Land care

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. Due to the region’s severe environmental conditions, and a history of poor pastoral practices such as overgrazing with sheep and cattle, coupled with overburning has lead to widespread desertification, 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 September to November hot dry season. The high humidity of the wet season of December to March moderates these extremes to in the thirties.

Rainfall patterns are highly erratic both in quantity and frequency, with an average precipitation
of 625 mm which 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 fire management is developed 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 (Heteropogan contortus). This pindan wattle country which covers almost half of the Kimberley region is considered of the lowest potential for development. The carrying capacity of such pindan was amongst the lowest of any land types in the Kimberley, especially since Birdwood Downs includes no river country or billabongs.

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. This “wattle chopping” is a more ecologically-friendly means of control than to the use of herbicides. Over the years, Birdwood Downs has demonstrated that as the improved pasture spreads and the native vegetation recovers from the overgrazing and compaction, fewer man-hours were needed to keep invasive weeds under control.

The half of the property which was not originally cleared of invasive wattle nor directly seeded benefitted from the spread of the better pasture species through ecological management of horses and cattle. They were the “weeders and seeders” – keeping undesirable species from seeding and spreading valuable species through their rotation. To make this possible Birdwood Downs invested in creating smaller paddocks and laneways to make the frequent moving of livestock easier. A control paddock is kept fenced and ungrazed as a long-term control to the other land uses at Birdwood Downs, so the impacts of pasture improvement and livestock can be gauged.

The improved pasture developed at Birdwood Downs increases sustainable stocking capacity over ten times that of native pasture in the Kimberleys, which lead to abundant production of cattle fodder. Cattle were also 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.

In 2010 the pasture management was evaluated. The first conclusion was that the work that was done during the previous four decades could be considered succesful. The second conclusion was that the pasture and weed situation had changed. Sida Cordafolia and Waltheria is heavily present in the prime paddocks and need a different method of control. Calytrix, which was always present, started to spread vigourously and when left unattended grows into a dense monoculture. This started a new regime of weed control. Sida and Waltheria are slashed several times a year to prevent these weeds to seed. Calytrix is cleared mechanically with bulldozer, slasher and plough and buffer zones are created between Calytrix forest and pasture to minimize the spread of seeds into good pasture areas.

In addition to this in 2015 experiments started with new pasture species. The tree Moringa Oleifera is considered a promising pasture. Several small plots of this tree are planted to evaluate their use as fodder for cattle and horses. The first indication is that this plant does well on the poor soils of Birdwood Downs Station.

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