Asparagus in winter, pears from Argentina, Peruvian blueberries and Californian almonds — these are just a few of the several thousand products shoppers can buy when they enter a supermarket.

It's something our ancestors a century ago likely never imagined, but we've become used to this bounty of choice when we select our food.

"It is truly peculiar to walk into a Carrefour Marche in France or Wal Mart here in the United States and see what's on offer," says Janet Chrzan, a nutritional anthropologist from the University of Pennsylvania. "We are living in a food environment which is unlike anything our species has ever encountered."

German supermarkets on the whole have more than 10,000 products. In the US, the average is more than 30,000, according to the American Food Industry Association. Consumers make decisions about which items to put into their shopping baskets in a matter of seconds. And those decisions have implications for the environment.

Food consumption is the main driver of negative environmental impacts generated by the average European citizen, according to the European Commission.

The problem with overconsumption

Food production accounts for around a quarter of the world's greenhouse gas emissions. Most of that comes from meat and dairy, which contribute almost 15% of global emissions. Producing food also causes other problems, such as pollution, biodiversity loss, contamination of soils and water shortages.

Food consumption has been increasing worldwide for decades. High-income countries, including the US and Germany, take in the most calories per capita. At the same time, the UN estimates that households globally throw away 11% of the total food available for consumption, although this statistic does not include low-income countries. So why do we buy more food than we can eat?

According to Chrzan, our species has an unconscious fear of hunger that could stem from a time when food was much harder to come by.

"We have an inborn desire as human beings, as biological beings, to ensure that we have food for ourselves and our children," she says.

"If you think that your environment is going to be risky, that you might not get a meal, or that you might run out of food in general, then you're going to hoard food."

How do we choose our food?

Besides the fact that humans need food to survive, there are a whole range of considerations influencing which products we buy at the supermarket. Shoppers are often heavily swayed by price — they choose what they can afford. But other factors such as marketing, health concerns, taste, convenience, sustainability and expressing identity or values might also play a role in the type of food we choose to buy.

Stefan Wahlen, a food sociologist at the University of Giessen in Germany, says despite small blips, people tend to eat the same food 95% of the time.

"You live in your routines, and even though you might be trying some new foodstuff, there's little variation in what we actually eat," he says, adding that these routines help us in "coping with the complexity of our daily lives."

When faced with an abundance of choice in the grocery store, consumers tend to make decisions that are quick and based on habit. Our consumer behavior is notoriously difficult to change because food choices and eating patterns are so embedded in the way we live.

But climate scientists say change, including moderating our diets, is exactly what's needed to bring down greenhouse gas emissions from food. That means eating less red meat and more plant-based foods. Opting for seasonal produce rather than buying, say, strawberries in winter can also make a difference.

The value-action gap

A 2020 survey looking at consumer attitudes toward sustainable food in 11 EU countries found cost was the main barrier to people buying the greener product, along with a lack of information and the challenge of identifying sustainable food options.

Two-thirds of consumers in the study by the Brussels-based European Consumer Organization said they were open to changing their eating habits for environmental reasons, with many willing to reduce food waste at home, buy more seasonal fruit and veggies and eat more plant-based foods. But only one in five were willing to spend more money for sustainable food.

Often other factors — be they brand, taste or price — take priority. A number of studies have documented this phenomenon, known as the "attitude-behavior gap" or "value-action gap" — the idea that while many consumers care about the environment, they don't necessarily choose more eco-friendly products.

Social change happens slowly

Wahlen notes that despite discussions over the past decade about the harmful effect of meat production on the environment, there has been little change in meat consumption in Germany — something he says could be linked to the idea of meat as a status symbol that emerged after World War II.

He believes gradual change is happening. But in order for new, sustainable products to catch on, he says they need to be convenient and fit in with consumers' existing routines and ways of preparing food.

"So it might be a meat patty made from the lab or made out of insects, but if it fits the ways of barbecuing [or] cooking in the home context, then it's more likely to be implemented."

Is behavior change even possible?

According to Chrzan, there need to be more efforts to "start critically educating people about ... their individual choices" and the impact they have on the planet.

It can be tricky for consumers to know which foods are ecologically sustainable, given that most products don't display their carbon footprints or how much land and water went into producing them. Chrzan says this information should be included on food labels.

Other measures that have been floated include subsidies and taxes to make eco-friendly products the more affordable choice. "Nudging" is another way to shift consumer habits without imposing financial incentives. For example, changing the way products are packaged, or increasing the visibility of more sustainable meat or plant-based meat substitutes in supermarkets.

Consumers' choices are ultimately only one part of the energy-intensive food system. But Chrzan says people can adopt more sustainable diets if they do a "critical assessment" of what they like to eat and make changes based on what is better for both their health and the planet. This, she says, can "take the psychological weight off of having to make the choice" every food shop.