The climate change paradox: Rainforests are being felled...

[jwl]

The dramatic demise of the world’s rainforests has caused concern for years while they have been chopped down at breakneck speed to grow crops and rear cattle – yet the planet has actually become greener in the past decade, with the total amount of plant coverage soaring.

The rise in vegetation is the result of a major tree-planting campaign in China and unintentional increases in grasslands and non-tropical forests in former Soviet states, Australia and Africa, as heavy rainfall and abandoned farms improve growing conditions, according to new research.

The net increase in vegetation is so substantial that the world’s trees and other plants store 4 billion tonnes more carbon today than they did in 2003, according to a study by the University of New South Wales and Australian National University.

Plants help to combat climate change by sucking CO2 out of the atmosphere and converting it into the food they need to grow, locking the carbon into their structures and helping to curb global warming in the process.

“The increase in vegetation primarily came from a lucky combination of environmental and economic factors and massive tree-planting projects in China,” said the lead author, Dr Yi Liu.

“Vegetation increases on the savannahs in Australia, Africa and South America as a result of increasing rainfall, while in Russia and former Soviet republics we have seen the regrowth of massive forests on abandoned farmland.”

The growth of plant cover has also been helped by the causes and effects of climate change. The overall increase in carbon in the atmosphere over the past decade as the world burned increasing quantities of fossil fuels played a small role as the “CO2 fertilisation effect” improved the growing conditions for plants.

Furthermore, as the warming planet melts ice and permafrost in the Arctic, the “tree-line” is moving north, experts said.

Pine and broadleaf forests have shown significant growth in the past 10 years, as have shrublands and savannahs. Meanwhile, grasslands and croplands showed a modest increase, according to the research, published in the journal Nature Climate Change.

But the decline in rainforests over that period has been significant – especially around the edge of the Amazon and in Indonesia’s provinces of Sumatra and Kalimantan.

Scientists say this is particularly alarming because rainforests are much richer and more diverse habitats than grasslands and other types of forests. They also absorb much more carbon per hectare than the savannahs and cropland that have filled in much of the gap left by the rainforests’ demise.

Although the growth in plants provides a welcome boost in the battle to curb climate change, the report warns that the increase in the amount of carbon being sucked out of the atmosphere is nowhere near big enough to counter the overall growth in carbon emissions during the period.

The report also warns that savannahs are a far less stable carbon sink than trees, meaning that much of the good work these habitats have done in absorbing CO2 could be quickly undone by a sustained dry spell.

The main cause of the strong growth in savannahs came from the higher rainfall they have seen in recent years – but the situation could rapidly reverse if they were to experience extended dry periods, said the co-author, Dr Pep Canadell.

“This study shows this capture of carbon is very sensitive to year-to-year changes in rainfall over savannah regions, both for Australia and for the global CO2 budget,” he said. The CO2 budget relates to the amount of CO2 that can be released into the atmosphere if the worst effects of climate change are to be avoided.

One of the most surprising findings was that Australia is greener today that it was a decade ago. This is despite ongoing land clearing, urbanisation and the recent droughts in some parts of the country.

However, the increase in vegetation has not been uniform. The largest increases are in northern Australia, with less increases in the south and a small decrease in the south-east.

http://www.independent.co.uk/environmen ... 57505.html

[madd0ct0r]

Interesting. Gaia theory rises again, just if the humans allow enough forest to become re-established...

[Simon_Jester]

The Gaia hypothesis states that ecological equilibriums will tend to self-maintain, because whenever a parameter of the system changes, negative feedback loops kick on.

[Note that the Gaia hypothesis does not assert that this MUST happen, or that some god makes it happen; it is simply a shorthand label for the idea that it DOES happen in some cases]

Here, we may be observing this- but human activity is changing the basic conditions upon which all equilibrium states rest. We're eating up the fisheries and diverting huge amounts of water and chopping down the rainforests and pumping extra CO2 into the air and planting trees in China.

So any safety we get out of negative feedback loops is temporary, in my opinion. Because of how many monkey wrenches we're throwing into the machinery.

[Adam Reynolds]

Doesn't the gaia hypothesis fail to fully account for evolution?

As a side note there is an amusing anecdote I remember somewhere about the question of whether AIDS was a response of Earth attempting to deal with homo sapiens. The best response was that if gaia intended for AIDS to kill humans, she would not have made trees that give us rubber.

Another other problem is that depending on the cirumcstances, planting trees can actually have a net warming effect compared to things like grasses as they absorb rather than reflect sunlight.

[Simon_Jester]

The Gaia hypothesis really doesn't have much to do with evolution since realistically they operate on different timescales. Climate change takes place on a timescale of thousands or tens of thousands of years; evolution, millions.

Over time, new organisms can evolve that will alter the basic equilibrium state of the climate or disrupt an existing equilibrium. The Gaia hypothesis does not exclude this. It simply states that there are many ecological systems that are made more stable than they appear by negative feedback loops.

The alternative hypothesis is, frankly, untenable. It would be the idea that ecological systems are UNstable in the absence of some major outside perturbation. If that were true, there would be nothing recognizable as an ecosystem to begin with, because species would not be able to adapt to such an unstable environment. I don't think complex life could emerge at all in the absence of an ecosystem that self-maintains naturally through negative feedback loops.
________________________

The Gaia hypothesis does NOT state that the Earth's ecosystem is sentient, that it creates diseases to get rid of individual animal species, or any such thing. That would be pseudoscience using "Gaia hypothesis" as a mask to pretend to be real science.

[Lonestar]

I have a book about the Appalachian Trail in Shenandoah National Park, in it there are some pictures of SNP(and George Washington National Forest) in the 20s. The Appalachians looked like moonscapes. Bill Bryson mentioned something similar about a photo form the 1920s of Vermont.

Now, the Eastern US is heavily wooded(at least partially because of our own "tree planting campaign" in the 30s through the CCC). Forest cover has increased dramatically in the past 100 years, even if we worry about places like the Amazon.

[Simon_Jester]

Deforestation of the Amazon is a thing to worry about not so much because it decreases the total amount of plant biomass on Earth.

It's because:
1) Tropical rainforests are huge reservoirs of biodiversity, and we are not so advanced (and may never be so advanced) a civilization that we don't benefit from being able to study the organisms that live there.
2) The Amazon basin is a rainforest in a specific place, and the consequences of deforestation there may have larger consequences for the global ecosystem, just as plowing up the grass of the prairies led to the Dust Bowl in the United States.

[madd0ct0r]

The Gaia hypothesis states that ecological equilibriums will tend to self-maintain, because whenever a parameter of the system changes, negative feedback loops kick on.

[Note that the Gaia hypothesis does not assert that this MUST happen, or that some god makes it happen; it is simply a shorthand label for the idea that it DOES happen in some cases]

Here, we may be observing this- but human activity is changing the basic conditions upon which all equilibrium states rest. We're eating up the fisheries and diverting huge amounts of water and chopping down the rainforests and pumping extra CO2 into the air and planting trees in China.

So any safety we get out of negative feedback loops is temporary, in my opinion. Because of how many monkey wrenches we're throwing into the machinery.

Hmm, good point. I've not observed any experiments where multiple aspects of a Gaia system where subject to external pressure simultaneously. I wonder if this could, in the far future, result in treaties based on forest area. Countires have to have a certain % of their area forested, and can buy and trade the land from elsewhere.