The crusade against climate change has now transcended its original scope of energy usage and its affiliated practices. Though a major contributor, owing to the billions of tons of carbon dioxide released into the atmosphere as the byproduct of burning fossil fuels, the energy sector, comprising energy use in buildings, industry and transportation, only accounts for around 73% of total global greenhouse gas emissions.

Chapter 5 of the IPCC's SRCCL (Special Report on Climate Change and Land) expounds upon food security in the context of climate change, shining a spotlight on the oft-overlooked correlation between the food system and global greenhouse gas emissions. It discloses that roughly 21-37% of the world's greenhouse emissions are ascribed to the food system, including but not limited to agriculture and land use, storage, transportation, packaging, processing, retail, and consumption. Moreover, the chapter sheds light on the impacts of food systems on climate change, a critical yet frequently disregarded factor in mainstream climate dialogues.

The report further categorizes food emissions into three distinct categories: agriculture, land use, and beyond farm gate. Agriculture, which includes emissions by crop and livestock activities within the farm gate, contributes 10-14% of total greenhouse gas emissions. Land use emissions, which account for land use and land use dynamics associated with agriculture, contribute 5-14% of total greenhouse gas emissions. Emissions beyond the farm gate, including food processing, retail, and consumption patterns, contribute 5-10% of total greenhouse gas emissions.

The report goes on to outline two key adaptation measures for achieving sustainable food systems: supply-side adaptation and demand-side adaptation. Supply-side adaptation measures focus on improving crop and livestock production, as well as transportation, storage, and processing. Meanwhile, demand-side adaptation measures involve changes in dietary patterns and reducing food waste.

It is worth noting that supply-side adaptations alone are insufficient to achieve sustainable food systems. Instead, demand-side adaptations are also necessary. One study found that if the entire world were to follow the average 2011 UK diet and meat consumption, 95% of global habitable land area would be needed for agriculture – up from 50% of land currently used. If one were to follow the average USA diet, this number would be 178%! Solutions to this may involve changes to one's diet, such as reducing the consumption of animal-based food products and increasing the proportion of plant-based foods, particularly pulses and nuts. Additionally, replacing red meat with more efficient protein sources is an effective demand-side adaptation measure.  By reducing pressure on land and water, such measures help to mitigate our vulnerability to climate change and input limitations.

Poore and Nemecek (2018) published a study in the journal Science that analyzed the environmental impacts of various food production systems. The study found that the production of animal-based foods, such as meat and dairy, had a much higher environmental impact compared to plant-based foods. The authors concluded that reducing the consumption of animal-based foods and increasing the consumption of plant-based foods could have a significant positive impact on the environment.

Specifically, the study found that the production of beef had the highest environmental impact, followed by lamb and cheese. On the other hand, the production of legumes and nuts had the lowest environmental impact. The study also found that the production of animal-based foods accounted for a disproportionate amount of greenhouse gas emissions, land use, and water use compared to plant-based foods.

The results of this study have been ingeniously visualized in the "Environmental Impacts of Food Production" topic of ourworldindata.org, where a comprehensive range of data pertaining to food supply can be readily accessed. This includes key indicators such as GHG emissions per kilogram of food product, GHG emissions per 100 grams of protein, land use, eutrophication, fresh water use, among others. Some major findings from this study are as follows:

1. Despite occupying a staggering 77% of all agricultural land, livestock and meat only account for a mere 18% of global calorie supply and 37% of global protein supply.
2. Emissions from livestock and fish farms, crops for animal feed and land use for livestock are responsible for a staggering 53% of global food systems emissions.
3. Eliminating beef and lamb alone can save 7.1 GtCO2e, eliminating them along with dairy can save 12.3 GtCO2e, eliminating all meat and dairy except for meat and fish can save 13.6 GtCO2e, while going fully vegan can save a whopping 14.7 GtCO2e.

However, most of the meat consumed is in developed countries, and changing diets there can have the most impact. Does changing diets have an effect here in Nepal? Although limited data exists for Nepal's national agricultural emissions, the Third National Communication (TNC) report provides some insights. In 2011, Nepal's agriculture, forestry, and other land use sector emitted a total of 37,984 Gg CO2-eq, with livestock contributing 46.5% or 17,664.07 Gg CO2-eq of these emissions. The United States Agency for International Development (USAID) report on "Greenhouse Gas Emissions in Nepal" attributes 50.1% of Nepal's emissions to the agriculture sector, with 54% of these emissions arising from enteric fermentation from livestock. These findings highlight the need to prioritize food systems when discussing climate change. As individuals concerned about climate change, we can adopt a "Think Global, Act Local" approach by reducing our carbon footprint through the consumption of fewer animal-based foods.