John Lynch is a Postdoctoral Research Assistant at Oxford Martin School. John's research focuses on the climate effects of meat and dairy production. He is interested in the greenhouse gas emissions associated with different livestock systems, and how these may develop based on demand for animal products, different agricultural practices, and emerging technologies.
John Lynch is a Postdoctoral Research Assistant at Oxford Martin School. John's research focuses on the climate effects of meat and dairy production. He is interested in the greenhouse gas emissions associated with different livestock systems, and how these may develop based on demand for animal products, different agricultural practices, and emerging technologies.
John Lynch, Postdoctoral Research Assistant at Oxford Martin School
The 26th United Nations Climate Change Conference (or ‘COP26’) [is] taking place in Glasgow. For the event to be a success, and keep our climate goals of limiting global warming to 1.5-2°C above pre-industrial temperatures in sight, countries will need to declare ambitious new climate pledges. Agriculture and land-use will likely be key to many mitigation plans. But how does agriculture contribute to global warming, and why is there now such a focus on land-use and the climate?
Although most people associate burning fossil fuels with climate change – and this is indeed the largest contributor to global warming – it is increasingly also recognised there are significant greenhouse gas emissions from agriculture.
For a start, we should remember that food production also uses energy, and currently much of this comes from fossil fuels, resulting in carbon dioxide (CO2) emissions. Replacing on-farm energy use with renewables should help us eliminate these emissions, and emerging technologies like electric tractors may help us achieve this transition. Farms also have the potential to generate renewable energy, through, for example, solar panels on barns or small-scale wind turbines. Agriculture itself may also play an important role in future energy systems, with anaerobic digestion of crop residues and food waste or energy crops helping power the grid.
Land-use represents another key source of CO2 emissions. In much of the World native habitats are being destroyed to make space for agricultural expansion. This leads to carbon previously locked up in vegetation being lost to the atmosphere. In the UK we are currently restoring forest rather than cutting down more woodland, but this is from a position of having already deforested most of our landscapes in the past. To meet our climate targets, and be able to meaningfully argue for habitat protection globally, we must increase land-based carbon sequestration and storage. In some places this will mean reducing the amount of land used for agriculture, but can also coexist with food production. For example, there is growing interest in silvopasture – integrating trees in grazing areas – and where soils have been degraded by intensive field operations we can change management to help restore and maintain soil carbon.
Another key source of agricultural greenhouse gas emissions come from our application of nitrogen – in both synthetic fertilisers and natural manures. Some of the nitrogen is lost to the atmosphere as nitrous oxide, a highly potent greenhouse gas. Reducing fertiliser usage and more efficient, targeted application methods could limit nitrous oxide emissions and also reduce the risk of runoff and associated water quality impacts.
Methane is another powerful greenhouse gas associated directly with agriculture, with livestock the largest source. Ruminant livestock (cows and sheep) belch out methane as part of their digestive process, while methane (as well as nitrous oxide) is also generated by livestock manures. Improved animal health and productivity, and better manure management, can help reduce livestock methane emissions.
Through more environmentally aware farming methods and ecologically sensitive land-use we therefore have the means to limit the climate impacts of agriculture, but the scale of the problem means we must also look to the bigger picture and the overall demand for different types of food.
The global population is growing and becoming wealthier, able to buy more resource-intensive foods: typically animal products. We don’t all need to turn vegan to limit global warming in line with the Paris Agreement goals, but we do have a responsibility to think about our consumption. In places like the UK, where on average we eat more than we need, waste a significant amount of our food, and consume a much larger proportion of animal-source foods than most other countries, it is right for us to consider what our fair share would be in a globally sustainable food system. If the whole World ate like the UK, it would almost certainly put our environmental targets out of reach.
Mitigating climate change presents a significant challenge to agriculture, and there will be difficult conversations ahead about how much we can or want to change our diets and landscapes. However, there is also cause to be optimistic, as we already have a number of plausible ways to reduce the environmental impacts of the food system. We need to start implementing these immediately, but if we do, and can rapidly scale them up, we can still meet our climate targets.
