By Alice Marcondes
If the relationship between the Amazon rainforest and the trillions of cubic meters of water that circulates through the air, from the equatorial Atlantic Ocean to the Andes, is altered, the resilience of this crucial biome for the planet's climate will be at risk, he warns a two decade experiment.
The Amazon is a living being of 6.5 million square kilometers, which occupies half the territory of Brazil and part of those of eight other countries (Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname and Venezuela) and it houses the largest reserve of fresh water on the planet.
In order to fully understand this complex ecosystem, scientists from Brazil and around the world created the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA, for its acronym in English).
After 20 years of research, the data collected constitutes an alert.
According to the National Institute for Space Research (INPE, for its acronym in Portuguese), an entity participating in the experiment, if in the coming years there are no effective policies to reduce the emission of greenhouse gases, the Amazon will reach the end of the 21st century. with 40 percent less rainfall and average temperatures of up to eight degrees above normal.
This would turn the Amazon into a source of carbon dioxide, rather than a reservoir of that greenhouse gas.
The International Energy Agency estimates that in 2010 the world's population released a record 30.6 gigatonnes of carbon dioxide into the atmosphere, mainly from the burning of fossil fuels.
"Research shows us that the forest has a great power of resilience, but also that this power has limits," physicist Paulo Artaxo, president of the LBA's International Scientific Committee, told Tierramérica.
"If we continue to burn so much carbon, the climate scenario for the Amazon region will be quite unfavorable to any resilience that the forest may develop. It will hardly survive such a great climate stress," he added. For data collection, the LBA ordered, among others instruments, with 13 towers between 40 and 55 meters high, installed in different parts of the jungle to measure the flow of gases, the functioning of the basic properties of the ecosystem, radiation and many other environmental parameters. The information collected is analyzed by scientists from various areas, in order to understand the jungle as an interrelated system.
“The perception of the scientific community that individual or disciplinary studies were not competent to explain the Amazon, led to the LBA. It was perceived that an integrated effort was necessary to explain the (tropical) forest from the physical, chemical, biological and human sciences, and from the relationship between them, "agronomist Antônio Nobre, a leading scientist who is also a member of the LBA, told Tierramérica. .
"When I started my studies at the LBA, my main part of the project was carbon. But carbon without water remains dry and the forest catches fire. If there is no transpiration, there is no carbon sequestration, because photosynthesis does not take place I perceived that the water cycle and the carbon cycle were inseparable ", he exemplified.
This integrated analysis showed that the Amazon is absorbing a small amount of carbon dioxide from the atmosphere, estimated at half a ton per hectare per year.
But that fixation varies greatly by region, depending on the degree of environmental disturbances. In areas close to places where human action caused significant degradation, absorption is reduced, and the Amazon, instead of incorporating carbon, emits it.
In addition, the absorption of carbon dioxide is counteracted "by emissions from deforestation and‘ burned ’", fires caused to extend agriculture, Artaxo added.
As in recent years burning has been drastically reduced, from 27,000 square kilometers in 2005 to around 7,000 square kilometers in 2010, "today the jungle has absorption as a predominant characteristic," he said.
But, with the changes that generate the greenhouse effect and the warming of the forest, the dry season tends to extend, creating a favorable scenario for more fires and more emissions of carbon dioxide.
"The release of solid particles into the atmosphere by the‘ burned ’alters the microphysics of the clouds and the rain fall regime," said Artaxo.
“In one of the studies of the experiment, it was found that the increase in 'queimadas' in (the northern state of) Rondônia extends the dry season between two and three weeks, feeding back the incidence of 'burns' and worsening their effect even more. on the functioning of the ecosystem ”, he continued.
In the "very severe" drought of 2005, "the Amazon lost a lot of carbon," he said. In a situation of more frequent "great droughts", it is possible that the forest becomes a "emitter of carbon dioxide and stops fulfilling an important environmental service," added Artaxo.
The extension of the dry season causes another phenomenon that was also studied in the LBA, the carbon emission of rivers.
“Small and medium-sized waterways emit significant amounts of gas. What I call carbon dioxide evasion from aquatic bodies occurs, and that happens because most of these rivers are saturated with carbon dissolved in the water, ”Artaxo said.
With the passage of time, this carbon "is released into the atmosphere in quite significant quantities. All the phenomena that alter the Amazonian ecosystem have a strong impact on the escape of gases from the rivers. With the increase in temperature, the emission increases. of gas, "he added.
To illustrate the consequences that an imbalance in the Amazon could have on the global climate, Nobre cited the research that became popular under the name "flying rivers", begun in the 1970s and turned into a consolidated project since 2007.
"We discovered that the action of the sun on the equatorial region of the Atlantic Ocean evaporates a large amount of water. This moisture is transported by the winds to the north of Brazil. About 10 billion cubic meters of water per year reach the Amazon in the form of steam. Part falls as rain, and part continues until it finds the wall of the Andes Mountains ", described Nobre.
In the Andean zone, it falls like snow and, when it melts, "feeds the rivers of the Amazon basin. Most of the rain that falls on the forest evaporates again," he added.
This humidity fluctuates over Bolivia, Paraguay and the Brazilian states of Mato Grosso, and Mato Grosso do Sul, in the west, Minas Gerais and São Paulo, in the east and southeast, and even up to the southern Paraná, Santa Catarina and Rio Grande do Sul. "And it carries most of the rains to all those regions," he explained.
The drought in the Amazon would damage that aerial river and "the rain cycle in those regions, which are very rich in agriculture," Nobre warned.
The LBA is today a program of the Ministry of Science and Technology, coordinated by the National Institute of Research of the Amazon, with the support of other entities.
Its researchers are expanding it to other areas, such as agropastoral systems and the behavior of carbon dioxide in soybean plantations.
"We have a huge job ahead" to understand "natural processes" and what "humans do in terms of altering ecosystems," concluded Artaxo.