by Richard Gray
25 April 2016

from DailyMail Website
 

Scientists used satellite data over the past 33 years to measure leaf cover.
Planet has got greener as plants have flourished in rising carbon dioxide.
Additional plant growth is equivalent to covering the US twice in greenery.
Rising carbon dioxide is responsible for 70 per cent of the extra greening.

 

 

Extra Plant Growth Caused by Greenhouse Gases

Could Cover the USA Twice

The pumping of excessive carbon dioxide into the atmosphere has widely been presented as setting our planet on a path towards disaster.

But a new study has revealed rising levels of the greenhouse gas due to humanity's actions is actually having a surprising side-effect - it is making the Earth greener.

Satellite data gathered over 33 years has shown there has been a 'persistent and widespread increase' in the growing season of plants.

 

The Earth is getting greener

with rising carbon dioxide levels,

researchers have revealed.

They found over the past 33 years,

leaf cover around more than half of the vegetated area

of the world has increased.

They say the extra greenery is equivalent

to covering the USA twice with plants
 

Scientists say up to half of the world's vegetated areas are now showing signs of increased leaf cover, with the majority caused by extra carbon dioxide in the atmosphere.

They added that the extra greening that has occurred in the past 33 years is equivalent to adding a green continent twice the size of mainland USA - around 6.95 million square miles.
 

HOW PLANTS USE CARBON DIOXIDE TO HELP THEM GROW

Plants use a process known as photosynthesis to trap carbon dioxide from the air within their tissues. They do this using the energy of the sun to combine carbon dioxide with water to produce sugars that form their tissues.

With increased levels of carbon dioxide and sufficient sunlight, plants can grow faster and bigger.

However, when carbon dioxide levels get too high it can become toxic to plants.

Professor Ranga Myneni, an earth scientist at Boston University who led the study, told MailOnline, however, this effect is unlikely to continue for ever.

He said while the additional plant growth was helping to soak up some of extra carbon being emitted into the atmosphere by human activity, it may start slowing down.

He said:

'Currently, about a quarter of the 10 billion tons of carbon that we emit in to the air each year, are being stored in the body of trees and in the soils.

'We do not know how long this will continue. This storage we do know is temporary. Experiments have shown that the CO² fertilization effect is temporary.

'The plants ultimately adjust to the higher levels of CO² in the air.'

The researchers used data from the Nasa-Modis and National Oceanic and Atmospheric Administration AVHRR satellite sensors from the past 33 years.

They used this to construct computer models to mimic the plant growth observed in the satellite data.

Around 85 per cent of the ice-free land on the Earth's surface is covered by vegetation. The area of all greenery on the Earth is equal to around 32 per cent of the entire surface of the Earth.
 

The scientists found much of the extra greening

due to rising carbon dioxide levels is occurring

around the tropics where large expanses

of tropical rainforest (pictured) can be found




The researchers used satellite data

to study how leaf cover has changed

around the world over the past 33 years.

They found many areas have seen a

dramatic increase in the amount of leaf cover

(illustrated above)

 

Dr Zaichun Zhu, a researcher at Peking University who also took part in the study, said:

'The greening over the past 33 years reported in this study is equivalent to adding a green continent about two-times the size of mainland USA and has the ability to fundamentally change the cycling of water and carbon in the climate system.'

Humans are thought to be emitting around 10 billion tons of carbon into the atmosphere every year.

Plants use carbon dioxide as part of the photosynthesis process to produce sugars by combining the gas with water using energy from sunlight. These sugars form much of the structures in plants and ultimately provide a valuable food source to animals.

The researchers, whose work (Greening of the Earth and Its Drivers) is published in the journal Nature Climate Change, say their findings are consistent with other studies that show how elevated carbon dioxide can increase plant growth.

They found that,

• carbon dioxide fertilization, as the effect is known, is responsible for 70 per cent of the observed greening trend

• nine per cent of the increased greening was due to extra nitrogen in the soil

• eight per cent was due to climate change

• four per cent of the greening was due to land cover change

The impacts of increased carbon dioxide was most prevalent over the tropics, where many of the large expanse of rainforest can be found. Climate change was responsible for additional greening mainly in higher latitudes where ice is melting and on the Tibetan Plateau.

However, they found the relationship between rising carbon dioxide levels and the increase in greening is complex rather than a simple correlation.

 

The researchers said there had been an increase

in the growing season in various parts of the world,

with up to 50 per cent of the vegetated area of the Earth's surface

benefiting from increased carbon dioxide (illustrated)

 

The results are likely to be seized upon by climate change skeptics who claim increasing carbon dioxide levels will not cause the levels of global warming predicted by many scientists.

However, the researchers behind the new study (Greening of the Earth and Its Drivers) said the impact of plants in reducing global warming in recent years by moping up carbon dioxide may now start to decrease.

Dr Philippe Ciais, another co-author of the study and associate director of the Laboratory of Climate and Environmental Sciences at Gif-suv-Yvette in France, said:

'The fallacy of the contrarian argument is two-fold.

'First, the many negative aspects of climate change, namely global warming, rising sea levels, melting glaciers and sea ice, more severe tropical storms, etc. are not acknowledged.

'Second, studies have shown that plants acclimatize, or adjust, to rising CO² concentration and the fertilization effect diminishes over time.'