Alpine ecologist creates pay dirt at old mining site in national park

''If you grabbed a handful, it ran through your fingers like sand. There was very little food for plants, invertebrates or soil microbes,'' she says.

Land repair is a patient and exacting science, because every damaged site is different. There's no generic set of rules to rely on, no quick fixes and the ecological solution is far more complex than ''just throwing a lot of plants around'', says Ms MacPhee, who describes her work as ''environmental engineering''.

It's taken roughly a decade to rebuild soil health at the heavily eroded Kiandra site, using slow- release organic fertiliser, biodegradable ''compost socks'', silicone-rich rice straw mulch from Murray-Darling Basin farms, dead wood to create habitat and microclimates for insects and, of course, a rabbit-proof fence. And all plants used for the project have been locally gown.

Ms MacPhee grows and harvests seed from a thriving plantation of thousands of native poa, an alpine tussock snow grass, established on land behind the Yarrangobilly caves guest lodge. The plantation, and nursery where other native plants are ''hardened-off'' to adjust to the alpine climate, use greywater and treated effluent from the guesthouse.

Volunteers (''there's a retired doctor and a couple of red-wine drinking intellectuals from Albury'') harvest the poa seed heads with sickles, laying the cut grass in rows to dry. Once the seed is picked and bagged, the dried poa heads are recycled as mulch. Last year, the plantation produced 300kg of seeds, with each seed head producing about one million seeds.

Ms MacPhee estimates one-third of the park's annual budget is spent on collecting and trucking sewage out from toilets at tourist venues, so the success of the Yarrangobilly poa plantation could point to future savings.

''What we've created can be used as a model for other parks,'' she says.

''It ticks all the sustainability boxes. By using the Yarrangobilly grey water on the plantation, we stop it entering the karst system of the caves. Poa love nitrogen, so they absolutely thrive on the waste water from the sewage treatment plant.''

Another ticked box is the use of rice straw mulch, sourced from Riverina rice farms using irrigation water provided by the Snowy Hydro scheme. Ms MacPhee uses about 50,000 bales a year in revegetation projects, mainly from farms at Coleambally and Yanco.

''There's no [such] thing as a weed-free bale of straw, but we've found weeds in rice straw won't persist because of the cold temperatures. The straw mats well, doesn't blow away and has a high silicone content. And it means the farms are giving back something of value in exchange for the water they've used.''

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