A new study from from Lawrence Livermore National Laboratory and the Dept. of Global Ecology at Stanford University, entitled “Combined climate and carbon-cycle effects of large-scale deforestation” has just been released, and it raises far more questions than it answers.
The fundamental conclusion of the report is that deforestation at higher latitudes actually causes global cooling, and deforestation in the tropics causes global warming. This is because replacing forests with grasslands is assumed to increase the reflectivity of the land – forests are darker than grasslands – which the researchers assert succeeds in having a cooling effect in the northern latitudes. In the tropics, however, where forests cause cloud formation, tropical deforestation is said to have a warming effect since clouds are more reflective than grasslands.
The most interesting statement in the entire report, one that anyone concerned with global warming should ponder closely, is the following:
“Although carbon-cycle effects have been taken into account in the promotion of afforestation as a climate change mitigation strategy, the biophysical effects of land-cover change have been largely ignored.”
Unfortunately this quote is not included in the summary press releases, and the full report is not available to the general public.
In the recently released IPCC report, one-third of global warming was asserted to be caused by changes in land status. But were these scientists yet considering all of the biophysical effects of land-cover change? Or are those effects being largely ignored?
It is easy to say common sense is of no use when trying to determine what might be causing global warming. But climate models, like economic models, are trying to make sense out of systems of nearly infinite complexity. When confronting chaos, common sense is a useful rudder. And to state the problem in plain terms, tropical deforestation is increasing, the justification for this is to combat global warming by growing biofuel, and the result is more global warming. It is an absolute disaster. And also don’t forget that droughts and extreme weather are often caused by tropical deforestation, not global warming.
Have the scientists who produced this study (or those who produced the most recent IPCC report) therefore identified all the biophysical effects on global warming? Did they consider the impact of lowered water tables which increase the capacity of the earth to absorb heat? Would that modify their calculations when they state there is no benefit to reforesting the temperate regions? Wouldn’t forest cover facilitate water retention and higher water tables, and wouldn’t forests shield the earth itself from heating, particularly if the water tables are depleted and the earth’s capacity to absorb heat is heightened? We have depleted our water tables by an order of magnitude in every agricultural valley and irrigated plateau on earth – over 10 million square miles.
Those who have made up their minds may say common sense is useless when debating the cause and the extent of global warming. Yet our world’s tropical rainforests have shrunk 60%, from 8.0 million square miles to less than 3.0 million, and our deserts have grown from 3.0 million square miles to 5.0 million, and over 10 million square miles of farmland is now conducting heat as never before due to lowered water tables. Elsewhere, another 7.0 million square miles of temperate and boreal forests have been lost.
Altogether, we have altered nearly 50% of the land surface of our planet in the last 150 years – and all of these changes have made those lands hotter. And yes, there are also .5 million square miles of very, very hot urban heat islands.
Before we lose another million square miles of tropical rainforest to the biofuel barons – burning away in the name of “CO2 neutral” energy production – perhaps we should take a much, much harder look at the “biophysical effects of land-cover change.”