How will elephant grass affect biodiversity?

Another Life:I like "miscanthus". The word sits happily on the tongue, like "hyacinth" or "alfalfa". "Elephant grass", however, is what will catch on, even if Miscanthus sinensis x "gigantea", to give it its full appellation, hasn't been within an ass's roar of an elephant, so to speak.

You'd need to ride an elephant to see over it in August, so perhaps that's what is meant. Next week's big national bioenergy conference will help to decide how much of the Irish countryside will be screened out by thousands of hectares of its silver-green reeds (or, in mid-winter, its rustling, wispy-topped, brown bamboo canes).

In the context of staving-off-the-end-of-civilisation-as-we-know-it (we need some shorthand for this), there can be little possible objection to growing miscanthus or willow as carbon-neutral biomass fuels for power-stations and backyard boilers. But given the hectarage (not a nice word) necessary to make much difference to the national carbon footprint, the impact on landscape, not to mention biodiversity, might be worth considering.

Miscanthus, first. The "sinensis" bit gives the origin away, along with one of its common names - Japanese silver grass. It's what they thatched the old farmhouses with (think of the early samurai films). The peasants sometimes used it for chopsticks and children made owls of the feathery spikelets of flowers. A European breeding programme to improve the plant for biomass crossed M. sinensiswith M. sacchariflorusto create "the naturally-occurring, pollen-sterile triploid hybrid" called gigantea.

So miscanthus plantations won't scatter viable seeds. That's just as well, for, once established (with chunks of rhizome, the tough underground stems) the plant grows spring after spring for 15 years or more. It needs very little fertiliser, but reaches a height of 2.5-3.5m.This incredible stemmage, 1cm thick and solid pith, makes 20 tonnes of oven-dried miscanthus equal in energy to 12 tonnes of coal, and 30 tonnes equivalent to 12,000 litres of oil.

In UK experience, the average yield per hectare of miscanthus is 13 tonnes a year, far below its promised potential for northern Europe. As climate changes in Ireland, strong regional factors may take effect. The plant likes a moisture-retentive soil, but summer droughts are promised for the east. The reeds need harvesting when they are dead and dry - about February - but will the sodden, gale-swept winters of the west let them dry, stay upright or be harvested in mud?

Thousands of Reps farmers might want to grow miscanthus on their increasingly redundant marginal land. The EU, it is said, would deny them the chance of grant-aid for such a "monocultural" crop - but what else are the rye-grass meadows it could replace? The first 1,400 hectares of miscanthus and short-rotation willow will be planted in Ireland this year, with grants for half the cost of establishment. It will be a few years, probably, before we decide what we feel about this new alien, dwarfing even the reeds of the Shannon. At least, unlike Sitka, it does change colour through the year, and glows quite fetchingly in autumn - gardeners, indeed, have a choice of miscanthus hybrids for decorative clumps.

But will more hedgerows be bulldozed to suit miscanthus-harvesting machinery? Will planning permission be needed to block out a neighbour's view? Ecologically, on the other hand, the early research on miscanthus is quite favourable, in notable contrast to ryegrass mown for silage or winter-sown wheat. Miscanthus leaves the soil covered with a soft mulch of dead leaves - just the job for earthworms, beetles and other detritivores. Three times as many spiders, of several more species, thrive in its dense network, along with more shrews and mice. The tally of birds has yet to be properly field-tested, but corncrakes, perhaps, nesting at the margins and reed warblers in the middle.

"Miscanthus," says Britain's environment ministry, Defra, "might be a useful game cover crop and nursery for young pheasants and partridges." Willow plantations, predictably, have much the same high score on biodiversity. Willows actually rank higher than oaks in their communities of plant-eating insects and mites. Among them, unfortunately, are little leaf-eating beetles that turn the goat willows of Ireland's roadside ditches a withered brown in late summer.

But any fine day now, their catkins will be buzzing with queen bumble-bees in search of a first feed of nectar. Still good to watch, even in the light of things to come.

The National Bioenergy Conference will take place at Dunboyne Castle, Dunboyne, Co Meath on Tuesday, March 6th, and on Wednesday, March 7th at the Clonmel Park Hotel, Clonmel, Co Tipperary