Human impact on South America expanded by 60% since 1985 - Mongabay.com

• Humanity’s impact on South American ecosystems expanded by 268 million hectares (1 million square miles) — an area of land the size of Kazakhstan or Argentina — since 1985, finds an analysis published in Science Advances.
• Using satellite imagery to detect change in land cover, a team of researchers from the University of Maryland and other institutions found that 713 million hectares (2.75 million square miles), or 40% of South America’s landmass, had been impacted by human activity by 2018.
• The study found that the area of natural tree cover in the region decreased by 16% during the period, whereas pasture use rose 23%, cropland use 160%, and plantation extent 288%. Conversion to cattle pasture accounted for the largest share of natural tree cover loss in the region.

Humanity’s impact on South American ecosystems expanded by 268 million hectares (1 million square miles) since 1985 as vast swathes of forest and grassland were converted for agricultural use, disturbed by logging or infrastructure, or urbanized, finds an analysis published in Science Advances.  

Using satellite imagery to detect change in land cover, a team of researchers from the University of Maryland and other institutions found that 713 million hectares (2.75 million square miles), or 40% of South America’s landmass, had been impacted by human activity by 2018. That area represents a 60% increase relative to the extent of impact in 1985.

“Nearly one-fifth of the South American continent underwent some type of land cover/land use change over our study period,” the authors, led by the University of Maryland’s Viviana Zalles, wrote. “The single most significant land change dynamic was the conversion of intact and degraded natural tree cover.”

Human impact across South American regions categorized by degree of modification or conversion and the intensity of land use and natural land cover type. “Pan-Amazon” includes the combined area of Colombia, Venezuela, Peru, Bolivia, Ecuador, Suriname, French Guiana, and Guyana and excludes Brazil. Lower insert shows percent increase over the study period for all human impact classes and for land cover/use change classes only (“seminatural land and secondary forest” and “land use” categories, excluding tree cover degradation dynamics). Image credit: Zalles et al 2021

The region’s tropical rainforests were the most affected.

“The tropical rainforest ecozone, which is primarily made up of the Amazon rainforest, experienced an increase in human impact on natural land of 134%,” the authors wrote. The largest relative increase occurred in the Amazon outside of Brazil, where human impact increased by 174%.

The study found that the area of natural tree cover in the region decreased by 16% during the period, whereas pasture use rose 23%, cropland use 160%, and plantation extent 288%. Conversion to cattle pasture accounted for the largest share of natural tree cover loss in the region.

“In South America, the most extensive human impact on land was the conversion of natural vegetation into pastureland.”

Intensive land uses include built-up area, settlements, cropland, pasture, and forestry and tree plantations. Image credit: Zalles et al 2021

Land cover/land use trends of cropland, pasture, and tree cover area for (A) the continent, (B) administrative regions, and (C) ecozones. The shaded area corresponds to 1 SE of the estimate. Note that the upper bounds of the charts for crop, pasture, and tree cover vary. All vertical axes are in million hectares. Image credit: Zalles et al 2021

The research also identified 55 million hectares of “disturbed natural land cover” that had “no discernable land use”, indicated that it had been degraded but wasn’t economically productive, suggesting such lands could be utilized to increase food or fiber production, or used for ecosystem restoration or allowed to regenerate naturally. Indeed, the study found evidence of natural tree regrowth on nearly 38 million hectares of land.

“Changes in land cover have important consequences to climate at regional and global scales by altering fluxes of energy, water, and greenhouse gas emissions,” wrote the researchers. “Given these threats, results here are a clarion call to improved land use policy formulation, implementation, and enforcement.”

Citation

Viviana Zalles, Matthew C. Hansen, Peter V. Potapov, Diana Parker, Stephen V. Stehman, Amy H. Pickens, Leandro Leal Parente, Laerte G. Ferreira, Xiao-Peng Song, Andres Hernandez-Serna and Indrani Kommareddy. Rapid expansion of human impact on natural land in South America since 1985. Science Advances 02 Apr 2021: Vol. 7, no. 14, eabg1620 DOI: 10.1126/sciadv.abg1620

Header image: Deforestation in Novo Progresso in the state of Para, Brazil. Image credit: Microsoft Zoom.

Cattle Pasture, Cattle Ranching, Deforestation, Drivers Of Deforestation, Environment, Forests, Land Use Change, Pasture, Rainforests, Remote Sensing, Research Briefs

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