Sir, – It is now well known that Irish aquatic ecosystems are badly damaged by nitrogen and phosphorus pollution. Lough Neagh and Lady’s Island Lake are the best known but by no means the only examples of the problem.
It is also well established that a large contribution to the problem is the excessive use of nitrogen and phosphorus in intensive farming.
The inefficient use of fertiliser makes this problem inevitable. Less than one-third of nitrogen imported into the country, either as fertiliser or animal rations, is re-exported as foodstuffs. The figures for phosphorus are somewhat better, with 60-70 per cent efficiency. The remainder is added to our terrestrial and aquatic ecosystems.
Consequently, for every tonne of nitrogen exported as protein in milk or meat, two additional tonnes are added to our already overburdened ecosystems. Such a policy must eventually lead to ecological ruin.
RM Block
The core problem here is a failure to recycle nutrients and greatly reduce the need for yearly imports. Stuart Mathieson’s excellent article in today’s Irish Times (“New alchemy can make value out of problematic phosphate”, Science & Climate, Page 8, July 9) highlights one essential area for research and development: the reuse of available phosphorus by treating agricultural waste as a raw material rather than an output, which society and nature must endure so that part of the agricultural industry may be profitable.
Any industrial process that has an efficiency of less than 30 per cent must be a target for ambitious engineers. Why it has taken over 30 years for research to understand this point suggests a deep unawareness of basic ecological science by the agricultural industry in Ireland?
I do not imply that nutrient recycling alone is the answer to nitrogen and phosphorus pollution. Far more difficult changes may be necessary to return our once wonderful lakes and rivers to their former role as sources of clean water and abundant fish.
To conclude however, as my colleagues and I did in the case of Lady’s Island Lake, that not only was the lake ruined by excess nitrogen inputs but that it cost several million euros in wasted nitrogen fertiliser to achieve this end, is also to conclude that some radical rethinking about agricultural practice might not be out of place.
Mathieson’s article is a good place to start. His ideas are even more relevant as phosphorus, unlike nitrogen, is a resource mined in a small number of countries. Exhaustion of these reserves is not inconceivable. – Yours, etc,
Dr CILLIAN RODEN,
North Kinvara,
Co Galway.
