by Adam Jones – click to order a photo or poster
I’ve covered this before, such as when NASA posted satellite data showing that the biosphere is booming thanks to CO2 fertilization. This new study from Goethe University in Frankfurt, Germany suggests that the Umbrella Thorn Acacia trees will make a comeback.
Tree trumps grass to rule the savannas
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.
###
Paper:
Steven I. Higgins and Simon Scheiter (2012). Atmospheric CO2 forces abrupt vegetation shifts locally, but not global. Nature, DOI: 10.1038/nature11238
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Hopefully we are equally skeptical of models that promise good news a century from now
So forestation and de-forestation are both bad things……or do I read this the wrong way?
Could the decimation of the large animal population of the Savana have anything to do with this uptick in tree growth? I would think the former large Elephant population could not have been all that friendly to slow growing trees. And what about increased urbanization of the Indiginous population? Seems that there might be numerous factors that might be at play here.
“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”
Save the barren wastelands of the planet from the threat of wuthering vegetation!
Experimental studies have generally shown that plants do not show a large response to CO2 fertilization.
Which planet have the flora they are referring to?
You must read old articles on “Musings from the ChiefIO” with subjects like
“CO2 is plant food”. There are lots of them, and many are humorous as well as informative.
e.g. http://pindanpost.com/2012/07/01/co2-is-plant-food-part-66-for-those-who-doubt/
And just why do greenhouses pump in CO2 if “Experimental studies have generally shown that plants do not show a large response to CO2 fertilization.”
It’s the lack of elephants, natures bulldozer, that’s the problem.
Interesting redefinition of the word “catastrophic”.
Apparently gradual catastrophes are likely.
I think Peter (@7.45) has it correct – the incerase in trees is a result of decreased grazing. You can see this anywhere there is a reduction in grazing animals and I don’t suppose African savannah’s are any different to other grasslands.
Their early statement is pretty bizarre “Experimental studies have generally shown that plants do not show a large response to CO2 fertilization.” Are they trying to say that all the glasshouse growers are wasting their money and that the collection of papers on CO2 Science are not experimental studies?
This smacks of an attempt at finding the cloud in the silver lining……
Anthony, I take it you read nature mag for the humor factor. But they are not even a good joke.
I am constantly amazed that these people have created their own illusory ‘static’ nature. Nature changes all the time (the real thing, not the magazine). This is how and why life changes. We should rejoice in more diverse habitats and opportunity for life, but suddenly it’s a Bad Thing.
Sheesh!
Only a modelist would think trees are catastrophic.
“this study showed that savanna trees were essentially CO2 starved under pre-industrial CO2 concentrations”
================
So, it would appear that Al Gore, the Team, Climate Science and the IPCC, in wanting us to cut back to per-industrial CO2 levels, are in fact advocating that we starve trees.
Looks like a natural cycle to me.
Trees grow – locals burn the trees for fuel (no alternative due to the green brigades madness) – more co2 plant food released – trees grow etc etc.
The “tree-ing” of savannas probably isn’t due to CO2 increase as much as it is due to ENSO oceanic-atmospheric oscillations providing necessary growing conditions for trees. And it could also be related to an increase in whatever animal spreads the seeds into the savanna. For example, might tree eating animals such as giraffs, be on the increase due to better preservation efforts? Animals like that are great seed spreaders.
re: “Experimental studies have generally shown that plants do not show a large response to CO2 fertilization.”
Does Higgins source that assertion? Because it would appear to be directly contradicted by the Science magazine article discussed here just a few days ago (Susanne von Caemmerer, W. Paul Quick, and Robert T. Furbank (2012). The Development of C4 Rice: Current Progress and Future Challenges. Science 336 (6089): 1671-1672.)
reducing the risk that a synchronous shock to the earth system will emanate from savannas.
Wow, that is a risk I would never have thought of…boy what great imagination! Catastrophic regime shifts? Are they expecting a Coup? Just think…those devilish savannahs, lurking…lurking, ready to pounce synchronously and shock the earth. Diabolical!
Jer0me says:
July 2, 2012 at 8:24 am
“I am constantly amazed that these people have created their own illusory ‘static’ nature.”
The most fundamental assumption of climate change alarmism: Change from some apparently immutable base line, one so small as to be hidden by the error bars. Yet it marches on, ambushing, er, or rebushing, savannahs everywhere. Shocking!
More baffle gab from the model people. My experience in the parkland of Alberta and Saskatchewan tells me fire is the most important component followed by moisture in the grasses vs trees balance. Something, by the way, known for generations.
What a dilemma!
More trees due to that evil changing climate…. We can’t have that! We must reduce CO2 so that we keep those lovely grasslands as they are…errr were…errr should be?
My question is: Will the Greens cut down the offending trees in the meantime to give the poor old grass a chance?
They may have to ask industrialists to sustainably harvest the trees (using green methods, of course) to keep the exact number that used to be where they believe it should be….
The spread of acacia may cause a dramatic difference, if true. Once established it is extremely hardy, with the deepest root system of any flora, it can reach down to a water table and is salt tolerant. In most places it does not create a dense forest, but rather a scattered tree line. But it hosts a large variety of fauna, including honey bees that will further impact. Both the leaves and green seed pods are edible. The mulch ring, while not great, will allow moisture retention and cooler temperatures.
Love the bit about “reducing the risk that a synchronous shock to the earth system will emanate from savannas”. Sounds pretty much like nature’s usual gradual re-accommodation to change to me, but of course “gradual” doesn’t sound very scary, unlike “synchronous shock” talk.
Jer0me says:
July 2, 2012 at 8:24 am
I am constantly amazed that these people have created their own illusory ‘static’ nature. Nature changes all the time (the real thing, not the magazine). This is how and why life changes. We should rejoice in more diverse habitats and opportunity for life, but suddenly it’s a Bad Thing.
Sheesh!
You are right, large areas of Africa have alternated regularly from forest to Savannah over the last million years or so.
We are seeing here the “the world was created in 1850” mindset of the AGW camp.
The only creative challenge in these people’s minds is how to make any change associated with increasing CO2 look like a dire catastrophe. So now the hymn sheet is “trees are bad, grass is good”. But hang on – when ecologists talk about deforestation in Brazil etc and conversion of forest to grass-based agriculture, then it was “trees are good, grass is bad”.
Where have I read something like that before?
O yes – it was in Animal Farm, by George Orwell. The pigs were taught to sing “two feet bad, four feet good”. But then Napolean and the ruling pigs learned to walk bipedally themselves, so the correct song was changed to “four feet bad, two feet good”.
So lets all sing along now: “carbon dioxide bad, extinction of plants and all life on earth GOOD” (not all that singable I guess…)
So….this is bad, right?
I remember a TV programme presented by Archbishop Attenborough about elephants changing the landscape from savannah to forest over generations. The following is from the WWF website.
“Elephants directly influence forest composition and density, and can alter the broader landscape. In tropical forests, elephants create clearings and gaps in the canopy that encourage
tree regeneration. In the savannas, they can reduce bush cover to create an environment favorable to a mix of browsing and grazing animals.”
Has elephant behaviour been taken into consideration in this study?
Elephants love grass and will knock down Acacia trees if they become too plentiful. They are one of the reasons that the savannah survives. Nature’s bulldozers indeed.