Anja Murray: Losing our lakes is a poor exchange for short-term economic gain

Watching the reflection of green hills and blue skies on a calm lake often brings a quietness of mind, surrounded by rippled reproductions of surrounding patchwork fields. 

But this reflection is more than just metaphorical, as lakes reflect the state of the land in the surrounding catchment area too.

As rainwater falls on fields and woods, it filters down through tree canopy or grassy sward and into the soil. Where there are trees and woodlands, water will filter through to lakes and other waterways very slowly — much of it evaporates before it even reaches the ground.

On grassy fields, water tends to run over the surface more readily, especially on ‘heavy’ or clayey soils. On deep and very free-draining soils, water can penetrate quite quickly, rapidly reaching streams, rivers, and lakes through subsurface flow. Land management makes a big difference too. Where fields have been ploughed and reseeded with just one or two types of grass, vegetation cover is not so dense, roots that help water infiltrate are meagre, and there is less life on the surface to cycle and slow the surface flow of water. Where tractors and other heavy machinery pass over often, soil can become compacted and less able to allow water to sink in. Fewer hedges and more field drains also facilitate water running from the land more quickly, so rainwater travels more rapidly into streams, rivers, and lakes.

When slurry or other nitrogen- and phosphate-rich fertilisers are applied to fields to boost grass growth, and the surface and sub-surface flows carry rainwater more rapidly into waterways, nutrient pollution becomes problematic. Unseasonal weather due to climate change exacerbates the problems. This is what we have been seeing since the summer months, as lakes across the country become swathed in unnaturally bright green algae. The horror of the nutrient overload in Lough Neagh has been widely reported, as one of the largest and most bountiful lakes in these islands is being reduced to an ecological dead zone.

This is an area on the Blessington lakes today, it supplies 50% of the water for the Greater Dublin Area.

We may not have an equivalent to Lough Neagh in the republic yet, but we will if we keep going on our current trajectory. pic.twitter.com/Ni0uZM3RLh

— Elaine McGoff (@ElaineMcgoff) October 3, 2023

Since July, there have been health warnings against lake swimming in dozens of locations across Ireland because of contamination with harmful algal blooms and the presence of toxic blue-green algae in the water — all boosted by artificially elevated levels of nitrogen and phosphorous in the water. Lakes that have been affected in recent months include Lough MacNean in Cavan, Blessington Lake in Wicklow (which also supplies drinking water to Dublin); Lough Derg between counties Galway, Clare and Tipperary; and Lough Leane in Killarney.

Drinking water for two million people in Ireland comes from lakes and reservoirs, and since contamination levels are through the roof in recent months, water treatment plants that process drinking water are having to apply extra treatment and chemical decontaminators to drinking water to make it safe.

For all the multitudes of mayflies, damselflies, freshwater fish, and water birds depending on lakes, the ramifications of ongoing excess nutrient contamination are severe. Whole layers of these ecosystems are obliterated by oxygen depletion, as the nutrient fuelled algal blooms suck up most of the oxygen in the water and only the most robust species are able to survive. Recovery can take decades.

There's a bus leaving from Liberty Hall in Dublin to Belfast at 9.30am for this crucial demo to help save Lough Neagh.

Return departure from Belfast to Dublin will be at 17.30.

Cost is €10 unwaged; €15 waged. pic.twitter.com/09f72GvdcA

— Ecojustice Ireland (@Ecojustice_Ire) October 13, 2023

These problems are not new. Harmful algal blooms have plagued many Irish lakes since the 1980s, though subsequent improvements in wastewater management, along with better regulation for pig and poultry farming, gave some relief.

However, since the lifting of the milk quotas in 2015, the rapid growth and expansion of the Irish dairy sector has had significant environmental impacts, among them the declining health of rivers, lakes and estuarine waters. While agriculture is definitely not the only source of water pollution (other major contributors include wastewater treatment, ‘point source’ effluent, domestic septic tanks, and plantation forestry) agriculture is recognised as the chief contributor.

The Irish dairy herd now consists of just over 1.5 million dairy cows, an increase of 40% since the ending of milk quotas. Land management has intensified during this time to facilitate increased productivity, and between 2014 and 2018 there was a 50% increase in milk production (from 5.5 billion litres in 2014 to 8.3 billion litres in 2020), 85% of it for export. Resultant economic gains have been significant: last year dairy farm incomes in Ireland jumped to record levels, and major dairy processors' profits continue to soar.

We could say that these profits are reflected in the health of Irish waterways. Not only in lakes, but also in the declining water quality in estuaries and coastal waters, especially in the south and southeast where nitrate levels from agricultural intensification have been most marked.

In 2023, we should know better than to trade away our lakes like this. Their value is far greater than the short-term economic profits that some are receiving in return. The general public is getting a very bad deal from the trade-off.