First the sobering reality

For decades Australia has been getting dryer. in the period from 1950 to today much of the most fertile parts of the country have been getting dryer at the rate of 50ml less rain per year every decade. That's 250 ml less rain over half a century on the east coast and less further inland while much of Australia is getting more rain . Source. Unfortunately the trend is not likley to change in the next few hundred years making todays rainfall levels the envy of farmers in the future.

Compunding rainfall changes our warmer planet increases evaporation meaning less moisture reaches into the soil where plants can access it, and less runs off into dams. Water in dams will evaporate faster and plants will loose water faster with higher temperatures. With that sobering news behind us there are plenty of things that farmers can do, below are just a few.

Soil Carbon

The under-appreciated sequestration or carbon in soils. Making money from soil carbon is a long way off, however there will be a place and potentially a good living in soil carbon. Measuring and monitoring changes in soil carbon is not easy and the lack of standards in this area is stalling development at the moment but it is well worth knowing how it could work on a farm.
http://www.carboncoalition.com.au/
http://www.amazingcarbon.com/

Interesting speakers at an Envrionment Business Australia forum on March 18 2009;
Plant stone technology – Professor Leigh Sullivan, Director, Southern Cross Geo-Science, Southern Cross University
Rangeland carbon – Tony Lovell, Director, Soil Carbon Pty Ltd
Forest sinks – Dr Andrew Grant, CEO, CO2 Australia

Also Ross Garnaut has suggested that marginal farmland be re-forrested to sequester carbon and provide farmers with income. "In this country there might be huge opportunities for doing that over the next 30 or 40 years," he told The Australian. "It basically could do the job for the next 20 to 30 years."

Wind and Solar Energy

While still very expensive the economics could quickly change with a rethink in government policy, given the right feed-in tariff even PV solar is viable. This would allow farmers to provide emission free energy into the grid and supplement farm income.
Given a good wind resource (coastal is great) an energy company might build and manage the facility and pay for the lease.
For those properties without good wind resource but lots of cloudless days solar thermal could provide an income from a low carbon economy with the right price signals from carbon trading or a feed-in tariff.

Checkout the solar links on the Google Earth page where you can pay a virtual visit to the oldest and largest solar installations in the west of the United States. Built in the late 1970's and early 1980's the 'Big Solar' projects use Solar Thermal technology that's not rocket science.
Using trough reflectors in what looks like long cattle drinking troughs oil is heated by the sun and, through a heat exchanger, generates steam to turn a turbine. At smaller scales water can be heated directly and the excess hot moist air used for heating and other processes such as pasteurisation or wool processing.

Bio Diesel

Potentially you have the ability to grow fuel.
Barney who is based at Charles Stury University is working on a Land & Water Australia funded contract to develop a strategy to revitalise rural Australia by making a transition to a biomass based economy. He believes that biomass energy from growing large areas of trees (which would produce wood alcohol) could be part of a renewable energy mix for Australia.
An article in the Melbourne Age (20-10-2008 Business Age page 3) gives a summary of how this would work on good and poor soils. Link to article

Bio-Char

Bio-Char (black carbon) is formed when organic matter such as wood is burned at 300 to 500 degrees C. under parital exclusion of oxygen to produce matter of about 75% carbon.
When bio-char is added to soils it can increase land fertility and water holding capacity. Increases in phosphorous, nitrogen, pH, nutrient availability as well as higher potassium, phosphorus, and zinc availability, and to a lesser extent, calcium and copper have been observed.
Adding bio-char to soils would 1/ increase water holding capacity 2/ increase crop yeilds 3/ sequester carbon in the soil directly and 4/ increase the amount of plant life and therefor carbon per hectare. The first two points would help today's farmer and the last two would help a future carbon farmer. The best responce in yeild is in nutrient-deficient, sandy soils which occur widely across Australia.
For a detailed study of Bio-Char (this example relevant to the Northern Territory but with relevance to all land types) visit http://www.dcm.nt.gov.au/__data/assets/file/0016/43144/20.pdf

Deep rooted, nitrogen fixing trees

Certain trees will fix nitrogen into the soil and improve forrestation rates in nutrient poor soil.
http://forums.permaculture.org.au/viewtopic.php?f=1&t=5936

Dairy

Genesis Now have done some great work for farmers in the dairy sector on energy efficiency.
Follow the link to their website http://www.genesisnow.com.au/html/dairy.htm

Follow-up

Also search on 'soil carbon' for contacts and information.
Find the man who claimed that he could 'grow soil' anywhere in Australia.