Agriculture can generate positive or negative environmental impacts depending on the specific activities undertaken on the farm. Agriculture is the principal land use in Ireland; hence environmental sustainability in agriculture is key to achieving national level objectives.
In the Teagasc National Farm Survey 2017 Sustainability Report, released today, the current set of NFS figures based environmental indicators focus on greenhouse gas (GHG) emissions, ammonia emissions, nitrogen and phosphorus use efficiency.
1. Greenhouse gas emissions
To minimise the extent and impacts of climate change, action is required to reduce global greenhouse gas emissions. Agriculture is the largest contributor to Irish greenhouse gas emissions by sector, with 33.3% of the national emissions total in 2017 (EPA, 2018). The agricultural sector is under pressure to reduce its emissions in the context of Ireland’s commitment to reduce national GHG emissions by 20% by 2020, under the current EU Effort Sharing Decision (ESD), while a more stringent target of a 30% reduction has been agreed
for 2030. Maintaining or even increasing food production will be very difficult while reducing aggregate emissions (Breen et al., 2010; Lynch et al., 2016b). Relevant indicators are required to track the progress being made in emissions reductions in agriculture and how this relates to the level of food production. The IPCC (Intergovernmental Panel on Climate Change) methodology is the principal method of estimating GHG emission indicators across different farm systems in this report, and are calculated as follows:
Total agricultural emissions are measured per farm, with emissions also disaggregated to show the emissions originating from different farm enterprises (dairy, cattle, sheep and crops).
b. Agricultural greenhouse gas emissions per unit of output/hectare are derived so that the total emissions of the farm can be decomposed into components relating to each of the farm’s main outputs (milk, cattle or sheep live-weight and crop outputs). In addition, GHG emissions per € of output and per hectare are used to illustrate greenhouse gas emissions per € of output that are generated on farms with dissimilar
levels of agricultural output.
c. Emissions from on-farm energy use per unit of relevant output measures emissions from electricity and fuel use associated with agricultural production activities on the farm. As per the IPCC methodology, these greenhouse gas emissions are considered separately from agricultural greenhouse gas emissions.
2. Nitrogen use
Nitrogen (N) is an important element in agricultural production, but the loss of excess N poses a significant risk to the aquatic environment. The nitrogen use indicators follow an input-output accounting methodology as described below.
a. Nitrogen balance (per hectare farmed), is used as an indicator of the potential magnitude of nitrogen surplus which reflects the risk of nutrient losses to water bodies, all other things being equal. It is calculated on the basis of N inputs less N outputs on a per hectare basis at the farm gate level.
b. Nitrogen use efficiency (NUE) is used to highlight the proportion of N retained in the farm system (N outputs / N inputs). This is a generic measure allowing comparison across disparate farm types at the farm gate level.
c. Nitrogen surplus per unit of output produced is a measure derived so that the total N surplus of the farm can be decomposed into components relating to each of the farm’s main outputs (milk, cattle or sheep live-weight and crop outputs). For dairy systems, it is also expressed in kg of milk produced per kg of N surplus.
3. Phosphorus use
Similar to nitrogen, phosphorus (P) is an important element in agricultural production and its loss poses a significant risk to the aquatic environment. Phosphorus use indicators, like N use indicators, also follow an input-output accounting methodology described previously.
However, it should be noted that unlike N, phosphorus can remain in the soils for significant periods of time and is available to be stored and mined, hence P balance and efficiency should be interpreted with caution without reference to the soil P status of the farm.
a. Phosphorus balance (per hectare farmed), is used as an indicator of the potential magnitude of phosphorus surplus which may result in nutrient losses to water bodies all other things being equal. It is calculated on the basis of P inputs less P outputs on a per hectare basis at the farm level.
b. Phosphorus use efficiency is used to highlight the proportion of P retained in the farm system (P outputs / P inputs). This is a generic measure allowing comparison across different farm types.
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