Green argument used against replanting trees

Another Life: When millions of Sitka spruce and lodgepole pine were planted on western bogs and hills in Ireland's "social forestry" of the mid-20th century, who could have guessed what a headache so many plantations would turn out to be?

Given the mature silvicultural knowledge existing by the 1950s, it seems incredible that conifers could have been planted on so many shallow peatland soils where winter storms would stunt them, tear them from the rock and topple them into each other like skittles.

Thinning the trees for better growth became pointless on such infertile ground. Two-thirds of Co Mayo and Connemara forests, for example, will never be thinned, but clearfelled. Even that disfiguring option is now in limbo as clearfell pollution of waterways is blamed for extinctions of Margaritifera, the freshwater mussel that acts as a "miner's canary" for Ireland's last pure rivers.

It was obvious from the beginning that conifer plantations on peat in areas of high rainfall would need fertiliser - notably, heavy dressings of slowly dissolving rock phosphate. Unlike mineral soils, peat does not retain the fertiliser, but nobody worried about the ecological implications. This kind of planting continued into the 1980s.

As plantations were clearfelled and the soil exposed to rain, unused phosphate has flowed downhill. In 2003 Dr Ted Cummins of UCD's Forest Ecosystem Research Group told of forestry ditches and streams running with phosphate at concentrations up to 806,000 micrograms per litre. In rivers with pearl mussels capable of reproduction, the phosphate level is about five micrograms per litre. In such pristine rivers it is phosphate - not nitrogen - that causes algal blooms, smothering the river bed and suffocating young mussels living in the gravel.

This is what seems to have happened in 2004 in the Owenriff River, which flows through Oughterard, Go Galway, and into Lough Corrib. A result has been a ministerial moratorium on clearfelling along Margaritifera rivers and even a temporary ban on new planting in such locations, whether by Coillte or private landowners.

Photographs published on the web by Friends of the Irish Environment show the big block of clearfell at Lettercrafoe Lake, Co Galway, that links to the Owenriff (see: http:// friendsoftheirish environment.net/pdf/clrfell.pdf). Bare ground, with its drainage channels, continues right to the water's edge. Once, it was peat silt from forestry operations that overwhelmed freshwater mussels and trout spawning beds, and silt traps are now a standard mitigating measure. But straw bales are no match for dissolved phosphate in the rainfall that is becoming typical of climate change.

Coillte resists any guilt in the matter, pointing to the decline of Margaritifera in unforested (but still polluted) rivers. The public tone of its spokesman, insisting on "science-based" proof of involvement, has been curiously at odds with the special concern for the welfare of the species expressed in Coillte's published plans for "sustainable" forestry.

Last spring, for example, the Co Mayo and Connemara District of Coillte circulated for public consultation a five-year strategic management plan giving detailed consideration to issues of landscape and nature conservation (see www.coillte.ie/managing_our_ forests/plans/w3.htm). It lists Margaritifera as "one of the most valuable" wildlife species of the region, notes "important populations" of the mussel downstream of one particular forest (Derrada in Co Mayo) and pledges steps to prevent enrichment of the river in agreement with the National Parks and Wildlife Service and the local fisheries board. Such proactive concern extends also to a vulnerable bat, to salmon rivers and to rare plants.

An ecological awareness runs, indeed, through much of the plan, even as it raises the probable need for further boosts of phosphate to trees with lagging growth. As late as the 1980s, apparently, thousands of hectares of Sitka were planted on peatland "in anticipation that site nutrition would be supplemented with fertiliser applied from a helicopter". This has been reviewed for "environmental sensitivities", actual cost-benefit, and the need to safeguard streams and rivers . As with the current rethink on clearfelling, substantial buffer zones would seem imperative.

A major key to all the future treatment of forestry on peatland is the 60-year-old Forestry Act that has compelled the replanting of every felled tree. "Environmental and economic priorities have shifted," says the Mayo-Connemara plan, "and the greater good is now served by releasing low production sites from forestry." Environmental arguments, it seems, can now be used to waive replanting, and many of the region's clearfelled, low-production forests may be left to regenerate largely from self-sown pine seedlings, without new drainage or fertiliser. Why not broadleaves? Because, say the western foresters, that would need much more of both.

Friends of the Irish Environment will, no doubt, continue to match Coillte's ecological promises against what happens on the ground. The NGO's Forest Network Newsletter, generally hostile and unforgiving, but often revelatory, is archived at the FIE website.