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Amazon Tipping Point
In the 1970s, Brazilian scientist Eneas Salati shattered
the long held dogma that vegetation is simply the
consequence of climate and has no influence on cli-
mate whatsoever (1). Using isotopic ratios of oxygen
in rainwater samples collected from the Atlantic to
the Peruvian border, he was able to demonstrate un-
equivocally that the Amazon generates approximately
half of its own rainfall by recycling moisture 5 to 6 times
as airmasses move from the Atlantic across the basin to
the west.
From the start, the demonstration of the hydrological
cycle of the Amazon raised the question of how much
deforestation would be required to cause the cycle to de-
grade to the point of being unable to support rain forest
ecosystems.
High levels of evaporation and transpiration that forests
produce throughout the year contribute to a wetter at-
mospheric boundary layer than would be the case with
non-forest.This surface-atmosphere coupling is more im-
portant where large-scale factors for rainfall formation
are weaker, such as in central and eastern Amazonia. Near
the Andes, the impact of at least modest deforestation is
less dramatic because the general ascending motion of
airmasses in this area induces high levels of rainfall in
addition to that expected from local evaporation and
transpiration.
Where might the tipping point be for deforestation-
generated degradation of the hydrological cycle? The
very first model to examine this question (2) showed that
at about 40% deforestation, central, southern and eastern
Amazonia would experience diminished rainfall and a
lengthier dry season, predicting a shift to savanna vegeta-
tion to the east.
Moisture from the Amazon is important to rainfall and
human wellbeing because it contributes to winter rainfall
for parts of the La Plata basin, especially southern Paraguay,
southern Brazil, Uruguay and central-eastern Argentina;
in other regions, the moisture passes over the area, but does
not precipitate out. Although the amount contributing
to rainfall in southeastern Brazil is smaller than in other
areas, even small amounts can be a welcome addition to
urban reservoirs.
The importance of Amazon moisture for Brazilian ag-
riculture south of the Amazon is complex but not trivial.
Perhaps most important is the partial contribution of dry
season Amazon evapotranspiration to rainfall in south-
eastern South America. Forests maintain an evapotranspira-
tion rate year-round, whereas evapotranspiration in pastures
is dramatically lower in the dry season. As a consequence,
models suggest a longer dry season after deforestation.
In recent decades, new forcing factors have impinged
on the hydrological cycle: climate change and widespread
use of fire to eliminate felled trees and clear weedy veg-
etation. Many studies show that in the absence of other
contributing factors, 4 degrees Celsius of global warming
would be the tipping point to degraded savannas in most
of the central, southern, and eastern Amazon. Widespread
use of fire leads to drying of surrounding forest and greater
vulnerability to fire in the subsequent year.
We believe that negative synergies between deforesta-
tion, climate change, and widespread use of fire indicate
a tipping point for the Amazon system to flip to non-
forest ecosystems in eastern, southern and central Amazonia
at 20-25% deforestation.
The severity of the droughts of 2005, 2010 and 2015-16
could well represent the first flickers of this ecological
tipping point. These events, together with the severe floods
of 2009, 2012 (and 2014 over SW Amazonia), suggest that
the whole system is oscillating. For the last two decades
the dry season over the southern and eastern Amazon
has been increasing. Large scale factors such as warmer
sea surface temperatures over the tropical North Atlantic
also seem to be associated with the changes on land.
We believe that the sensible course is not only to strictly
curb further deforestation, but also to build back a margin
of safety against the Amazon tipping point, by reducing
the deforested area to less than 20%, for the commonsense
reason that there is no point in discovering the precise
tipping point by tipping it. At the 2015 Paris Conference
of the Parties, Brazil committed to 12 million ha of re-
forestation by 2030. Much or most of this reforestation
should be in southern and eastern Amazonia. The hydro-
logical cycle of the Amazon is fundamental to human well-
being in Brazil and adjacent South America.
– Thomas E. Lovejoy and Carlos Nobre
REFERENCES
1. E. Salati, A. Dall ‘Ollio, E. Matsui, J. R. Gat, Recycling of Water in the Amazon,
Brazil: an isotopic study. Water Resour. Res. 15, 1250–1258 (1979).
2. G. Sampaio,C. A. Nobre, M. H. Costa, P. Satyamurty, B. S. Soares-Filho,
M. Cardoso, Regional climate change over eastern Amazonia caused by pasture
and soybean cropland expansion. Geophys. Res. Lett. 34, L17709 (2007).
10.1126/sciadv.aat2340
Citation: T. E. Lovejoy, C. Nobre, Amazon Tipping Point. Sci. Adv. 4, eaat2340 (2018).
Thomas E. Lovejoy is
University Professor
in the Department of
Environmental Science
and Policy at George
Mason University. Email:
tlovejoy@unfoundation.org
Carlos Nobre is a Member
of the Brazilian Academy
of Sciences and Senior
Fellow of World Resources
Institute Brazil.
on February 22, 2018http://advances.sciencemag.org/Downloaded from
Amazon Tipping Point
Thomas E. Lovejoy and Carlos Nobre
DOI: 10.1126/sciadv.aat2340
(2), eaat2340.4Sci Adv
ARTICLE TOOLS http://advances.sciencemag.org/content/4/2/eaat2340
REFERENCES http://advances.sciencemag.org/content/4/2/eaat2340#BIBL
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... This imagined story draws on news reports regarding the 2017-18 drought (e.g., AP 2018) and Lovejoy and Nobre (2018). ...
... Just a few years ago, it was thought that this tipping point would be reached at a deforestation level of 40 percent of the Amazon Rainforest. n However, in light of the "negative synergies between deforestation, climate change, and widespread use of fire," scientists warn that the tipping point is likely closer to the loss of 20-25 percent of total forest area (Lovejoy and Nobre 2018). o The region has already been 18 percent deforested, p and 2021 saw the highest annual rate of deforestation in a decade in the Brazilian Amazon. ...
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... ureia). Além disso, a mudança no uso da terra causada pela conversão de florestas em agricultura ou pecuária afeta as propriedades físicas e biológicas da superfície terrestre, com impacto potencial no clima regional e global (Lovejoy;Nobre, 2018). ...
... ureia). Além disso, a mudança no uso da terra causada pela conversão de florestas em agricultura ou pecuária afeta as propriedades físicas e biológicas da superfície terrestre, com impacto potencial no clima regional e global (Lovejoy;Nobre, 2018). ...
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... The tipping point percentage has trended down over time due to the anticipated impacts of increasing thermal stress and reduced resilience (Boulton, Lenton, and Boers 2021;IPCC 2014;Lenton et al. 2008). A recent estimate puts it as low as 20 percent, worrisome given 16 percent of the Amazonian forest has already given way to fields and pastures, or 20 percent of Brazil's portion (Lovejoy and Nobre 2018;Walker et al. 2019). Recent analyses suggest that regional climate changes already underway will independently trigger extensive forest loss just past mid-century (Walker 2020). ...
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... If they are reduced sufficiently, remaining forests may become drier and more prone to fire and disease. In the Amazon, this process is expected to become irreversible once 20-40 percent of its forests have been cleared [136][137][138]. The lower end of this threshold range has already been crossed, and deforestation is accelerating [139]. ...
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... Negative synergies between deforestation, widespread use of fire, and climate change suggest that Amazonia is heading toward irreversible ecosystem change (Lovejoy and Nobre, 2018;Boulton et al., 2022). Amazonia is losing globally important ecosystem services (Levis et al., 2020), directly affecting human communities that depend on forest resources. ...
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... Deforestation can accentuate the environmental temperature increase in the Amazon. According to Lovejoy and Nobre (2018), when the level of deforestation reaches between 20% and 40% (17% is the current level) forest systems will be able to recover (tipping point) which will cause a significant increase in the biome temperature and therefore drive many organisms to the limit of their thermal tolerance. And of course, the current high rates of deforestation ( Jaff e et al., 2021) cause a loss of carbon sinking capacity which results in a vicious circle making the whole system even hotter. ...
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The Amazon has a rich history of tectonic and climatic effects that have given rise to vast, complex and dynamic interconnected landscapes. The dynamics of the system can be observed today by the oscillation of river water levels, variations in oxygen levels, pH and temperature, and the biological diversity that exists in the different systems throughout the year. This continuous environmental diversity has contributed to the emergence of a rich ichthyofauna that has developed a vast set of adaptations at all levels of biological organization to cope with the continuous environmental challenges of the biome. However, the environmental structure that was formed over some 65 million years, i.e., since the beginning of the Andes uplift, is today confronted with many challenges of a, shall we say, new era—the Anthropocene. These challenges include metal pollution, urban pollution, pesticides, oil, hydroelectric construction, and, most importantly, the effects of climate change. Many of the evolutionary adaptations incorporated by fish are not sufficient to neutralize the effects of these new challenges, many of which have synergistic effects with each other or with the natural challenges that occur in the Amazon (hypoxia, low pH, low ionic availability, naturally warmer waters). Thus, it is important that we can anticipate the responses of Amazonian fishes to the challenges imposed by their environments in order to better manage the Amazon rainforest.
... The thresholds that could lead the BGI to its tipping point are not known (REYER et al., 2015). For the Amazon, for example, Lovejoy and Nobre (2018) affirm that 20 to 25% of deforestation would destabilize the Biome. All of Piauí's municipalities already have a higher rate than 25% of other land covers besides the BGI, which should be a point of concern for the territorial and environmental planning of the state. ...
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Chapter
Exponential increases in various human activities in the Anthropocene era are indicated to have led to rapid alteration in the environment such as climate change and ecosystem impairment. Scientists are seriously discussing the planetary health and threshold for climate stabilization and for safe human life. Food system including agriculture is one of major drivers to climate change, and at the same time, climate change has significant impacts on human health through food system. This chapter discusses various impacts of climate change as most pressing food safety challenges at present and in the near future. Temperature rise is increasing chance of people to be exposed to foodborne hazards, and multiple pathways are demonstrated to mediate climate change and increasing adverse health impact through food safety. Evidence-based food safety risk management is necessary, and inter- and trans-disciplinary researches with cross-sectorial collaboration should be promoted to address these challenges.
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This Report provides a comprehensive, objective, open, transparent, systematic, and rigorous scientific assessment of the state of the Amazon’s ecosystems, current trends, and their implications for the long-term well-being of the region, as well as opportunities and policy relevant options for conservation and sustainable development.
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Received 7 May 2007; revised 7 August 2007; accepted 9 August 2007; published 13 September 2007. (1) Field observations and numerical studies revealed that large scale deforestation in Amazonia could alter the regional climate significantly, projecting a warmer and somewhat drier post-deforestation climate. In this study we employed the CPTEC-INPE AGCM to assess the effects of Amazonian deforestation on the regional climate, using simulated land cover maps from a business-as-usual scenario of future deforestation in which the rainforest was gradually replaced by degraded pasture or by soybean cropland. The results for eastern Amazonia, where changes in land cover are expected to be larger, show increase in near-surface air temperature, and decrease in evapotranspiration and precipitation, which occurs mainly during the dry season. The relationship between precipitation and deforestation shows an accelerating decrease of rainfall for increasing deforestation for both classes of land use conversions. Continued expansion of cropland in Amazonia is possible and may have important consequences for the sustainability of the region's remaining natural vegetation. Citation: Sampaio, G., C. Nobre, M. H. Costa, P. Satyamurty, B. S. Soares-Filho, and M. Cardoso (2007), Regional climate change over eastern Amazonia caused by pasture and soybean cropland expansion, Geophys. Res. Lett., 34, L17709,
  • T E Lovejoy
  • C Nobre
Citation: T. E. Lovejoy, C. Nobre, Amazon Tipping Point. Sci. Adv. 4, eaat2340 (2018).
Recycling of Water in the Amazon, Brazil: an isotopic study
  • E Salati
  • A Ollio
  • E Matsui
  • J R Gat
  • Salati E.