The practice of farming livestock plays a significant role in New Zealand’s primary industry and food production systems. However, it also has a substantial impact on the environment.
In this article, we compare the farming impact on the environment of the two ruminants most commonly farmed in the country: cows and sheep.
By looking at aspects such as greenhouse gas (GHG) emissions, land use, water consumption, and more, we can better understand the unique challenges posed by each species and potential solutions for more sustainable farming practices.
“From an environmental perspective, a given number of cattle tends to have a greater impact on their environment than an equivalent number of sheep owing to their greater mass, higher feed requirements and increased output of waste in the form of faecal matter and methane emissions.” – EHINZ
Image Source: AgResearch.
Greenhouse Gas Emissions
Methane is widely considered the most significant GHG in ruminant farming and is released into the atmosphere when the animal burps or farts. Methane is a byproduct produced by the fermentation of food in the stomach and lasts in the atmosphere for around 12 years.
Another GHG is carbon dioxide. Cows and sheep, like all other livestock, contribute to carbon dioxide emissions primarily through indirect processes related to land use changes, energy consumption during the production, distribution, and processing of animal products and animal feed, and the decomposition of animal waste products (manure, carcasses etc.).
It’s important to note that methane is more potent as a greenhouse gas than carbon dioxide in the short term, but persists for a shorter time in the atmosphere. It breaks down over time, typically within a decade or so. On the other hand, carbon dioxide can persist in the atmosphere for centuries, and, as such, has a cumulative effect on the environment.
When it comes to comparing the GHG emissions of New Zealand ruminant farming to other countries, our farmers are doing a great job! The carbon footprint of New Zealand sheep meat is just under 15 kgs of CO2 equivalent emissions per kilo, with New Zealand beef meat’s carbon footprint just under 22 kgs. New Zealand’s on-farm carbon footprint is almost half the average of most other countries, and even when exported, our total carbon footprint is lower or very similar to domestically-produced red meat in those markets.
Regarding dairy farming, housed dairy sheep and dairy cow systems have higher GHG emissions than outdoor systems. Outdoor systems are typical in New Zealand with both cows and sheep. Hopefully, as sheep milk continues to grow in popularity worldwide and in New Zealand, we’ll see similar studies emerge to further compare ovine to bovine dairy operations.
Mitigating the Effects of GHGs
Efforts to reduce the carbon and methane emissions from livestock production systems include improving animal diets, genetic selection for lower methane-producing animals, better manure management practices, and sustainable land-use practices.
New Zealand farms have significant amounts of native bush plantings and plantation forests, both of which help ease the impacts of GHGs by drawing carbon from the atmosphere and storing it. When considering the effects of these plantings, some studies suggest that New Zealand farms are already operating close net zero carbon emissions.
The New Zealand Government’s Climate Change Response (Zero Carbon) Amendment Act 2019 provides guidelines that support the global effort to reduce emissions and lessen the effects of climate change.
New targets set for New Zealand include to:
- reduce net emissions of all greenhouse gases (except biogenic methane) to zero by 2050; and,
- reduce emissions of biogenic methane to 24–47 per cent below 2017 levels by 2050, including to 10 per cent below 2017 levels by 2030
Watch the video below from the CLEAR Center at UC Davis to learn how livestock farming can actually be considered as a solution to reducing GHGs in the atmosphere as part of the natural carbon cycle.
Water Consumption and Freshwater Contamination
Between 2002 and 2017, the total area of irrigated agricultural land in New Zealand nearly doubled from 384,152 to 746,739 hectares. Additionally, almost 84% of all irrigated land is found in the South Island, primarily in Canterbury and Otago.
Nationwide, water for agricultural use predominantly (73%) comes from our rivers and lakes. Drawing from them affects the speed and volume of water flow, in turn affecting overall water quality. A reduced water flow leads to the build-up of contaminants like toxic algae, bacteria, and chemicals from run-off.
Another source of freshwater contamination is nitrogen. Nitrogen leaching occurs when excess nitrogen moves through the soil and into groundwater or surface water reserves. This can cause contamination of drinking water sources. Livestock urine is the predominant source of nitrogen leached from the soil.
The extent of nitrogen leaching varies between cows and sheep due to differences in diet, physiology, waste management, and the farming practices used. AgResearch has been looking into the differences between dairy sheep and dairy cow farming in New Zealand and preliminary findings show that nitrogen leaching losses from the urine of sheep were approximately 50% lower than from cows.
Dairy sheep are proving to be a viable option for livestock farming in New Zealand, particularly in nitrogen-stressed catchments.
Land Use, Biodiversity, and Habitat Impact
The livestock industry has led to significant land use changes globally, including deforestation to convert forests and other areas into pasture for grazing or cropland for animal feed production.
When forests are cleared, the carbon stored in the trees and soil is released into the atmosphere as carbon dioxide. As mentioned, this contributes to GHG emissions by reducing those ecosystems’ carbon sequestration capacity (how much they remove from the atmosphere).
Comparing the impact between cows and sheep is complex and dependent on various factors.
Cows typically require more land per individual than sheep due to their larger size and higher energy requirements. The average stocking rate for sheep in New Zealand is 12 per hectare, compared to an average of 3.2 cows per hectare.
The habitat impact of livestock farming in New Zealand has been significant in terms of historic land clearance for pasture. Sheep farming can have a lower habitat impact compared to cows, primarily because it tends to be less intensive, and sheep can often graze on natural pastures. Areas of the country with intensive dairy farming led to a reduction in native vegetation and biodiversity. This is particularly evident in regions where land is converted from forests or wetlands to accommodate dairy operations.
While sheep farming also impacts biodiversity, it is generally considered to be less destructive to natural habitats compared to intensive dairy farming with cows.
When it comes to soil degradation, cows being heavier animals compared to sheep exert greater pressure on the soil, leading to more significant soil compaction. This can reduce water infiltration and root penetration, which may result in soil erosion and decreased soil quality.
Cows often graze grass more aggressively, potentially causing damage to the grass roots and soil structure. Sheep tend to graze more selectively and may leave a larger proportion of grass behind meaning their grazing behaviour can be less damaging to the soil.
On hilly or sloped terrain, sheep are sometimes preferred for their ability to graze in a way that can help reduce soil erosion.
In cases of overgrazing where pasture is consumed faster than it regrows, the soil may be left exposed to erosion. Both cows and sheep can be a problem without proper land management practices.
Conclusion
In comparing the farming impact on the environment of cows and sheep, sheep are, generally speaking, more environmentally friendly due to their lower greenhouse gas emissions, reduced land and water requirements, and more negligible impact on biodiversity and habitats. As such, dairy sheep may prove to be a more suitable option for agricultural land use in particular areas of the country.
However, it’s important to note that sustainability practices vary widely, and the impact of any farming largely depends on factors such as land management practices, feed sources, breeding/genetics, and regional factors including geography and climate, regardless of the type of animal.
Sustainable farming is a critical part of New Zealand’s red meat and dairy sectors. Moving forward, promoting sustainable practices such as rotational grazing, reduced use of feed crops, and responsible land management can further mitigate the environmental effects of both cattle and sheep farming.
Ultimately, a shift towards more sustainable livestock farming methods suited to the local environment is necessary to lessen the overall impact on our planet to ensure a healthier, more sustainable future, and firmly position our country as a global leader in this area.
If you’d like to take an aerial tour of Jones Family Farm, you can do so here!
References
AgResearch. (n.d.). Some Environmental Attributes of Dairy Sheep Farming. Retrieved October 4, 2023, from https://www.agresearch.co.nz/assets/Uploads/Dairy-sheep-New-Zealand-environmental-attributes-2021.pdf
Beef + Lamb New Zealand. (2022, November 8). New Zealand beef and lamb among the most carbon efficient in world | Beef + Lamb New Zealand. https://beeflambnz.com/news/new-zealand-beef-and-lamb-among-most-carbon-efficient-world
Case, B., & Ryan, C. (2020). An analysis of carbon stocks and net carbon position for New Zealand sheep and beef farmland. Department of Applied Ecology, School of Science, Auckland University of Technology. https://beeflambnz.com/sites/default/files/news-docs/BL_Carbon_report_for_review_final_submit.pdf
EHINZ. (n.d.). Environmental Health Indicators: Water – Agricultural Activity. Environmental Health Intelligence New Zealand; Massey University. Retrieved October 4, 2023, from https://www.ehinz.ac.nz/indicators/water/recreational-water/agriculture/
Lynch, J. (2020, May 15). Can we keep farming cows and sheep without dangerously warming the planet? LEAP; The University of Oxford. https://www.leap.ox.ac.uk/article/can-we-keep-farming-cows-and-sheep-without-dangerously-warming-the-planet
Ministry for the Environment. (2019, April 17). Nitrate leaching from livestock time series 1990–2017 – Environmental Reporting | | GIS Map Data | MfE Data Service. https://data.mfe.govt.nz/table/99876-nitrate-leaching-from-livestock-time-series-19902017/
Parliamentary Counsel Office. (2019, November 13). Climate Change Response (Zero Carbon) Amendment Act 2019 No 61, Public Act Contents. New Zealand Legislation. https://www.legislation.govt.nz/act/public/2019/0061/latest/LMS183736.html
Waikato Regional Council. (2015, May). Nitrogen leaching cow intensity and urine – a challenge to water quality. ICM Factsheet Series no. 4. (S3945). https://www.waikatoregion.govt.nz/assets/WRC/WRC-2019/CNM-factsheet-nitrogen-leaching_4-v2.pdf
