Three years ago I wrote in this column about research that showed land clearing in Western Australia’s southwest had contributed to the region’s plummeting rainfall.

Since then US research has found that deforestation in one area influences rain elsewhere.

Deforestation in the Amazon reduces rain in Mexico; land clearing in Central Africa reduces rain in the US Midwest, and forest removal in south-east Asia affects rainfall in China and Europe’s Balkan peninsula.

Removing trees affects the amount of heat and moisture released into the atmosphere; this changes air pressure and circulation patterns, and sends storm systems off their typical paths.

Now Queensland research has concluded that 150 years of land clearing has added significantly to the warming and drying of eastern Australia.

A team led by Dr Clive McAlpine from the University of Queensland says the 2002-03 El Nino drought in eastern Australia was on average two degrees hotter because of the land clearing, and the region’s average summer rainfall has decreased between four and 12 per cent for the same reason.

The link between tree clearing and rain is due to heat and moisture transfer to the atmosphere.

Trees access water deep in the ground and hold the moisture in their canopies. They absorb sunlight and emit heat which creates thermal currents that take the moisture from the leaves up into the atmosphere, where it condenses as rain.

When trees are removed, heat is reflected rather than absorbed, which means less moisture evaporates into the atmosphere and, in the long run, less rain falls.

Other US research has found that regional climate is impacted by the type of land use after clearing.

Areas left with bare ground had the most profound impact, raising temperatures up to two degrees. Croplands had the second most significant climate impact, followed by pastures.

Clive McAlpine says the message from the research is clear.

"We need to recognise that the land surface and how we manage the land has a strong feedback to the climate and that’s going to become even more important as our climate changes," he said.

You can read his team’s research paper Modelling impacts of vegetation cover change on regional climate at http://www.omc.uq.edu.au/news/documents/ModellingImpactsVegetationCover.pdf