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Study Finds Plant Growth Surges as CO2 Levels Rise

By Tim Radford, Climate News Network

LONDON – Australian scientists have solved one piece of the climate puzzle. They have confirmed the long-debated fertilization effect.

Plants build their tissues by using photosynthesis to take carbon from the air around them. So more carbon dioxide should mean more vigorous plant growth – though until now this has been very difficult to prove.

Arid areas could be transformed by green plants as carbon dioxide levels rise.
Credit: Samat Jain

Randall Donohue of the Commonwealth Scientific and Industrial Organization in Canberra, Australia, and his colleagues developed a mathematical model to predict the extent of this carbon dioxide fertilization effect.

Between 1982 and 2010, carbon dioxide levels in the atmosphere increased by 14 percent. So, their model suggested, foliage worldwide should have increased by between 5 and 10 percent.

Measuring uncertainties

It is one thing to predict an effect, quite another to prove it. Satellite observations can and successfully do measure seasonal changes in vegetation, the growth of deserts, the change from open prairie to savannah, the growth of new trees in the tundra and so on, but it’s very difficult to be sure that these changes have anything to do with carbon dioxide fertilization: changes in temperature and rainfall patterns would also have an impact.

Also, some regions – tropical rainforests, for example – are already completely covered by forest canopy: orbiting satellites are unlikely to measure much change there.

Donohue and his team, in a study appearing in Geophysical Research Letters, the journal of the American Geophysical Union, looked at those regions where leaf cover really would stand out, and where carbon dioxide fertilization would be the best explanation for new growth.

These were the warm, dry places: while the researchers focused on changes in arid regions in North America’s south-west, Australia’s Outback, the Middle East and parts of Africa, they also had to find a technique that allowed for natural seasonal and cyclic changes, alterations in land use and so on.

They calculated that in these conditions, plants would make more leaves if they had the water to do so. “A leaf can extract more carbon from the air during photosynthesis, or lose less water to the air during photosynthesis, or both, due to elevated CO2,” says Donohue. That is the CO2 fertilization effect.

More carbon dioxide should mean more vigorous plant growth – though until now this has been very difficult to prove.
Credit: flickr/Phuong Tran

Calculating greenness

The team averaged the greenness of each location over three year periods, and then grouped the greenness data from different locations according to known records of rainfall. They also looked at variations in foliage over a 20 year period. In the end, they teased out the carbon dioxide fertilization effect from all other influences and calculated that this could account for an 11 percent increase in global foliage since 1982.

This is what’s called negative feedback with at least some of the increasing levels of carbon dioxide being absorbed by extra plant growth. It could also be good news for biodiversity, and good news for food security: plants are the primary producers that feed all animals.

Trees are likely to invade grasslands in the drier regions, and their deep roots are better equipped to tap groundwater and at the same time stabilize the soils.

“Even if nothing else in the climate changes as global CO2 levels rise, we will still see significant environmental changes because of the CO2 fertilization effect,” says Dr. Donohue.

Tim Radford is a reporter for Climate News Network. Climate News Network is a news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.


By Roger Bird (Colorado Springs, CO, USA)
on June 9th, 2013

Too bad human beings won’t be contributing to the rise in CO2 levels soon.  Cold fusion or LENR and Rossi’s E-Cat have been proven to be real.  It is getting close to becoming a commercial product.  Check out these websites:

Check out what this Nobel Prize winner has to say about LENR.

Elforsk (Swedish for “Electricity Research”) happily admits on their site that they paid for the tests and are happy with the results.

And this site gives an excellent round up:

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By Richard Arndt (Springfield OR 97477)
on October 2nd, 2014

When cold fusion is released to the public we can rejoice. Until then mankind is releasing CO2 and CH4 into the atmosphere at alarming rates.

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By Philip Haddad (Alvin, TX 77511)
on June 10th, 2013

It is unfortunate that the Kyoto “scientists” did not even mention the fact that when fossil fuels are burned (primarily for their heat content) CO2 is a by-product that can alert us to the fact that heat is being produced, not only by fossil fuels, but also from nuclear power. Yes,nuclear power produces twice as much total heat as its electrical output.. It is heat, not CO2 that is responsible for the melting of about one trillion tons of glaciers annually. It will not matter that nuclear is CO2-free . Equally ridiculous is the notion that environmental damage can be equated or predicted by the artificial “carbon sensitivity” numbers. Glaciers are melting but the rise in temperature is minimal due to the cooling that is obtained from the melting as well as that from photosynthesis whereby 5000 btus of solar energy are removed for each pound of CO2 converted . Were it not for this cooling, atmospheric temperature would rise almost 0.2*F annually. Present energy consumption exceeds 16 terrawatts. That is 50x10E16 btus per year emitted into an environment whose atmosphere has a mass of 1166 x10E16 pounds. Where else can this heat go? Doesn’t the greenhouse gas retard the escape of this energy as well as that from solar radiation? Does the increase in CO2 add or lose heat ( increased greenhouse vs increased photosynthesis)?

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By karlos (perth/WA/Australia)
on January 15th, 2014

the burning of coal is rectifying the depletion of CO2 from the atmosphere caused by plants across the millennia
an explanation can be found here: - plants evolved under far higher levels of CO2, but they removed a lot of it and over time this has accumulated and fossilized into coal - by burning the coal we are just returning it from whence it came..  Had the plants continued to plunder the air without humans digging up and burning the coal the trend may have continued and plants may have dropped the CO2 levels down to 200ppm - and at 200ppm, C3 photosynthesizing plants (97% of plant life) die.

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By Richard Arndt (Springfield OR 97477)
on October 2nd, 2014

So by your statement you acknowledge that CO2 emissions are increasing due to human activity. Indeed plants did evolve under much different circumstances several million years ago.  The carboniferous period produced most of the coal we extract from the earth today. The geologic record doesnt dispute this claim. However that was several hundred million years ago and Earth’s ecology looked much different. Evolution is a slow process. The rate in which mankind is changing our current environment is so out of balance with time that entire species are put into peril. Organisms may well go extinct in the next 40-100 years causing who knows what repercussions through the life cycle. One example is the current effect on sea plankton.

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By Grady (Zapata TX 78076)
on July 1st, 2014

So if the planet is warming and seas are rising (getting a larger surface area) then the natural result is MORE precipitation. That means the replenishment of the ice caps, glaciers, deserts turning to tropical forests as the Sahara once was, etc.

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By Richard Arndt (Springfield OR 97477)
on October 2nd, 2014

There indeed has been more precipitation over the last 40 years. The problem is that hydrogen in its gaseous form is an indirect greenhouse gas. So more hydrogen in the atmosphere means even higher temperatures which leads to more melting. Which leads to more precipitation etc…

This however is not really the problem.  The problem is albedo. Ice reflects the suns ray much more efficiently than water. Water absorbs more of the suns rays than ice causing the earth to absorb more heat. Which leads to more melting etc…

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