The world came together last week for the UN general assembly, and climate crisis was high on the agenda. Many of the discussions focused on changing the energy and transport sectors to mitigate potential catastrophe. Climate activist Greta Thunberg traveled to New York on an emissions-free yacht to deliver her speech at the UN climate summit. The point of her journey was to raise awareness that transatlantic flights generate significant greenhouse gases. That message is getting across: people are putting limits on the number of flights they take each year to conferences, workshops and holidays.

What was not high on the agenda was the impact food systems have on greenhouse gas emissions and other environmental degradation. A slew of high-level reports produced over the last few months all argue that if the world is to make an impact on climate crisis, the food system needs to be radically reshaped.

The way we produce food, the way food is manipulated and moved around the world, and what we as citizens decide to put on our plate, matter for the climate crisis. Food systems contribute 21% to 37% of global greenhouse gases, and are significant contributors to deforestation, biodiversity loss and declining water tables. The Amazon forest fires in Brazil are directly related one way or another to food production.

Perhaps the biggest problem: livestock. They use a third of global cropland and contribute 15% of global greenhouse gas emissions. A recent New Yorker article noted that “[every] 4lbs of beef you eat contributes to as much global warming as flying from New York to London – and the average American eats that much each month.”

While red meat is generally considered the most resource-intensive food on the planet, the factors that determine whether a given meat is sustainable are complicated. Meat production can be environmentally friendly and efficient when it uses lands of low-opportunity costs, not suitable for crop production or significant carbon sequestration. Meat production can also be efficient in intensive, high-welfare animal systems like free-range pork and poultry. It can be more environmentally friendly when it uses feed that does not compete with human food.

Every four pounds of beef you eat contributes to as much global warming as flying from New York to London

As producers embrace new technologies to ensure animal systems are sustainable, we can make our own personal changes. Many people eat more red and processed meat than they need to, and there remains a lot of confusion about the health and environmental impacts of consuming meat. Red meat consumption per capita has been static since the 1990s. In contrast, we see a rapid growth in consumption per capita for pork and poultry (up to 300% in places in the last 25 years).

The sheer growth of the world’s population is driving the increased demand for animal source foods. Some countries consume very high levels of red meat, such as those in the OECD and Latin America; other countries have very low consumption levels, such as many parts of Africa and south Asia. Still, consumption is low in low-income countries in comparison to high-income countries.

The IPCC and Eat-Lancet reports recommend that those who consume high amounts of meat consider a “flexitarian” diet. This diet is largely composed of vegetables and fruits, whole grains, legumes, nuts and unsaturated oils. It includes high-quality meat, dairy and sugar, but in quantities far lower than are currently consumed in wealthier societies.

How should consumers make the shift? People could consider being a vegetarian by day and allow themselves small servings of animal source foods in the evening; go meatless on Mondays, as some schools and institutions already have; embrace tasty Asian cuisines, which tend to be more plant-based; or try out alternative plant protein options such as the Impossible Burger or Beyond Burger. Start with kids – school meals are a great way to form healthy and sustainable habits early on. Learn where your food (and meat) comes from. Who produced it and how? Support food producers who make efforts to produce low-impact meats. If you are going to go for red meat, choose quality over quantity: eat more meat cuts and less processed meat. And waste nothing.

But for the world to make this shift, we need governments and the food industry to make it easier. We need investment in public health information and the implementation of policies that promote healthy eating that is affordable, safe, convenient and most of all, tasty.

What we eat matters. Not only for ourselves and the planet, but for the youth who were out marching on the streets last week in the name of their future and right to live on this planet.