearby river to evaporate on land.
"At home my husband is the boss, but here, in the salt flats, it's me," Diouf said, breaking into an infectious laugh.
The same year Diouf leased her plot of land, a presidential decree mandated that all salt harvested in Senegal be iodized. It's a public health strategy widely considered to be the most effective way to prevent iodine deficiency
, which can cause goiter (swollen thyroid glands in the neck), stunted growth and mental impairment -- health issues that had long plagued parts of Senegal. And it's cheap to do -- each ton of salt needs about 6 ounces of potassium iodate, which costs only $4.25.
In most developed countries around the world, table salt has been fortified for nearly a century, which is why the concept of iodine deficiency is almost unheard of in places like the United States.
But not here.
Despite being the largest salt producer in West Africa (Senegal mines nearly 500,000 tons annually), iodine deficiency is still a stubborn problem across the country. Experts say that's down to quality control. Most Senegalese people get their salt from small scale artisanal harvesters, like Diouf, who make up about one-third of the country's overall production. But many fail to iodize their salt effectively.
Those quality issues are why the Iodine Global Network, Global Alliance for Improved Nutrition and others are pushing for Senegal to pivot from supporting small scale producers to deploying iodized salt industrially instead: in processed foods, condiments and seasonings, such as stock cubes
Only 37% of Senegalese households have access to adequately iodized salt, according to a 2015 nationwide survey, and the situation is worse in rural areas. For comparison, approximately 70% of all households globally had access in 2013.
And the need for iodine, which is critical to brain development, increases during pregnancy and infancy. In 2015, 30% of pregnant women in Senegal were iodine deficient, according to the same survey. Without the essential nutrient, they risk losing babies in miscarriages, or giving birth to children with permanent neurological damage. Even a slight deficiency can lower a child's I.Q. by 10 to 15 points.
Other than iodized salt, sources of iodine include seafood, as well as some dairy products and grains
(depending on the soil where it's grown). But in rural regions of Senegal, those foods aren't always part of an average diet -- especially for those struggling with poverty and food security.
So Diouf, supported by Canadian-based non-governmental organization Nutrition International
, has taken on the mantle of local businesswoman and evangelist, going door-to-door to raise awareness about the importance of iodine. As a result, Marie's village, where she is known as "the queen of salt," seems to buck nationwide data that shows access to adequately iodized salt is lowest in harvesting areas.
Only 11% of populations living in salt harvesting regions have access to iodized salt, compared to 53% in urban areas, according to the 2015 government study.
Adama Nguirane, the regional representative for the government's universal salt iodization project
, says this disparity is down to a few factors, but chief among them is a lack of means. It's difficult to convince people to buy iodized salt when they can get it in their backyards for free.
That's why it is critical to get women like Diouf involved in the supply chain, Nguirane says, because they're the ones cooking meals for their families and taking care of the children.
"I believe in the development of my country and it's essential that we fix this problem for our children and our future," Nguirane said. "Marie is the model, and we rely on her to show us the way."
Menno Mulder-Sibanda, a senior nutrition specialist with the World Bank, which has a long-standing partnership with the Senegalese government, says that reducing iodine deficiency is an "essential" part of investing in the economic growth of a nation, and, given the limited agricultural promise of Senegal, the key driver of its future will be in new service-oriented businesses and technology.
"There is a moral question, of not acting on something that is so, in a way, manageable," Mulder-Sibanda said. "Obviously salt iodization in a country like Senegal is tremendously difficult to implement as a public response. But it baffles me that we haven't moved on this issue."
Pape Coumb Ndoffene Faye, the headteacher at the village's elementary school, says he has noticed a big difference in his students' achievement as a result of Diouf's work. "Since the project began, I know children have been getting iodized salt at home and in the canteen here, and mental capacity has improved," Faye says, adding that the school now ranks fourth out of 31 for test results in the region.
Faye, who has been working as headteacher since 2004, adds: "If we look at it as a curve, it's been going up since I started."
Diouf has high hopes for her 13-year-old daughter Fatou, a graduate of Ndiemou elementary. She now walks about 2.5 miles to her middle school each morning. Diouf wants to see her become a powerful CEO, a diplomat, or even the first female president, one day.
Her aspirations may be high, but they feel attainable. President of Senegal Macky Sall was born in the city of Fatick, just 5 miles from Ndiemou, where he served as Mayor from 2009 to 2012. Local people here have a lot of pride in his success, but the region has changed little since his time in office -- it's still among the poorest in Senegal.
Elsewhere in the country, however, Sall's vision for the future looks bright.
On the road to Fatick from Dakar, Senegal's investment in technology and services is embodied in the promise of a glittering, futuristic city: Diamniadio. It's the crown jewel in Sall's Emerging Senegal plan
, which aims to alleviate poverty and get Senegal on the road to development by 2035.
Critics have called the $2 billion urban center
a vanity project for Sall, who is running for reelection in February.
In any case, it's clear that if basic levels of nutrition aren't delivered in places like Fatick, parts of the population will be left behind on Senegal's road to economic fulfillment.
Still, Diouf is hopeful.
"Macky Sall won't be here forever, we want our children to be prepared to replace him."
Meissa Seck contributed to this report from Fatick.