Geological evolution, hydroclimatic cycles and tipping point mark the third day of SPSAS Amazônia

On the third day of the São Paulo School of Advanced Science Sustainable and Inclusive AMAZONIA the course participants had the opportunity to discuss the geological evolution of the Amazon with Paulo Eugênio de Oliveira. Paulo Eduardo De Oliveira, from USP, spoke about the geological evolution that led to the constitution of the Amazon as we understand it today. He highlighted the role of the great meteor that hit the Gulf of Mexico 66 million years ago and that triggered an irreversible change in the Neotropical region. “Even though the meteor extinguished the dinosaurs, this event was fundamental for the constitution of the Amazon, because it boosted the evolution of the Neotropical flora,” explains Oliveira.

The soaring of the Andes, during the Cenozoic, also played a decisive role in altering the Amazon rainfall regime and generating the enormous biological diversity it harbors. “The diversification of birds, mammals, insects and amphibians was boosted especially 10 million ago with the new drainage configuration established.”

De Oliveira also called attention to the marine influences that affected the area during the Miocene (about 20 million years ago). “One evidence is the presence of the beach apple in the Amazon, a plant that is typical of the coast,” De Oliveira explained. The similarity between the DNA of the Amazon and Caribbean porpoises is also another clue to the great marine incursions that happened in the region millions of years ago.

The hydroclimatic system of the Amazon along with water recycling and climate regulation in the Amazon was the topic addressed by Marcos H. Costa, from the Federal University Viçosa. The professor explained the process of precipitation formation and how deforestation can alter this characteristic so striking of the Amazon region. “Atmospheric moisture is the basic element for the formation of precipitation, in deforested areas there is less moisture and water cycling which reduces the precipitation rate increases the temperature of the soil surface, reduces evapotranspiration, increases the reflection capacity of radiation, the albedo”

Luiz Aragão, from INPE, presented data showing that the degraded areas (forest edge, burned areas, isolated fragments) have already surpassed the area of deforested forests in the Amazon. “The functioning and species of these forests are different from a natural forest,” explains Aragão. Knowing the heterogeneity of the structure of Amazonian forests is fundamental to calculate the total carbon balance, because degraded forests reduce the amount of carbon that a primary forest stores. “We often see that these forests can recover the average height, but not the biomass, because the species that colonize the area after the disturbance are ‘light forests’,” adds the researcher.

Paulo Artaxo, from USP and member of the IPCC, updated the group on the most recent data from international bodies that assess and monitor climate change. The UN’s World Meteorological Organization (WMO) released a report at the beginning of the COP27 in Egypt that pointed out that the global CO2 average is rising. Among greenhouse gases, CO2 continues to lead with 66% followed by 16% methane.

Brazil is seventh in CO2 emissions, sixth in historical emissions and fourth in per capita emissions. “It is possible that Brazil will also have to split the bill for climate change,

The change in the concentration of greenhouse gases generates many systemic changes on the planet. Among them, the researcher highlighted the change in the planet’s natural energy balance. “Three hundred years ago, all the energy that went in, came out. Now it doesn’t. We are changing the rate of return.” So far, the planet’s average temperature increase has been 1.2 degrees. However, as the researcher explains, this occurs because most of the surfaces are water, which takes longer to heat up, unlike the continent, which already coexists with average temperature increases above the limit of 1.5 degrees, the target set in the Paris agreement.

The increase in temperature, changes the circulation of water vapor in the atmosphere. It changes the flow of water vapor, and hence the rainfall regime. “Imagine that just one gas was able to greatly change the energy balance of the planet.” For Artaxo, everything indicates that we are leading the planet towards a warming that should vary between 3 and 4.5 C.

And he ends with the provocation “Is there a global tipping point?”, in other words, could it be possible to reach an irreversible point of restoration of the planet?

Finally, Simone Vieira, from Unicamp, brought information from the Atlantic Forest as a counterpoint of a tropical forest historically overexploited and occupied. The Amazon has more above-ground biomass than the Atlantic Forest, mainly due to the size of the trees in the Amazon that can reach 40 to 50 meters, but the Atlantic Forest has incredible dimensions considering the conditions of the region. “The Atlantic Forest is an unexpected forest, because it grows on a sloping terrain, with shallow, nutrient-poor and very acidic soil. But these forests have a great potential to store carbon in the soil, unlike the Amazon which stores a lot of carbon in the trunks.”

And all the carbon that is stored in the soil can easily go into the atmosphere. The increase in temperature, increases the decomposition rates and causes the release of this carbon stored in the soil to the atmosphere. “We have a carbon pump in the soil of the Atlantic Forest. As long as it is stored it is great, but this stock is also very sensitive to temperature variation” complements Professor Carlos Joly, from Unicamp and coordinator of the School.