Birdwood Downs Station
Gibb River Road, 20km out of Derby
PO Box 124 Derby WA 6728
ph: 08 9191 1275
Land restoration and pasture development: past and future
Birdwood Downs is located in the coastal ecosystem of the Kimberley region in the semi arid tropical pseudo monsoonal climatic region of North Western Australia. The region’s severe environmental conditions, and a history of poor pastoral practices such as overgrazing, coupled with overburning has lead to land degradation and marginal economics.
The climate has some extremes. Temperature ranges from 4 degrees centigrade at night during the June to August cool dry season to 47 degrees during the day during the October to November hot dry season. The high humidity of the wet season of December to March moderates these extremes to in the high thirties.
Rainfall patterns are highly erratic both in quantity and frequency, with an average precipitation of 625 mm which mostly falls from December to April. Several times during the wet season the rains, often torrential, are driven by cyclonic weather systems. Rainfall ranges between 100 mm and 1500 mm per year.
Each year there are bush fires during the hot dry season often driven by strong easterly winds. A program of controlled burning is used to make use of the natural need of fire to rejuvenate species diversity and prevent land degradation and damage by uncontrolled hot fires.
Birdwood Downs is situated on a series of stabilized sand dune ridges roughly a kilometer apart with sandy loam in the valleys on the ecotone with the coastal marsh. In the areas bordering the marsh in the transition zones yellow clays and silts predominate in the valleys between the dunes. These old weathered tropical soils are very low in macro- and micro-nutrients. A high level of iron and aluminium in the soils binds phosphorus which is therefore unavailable for uptake by plants. Due to the overgrazing in the past, vast areas have been overrun by secondary succession and increaser species- Acacia scrub and annual grasses such as Spear grass. This pindan wattle country which covers almost half of the Kimberley region is considered of the lowest potential for development.
After the initial mechanical clearing of the invasive woody weeds, around half the property has been planted with improved grasses and legumes to restore productivity. Around four hundred acres were kept free from re-invasion by Acacia wattle through manual uprooting. Over the years, Birdwood Downs has demonstrated that the improved pasture spreads and the native vegetation recovers from the overgrazing and compaction.
The improved pasture developed at Birdwood Downs increases sustainable stocking capacity over ten times that of native pasture in the Kimberleys. Cattle were used for selective grazing to assist seed production and for pasture upgrade, and to serve as a demonstration of the increased weight gains possible with developed savannah pasture.
Under new owners Birdwood Downs is the home of several innovative projects. The plan is to develop and demonstrate a sustainable pasture management model on a commercial and profitable scale, which at the same time will include carbon sequestration to contribute to the control of climate change.
The projects will look at the impact of invasive woody weeds on groundwater recharge on Pindan soils. Anecdotal evidence suggests the removal of wattle forrest and the re-establishment of the grasslands could see more than 3 million litres per hectare recharged into groundwater storages. That could equate to 5 GL of additional recharge to the groundwater.
The property will also see agronomic trials of a new phosphate product from a deposit near Willare. The phosphate deposit, which is being developed in partnership with Traditional Owners, aims to determine the potential for a local organic fertilizer product for the Kimberley.