Trees bring rain

Land clearing in a paddock outside Moree NSW
Source: The Guardian

My mother used to say that, and I didn't believe her.  Arrogant pup!  Here's an excerpt from a deeply depressing Guardian article about land clearing in Australia which explains how the process works:

Prof Clive McAlpine from University of Queensland explains that not only does land clearing release greenhouse gases into the atmosphere, it also has an effect on climate, well beyond the emissions.

“It causes warming locally, regionally and even globally, and it changes rainfall by altering the circulation of heat and moisture,” he says.

“Trees evaporate more water than any other vegetation type – up to 10 times more than crops and pastures. This is because trees have root systems that can access moisture deep within the soil.”

The increased evaporation and rough surface of trees create moist, turbulent layers in the lower atmosphere, he says. “This reduces temperatures and contributes to cloud formation and increased rainfall. The increased rainfall then provides more moisture to soils and vegetation.

“The clearing of deep-rooted native vegetation for shallow-rooted crops and pastures diminishes this process, resulting in a warmer and drier climate.”

McAlpine argues that we should be replanting in the north-west of NSW and south-west Queensland to achieve a tree density of 40% to stabilise the local climate. Grazing would still be possible underneath the tree cover.

This is why the centre of continents at the equator have high precipitation.  At the coasts, the rain come from moist air from the sea.  But it falls on rain forests, and the trees transpire water vapour into the air.  In the tropics, an acre of rain forest puts more water vapour into the air than an acre of sea.  This water vapour then falls on forests further inland and the process is repeated.  So even in the heart of the continent, there is rain and rain forest, and the two go together.  Which is why land clearing can create a desert. 

As a species, we seem bent on destroying our world.