LOS ANGELES — Each day, an army of trucks delivers tens of thousands of pounds of fresh fruit and vegetables to Mexico City's Central de Abasto, one of the world's largest wholesale food markets.

Most of the produce finds its way to people's kitchens, and eventually their stomachs. But around 420 tons goes bad each day before it can be sold. It ends up, like so much food around the world, in a landfill.

Globally, a staggering one third of all food that is produced is never eaten. That waste — more than 1 billion tons annually — fuels climate change. As organic matter decomposes, it releases methane, a greenhouse gas that is much more potent than carbon dioxide when it comes to warming the planet.

The United Nation estimates that up to 10% of all human-produced greenhouse gases are generated by food loss and waste. That's nearly five times the emissions from the aviation industry.

For many years, scientists and policy makers have been largely focused on addressing other drivers of climate change, especially the burning of fossil fuels, which is by far the largest contributor to global emissions.

But food waste has recently been drawing more international attention.

The issue was on the agenda at this month's United Nations climate summit in Azerbaijan, where for the first time, leaders signed a declaration calling for countries to set concrete targets to reduce methane emissions caused by organic waste.

Only a handful of the 196 countries that have signed the Paris Agreement on climate change have incorporated food waste commitments into their national climate plans, according to the UK-based nonprofit Waste & Resources Action Program.

Many more nations are like Mexico, which is just beginning to assess how it can reduce the 20 million tons of food wasted annually here.

A recent report by the World Bank identified several waste hotspots in the country, including the Central de Abasato, which stretches across 800 acres on the south side of the capital.

In the dense warren of stalls, the best-looking produce is displayed prominently: ripe bananas, glistening limes and orderly rows of broccoli and asparagus. In the back are fruits and veggies that no longer look perfect: mushy papayas, wilting spinach and bruised tomatoes.

A few years ago, market organizers launched an initiative to collect the produce that looks too old to sell but is still perfectly usable. They donate it to food banks and soup kitchens. Organizers say they've reduced the amount of food that is thrown out by about a quarter since 2020 — and have provided meals to tens of thousands of hungry people.

"It's much better to donate," said Fernando Bringas Torres, who has sold bananas at the market for more than four decades. "This food still has value."

Environmental activists say reducing food waste is one of the most attainable climate solutions, in part because its not politicized.

Asking companies and consumers to cut back on the food they send to landfills is far less charged than urging a reduction in meat consumption, energy use or the number of gas-fueled cars on the road.

"People on the left and the right both have a gut reaction to it because it is a waste of resources," said Christian Reynolds, a researcher at the Center for Food Policy at City University in London. Reducing waste "is not a silver bullet" to stop global warming, Reynolds said. "But it's up there with the things you've got to solve, and it's a useful way to open doors around climate change."

Scientists say cutting back on waste is valuable because methane traps heat at a much higher rate than carbon dioxide.

Methane emissions are to blame for about 30% of the recent rise in global temperatures. U.N. climate leaders say slashing them is a vital "emergency brake" that will help curb the extreme weather already seen across the world today.

About 20% of methane emissions come from food loss and waste, an umbrella term that describes all food that is produced but not eaten.

It includes crops destroyed by pests or extreme weather, produce or meat that spoils in transport because of faulty packaging and food that goes bad at market before it can be sold. It also includes all food purchased by individuals or served at restaurants that ends up in the trash.

The data on food waste are stunning:

•It takes an area the size of China to grow the food that is thrown away each year.

•Globally, around 13% of food produced is lost between harvest and market, while another 19% is thrown out by households, restaurants or stores.

•Food waste takes up about half the space in the world's landfills.

•An estimated 316 million pounds of food will be wasted in the United States on Thanksgiving alone, according to the Chicago-based nonprofit ReFED. That's the equivalent to half a billion dollars worth of groceries thrown away in a single day.

Experts say some food waste in inevitable. Humans need food to survive and it degrades quickly. Modern food systems are built around the transport of products across long distances, increasing the likelihood that some things will spoil.

But they say there are relatively pain-free ways to reduce waste at all stages — from producer to consumer.

The simplest thing is to reduce the amount of extra food being produced in the first place.

But other solutions include fixing inefficient machinery that makes it hard to harvest all of a crop, bettering poor roads that prevent food from making it from farm to table and improving packaging, so food stays good for longer.

At the end of the chain, restaurant workers can be better trained to prepare food in a way that avoids waste. Retailers can be encouraged to avoid over-buying and to stop the practice of stocking only perfect-looking produce and discarding the rest. And consumers can be encouraged to eat all of what they buy and lower the temperatures on their refrigerators to delay food from going bad.

There has also been a major push to get retailers to change how they label foods, given that many consumers throw out products if they are past their sell-by date. "We should be making sure that our food safety policies are not getting in the way of our climate goals," Reynolds said.

California Gov. Gavin Newsom recently signed a bill, AB 660, that would bar food-sellers from using the term "sell by" on packages, requiring them to switch to "use by" or "best if used by." Advocates say it would dissuade Californians from throwing away food that is still good.

Other efforts are focused on recovery and redistribution — getting food that is about to spoil into the hands of hungry people. Each year 783 million people around the world go hungry, with a third of the global population facing food insecurity.

World leaders "are starting to make the connection between the the climate impact and social impact," said Ana Catalina Suárez Peña, an advocate with the Global FoodBanking Network, which works with food banks in more than 50 countries.

Her organization recently developed a calculator for food banks and businesses that allows them to measure the volume of methane avoided by curbing food waste.

The group found that six community-led food banks in Mexico and Ecuador prevented a total of 816 metric tons of methane over a year by redistributing food that would otherwise have gone to landfill. That is the equivalent of keeping 5,436 cars off the road for a year.

Tools to measure food waste — and the savings generated from avoiding it — are an important part of tackling the problem, said Oliver Camp, a food systems adviser at the COP summit.

Though he was heartened by the summit declaration calling on countries to set targets for avoiding food waste in their climate plans, he said there was still much progress to be made. Countries need to implement a "comprehensive, costed national strategy based on data as to where food loss and waste is occurring, and evidence-based interventions to avoid it," he said.

The World Bank analysis of Mexico found that most of the country's emissions come from the energy and transportation sectors, but that the food wasted here is the fifth biggest contributor.

"There is an overproduction by farmers," said Adriana Martínez, 48, who runs a stall at the Central de Abastos that she inherited from her late father. She said customers "only want food that looks perfect."

Each week, about 30% of her product begins to go bad. In the past, she would have sent it to the overflowing dumpsters that sit behind the market. But now she calls up a market organizer who connects her with a local food bank.

Martínez said her father, who grew up poor, would be happy knowing that food from the stand is helping other people instead of decomposing in a dump. "He knew hunger," she said. "And he hated waste."

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