Discipline: environment; Keywords: Greenhouse gas emissions, carbon sinc, pasture-based dairy farms, soil carbon levels, soil health, biodiversity.
Dairy has been targeted as a source of greenhouse gas emissions (GHG). However, research has shown that grazing livestock on pasture-based dairy farms restore carbon to the soil, enhancing its biodiversity and countering climate change. This poses the question: If farms can have a positive impact, but are also a source of negative impact, what is the net effect? This is an important consideration when assessing the negative contribution that dairy farming makes to climate change. The company Trace & Save determines both soil carbon and GHG emissions yearly on pasture-based dairy farms in the South-eastern Cape which enables assessment of the net carbon emissions on these farms. It is important to understand the potential positive impact that dairy farming can have. The aim of the study by the author cited below was to assess the relative impact of dairy farms on climate change by adding GHG emissions to soil carbon change. An increase in soil carbon is recorded as a negative emission, and therefore mitigates the impact of GHG emissions, whereas the net emissions give a true indication of the impact of pasture-based dairy farms.
Soil carbon levels are assessed annually, across the entire farm, by taking composite soil samples and analysing them for total carbon %, using LECO. Also, a carbon footprint assessment is carried out each year, which calculates the total GHG emissions resulting from the respective farming practices. These emissions are from practices both on-farm and emissions caused by products bought by the farm. The measurement of both factors allows assessment of net carbon emissions. The assessment has been conducted on 45 farms, 44 across the Eastern Cape and one in the Southern Cape. In addition to these measurements, but which are not reported here, Trace & Save also assesses soil health, water use efficiency, nutrient-use efficiency, biodiversity conservation, people wellbeing and animal welfare each year on the participating farms. These assessments assist farmers to identify the impact of changes in management practices to the sustainability of their farms, and to identify opportunities for further improvement.
The combined average trend of all 45 farms demonstrates an increase in soil carbon of 8.9 tons CO2e per ha per year and GHG emissions of 27.5 tons CO2e per ha per year. This implies a net carbon emission of 18.6 tons CO2e per ha per year. In real terms, these 45 dairy farms have a net negative effect which is 68% of what is generally understood and discussed. However, there are seven farms which had negative net carbon emissions for the duration of the study. This should not detract from the emission impact of the other 38 farms, which remain a challenge. It should be noted that of these farms, only 15 of them are not making the positive contribution of increasing soil carbon.
These results are exciting for farmers, the dairy industry and for consumers. For farmers, it shows their commitment to become more sustainable. Increased soil carbon is also indicative of improved soil health, which is beneficial to farmers. It allows the dairy industry to redress the misrepresentation of dairy farmers only having negative environmental impacts. For consumers, it provides evidence of positive actions taken by farmers to safeguard the environment.
C. Galloway, 2020. South Africa: A journey towards negative net carbon emissions on dairy farms by building carbon sinks. In: 2020 IDF Dairy Sustainability Outlook • Issue N° 3, p 26