Some people, like myself, made a conscious decision to exclude various animal products from their diets, believing that this is an inevitable requirement if our species intends to live on Earth sustainably in the numbers we exist today.
I am aware of the following ways how vegetarianism / veganism benefits the Earth and humans who inhabit it:
- it reduces our carbon footprint and contributes towards tackling the climate change.
- due to a significant energy loss when moving up the food chain (about 90% is lost), consuming the primary producers of food (photosynthesizing plants, algae, etc.) seems to be an effective way of solving the global food crisis, which is caused by a rapid growth of human population that consumes at an ever faster rate the limited resources of the Earth.
- it reduces the amount of pollution associated with livestock, such as air and water pollution. For example, agricultural runoff, among other things, causes eutrophication of water bodies and death of marine organisms. This can be viewed as a conservation and biodiversity issue.
- it reduces deforestation, because large areas of forests are being destroyed to grow crops that are eaten by livestock.
- it reduces soil erosion associated with overgrazing by cattle.
- it addresses the growing concern in increase of antibiotic-resistant strains of human pathogens, which is associated with the use of antibiotics for livestock, compromising its effectiveness for humans.
I want to answer the question whether practices of vegetariansim or veganism, if implemented by the majority of the world population, could conceivably have a significant and positive effect on the issues outlined above or even solve them altogether. I am particularly interested in evaluating the consequences that such a change might have -- are there any potential negatives in moving entirely to plant farming?
To avoid making your answer an opinion, let me suggest you to focus on existing surveys and modeling, or back-up your opinion with data.