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.