Farms that have taken part in GLAS over the last five years have seen a reduction in nutrient and sediment losses of between 3% and 10%.

Losses of nitrogen, phosphorus, sediment, nitrous oxide, and methane were all reduced on GLAS farms, according to an in-depth modelling exercise, conducted as part of a wider GLAS evaluation by the UK consultancy ADAS.

In total, 32% of agricultural land in Ireland is managed by farmers in GLAS.

However, the percentage of the national pollutant load accounted for by these farms is lower, ranging between 25% and 28%.

The report said the percentage of losses is lower than the portion of land because dairy farms, “which typically have the highest pollutant load intensity”, are less likely to be in GLAS.

Nationally, the estimated reduction in pollutant loss was highest for phosphorus at 10%.

GLAS farmers were also estimated to have reduced nitrate loss by 6%, nitrous oxide loss by 5%, and methane by 3%. Sediment loss reduction was estimated at 4%.

There were significant differences in the benefit of the scheme across farm types.

Reductions on dairy farms in the scheme were between 3% (sediment) and 15% (phosphorous) compared to less than 1% for all five on sheep farms.

This is mainly due to the fertiliser use and stocking rates on these farms before joining GLAS.

When considered with all farms, including the two-thirds not in GLAS, the effects of the scheme are lessened, with the national impact estimated at 3% or less for all pollutants. There were bigger drops for dairy as only 13% of the pollutant load comes from GLAS farms.

The report outlined that the more farms in the scheme, the greater the reduction.

The reduction across all of the metrics, bar sediment, were mainly due to the Low Input Permanent Pasture action, which limits fertiliser use in fields and therefore the number of livestock.