Some more science to throw in the pot. The IPCC (bureaucrat-led)
hysteria is already beginning to simmer down. Maybe the following
will help to finally put it to sleep -- at least for a few years
while sufficient scientific data continues to be collected and
assessed in this complex subject.
Keith
----------------------
CO2 Is Greening The Planet: Savannahs Soon To Be Covered By Forests
Science News -- Sunday, 01 July 2012
A new study published today in "Nature" by authors from the
Biodiversity and Climate Research Centre and the Goethe University
Frankfurt suggests that large parts of Africa's savannas may well be
forests by 2100. The study suggests that fertilization by atmospheric
carbon dioxide is forcing increases in tree cover throughout Africa.
A switch from savanna to forest occurs once a critical threshold of
CO2 concentration is exceeded, yet each site has its own critical
threshold. The implication is that each savanna will switch at
different points in time, thereby reducing the risk that a
synchronous shock to the earth system will emanate from savannas.
----
Tropical grasslands, savannas and forests, areas the authors call the
savanna complex, are expected to respond sensitively to climate and
atmospheric changes. This is because the main players, grasses and
trees, differ fundamentally in their response to temperature, carbon
dioxide supply and fire and are in an unrelenting struggle for the
dominance of the savanna complex. The outcome of this struggle
determines whether vast portions of the globe's tropical and
sub-tropical regions are covered with grasslands, savannas or
forests. In the past such shifts in dominance have played out in
slow motion, but the current wave of atmospheric changes has
accelerated the potential rate of change.
Experimental studies have generally shown that plants do not show a
large response to CO2 fertilization. "However, most of these studies
were conducted in northern ecosystems or on commercially important
species" explains Steven Higgins, lead author of the study from the
Biodiodversity and Climate Reseach Centre and Goethe-University. "In
fact, only one experimental study has investigated how savanna plants
will respond to changing CO2 concentrations and this study showed
that savanna trees were essentially CO2 starved under pre-industrial
CO2 concentrations, and that their growth really starts taking off at
the CO2 concentrations we are currently experiencing."
The vegetation shifts that the Higgins and Scheiter study projects
are an example of what some theorists call catastrophic regime
shifts. Such catastrophic regime shifts can be triggered by small
changes in the factors that regulate the system. These small changes
set up a cascade of events that reinforce each other causing the
system to change more and more rapidly. The study demonstrated that
the savanna complex showed symptoms of catastrophic regime
shifts. "The potential for regime shifts in a vegetation formation
that covers such vast areas is what is making earth system scientists
turn their attention to savannas" comments Higgins.
Knowing when such regime shifts will occur is critical for
anticipating change. This study discovered that locations where the
temperature rise associated with climate change occurs rapidly, for
example in the center of southern Africa, are projected to switch
later to forest as the high rate of temperature increase allows the
savanna grasses to remain competitive for longer in the face of
rising atmospheric CO2 concentration. This means that even though a
single location may experience its catastrophic regime shift, the
vegetation change when averaged over a region will be smoother. Such
gradual transitions in regional vegetation patterns will reduce the
potential for shocks to the earth system. "While this may seem
reassuring, we have to bear in mind that these changes are still
rapid when viewed on geological time scales", says Higgins.
The practical implications of the study are far reaching. For
example, the study identified a belt that spans northern central
Africa where fire suppression would encourage savannas to transition
to forests. "So if you wanted to sequester carbon as part of a carbon
mitigation action, this is where you should do it" explained Higgins
"with the caveat that where this will work is shifting as atmospheric
conditions change." A worrying implication is that the grasslands and
open savannas of Africa, areas with unique floras and faunas, are set
to be replaced by closed savannas or forests. Hence it appears that
atmospheric change represents a major threat to systems that are
already threatened by over-grazing, plantation forestry and crop production.
>>>>
Keith Hudson, Saltford, England http://allisstatus.wordpress.com
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