Because you need considerably more resources to grow meat than you need to to grow a nutritionally equivalent amount of vegetables.

The basic problem is that to get 1000 calories of beef, you need to feed the cow something like 10,000 calories. So growing a cow is actually growing an entire field of wheat/corn/etc., then feeding it to the cow, then eating the cow.

Farming all of those crops for the animals takes up a lot of land, consumes fresh water, produces wastes, and uses oil/gas (for farm equipment directly, or to produce things like nitrogen fertilizers) which produces co2. Cows also produce methane (that's the fart thing) which is a bad greenhouse gas.

You could just eat the wheat/corn/etc. directly (most of the time) and skip the meat step therefore saving a massive amount of environmental impact.

Meat sure is tasty though.

• Ethical reasons: hundreds of billions of animals are killed every year (not counting fish), after living a miserable and short life.
• Environmental: greenhouse emissions (CO2 and methane), deforestation for pastures, water pollution, are all caused by animal agriculture. If everyone went vegan we'd need only 25% of the land we currently use for agriculture.
• Health: there is some evidence that meat causes cancer, and convincing evidence that processed meat causes cancer. Also, the use of antibiotics for animals can lead to the development of antibiotic-resistant bacteria.

Cow farts are methane, which are a more aggressive form of greenhouse gas, though with shorter lifespan.

Here's more info about meat and the environment.

A lot more water to make the food for cows than what humans consume.

A lot more food to feed a cow than what it would take to feed the human the same type of food.

And the growth of that food to keep feeding these animals in large batch is pretty much creating dead areas of land that gets ruined if it’s not carefully monitored. And the run off into the water supply is a problem. This is why industrial level of farming is really really bad for the environment.

You’re supposed to move cattle around in pastures for regrowth and not entirely decimate it. The capitalists do not care about that until a court summons tells them to care about that.

Currently there’s some better methods however the consumption stays high.

Health wise : all meat diets (meat at every meal) can produce issues in your body.

Cured meat or heavy salted meat can lead to heart issues and kidney stones.

You should mix in some fruit and vegetables and maybe even substitute some entire meals so that meat is consumed only a few times a week if only for your body’s sake. Your taste buds aren’t the same organ as your heart. They aren’t the organs that make your body stay alive.

Your edit is actually missing the biggest reason--all the energy and water it takes to raise the meat. It's just not sustainable.

The core issue is soil quality. Without sufficient organic content in the soil, all our food, whether it be plant or meat, has drastically reduced nutritional content meaning we need to consume more for the same effect. We're heading for a global food shortage because of the one key issue. Healthy soil also sequesters an enormous amount of carbon from the atmosphere. So instead of fighting the beef vs tofu wars, we should be focusing on encouraging agricultural practices that enrich soil rather than destroy it. We have about 50 years of crop cycles left before the majority of arable earth turns to sand.

Shifting your diet to be more plant-based is a good idea, but it's not the crux of the issue.

Most tree and forest loss is from making land for grazing.

Ask the cow what she thinks?

To learn more about the environmental impact of meat consumption, I recommend this Our World in Data article: https://ourworldindata.org/environmental-impacts-of-food

I would highlight this chart: https://ourworldindata.org/grapher/ghg-per-protein-poore?country=Pig+Meat~Beef+%28beef+herd%29~Eggs~Lamb+%26+Mutton~Grains~Milk~Other+Pulses~Poultry+Meat~Tofu+%28soybeans%29~Peas~Nuts~Groundnuts~Fish+%28farmed%29~Cheese~Beef+%28dairy+herd%29~Prawns+%28farmed%29~Tofu

For example, getting 100 g of protein from beef emits ~ 50 kg of CO2. Getting 100 g of protein from tofu only emits ~ 2 kg of CO2.

Because the amount of resources required to raise the livestock required to support the free market of meat is unsustainable. Also the impact of all that livestock is a huge contributor to climate change. So besides the moral argument of it being wrong to eat another living beings there is a very real danger to ourselves in the future.

I think everything has been addressed. I just wanted to clarify that the methane is from cow burps, not farts.

Feeding cows takes up a lot of land, which often requires deforestation.

Because it's speciesism. If we started giving birth to humans to eat them, that would be absolutely outrageous, but to do that to animals seems perfectly fine to most people. Animals have the same desire as we do not to be killed or abused, and to live a happy life.

You're not getting many answers yet regarding nitrogen.

As a preface: When it comes to climate and environmental concerns with respect to agriculture, the word "nitrogen" does usually not refer to the completely harmless atmospheric nitrogen (N2). Instead, it refers to various compounds that contain nitrogen.

Nitrogenous pollution from cattle comes in two shapes:

The first is methane (NH3). A single cow burps and farts out about 100kg of methane each year. Methane is a greenhouse gas that's 28 times as potent as CO2. This means a single cow is responsible for as much as 2800kg equivalent in CO2 each year due to burps and farts alone. For reference, the CO2 per capita emissions globally are about 4 tons (4000kg) per year, for all sources combined. Cows, relatively speaking, therefore produce a huge amount of CO2 equivalent.

The second is all the nitrogenous compounds in their excrements. This acts as a fertilizer on soil and in the water. While that sounds good, it leads to various unwanted effects. One is that agricultural runoff causes algal blooms in water that then ends up killing a significant amount of marine life. Another is that nutrient-rich soils tend to seriously decrease plant species diversity. Many native and wild plants actually need nutrient-poor soils to thrive. Those plants will get outcompeted by a small group of fast-growing plants that do well in all the cow-poop-infested soil. These compounds also tend to travel far, via agricultural runoff or even via the air, so ecosystems far away from farms are also impacted.

There is a lot of waste from the agricultural process that needs to be considered as well, like fertilizer run off into rivers, etc.

IMO what's bad is not meat consumption itself, which we were able to do sustainably for millennia and it was never really a problem. The problem is that now you're getting too much of it way too easily. Eating too much meat is a problem because it perpetuates demand for unethical mass-production of meat and livestock are made to suffer as a direct result.

The main issue is probably less meat itself than the ginormous quantities we consume.

Most livestock farming is intensive, meaning they can't rely on grazing alone and need extra food sources, typically corn. They emit methane, a greenhousing gas on steroids.

That grain is produced through very intensive agricultural methods because we can't get enough of it. It consumes ridiculously large amount of water and slowly degrades the soils. Nitrates eventually end up in the sea, causing algea to proliferate while other lifeforms are suffocated. See the dead zone in Mexico's gulf.

71% of agriculture land in Europe is dedicated to livestock feeding.

The percentage must be similar or higher in America, and don't count North America alone: without grains from Brazil, we're dead. Period. So next time you hear the world blaming Brazil for deforestation, keep in mind that a large share of it is to sustain livestocks...

Cattle farming in the USA is heavily subsidized, by allowing farmers to use federal land for grazing for free (I believe something similar is in place in Canada?). The claim they "take care of the land" is absurd: nature has been doing that for millenias without needing any help. First nations have been living in these lands also without supersized cows herds and it was going alright. Farms actually prevent wildlife to take back its place.

But I wouldn't blame them. People in North America (among others, and I live in Canada, definitely me too) eat indecent and unhealthy quantities of meat, and that has to come from somewhere.

Now, simple math will tell you: if everyone in the world was consuming meat in the same quantities as us, there would'nt be enough suitable land on Earth to grow the corn that needs to go with it.

Another thing is not all meats are equal in terms of pollution. From the worst to the least bad, in equivalent kgCO2 per kg of meat you can actually eat: -Veal: 37 -Chicken (intensive, in cage): 18 -Beef: 34 -Pork: 5--7 -Duck, rabbit, pork: 4--5 -Chicken ("traditonal, free range): 3--4 -Egg (for comparison): <2

You can appreciate the orders of magnitude!

There are only 2 ways out of this:

• reduce meat consumption, and pick it right
• grown meat (meat made without the animal around it, in machines)

One can be done today, starting with your next meal. We don't need meat every meal, we don't even need meat every day, but it is true that going full vegetarian force a certain gymnastic to get all the nutriments one need.

The other solution is barely getting there, so there are still unknown (food quality, resources consumption, etc.) and the economics may not help it taking off.

The third (and let's face it: current approach at national level everywhere on this issue) option is to do nothing and keep going as if the problems didn't exist. This is guaranteeing a famine in the coming decades. When we'll fail to feed our livestock, and it will start dying, it will be too late to turn around and get the whole agriculture sector to transition. These things take many years.

We're trying to reduce our meat consumption at home, or to favor the least impacting ones. We still eat too much meat, but I hope we can gradually improve.

because you have to kill a living thing for it