Talks

Why our blue planet is getting greener

 By Nicholas Newman

Most people would be surprised to learn that the earth is now greener than the 1980s…

This is the surprising finding revealed in a paper, China and India lead in greening of the world through land-use management”, published in the February 2019 edition of Nature Sustainability by Chi Chen, graduate researcher, and Boston University professor Ranga Myneni. Their analysis of NASA’s Terra and Aqua satellite images 2000-2017, taken each day since the 1980s, reveals that leaf coverage has increased by 2.3 percent in each decade of surveillance. This translates into an additional five and a half million more square kilometres of leaf coverage over two decades—a substantial increase in the earth’s natural carbon capture and storage system—largely provided by humans. In addition, they looked for changes in land-use patterns in plant-covered regions, particularly the depletion of the rainforest in favour of cattle ranching in Brazil, and the impact of anti-desertification efforts in Africa, as well as reforestation and intensified agriculture efforts in China, India and Jordan. Their study, based on data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS), an advanced satellite imaging analysis technology, concludes that not all vegetation is equal when it comes to their ability to absorb carbon.

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Greening of China and India (NASA)

Where are the changes?

While 5% of the world is browning due to the destruction of rainforests in eastern Brazil and Indonesia, overall some 30% of the world’s landscape is becoming greener. The world’s two most populous countries, China and India, are leading this trend, most notably by expansion and intensification of agriculture to feed their growing populations and by a massive tree-planting program in China. According to Chi Chen, “China and India account for one-third of the greening, but contain only 9% of the planet’s land area covered in vegetation”. The findings are surprising, he adds, specifically, “considering the general notion of land degradation in populous countries from over-exploitation”.

Drivers of change

The greening of the planet owes much to the “fertilization effect”, which is caused by an increase in burning of fossil fuels that increase the CO2 in the atmosphere. The result is a boosted process of photosynthesis, provided there is sufficient water, light and nutrients, which in turn allows plants to absorb more gas. This stimulates production of new leaves. Humans are also contributing to increased greening by planting crops and trees. Reforestation is another leading cause of the increase in global vegetation, most notably in China and Africa.

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OISCA Reforestation Project in Guiyang, Guizhou - Community and Human Resource Development through capacity building, agriculture and environmental conservation and restoration (oisca-international.org)

The greening of China is largely due to an increase in forest planting programs (42%) and an expansion of agriculture (32%). In contrast, the reverse is true in India as agriculture contributes the lion’s share of greening at 82%; tree planting accounts for just 4.4%. In both countries, food productivity has risen since 2000 thanks to the modernisation of farming, which has facilitated multiple crop harvests from the same piece of land aided by increased mechanisation, application of fertilizers and better irrigation.

 Not all plants are equal

In terms of carbon absorption, trees are more effective than farmed crops, which is confirmed by a number of other research findings that show trees not only absorb more carbon but for a long period of time. Conversely, crops hold carbon for a short period before releasing it back into the atmosphere. The value of trees as natural carbon storage systems is widely recognised, so much so that China’s Three-North Shelter Forest Program, which began in 1978 and is estimated for completion in the mid-century when it will be 4,500 kilometres (2,800 miles) long, will not only protect major cities from the expansion of the Gobi Desert but also deserves environmental plaudits.

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Africa’s Great Green Wall, or more formally The Great Green Wall for the Sahara and the Sahel Initiative, is the intriguing but misleading name of an enormously ambitious and worthwhile initiative to improve life and resilience in the drylands that surround the Sahara (IFRC, Flickr)

Since 2007, tree planting has taken off in Africa with the Green Great Wall planting program, which runs along the Sahel region from Senegal in the east of Africa to Djibouti in the west. As part of this program, Nigeria has restored approximately 12 million acres of degraded land; Ethiopia has reclaimed 37 million acres.

The value of trees

Studies have shown that reforestation in Europe and elsewhere have been an important means of reducing carbon emissions while also reducing the environmental damage such as floods from heavy rainfall. In the absence of trees, rainwater runs off the soil into rivers and streams and raises the water level. Trees help to keep soil in place and their roots absorb the water. However, it is as carbon sequesters that trees are proving most valuable.
Research suggests that covering 900m hectares of land—roughly the size of the continental US—with trees could capture and store about two-thirds of the carbon that humans have already put into the atmosphere, or up to about 205 billion tons. According to a reports, this might even be a conservative estimate. A Science study, “The global tree restoration potential,” shows that the world could support reforestation of some 3.5 million square miles, which could remove 750 billion tons of CO2, enough to fix the climate.

Mankind is invaluable to the greening of the planet

The Boston University team concluded that human land use is a “key driver of the ‘Greening Earth,’ accounting for over one-third of the observed net increase in green leaf area”. This finding is supported by Ramakrishna Nemani, senior earth scientist at NASA Ames Research Centre, who notes that “when the greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilization from the added carbon dioxide in the atmosphere. Now with the MODIS data, we see that humans are also contributing”. The researchers recommend that future earth system models should include “crop rotation, irrigation and fertilizer use, fallowing and abandonment of land, afforestation, reforestation and deforestation—all of which influence atmospheric carbon in different ways”.

READ MORE: Reforestation around the world by Thomas Schueneman

about the author
Nicholas Newman
Freelance energy journalist and copywriter who regularly writes for AFRELEC, Economist, Energy World, EER, Petroleum Review, PGJ, E&P, Oil Review Africa, Oil Review Middle East. Shale Gas Guide. https://nicholasnewman.contently.com/