Vegetation creates rain – true fact

Wednesday, February 15, 2017

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Just because it’s been done before, doesn’t mean it should be done again. 

European colonisation brought logging into the Bellingen Shire and throughout Australia. It was the keystone for large-scale development providing both housing and an agricultural base.

But more than 200 years later, a comprehensive review of 150 scientific papers on land-clearing and rainfall, conducted by Dailan Pugh of the North East Forest Alliance, concludes deforestation has wreaked havoc on the country’s climate.

In short: vegetation creates precipitation and Clearing Our Rainfall Away summarises the evidence of how land-clearing affects rainfall.

“Climate change results from many human activities, one of those is land-clearing and deforestation,” Mr Pugh said.

“The evidence is overwhelming: clearing native vegetation reduces rainfall, increases temperatures and intensifies droughts. With NSW experiencing record-breaking temperatures it’s time for the governments to end the policies that are contributing to it.”

Mr Pugh said vegetation does not just respond to rainfall, it actively generates its own.

“It recycles water from the soil back into the atmosphere through transpiration; creates the updrafts that facilitate condensation as the warm air rises and cools; creates pressure gradients that draw moist air in from afar; and, just to be sure, releases atmospheric particles, which are the nuclei around which raindrops form,” he said.

“The transpiration of vegetation also results in evaporative cooling whereby the surface heat is transferred to the atmosphere in water vapour. The resultant clouds also help shade and cool the surface.

“It has been estimated that since European settlement, land-clearing in eastern Australia has directly resulted in an average summer rainfall decrease of 4-12 per cent and a warming of around 0.4 to two degrees.”

The stark warning is not unprecedented – excessive land clearing is associated with the downfall of many civilisations. However, what is new is the magnitude of the consequences.

“While rising carbon dioxide emissions are responsible for much of our climate woes, they are not the whole problem,” Mr Pugh said.

“Overwhelming evidence from around the world shows land-clearing has directly caused a significant reduction in regional rainfalls and an increase in land temperatures.

“These impacts have been compounded by the release of CO2 stored in trees which adds to the ‘greenhouse effect’, with land-clearing contributing around a third of the world’s CO2 emissions in the past two centuries.”

Clearing Our Rainfall Away comes at a time when key stakeholders are unwilling to commit to environmental plans that will turn the tide of climate change.

Scientists do not confuse hypotheses with conclusions, and thus it takes time – decades and decades to compile data – and this fact has not been lost on those with vested interests. Public relations gurus and a bevy of political heavyweights have railed against environmentalists and spruiked to the community for support. They’ve downplayed the long-term effects of many climate change factors, including broad-scale logging.

However, governments change, and so too can policy – and as such NEFA continues to lobby for changes to the state’s native vegetation act.

“We ask the new premier, Gladys Berejiklian, to reconsider the Baird government's draconian legislation that has reopened NSW's remnant native vegetation for broad-scale clearing,” Mr Pugh said.

“With temperatures and droughts increasing in severity we cannot afford to add to our woes.

“Removing deep-rooted forests and woodlands has also resulted in rising water-tables and brought long-buried saline ground-waters towards the surface, already making 7.5 million hectares of NSW’s agricultural lands at risk of dry land salinity.

“It is important that premier Berejiklian recognises that if she approves the clearing of our forests and woodlands, she is approving rainfall reductions, temperature increases, and making more farmland unproductive.

“The premier must take action to rein in the worst aspects of Baird’s climate vandalism.”

 

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