The following is an edited excerpt from “Bread, Wine, Chocolate: The Slow Loss of Foods We Love” (HarperOne, 2015).

More than 1,000 varieties of bananas are grown in the world, but only one variety is widely sold in stores. (Hotli Simanjuntak/European Pressphoto Agency)

The following is about food, but it’s really about love. It’s about that moment when you find yourself savoring something so wholly and intently, you never want to let it go. I thought this love, at least in the culinary sense, could be found only in superlative places: a secret supper club in London, a hidden bistro in Paris or a roadside dhaba in Mumbai. But I know now that the greatest love is found in humble places: in my morning coffee, in a morsel of bread or in a bite of chocolate. And that to pay closer attention to these ordinary pleasures isn’t just to see them anew but to experience them in a whole new way.

I had forgotten how to do this. I had forgotten how to be present to what was right in front of me, knowing only how to love what shouted for my attention. Until I realized I could lose them. Embedded in every conversation about feeding people, conserving natural resources and ensuring a healthy diet, both now and in the future, is the threat of the loss of agricultural biodiversity: the reduction of the diversity in everything that makes food and agriculture possible, a shift that is the direct result of our relationship with the world around us.

I know it feels counterintuitive to contemplate loss, particularly against the backdrop of floor-to-ceiling aisles in supersized supermarkets. In a Walmart (the No. 1 grocery chain in America) in Winston-Salem, N.C., I counted 153 flavors of ice cream and eight brands of yogurt. But then I looked further. The choices are superficial — primarily in flavor and secondarily in brand, most of which are owned by the same company. In addition, more than 90 percent of every container of yogurt, milk and ice cream is made with milk from one breed of cow, the Holstein-Friesian, known as the highest-producing dairy animal in the world.

Bananas — America’s most popular fruit — carried only a single descriptor: “banana.” Although no variety was listed, I know it was the threatened Cavendish. There are more than 1,000 varieties of bananas grown in the world; however, the one that ends up on supermarket shelves isn’t the one that has the best texture or taste but one that transports easily and has, so far, managed to beat back disease.

I saw six kinds of apples, including Granny Smith, Gala, Fuji and the mealiest, most inappropriately named apple: Red Delicious, bred for beauty, not taste. Apples were among the first fruits to be cultivated. The original was probably small and tart, closer to what we think of as a crab apple. But, through breeding, we slowly transformed its texture, taste, color, size and level of sweetness. There are now 7,500 varieties of apples grown all over the world, fewer than 100 of which are grown commercially in the United States. In fact, nearly every historic fruit and vegetable variety once found in the United States has disappeared.

Selective breeding has transformed apples in terms of taste, texture and other characteristics. Nearly every historic variety of apple — and of every fruit and vegetable once found in the United States — has disappeared. (Ty Wright/Bloomberg)

For millennia, we’ve made decisions about what to grow or not grow, and what to eat or not eat. That’s what agriculture is: a series of decisions we, and our ancestors, have made about what we want our food and food system to look and taste like. But our ability to make those decisions — and indulge in our pleasures — is being compromised in ways that are unprecedented.

Take, for example, the pistachio. The transformation of the pistachio industry was the unintended consequence of political strife, part of a cascade effect of trade restrictions that were meant to punish the captors of hostages. It had nothing to do with food or farmers.

Iran used to be the center of the world’s pistachio industry. Those little green nuts are actually seeds that Persians bred to split open, and they come from the same family of plants (Anacardiaceae) as mangoes, cashews and poison ivy. An integral part of Middle Eastern foods and celebrations, pistachios originated in Afghanistan and are one of Iran’s biggest exports after petroleum. Evidence of the nuts dating back to 6 B.C. has been found in both of those countries.

In 1929, botanist William E. Whitehouse traveled to Persia (now Iran) to collect pistachios in hopes of finding a variety that would be suitable for growing in America. Of the 20 pounds of nuts he gathered, only one variety flourished — in California’s San Joaquin Valley. To put that in perspective, a single nut weighs one-40th of one ounce. There are 320 ounces in 20 pounds. Out of everything he collected, one nut (seed) took root.

Food is bound to place. That small female nut was, at that time, the only one that could handle the climate and other environmental conditions of the United States. Whitehouse named the pistachio Kerman, after a famous carpetmaking city near the birthplace of the nut. The tiny but mighty Kerman built a fledgling American pistachio industry that started to blossom in the 1960s and exploded decades later when, in 1980, President Jimmy Carter instituted a full trade embargo on Iran as a result of the 444-day hostage crisis. That included all agricultural products.

The ban devastated the Iranian pistachio market and empowered the United States to build its capacity for pistachio cultivation. Today, America is one of the world leaders in its production. The nearly 520 million pounds of pistachios that were grown domestically in 2014 descended from that one Kerman, a variety that represents almost all of what is planted.

When I first learned of about the loss of biodiversity, and the many reasons it has occurred, I was incredulous. I had spent my life obsessed with food — and it was disappearing? Why hadn’t I heard about this? How was this possible? The answer lies in the fact that many of these changes have happened slowly, over time. These losses in food are buried in the soil, tucked in beehives and hidden in cattle feedlots. They start with microorganisms invisible to the naked eye and echo through every link in our food chain — from soil to seed to pollinator, from plant to fish to animal — compromising the very ecosystems that make much of our food possible.

Nuts for sale at a shop in Iran. A pistachio nut collected in Iran in 1929 eventually became the foundation of a competitive pistachio market in the United States. (Ebrahim Noroozi/Associated Press)

Although some places in the world are experiencing an increase of diversity in certain parts of their diet, the general trend is the same one we see in phones and fashion: standardization. Every place looks and tastes more similar, and the country that sets this trend is America. The refined carbohydrates, animal proteins and added fats and sugars that make up the majority of our diets have also become the template diet for the world.

This increase in sameness is what conservationist Colin Khoury and co-authors of the most comprehensive study to date on the diversity (and lack thereof) of our food supply call our “global standard diet.” The researchers analyzed 50 years of data on major crops eaten by 98 percent of the population. They found that diets around the world have expanded in terms of amount, calories, fat and protein, and that a greater number of our calories now come from energy-dense foods, such as wheat and potatoes. In areas facing food insecurity, this is a very good thing.

The researchers also learned that agrobiodiversity within our dietary staples has increased. Another good thing. In Vietnam, 80 percent of calories from plants used to come from rice; now corn, sugar and wheat have risen in importance, and calories from rice have dropped to 65 percent. In Colombia, palm oil used to be nonexistent. Now nearly half of Colombians’ plant-based fat comes from palm, and the country is the third-largest producer of palm oil in the world.

But this availability obscures the more challenging truth that Colin and his colleagues discovered: Globally, foods have become more alike and less diverse. As the amount of food around the world has shrunk to just a handful of crops, regional and local crops have become scarce or disappeared altogether. Wheat, rice and corn, plus palm oil and soybeans, are what we all eat now — the same type and the same amount.

Yes, this increase in carbs, fats and proteins has helped feed hungry people, but on a global scale it has also increased our chances of becoming what author Raj Patel calls “stuffed and starved.” The world overconsumes energy-dense foods but eats fewer foods rich in micronutrients (the small but essential amounts of vitamins and minerals we need for healthy metabolism, growth and physical development). While 795 million people go hungry, over 2 billion people are overweight or obese. Both groups suffer from micronutrient malnutrition.

The global standard diet is changing the biodiversity of nearly every ecosystem, including the 100 trillion bacteria that live in our gut, part of what’s known as our microbiome. The foods and drinks we consume add to or, increasingly, detract from the diversity of our intestinal flora and have implications for how healthy or unhealthy we are over the long term.

Simran Sethi, author of "Bread, Wine, Chocolate." (Cem Ersavci/For Dumbo Feather, from HarperOne)

(From HarperOne)

The factors that contribute to this change are complex and interconnected, but the main reason for this shift is that we’ve replaced the diversity of foods we used to eat with monodiets of megacrops, funneling our resources and energy into the cultivation of megafields of cereals, soy and palm oil. As farmers from all over the world move toward growing genetically uniform, high-yielding crops, local varieties have dwindled or disappeared altogether. That is why we are now facing one of the most radical shifts we have ever seen in what and how we eat — and in what we’ll have the ability to eat in the future.

According to the Food and Agriculture Organization of the United Nations (FAO), 95 percent of the world’s calories now come from 30 species. Of 30,000 edible plant species, we cultivate about 150. And of the more than 30 birds and mammals we’ve domesticated for food, only 14 animals provide 90 percent of the food we get from livestock. The loss is staggering: Three-fourths of the world’s food comes from just 12 plants and five animal species.

While those numbers are rough estimates, they speak to a startling trend: We rely on fewer species and varieties for food and drink, a treacherous way to sustain what we need to survive. It’s dangerous for the same reason investment experts tell us to diversify our financial holdings: Putting all our eggs in one basket (either figuratively or literally) increases risk.

A reduction in agrobiodiversity places us in an increasingly vulnerable position, where warming temperatures or a single pest or disease could severely compromise what we grow, raise and eat. This was, in part, the cause of the Irish potato famine of the 1840s, when one-third of the population was dependent on potatoes for food and one-eighth of the population (about 1 million people) died when a disease known as potato blight ravaged the crop. It has also contributed to Southern corn leaf blight, which wiped out one-fourth of American corn in 1970. And now it exacerbates the proliferation of wheat rust, known as the “polio of agriculture,” which is threatening 90 percent of African wheat.

Crop scientists in Kenya examine wheat for rust — a condition threatening 90 percent of African wheat — at the Kenya Agricultural Research Institute’s station near the village of Njoro. (Sharon Schmickle/For The Washington Post)

It’s why plant geneticists are working around the clock to develop a new type of banana to replace the Cavendish, a variety that was introduced when the soil fungus Fusarium oxysporum in the 1950s, wiped out the Gros Michel, the banana that used to be the one on store shelves. Those Cavendishes are now succumbing to Tropical Race 4, a strain of the same fungus that decimated the Gros Michel.

No matter where you live, you have the memory of something you used to eat that is no longer a part of your diet — something your grandmother used to make, something a small shop used to carry. Something you have lost. This extinction is a process; it happens one meal at a time.

Fortunately, a lot of these changes have occurred in the past few decades, which means they can change again. That is, of course, as long as we sustain the diversity found in the wild, on farms and in stored collections that contain the traits we might need now or in the future: immunity to a disease, greater adaptation to a changing climate, the possibility of higher yields or greater nutritional value — and delicious taste.

But in order to support this diversity and facilitate change, we have to start to think differently about the food in our fields and on our plates, and be more discriminating about its sources. “How do we buck the system just a little bit?” Colin Khoury asks. “Think of oil. We’re definitely eating more of it: soybean oil, then palm oil — much more than other oils around the world. Although it isn’t immediately obvious that eating olive oil would be radical, in the big picture that’s exactly what it is. Eating olive oil is now a radical act. Eating anything that’s not rice, wheat, corn, soy or palm oil is radical.”

The revolution starts here, on our plates, by looking at the pillars of our own diets and by making simple changes. The way to take back this power for ourselves is to understand why we eat what we eat. And to understand what we’re losing — so we know what to reclaim.

Reprinted with permission by HarperOne, a division of HarperCollinsPublishers. Sethi is a journalist and educator focused on food, sustainability and social change.