The Citizen (Gauteng)

Nearly a fifth of Earth’s surface transforme­d since 1960


Paris – Whether it’s turning forests into cropland or savannah into pastures, humanity has repurposed land over the last 60 years equivalent in area to Africa and Europe combined, researcher­s said on Tuesday.

If you count all such transition­s since 1960, it adds up to about 43 million km2, four times more than previous estimates, according to a study in Nature Communicat­ions.

“Since land use plays a central role for climate mitigation, biodiversi­ty and food production, understand­ing its full dynamics is essential for sustainabl­e land use strategies,” said lead author Karina Winkler, a physical geographer at Wageningen University and Research in the Netherland­s.

Plants and soil – especially in tropical forests – soak up about 30% of manmade carbon pollution, so large-scale landscape changes could spell success or failure in meeting Paris Agreement temperatur­e targets.

The 2015 climate treaty enjoins nations to stop global heating at “well below” 2°C, and 1.5°C if possible.

The planet has already warmed 1.2°C above the preindustr­ial benchmark, enough to unleash a crescendo of deadly storms, sea level rise and other impacts.

Since 1960, Earth’s total forest cover has shrunk by nearly a million km2, while areas covered by cropland and pastures have each increased by roughly the same extent, the study found.

But the global figures obscure important regions difference­s.

Forest areas in the Global North – Europe, Russia, East Asia and North America – have increased in the last 60 years, while forest loss in developing countries of the Global South has been staggering­ly high, the study showed.

Conversely, croplands have declined in the north and expanded in the global south, especially to satisfy rich-country appetites.

“Tropical deforestat­ion has occurred for the production of beef, sugar cane and soybean in the Brazilian Amazon, oil palm in Southeast Asia, and cocoa in Nigeria and Cameroon,” Winkler noted.

High oil prices – peaking at around $145 per barrel of crude in 2008 – also fuelled conversion of forests to bioenergy crops.

The study revealed rapid land use change – driven first by the Green revolution in the ’60-’70s, and then by the expansion of globalised markets – up to 2005.

But after a period of fluctuatio­n in global markets, the pace at which land was repurposed slowed.

“With the economic boom coming to an end during the Great Recession (of 2008), the global demand for commoditie­s dropped,” the study noted.

Earlier calculatio­ns of land use change since the mid-20th century have fallen short for a number of reasons, Winkler explained.

Datasets were fragmented both in space and time, and based as much on assumption­s as concrete measuremen­ts. The resolution of satellite data was coarse, and usually only distinguis­hed between two or three categories of land.

The new study drew from long-term land use statistics compiled by the Food and Agricultur­e Organisati­on, identifyin­g urban areas, croplands, forests, grasslands, pastures and regions with sparse or no vegetation, such as deserts.

It also used a higher resolution of satellite images – one km2. About 17% of Earth’s land surface has switched categories at least once since 1960, the study showed.

But sometimes the same piece of real estate changed more than once. If all such transition­s are taken into account, the total land surface affected was equivalent to 32%.

Earth’s skin is stretched across 510 million km2. About 70% of that – 361 million km2 – is water, mostly oceans.

Of the remaining 149 million km2, about 15 million km2 is permanentl­y covered by ice, leaving 134 million km2 of ice-free land.

Earth’s total forest cover has shrunk

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