Vegetarianism may the best option for feeding the growing global population without resorting to widespread deforestation, scientists in Austria have shown.
With the global population rising steadily, more and more land is required to grow crops for food, energy and materials.
A sizeable area of the world’s forests has already been cleared to provide the necessary land for grazing animals and growing crops.
But these forest ecosystems are also home to a big chunk of the planet's biodiversity. They also take in carbon dioxide (CO2) from the atmosphere.
Conversion of forest to agricultural land also alters how water drains off the land, leading to leaching of nutrients and soil erosion, which can leave land barren, impoverished and unproductive.
Now, using estimates for food and population demands compiled by the United Nations' Food and Agricultural Organisation, Austrian Institute of Social Ecology scientists Karlheinz Erb and his colleagues have modelled different scenarios for feeding the world in 2050 without resorting to further deforestation.
Writing in Nature Communications, the team found that the human diet had the biggest impact on how many of the options were viable.
Meat-free menus, such as veganism and vegetarianism, gave the highest number of feasible scenarios.
The team varied a range of factors including crop yield, diet, and land use. By looking at the interplay of these different parameters, 500 future scenarios were produced and the feasibility of each one was assessed.
When modelling the human diet, Erb and his colleagues set out five typical diets. The meat, vegetarian and vegan diets were based on nutritional recommendations from the United States Departments of Agriculture (USDA) and Health and Human Services (HHS), in combination with a UN population report from 2012.
A "business as usual" (BAU) diet was also considered, where the average global consumption remains roughly the same in each region, alongside a "rich" diet in which global diets converged to match average North American consumption.
Around two thirds of the 500 options were declared feasible or "probably feasible" for a world with zero-deforestation.
For the scenarios where the human diet was vegan, 100% of the options were feasible, whilst with the vegetarian diet, the figure was 94%.
However, if the rich western-style diet were to become the global average, only 15% of the scenarios were possible without deforestation.
Despite meat-free diets providing the widest range of feasible options, it could still be possible to have a diet including meat, but factors such as the crop yield and crop land expansion into other non-forested areas became more important.
A combination of the rich diet and low-yielding, organic farming techniques resulted in no feasible scenarios.
Although the model doesn’t consider political and economic factors, the team are positive about the results.
"The general finding here I think is that it’s actually good news," says Erb. "The belief that deforestation is a necessity is not true but we see that there are many options that we can feed people without encroaching on the forests."