Climate myths: Higher CO2 levels will boost plant growth and food production
17:00 16 May 2007 by
David Chandler and Michael Le Page
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The title is an opinion expressed by Chandler and Le Page that CO2 levels booting plant growth and food production is a myth. Oddly, their evidence points to the contrary.
According to some accounts, the rise in carbon dioxide will usher in a new golden age where food production will be higher than ever before and most plants and animals will thrive as never before.
fact, some accounts have said thus throughout modern history If it sounds too good to be true, that's because it is.
This statement is what we call a sound bite. It is an opinion expressed by the authors. It worked cause it got you all hot and bothered.
CO2 is the source of the carbon that plants turn into organic compounds,
fact and it is well established that higher CO2 levels can have a fertilising effect on many plants
fact , boosting growth by as much as a third
fact .
However, some plants already have mechanisms for concentrating CO2 in their tissues, known as C4 photosynthesis,
fact so higher CO2 will not boost the growth of C4 plants
this is a lie, even c4 plants benefit, albeit less than other plants from higher levels of co2 see C4 Plants.
Where water is a limiting factor, all plants could benefit
fact. Plants lose water through the pores in leaves that let CO2 enter.
fact Higher CO2 levels mean they do not need to open these pores as much, reducing water loss.
fact
However, it is extremely difficult to generalise about the overall impact of the fertilisation effect on plant growth.
opinion Numerous groups around the world have been conducting experiments in which plots of land are supplied with enhanced CO2,
fact while comparable nearby plots remain at normal levels.
fact
These experiments suggest that higher CO2 levels could boost the yields of non-C4 crops by around 13 per cent.
fact
Limiting factors
However, while experiments on natural ecosystems have also found initial elevations in the rate of plant growth, these have tended to level off within a few years. In most cases this has been found to be the result of some other limiting factor, such as the availability of nitrogen or water.
IOW the author says plants need water, fertilizer, and co2. Yeah well duh.
The regional climate changes that higher CO2 will bring, and their effect on these limiting factors on plant growth, such as water, also have to be taken into account.
correct, plants needs water, food, co2, and sunlight.These indirect effects are likely to have a much larger impact than CO2 fertilisation.
The authors are using fear uncertainty and doubt to make suppositions here.
For instance, while higher temperatures will boost plant growth in cooler regions, in the tropics they may actually impede growth.
Note the use of the indefinite term "may." IOW the author is again making suppositions.
A two-decade study of rainforest plots in Panama and Malaysia recently concluded that local temperature rises of more than 1ºC have reduced tree growth by 50 per cent (see Don't count on the trees).
Are we talking about just trees or plants? Was there a shortage of water, or extra cloud cover as well coincident with the temperature rise? You'll note that was not mentioned. The article discounts all plant growth here, based on less growth of one particular region, presumably of one particular type of tree. All supposition and opinion without more facts.
Another complicating factor is ground level ozone due to air pollution, which damages plants. This is expected to rise in many regions over the coming decades and could reduce or even negate the beneficial effects of higher CO2 (see Climate change warning over food production).
In the oceans, increased CO2 is causing acidification of water. Recent research has shown that the expected doubling of CO2 concentrations could inhibit the development of some calcium-shelled organisms, including phytoplankton, which are at the base of a large and complex marine ecosystem (see Ocean acidification: the other CO2 problem). That may also result in significant loss of biodiversity, possibly including important food species.
Note to the use of "could" and "possibly" here. The author has no facts and instead introduces fear, uncertainty, and doubt covering his ass by using indefinite terms.
Levelling off
Some have suggested that the increase in plant growth due to CO2 will be so great that it soaks up much of the extra CO2 from the burning of fossil fuels, significantly slowing climate change. But higher plant growth will only lock away CO2 if there is an accumulation of organic matter.
Author implies organic matter is bad for us.
Studies of past climate changes suggest the land and oceans start releasing more CO2 than they absorb as the planet warms.
Correct. As the recent ice age receeds the planet is warming up releasing co2. The latest IPCC report concludes that the terrestrial biosphere will become a source rather than a sink of carbon before the end of the century.
Correct. Carbon based life is a sink for carbon.
What's more, even if plant growth does rise overall, the direct and indirect effects of higher CO2 levels will be disastrous for biodiversity.
Oh that's funny. Success in some plants will be harmful to plants that preferred the ice age. ROFL true but funny as hell. We must bring back the ice age! ROFLBetween 20 to 30% of plant and animal species face extinction by the end of the century, according to the IPCC report.
Yes species die off and are replaced by new species all the time. See Darwin for a more detailed explanation.
As for food crops, the factors are more complex. The crops most widely used in the world for food in many cases depend on particular combinations of soil type, climate, moisture, weather patterns and the infrastructure of equipment, experience and distribution systems. If the climate warms so much that crops no longer thrive in their traditional settings, farming of some crops may be able to shift to adjacent areas, but others may not. Rich farmers and countries will be able to adapt more easily than poorer ones.
The author is saying more farmers will be more productive in more places, and somehow that is a negative against existing farmers in traditional spots. But yes prime growth areas change with weather patterns. This is obvious. The only thing constant with weather, is change.
Predicting the world's overall changes in food production in response to elevated CO2 is virtually impossible.
Correct. Global production is expected to rise until the increase in local average temperatures exceeds 3°C, but then start to fall.
Funny how he says virtually impossible then proceeds prognosticate... ROFLIn tropical and dry regions increases of just 1 to 2°C are expected to lead to falls in production. In marginal lands where water is the greatest constraint, which includes much of the developing world but also regions such as the western US, the losses may greatly exceed the gains.
Again note the suppositions outlined by the use of "may" and "expected." All FUD here.
