The climate of much of the southeastern Amazon has gone into irreversible collapse and the remaining forest is dying from the heat and drought. The Amazon as a whole is now emitting more carbon than it is taking up as fires rage and trees die under the mismanagement of Brazil’s far right president Jair Bolsanaro. Carbon emissions are greater than uptake not counting the CO2 emissions from fires because the climate in southeast Amazonia is warming and drying, killing the remaining forest. The forest cooled and humidified this region, but it crossed a tipping point when over 30% of the trees were cut and burned. Past the tipping point of 30% deforestation the climate is not capable of supporting forest because it is too hot and dry.
The forest was cut and burned to make way for soybean farming, but additional acreage is being developed at a loss to existing acreage as the Amazon’s climate collapses. The hotter, dryer conditions that follow the loss of forest result in each new acre turned over to farming causing a net loss of soybean production overall.
The whole of the Amazon rainforest is not yet lost. Large areas of forest are still intact in the northwestern half of the Amazon and the climate is still wet enough to support trees. Maintaining the remaining intact forest is the key to preserving the huge natural water pump that stabilizes rainfall patterns and the flow of the Amazon’s rivers. Apart from the global benefit of capturing carbon, the trees provide a net benefit to Brazil by cooling the climate and maintaining stable river flows. In a warming and drying climate there is no going back to rainforest once the critical number of trees is lost. The climate will be permanently warmer and dryer supporting grass, not forest and permanent drought will cause regional agricultural production to plummet. Plans to make money by developing the Amazon are a mirage. The forest provides more economic benefit than alternatives.
A study, just published in the journal Nature, found that the Amazon, as a whole is emitting a billion tons (English units) of CO2 per year with uptake of half a billion tons by intact forest overwhelmed by emissions of 1.5 billion tons by burning and dying forest.
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The global implications of this catastrophe in Amazonia are huge. Global forests have been removing CO2 and methane from the atmosphere, reducing the impacts of increased greenhouse gas emissions and lowering the climate sensitivity to emissions. Forests stressed by drought turn from carbon sinks to carbon emitters, raising the impacts of additional greenhouse gas emissions. If deforestation of the Amazon continues a vast sink of carbon will turn into a vast region of emissions.
Another just published study shows that methane emissions have been increasing in Amazonia in response to increasing temperatures, adding another greenhouse gas amplification to the impacts of deforestation. acp.copernicus.org/...
Abstract: "We use a global inverse model, satellite data and flask measurements to estimate methane (CH4) emissions from South America, Brazil and the basin of the Amazon River for the period 2010–2018. We find that emissions from Brazil have risen during this period, most quickly in the eastern Amazon basin, and that this is concurrent with increasing surface temperatures in this region. Brazilian CH4 emissions rose from 49.8 ± 5.4 Tg yr−1 in 2010–2013 to 55.6 ± 5.2 Tg yr−1 in 2014–2017, with the wet season of December–March having the largest positive trend in emissions. Amazon basin emissions grew from 41.7 ± 5.3 to 49.3 ± 5.1 Tg yr−1 during the same period. We derive no significant trend in regional emissions from fossil fuels during this period. We find that our posterior distribution of emissions within South America is significantly and consistently changed from our prior estimates, with the strongest emission sources being in the far north of the continent and to the south and south-east of the Amazon basin, at the mouth of the Amazon River and nearby marsh, swamp and mangrove regions. We derive particularly large emissions during the wet season of 2013/14, when flooding was prevalent over larger regions than normal within the Amazon basin. We compare our posterior CH4 mole fractions, derived from posterior fluxes, to independent observations of CH4 mole fraction taken at five lower- to mid-tropospheric vertical profiling sites over the Amazon and find that our posterior fluxes outperform prior fluxes at all locations. In particular the large emissions from the eastern Amazon basin are shown to be in good agreement with independent observations made at Santarém, a location which has long displayed higher mole fractions of atmospheric CH4 in contrast with other basin locations. We show that a bottom-up wetland flux model can match neither the variation in annual fluxes nor the positive trend in emissions produced by the inversion. Our results show that the Amazon alone was responsible for 24 ± 18 % of the total global increase in CH4 flux during the study period, and it may contribute further in future due to its sensitivity to temperature changes."
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The authors of the study published in Nature, interviewed by the Guardian, explained that we need a global agreement to stop Amazon deforestation and the worsening climate crisis.
www.theguardian.com/...
Luciana Gatti, at the National Institute for Space Research in Brazil and who led the research, said: “The first very bad news is that forest burning produces around three times more CO2 than the forest absorbs. The second bad news is that the places where deforestation is 30% or more show carbon emissions 10 times higher than where deforestation is lower than 20%.”
Much of the timber, beef and soy from the Amazon is exported from Brazil. “We need a global agreement to save the Amazon,” Gatti said. Some European nations have said they will block an EU trade deal with Brazil and other countries unless Bolsonaro agrees to do more to tackle Amazonian destruction.
The research, published in the journal Nature, involved taking 600 vertical profiles of CO2 and carbon monoxide, which is produced by the fires, at four sites in the Brazilian Amazon from 2010 to 2018. It found fires produced about 1.5bn tonnes of CO2 a year, with forest growth removing 0.5bn tonnes. The 1bn tonnes left in the atmosphere is equivalent to the annual emissions of Japan, the world’s fifth-biggest polluter.
www.nature.com/...
Abstract
Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades1,2,3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1,2,3. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 20184. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5,6,7,8,9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10.
The beneficial agricultural economics of rainforest protection was analyzed in this World Development report.
www.sciencedirect.com/...
Rising temperatures are projected to profoundly impact the productivity of soybeans. Studies from the recent past found each additional day of heat above 30 °C reduced soybean yields by 1% to 5% (Hsiang et al., 2013, Schlenker and Roberts, 2009). Although the high latitudes are projected to see the most rapid rise in mean temperatures from increased greenhouse gas concentrations (IPCC, 2014), the tropics are among the regions projected to see the highest rate of increase in extreme heat events (Fischer and Knutti, 2015, Suarez-Gutierrez et al., 2020). Areas of the tropics seeing the combination of increased greenhouse gas emissions and increased ecosystem conversion could see compounded likelihoods of warming and heat extremes (Zscheischler et al., 2018).
A number of mechanisms operating at scales from tree to biome explain the increased heat risk that can occur after tropical ecosystem conversion (Alkama and Cescatti, 2016, Silvério et al., 2015, Winckler et al., 2017, Zeppetello et al., 2020). These mechanisms include disruptions to the amount of heat absorbed by the earth’s surface, changes in precipitation and cloud patterns, and reduced cooling associated with a reduction of evapotranspiration by plants following land use change (Alkama and Cescatti, 2016, Bonan, 2008). Such changes to the climate, which stem from changes in the biosphere and are not caused by greenhouse gas emissions, are known as biogeophysical climate change (Bonan, 2008). Climate change caused by greenhouse gas emissions, on the other hand, is known as biogeochemical climate change.
Over the period 2000–2017, lost evaporative cooling in Brazil was in many instances the single biggest cause of warming in the agricultural frontier (Alkama and Cescatti, 2016, Silvério et al., 2015). Some agricultural locations in the region experienced mean daily maximum near-surface air temperatures as much as 4 °C in excess of expected temperatures absent land conversion (Alkama & Cescatti, 2016). Warming also stems from neighboring ecosystem conversion. Cohn et al. (2019) found that a 25 percentage point decline in forest cover at a distance of 1 km to 50 km from locations of temperature observation caused an increase of 0.4–1.1 °C in daily maximum temperature. Given that many regions of Brazil have in recent years experienced forest cover declines of this magnitude, these findings, taken together, suggest a potentially sizable economic consequence for soy from changes in ecosystem area.