The expansion of cultivated areas, to the detriment of natural environments, is much greater than expected.  

According to a recent study using Landsat satellite data, the area of cultivated land worldwide, excluding grasslands and permanent crops, increased by 102 million hectares (9 million hectares) between 2000-03 and 2016-19, about three to four times more than FAO statistics suggest. This expansion has accelerated since the beginning of the 21st century, encroaching on forests and savannahs and increasing greenhouse gas emissions. Africa and South America are responsible for half and more than a third of the expansion of arable land, respectively. The increase in cultivated areas is even greater if orchards and shrub plants such as cocoa, coffee, and oil palm are included, posing a formidable challenge for preserving ecosystems and combating climate change.

A study by researchers from the Universities of Maryland and Texas and the National Polytechnic Institute of Mexico, recently published in Nature Food[1], sheds new light on the evolution of cultivated areas in recent decades. Using high-precision satellite data (resolution of 30 meters per pixel) provided by the Landsat program of the American space agency (NASA), it assesses the changes in the area dedicated to herbaceous plants, annual and perennial, intended for human and animal consumption or for energy production in different regions. The cultivated area, thus defined, increased from 1.14 billion hectares over the period 2000-03 to 1.24 billion hectares over the period 2016-19. This area is distributed relatively evenly between the Europe-North Asia regions on the one hand, and Southwest Asia on the other (20 % each), Africa (17 %), as well as Central and North America on the one hand, and Southeast Asia on the other (15 % each). This is followed by South America (9 %) and Oceania (3 %). The trends recorded in these different geographical areas are very contrasting.

Half of the expansion of cultivated land is due to Africa

In about twenty years, Africa has expanded its cultivated areas by more than a third, accounting for 52 % of the increase observed on a global scale. (painting)The increase was particularly rapid in a small group of countries (Angola, Ivory Coast, Democratic Republic of Congo, Mozambique, Zambia). In relative terms, however, it was in South America that the growth in areas was most sustained (+49 % in total, +77 % in Brazil); it explains 36 % of the overall increase. The decrease in areas observed in Southeast Asia (-1 %) may be surprising, but it is probably due to the fact that the definition of cultivated land used in the study excludes oil palm.

Expansion accelerates

The annual rate of expansion of cultivated areas has increased significantly over a dozen years, from 5.1 million hectares over the period 2004-2007 to 9 million over the period 2016-2019. In Africa, this rate has more than doubled, from 1.7 million to 3.9 million hectares per year, a level much higher than that observed in South America (1.5 million hectares). It is true that the recent acceleration of deforestation in the Amazon is beyond the time frame of the study.

A gross increase twice as strong

A major contribution of the study is the decomposition of the evolution clear cultivated areas, increasing and decreasing brutes. Gross area growth (217 million hectares) since the beginning of the 21st century has been more than twice as strong as net growth (102 million hectares). The ratio between gross and net increase in cultivated land is even much higher in some regions. (painting). However, it is the gross expansion of cultivated land that has the greatest impact on the climate and biodiversity.

Overall, nearly half of the gross increase in cultivated areas (79 billion in Africa) has occurred at the expense of natural vegetation, primarily forests. The other half comes from the cultivation of previously abandoned grasslands and farmland. Only 16 billion of the gross decrease in cultivated areas is due to their return to natural vegetation. Areas restored in this way store proportionally much less carbon and support much less biodiversity than areas that have not been cleared, because land restoration takes a long time to produce its full effects.

An underestimated phenomenon

According to the World Resources Institute, a US think tank, FAO statistics, the main official source of information on land use, tend to significantly underestimate the expansion of cultivated areas. In fact, these statistics show, between 2003 and 2018, an increase in arable land – a concept close to that of cultivated area used in the study – of 35 million hectares (3 %), three times lower than the 102 million hectares (9 %) highlighted by satellite data between the periods 2000-03 and 2016-19. The gap is even higher, around 1 to 4, if we compare the latter to the extension of arable land reported by the FAO between 2000 and 2019, i.e. 24 million hectares (2 %)[2].

The reasons for the discrepancy between FAO figures and satellite data are not entirely clear.[3]This appears to be due to methodological differences, but also probably results from the fact that UN statistics are based on declarations by States, which may have an interest in understating or overstating, as the case may be, the figures relating to changes in cultivated areas.

An ecological challenge

According to the FAO, the area planted with permanent crops, including cocoa, coffee, oil palm, etc., not included in the study, increased by 36 million hectares (27 %) between 2000 and 2019. If we add the extension of arable land, the total cultivated area would have increased by 63 million hectares according to the FAO and by around 138 million hectares if we use the figures from the study. These figures question the capacity of agriculture to produce more, to feed a rapidly growing world population, while reducing pressure on the climate and natural environments.

Assuming that current trends continue, particularly with regard to increases in yields and irrigated areas, FAO estimates the need for additional arable land between 2012 and 2050 at 165 million hectares (11 %)[4]The World Resources Institute, for its part, anticipates a comparable increase in all cultivated areas, including permanent crops, of 171 million hectares between 2010 and 2050. It should be noted that this is a net growth in areas, which implies, as indicated above, a much stronger gross growth in cultivated land, which varies greatly depending on the region.

The WRI also predicts an expansion of pastures by 401 million hectares, linked to the increased demand in most developing countries for dairy products and ruminant meat. In total, according to its estimates, the area used for crops and livestock could therefore increase by 572 million hectares between 2010 and 2050, or even 593 million hectares if the needs of aquaculture, which is also expanding, are included.[5]To avoid an ecological disaster, several levers will have to be used: transformation of agricultural production systems, modification of eating habits, reduction of losses and waste, etc., and public policies adapted accordingly. The diagnosis is known, the study published in Nature Food reinforces the urgency of action.