Single biggest way to reduce your impact on the Earth? Stop eating meat and dairy.
This report makes for interesting reading: https://science.sciencemag.org/content/360/6392/987/tab-pdf
Also summarised here by The Guardian: https://www.theguardian.com/environment/2018/may/31/avoiding-meat-and-dairy-is-single-biggest-way-to-reduce-your-impact-on-earth
Key quotes from the report:
'...the impacts of animal products can markedly exceed those of vegetable substitutes. To such a degree that meat, aquaculture, eggs, and dairy use 83% of the world’s farmland and contribute 56-58% of food’s different emissions, despite providing only 37% of our protein and 18% of our calories.'
'Today, and probably into the future, dietary change can deliver environmental benefits on a scale not achievable by producers. Moving from current diets to a diet that excludes animal products has transformative potential, reducing food’s land use by 3.1 billion hectares (a 76% reduction)'