THE most brightly lit parts of the country expose people to 166 times more artificial light than the darkest corners.
atellite recordings show a wide range of light intensity across the country, but overall Ireland is more dimly lit than other European neighbours included in the study.
The study, covering 2015 and 2019, also shows that average artificial light intensity fell during that time but the Central Statistics Office (CSO), which compiled the data, cautions that could be down to greater use of LED bulbs which glow more softly.
Artificial light at night is of growing interest to researchers because of concerns over the disturbance excessive light levels can cause to human sleep patterns and health, and to animal behaviour.
Excessive lighting also wastes electricity, a growing concern as cities try to boost energy efficiency and cut carbon emissions.
In Ireland, as in most countries, the ‘bright lights, big city’ rule applies, with urbanisation and light intensity closely linked. But the variations can be startling even within urban areas.
Artificial light intensity in Dublin in January 2019 was on average 11.53 units compared to just 0.52 units on average in the least lit county, Leitrim.
But within Dublin the local electoral area of Pembroke South Dock had an intensity of 69.94 units and the North Inner City measured 59.15 units.
During the same observation period, south and west Kerry measured just 0.42 units and west Mayo, 0.45 units.
These areas include Ballinskelligs and Ballycrory National Park which are part of the ‘Deep Sky Reserves’ initiative where, as far as practical, artificial light is kept to a minimum to allow for enjoyment and study of the natural night skies so low readings were expected there.
Other areas with very low light emissions include Connemara in Co Galway; Ballinamore and Manorhamilton in Co Leitrim; west Co Cork; west Clare; and Glenties in Co Donegal.
The top ten brightest areas were all in Dublin while the top five brightest counties were Dublin, Louth, Kildare, Meath and Limerick and the lowest lit were Leitrim, Mayo, Kerry, Roscommon and Sligo.
Of the three other countries in the study, the UK and Portugal had average levels twice as high as Ireland while the Netherlands was on average seven times brighter.
The CSO frontier series publication analysed satellite data to estimate artificial light emissions in Ireland between 2015 and 2019.
Source: Irish News