Carbon and Beyond: The Biogeochemistry of Climate in a Rapidly Changing Amazon

Abstract

The Amazon Basin is at the center of an intensifying discourse about deforestation, land-use, and global change. To date, climate research in the Basin has overwhelmingly focused on the cycling and storage of carbon (C) and its implications for global climate. Missing, however, is a more comprehensive consideration of other significant biophysical climate feedbacks [i.e., CH4, N2O, black carbon, biogenic volatile organic compounds (BVOCs), aerosols, evapotranspiration, and albedo] and their dynamic responses to both localized (fire, land-use change, infrastructure development, and storms) and global (warming, drying, and some related to El Niño or to warming in the tropical Atlantic) changes. Here, we synthesize the current understanding of (1) sources and fluxes of all major forcing agents, (2) the demonstrated or expected impact of global and local changes on each agent, and (3) the nature, extent, and drivers of anthropogenic change in the Basin. We highlight the large uncertainty in flux magnitude and responses, and their corresponding direct and indirect effects on the regional and global climate system. Despite uncertainty in their responses to change, we conclude that current warming from non-CO2 agents (especially CH4 and N2O) in the Amazon Basin largely offsets—and most likely exceeds—the climate service provided by atmospheric CO2 uptake. We also find that the majority of anthropogenic impacts act to increase the radiative forcing potential of the Basin. Given the large contribution of less-recognized agents (e.g., Amazonian trees alone emit ~3.5% of all global CH4), a continuing focus on a single metric (i.e., C uptake and storage) is incompatible with genuine efforts to understand and manage the biogeochemistry of climate in a rapidly changing Amazon Basin.

Climate and crown damage drive tree mortality in southern Amazonian edge forests

“…These results indicate that trees in the Amazon‐edge forests are particularly susceptible to disturbances, such as high winds (Arriaga, 2000; Putz, 1984; Ribeiro et al, 2016), and they show that the exceptional stem mortality rates observed in these forests (Marimon et al, 2014) are related to high rates of crown and trunk breakage. These forests are more subject to habitat fragmentation due to the conversion of forested areas to agricultural areas (Covey et al, 2021). These forests also exist in drier climates, with less annual rainfall and more intense seasonal water deficits, than most of Amazonia (Brando et al, 2014; Malhi et al, 2015).…”

“…Southern Amazonian edge forests have a unique species composition, due in part to the overlap of species between this and the adjacent biome, the Cerrado (savanna) (Morandi et al, 2016). These forests have been suffering from advances in agriculture, which has considerably increased habitat fragmentation and carbon loss in recent decades (Covey et al, 2021; Gatti et al, 2021; Silva Junior et al, 2020). In addition to the high levels of fragmentation, the remaining forests have been affected by increasing temperatures, frequent fires, drought events and the long‐term lengthening of the dry season (e.g.…”

“…Araújo et al, 2021; Reis et al, 2018; Silvério et al, 2019)—making this now the hottest, driest and most degraded region in the Amazon (e.g. Alvares et al, 2013; Covey et al, 2021; Matricardi et al, 2020; Sombroek, 2001).…”

Extractivisms, existences, and extinctions

“…Thus, it consumes the places that lie in its path and it needs new frontiers to consume via deforestation. The Amazon is already at a tipping point and seems to be causing more greenhouse gas emissions than it is absorbing, as so much of the forest has been burned and turned into pastures and plantations that emit carbon, methane, and other gases (Covey et al 2021). On top of that, global emissions are making it harder to stop these processes of deforesting the Amazon.…”

Circular Carbon Economy (CCE): A Way to Invest CO2 and Protect the Environment, a Review

“…Natural experiments, based on real-world observations, indicate that global warming of no more than a few tenths of a degree can result from such an increase in carbon dioxide [4]. Recent research also shows that methane emissions outpace the impact of carbon sinks from trees in wooded wetlands [5].…”