Africa's savannahs may all change into forests before the turn of the century due to excess CO2

[The Lawspeaker]

Africa's savannahs may all change into forests before the turn of the century due to excess CO2 in the atmosphere

A study suggests that some of Africa's savannahs - large areas sparse vegetation other than grass - may become forests by the end of the century.

Research from The Biodiversity and Climate Research Centre and the Goethe University Frankfurt suggests that a build-up of carbon dioxide in the soil will force an increase of tree cover throughout Africa.

When CO2 in the air and soil reaches a certain density, it forces trees to increase their size and foliage, meaning the open-sky savannahs may end up with a tree canopy.



http://i.dailymail.co.uk/i/pix/2012/06/29/article-0-12113990000005DC-800_634x379.jpg
The savannahs may change to forests within 100 years, according to new research which believes CO2 may lead to rapid tree growth


Because each site has an individual 'threshold', it is likely that separate savannahs will begin to change at different times, by many of them will switch before 2100, according to the researchers.

According to Science Daily (http://digg.com/newsbar/topnews/white_rot_fungi_slowed_coal_formation_scientific_a merican), experimental studies show that plants do not show a large response to CO2 fertilisation.

But Steven Higgins, lead author of the study, said: 'Most of these studies were conducted in northern ecosystems or on commercially important species.

'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.'



http://i.dailymail.co.uk/i/pix/2012/06/29/article-0-047690AD000005DC-531_306x423.jpg
The savannahs of Africa are generally grassland with some trees - but they may be forests within 100 years.

Some theorists call this abrupt switch a 'catastrophic regime shift', where a big switchover happens rapidly. These are normally caused by small changes in the area's regulation systems, but the small changes have a 'butterfly effect', where large-scale processes are set into motion.

The study found that locations where the temperature rise associated with climate change occurs rapidly, for example in the center of southern Africa, will switch to forests later as there is a high rate of temperature increase, which means the savanna grasses can remain competitive for longer.

This means that areas will adjust over differing time-scales, which will reduce shocks to the biosphere. While the changes will be a 'catastrophic regime change' for the area, when the change is averaged over the area, it will be smoother and more gradual..

Higgins said: 'While this may seem reassuring, we have to bear in mind that these changes are still rapid when viewed on geological time scales.'


Source: Daily Mail (http://www.dailymail.co.uk/sciencetech/article-2166470/Africas-savannahs-change-forests-turn-century-excess-CO2-atmosphere.html) (29 June 2012)

[Albion]

It is important to note that during different eras of history there have been plants much larger than now during periods of high CO2. On the other hand high oxygen leads to larger animals.


These two scenarios alternate in my opinion - the high amount of CO2 creates an over-abundance of flora which releases a great deal of oxygen, this in turn allowing animals to get bigger. The sheer amount of CO2 being taken in by plants has a cooling affect on the earth.
As animals get bigger they eat much more and so reduce the total amount of plant life which leads to a lower CO2 uptake whilst the animals continually expel yet more CO2, leading to warming and a lower amount of oxygen.
As oxygen levels fall so does size in animals and and this leads to plants being able to thrive and the cycle goes back to step one and carries on continually in an endless cycle (unless the cycle is broken somehow).



It has been known for years that growing plants in controlled conditions where CO2 is more abundant leads to better growth. In glasshouses they often increase CO2 levels slightly for this reason (at a safe level).

The reaction in plants is primarily between sunlight and carbon dioxide and this results in forms of sugar. This sugar is what the plant feeds on (as well as minerals and water drawn from the soil) with the main by-product being oxygen.

So it is obvious that an increase in CO2 will lead to increased plant growth and perhaps an increase in oxygen too. So some warming may be beneficial, it may lead to large, more abundant flora and larger fauna (including humans - when a species becomes "drunk on oxygen" it slowly evolves to grow bigger in size).

Anything that greens up Africa can't be bad, but I do not wish to see the Sahara as a savannah as it was a few millennia ago. Then sub-Saharan Africans could practically swim to Europe.

[Pretan]

^Indeed, during the times of the dinosaurs, CO2 was far far higher than it is now.

[Albion]

^Indeed, during the times of the dinosaurs, CO2 was far far higher than it is now.

Yes, step 3 in my theory was interrupted by the meteor that hit the Yucatan.

I think that past the Last Glacial Maximum our climatic peak was the Atlantic Period. During that period there are a few things that point to a much warmer climate:

Grapes grew as a native species much further north in Germany and maybe even Denmark
Lime trees set viable seed in England in most years and were a common tree (they're not now - it's not warm enough in most years for them to have viable seed).
The tree line spread further north and up into mountains that it isn't at now.
Dartmoor and other British uplands were quite nice places to live and had many villages (they can still be seen on Dartmoor). Now they're barren, wet and cold places to live fit only for sheep.


Softwood forests were replaced by hardwood. Quercus, Tilia, both cordata and platyphyllos, beech, oak, hazel, linden, Ulmus glabra, alder, and ash replaced Betula and Pinus, spreading to the north from further south.


In northeast Europe, the Early Atlantic forest was but slightly affected by the rise in temperature. The forest had been pine with an underbrush of hazel, alder, birch, and willow. Only about 7% of the forest became broad-leaved deciduous, dropping to Boreal levels in the cooling of the Middle Atlantic. In the warmer Late Atlantic, the broad-leaved trees became 34% of the forest.
Along the line of the Danube and the Rhine, extending northward in tributary drainage systems, a new factor entered the forest country: the Linear Pottery culture, clearing the arable land by slash and burn methods. It flourished about 5500–4500 BC, falling entirely within the Atlantic. By the end of the Atlantic, agricultural and pasture lands extended over much of Europe and the once virgin forests were contained within refugia. The end of the Atlantic is signaled by the "Elm decline", a sharp drop in Elm pollen, thought to be the result of human food-producing activities.[5] In the subsequent cooler Sub-Boreal, forested country gave way to open range once more.


The Dalmatian pelican (Pelecanus crispus), which is now found only as far north as south-eastern Europe, has been found in Denmark.


The climate cooled to around its current level from then onwards, but whether it cools and we resume the Ice Age or warms and it is put on pause is anyone's guess. Technically an Ice Age is defined as when there is ice at the poles.
Some have suggested that we're delaying the Ice Age by putting so much carbon dioxide into the atmosphere whilst other people say this will melt the ice caps which in turn will cool and ultimately stop the Gulf Stream.
The Gulf Stream warms us and it is only when you look at some maps that you realise just how out of place Europe's climates really are.


Whilst Europe and the Pacific North West are warmed by sea currents, most temperate areas are actually cooled by them.

http://img835.imageshack.us/img835/9107/climate2.jpg
Temperate climates

http://www.indiana.edu/~geol105/images/gaia_chapter_4/oceancirculation.jpg
Map of sea currents.

http://img812.imageshack.us/img812/5286/climate1.png
British Isles and places at similar latitudes for comparison


Really if the Gulf Stream stopped then I'd hope for a climate like Newfoundland because that would be the mildest climate we'd get if that happened, likely worse. At least we have the technology to survive fairly well if that did happen, but we'd either have to loose 80% of the population or import almost all food. The sea would still keep our climate milder than the continent - shorter, cooler summers but warmer winters, but the Irish Sea and English channel could potentially freeze (depends a lot on the salt content as well as temperature).
People forget just how far north Europe really is.

[Albion]

When CO2 in the air and soil reaches a certain density, it forces trees to increase their size and foliage, meaning the open-sky savannahs may end up with a tree canopy.

I wouldn't say it forces them too, but rather plants will naturally exploit this extra energy source if it is there (see my earlier photosynthesis explanation).
Some plants are more efficient than others, slow growing plants won't suddenly take over the savannah and as it happens that is what most of East Africa's tree species are - slow growers.
Slow growth is associated with plants adapted to drought to a certain extent.