In:
Science, American Association for the Advancement of Science (AAAS), Vol. 379, No. 6630 ( 2023-01-27)
Abstract:
The Amazon is a critical component of the Earth climate system whose fate is embedded within that of the larger planetary emergency. The Amazon is the most species-rich subcontinental-scale ecosystem and is home to more than 10% of all named plant and vertebrate species, concentrated into just 0.5% of Earth’s surface area. The Amazon rainforest is also a critical component of the Earth climate system, contributing about 16% of all terrestrial photosynthetic productivity and strongly regulating global carbon and water cycles. Amazonian ecosystems are being rapidly degraded by human industrial activities. A cumulative total of 17% of the original forest have already been cleared, and 14% replaced, by agricultural land use. After millions of years serving as an immense global carbon pool, under further warming the Amazon rainforest is predicted to become a net carbon source to the atmosphere. Some regions have already made the transition, with forest respiration and burning outpacing forest photosynthesis. ADVANCES In this Review, we compare rates of anthropogenic and natural environmental changes in the Amazon and South America and in the larger Earth system. We focus on deforestation and carbon cycles because of their critical roles on the Amazon and Earth systems. Data for South America were compiled for the Science Panel for the Amazon (SPA) Assessment Report, which details the many dimensions of the Amazon as a regional entity of the Earth system. The SPA report, coauthored by 240 scientists from 20 countries, documents epoch-scale transformations in Amazonian biodiversity, ecosystem function, and cultural diversity. We found that rates of anthropogenic processes that affect Amazonian ecosystems are up to hundreds to thousands of times faster than other natural climatic and geological phenomena. These anthropogenic changes reach the scale of millions of square kilometers within just decades to centuries, as compared with millions to tens of millions of years for evolutionary, climatic, and geological processes. The main drivers of Amazonian habitat destruction and degradation are land-use changes (such as land clearing, wildfires, and soil erosion), water-use changes (such as damming and fragmenting rivers and increased sedimentation from deforestation), and aridification from global climate change. Additional important threats come from overhunting and overfishing, introduction of invasive exotic species, and pollution from the mining of minerals and hydrocarbons. OUTLOOK Given the outsized role of the Amazon in our planetary hydrological cycle, large-scale deforestation of this region is expected to push the whole Earth system across a critical threshold to a qualitatively different global climate regime. Quite aside from biodiversity losses, such a transformation will have multifarious and catastrophic consequences for human welfare, including widespread water and food insecurity that will lead to mass migrations and political instability. The key message is that Amazonian environments are being degraded by human industrial activities at a pace far above anything previously known, imperiling its vast biodiversity reserves and globally important ecosystem services. The Amazon is now perched to transition rapidly from a largely forested to a nonforested landscape, and the changes are happening much too rapidly for Amazonian species, peoples, and ecosystems to respond adaptively. Policies to prevent the worst outcomes are known and must be enacted immediately. We now need political will and leadership to act on this information. To fail the Amazon is to fail the biosphere, and we fail to act at our peril. Amazon deforestation is accelerating from a combination of anthropogenic drivers, including drier climatic conditions and policies that favor industrialized agriculture. (Top left) Map of Amazon showing location of wildfires, 1985 to 2021. (Right) Recently burned primary forest near Rurópolis, State of Pará, Brazil, 17 September 2020. (Bottom left) Rate of deforestation in the Brazilian Amazon is now rising rapidly under environmental policies of the Bolsonaro administration. After millions of years serving as an immense global carbon pool, the Amazon rainforest is becoming a net carbon source to the atmosphere. CREDITS: (MAP) ESRI, GARMIN-GEBCO, NOAA NGDC; (PHOTO) MARIZILDA CRUPPE/AMAZONIA REAL
Type of Medium:
Online Resource
ISSN:
0036-8075
,
1095-9203
DOI:
10.1126/science.abo5003
Language:
English
Publisher:
American Association for the Advancement of Science (AAAS)
Publication Date:
2023
detail.hit.zdb_id:
128410-1
detail.hit.zdb_id:
2066996-3
detail.hit.zdb_id:
2060783-0
SSG:
11
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