Plant-based diets and the environment

The review by Kalmpourtzidou and colleagues found wide variation across diet categories and regions, but scenarios explicitly reducing meat tended to have smaller carbon footprints than current diets or scenarios centered only on conventional dietary guidance. It also cautioned that a label such as “plant-based” does not determine impact by itself.

Scarborough and colleagues found the same broad direction in a different design: estimated emissions increased as the amount of animal-based food in observed UK diets increased. That association remained despite substantial variation in food sourcing and production.

The two future-looking studies ask a narrower question. In Kozicka and colleagues’ 50% global substitution scenario, agriculture and land-use emissions in 2050 were 31% below 2020 levels. Humpenöder and colleagues modeled a largely plant-based flexitarian transition and found that it made 1.5°C pathways more feasible by reducing food-system emissions—particularly agricultural methane—and pressure for carbon-dioxide removal. Neither result predicts that adoption or supporting policy will occur.

Land is where dietary composition can create effects beyond the farm boundary. Scarborough and colleagues estimated much lower land use for lower-animal-food dietary groups in their UK sample. Kozicka and colleagues modeled the system-wide mechanism: replacing part of projected animal-product demand reduced feed demand and agricultural area, and nearly halted net forest and natural-land loss in the 50% scenario.

Spared land is not the same as restored habitat. Kozicka and colleagues modeled additional restoration separately; the extra carbon and biodiversity gains appeared only when restoration was actively implemented in former forest ecosystems. Economic responses, trade, local livelihoods, land tenure, and restoration policy therefore affect what a dietary shift produces on the ground.

Singh and Persson add historical context by attributing commodity-driven deforestation from 2001 through 2022. Their results identify cattle-related pasture expansion as a major driver, alongside oil palm, soy, rubber, cocoa, coffee, staple crops, and forestry commodities. The study strengthens the connection between food production and forest pressure, but it does not estimate how consumer dietary change would alter that pressure.

Biodiversity effects in this evidence set are largely tied to land occupation, habitat conversion, and restoration. Scarborough and colleagues estimated lower potential biodiversity loss as animal-food consumption declined. Kozicka and colleagues modeled smaller future declines in ecosystem integrity when reduced livestock demand was paired with restoration.

Water and nutrient outcomes require more caution. The systematic review found that water results varied by dietary composition and geography. In Kozicka and colleagues’ global 50% substitution scenario, water use in 2050 was 10% below 2020. Nitrogen inputs were 27.8 million tonnes lower than the 2050 reference pathway, but still 34 million tonnes above 2020. Both results depend on ingredient recipes, processing efficiency, regional production, and trade. A plant ingredient can still carry a high local water, fertilizer, or habitat burden.