Mine reclamation in Western Australia
By Laurie Scott
In 1997 I won a travel scholarship from the Royal Botanic Gardens, Kew, for a project I submitted as part of my Kew Diploma course work. My project, `Mine Reclamation and the Reintroduction of Native Plants in Western Australia‘, looked at how land becomes degraded through mining and how the native vegetation can be restored and the ecosystem functioning reinstated.
I arrived in Perth on 1st September and began work at King’s Park and Botanic Gardens. King’s Park, which covers 400 ha, was established late in the last century, but it was not until 1901 that it took its present name. Seventeen ha is devoted to the Botanic Garden and the remainder is made up of bushland, dominated by Jarrah and Banksia forests. Such a large tract of bushland is quite unique for an urban situation and King’s Park is very proud of this area of native flora.
My first assignment was the Escarpment Project. The escarpment is a long, narrow and very steep piece of land originally mined for limestone; Perth Town Hall was built from limestone quarried here. After extraction, the area was devoid of vegetation, leaving it susceptible to erosion. To alleviate the erosion exotic plants, such as Agaves, were introduced to stabilise the soil. These have taken over and now present a problem in themselves. The Escarpment Project aims to determine what exactly constitutes land disturbance and how this can be rectified causing the least amount of damage to the native vegetation. Few studies exist on urban bushland (which is different from normal bushland), so this was groundbreaking research. The Project is being sponsored by W.M.C., one of the very large mining concerns based in W.A., with offices in Perth’s tallest building.
Our first task was to survey and map the entire area (never thought I’d use the surveying techniques I learned during my second year at Kew!). We then did a complete vegetation survey, listing the dominant trees, shrubs, herbaceous material and weeds. Working on the Escarpment Project provided me with my first trip out into the bush and my first taste of W.A.’s vast flora.
Attempts to re-establish native plants by seed were unsuccessful until the South Africans discovered that plants which are members of fire climax communities require the stimulus of fire in order to germinate. Some plants, such as hard seeded Legumes like Acacia, needed the heat to crack the seed coat, while others react and germinate only after exposure to smoke.
My second work assignment was in the Smoke Unit. The very resourceful staff in the Lab had assembled their own smoke machine using a small tent (like those used by BT when doing repairs in the street), which was sealed to be airtight. A hose from a Hoover led from the tent to a large metal drum. Also attached to the drum was a second hose which ran to a small pump powered by a car battery. Debris from the forest floor was piled into the drum and set alight. The pump circulated just enough air to avoid flames but still move the smoky air through the hose and into the tent which was full of seed trays. The seeds were left to smoke for one hour, or until the compost turned the colour of cardboard. We were conducting trials on the amount of time required for smoking and the efficiency of different burning material, such as Dryandra and Banksia.
I spent most of my time working on the Tip Site Project and enjoyed it the most. For many years this 50 metre by 80 metre site, in the bushland of King’s Park, was used as a domestic and industrial rubbish tip; dumping was finally discontinued in 1990. King’s Park Lab saw this site as an excellent opportunity to amalgamate all their information on reclamation and ecological restoration to return the site to native bushland. After many years of heavy machinery running over it, the site was assumed to be compacted. After testing, the soil was indeed very compacted and needed to be ripped. However, this action produces bare ground, a perfect surface for weed invasion.
The second part of the project involved a floral survey of the bush to establish not only which plants to include in the seed mix for the site, but the correct proportions of each plant. Again, we ran 10 transects of 100 metre through the bush. At each one metre mark we noted all vegetation, including weeds (this was a monitoring measure), giving us a total of 1,000 readings. This survey proved an excellent method for me to familiarise myself with W.A.’s flora! By the end of the first day I could recognise at least 50 plants.
While conducting the vegetation survey, we also took special note of any seed that was nearly ripe. When ripe, this seed will be gathered and, according to the results of the survey, the seed mix will be prepared. Seed provenance is very important as it protects genetic integrity and promotes variation. Therefore, seed will be gathered from as close to the Tip Site as possible. The site will be seeded, but before seeding, the hard coated seeds such as the Legumes will be boiled for one minute. The other seeds will all receive smoke treatment. The recalcitrants must be propagated by tissue culture and planted out by hand.
Towards the end of my stay in Australia, King’s Park hosted the annual Wildflower Festival, which is a celebration of W.A.’s marvellous, unique flora. Many nurseries and wildflower societies staged exhibits.
Winning a scholarship at Kew and being given the opportunity to actually complete my project was a rare and unforgettable experience for me. I learned a great deal about the flora of W.A. and about land degradation and reclamation practices and how these are being used to restore the Jarrah Forest.