FACE-ing the Amazon's Future

Few of us have felt or smelled the Amazon. At least we can hear it. YouTube videos with “sounds of the Amazon” will get you a glimpse of what biogeochemist Lucia Fuchslueger was surrounded by for more than two years. The ceaseless buzz of insects. The piercing call of the little piha birds - loud as a rock concert - contrasting the toucan’s surprisingly delicate chirping. 

Sounds catapult the scientist right back to the heat, the sweat, and the scorching sun. How much cooler it was in the shade of those incredible trees! She will recall monkeys looking like little monsters; pythons blocking the dirt path; palm trees with finger-long thorns on the underside of their leaves. “You have to be careful all the time”, she says laughingly. “It is all very much alive… It is great.” 

The Amazon still is great, a place of superlatives despite all cutting and burning for short-term human conveniences: steaks or wooden floors, toilet paper or leather, fast-growing “energy” trees or aluminium foil. It is the world’s largest forest, home to 400 indigenous peoples, and around 30 million other humans. Its biodiversity is unparalleled, with 15.000 species of trees alone, and thousands of species of fish, birds, amphibians, reptiles, insects… 

”The Amazon is of global importance as a carbon sink, which means it is stroing and absorbing huge amounts of CO2", says Fuchslueger. The Amazon river - the largest stream in the world - carries one fifth of the planet’s flowing freshwater. Even more water is flying in the air above it. 50 to 80% of the rain poring down in the region is self-produced by its trees. More water is coming from the Atlantic. Strong winds move the moisture towards the Andes where the flying rivers turn south. Without a functioning Amazon, the corn belts and green pastures from Southern Brazil to Argentina would turn into drylands or deserts.

The biome is considered one of the tipping elements of the global climate system. A dieback would not only turn the precious rainforest into a savannah - an epic catastrophe in itself. It would also affect ecosystems and ocean currents, climate and weather patterns around the globe, not speaking of the vast socio-economic impacts. Although not every detail of the consequences is yet fully understood, it is clear they would be massive. Experts fear the tipping point could be reached when a quarter of the trees are lost. So far, at least a fifth of the rainforest has been cleared; another 6% or more are severely degraded. 

Already, droughts are starting earlier, lasting longer, some appearing in places that used to be soaking wet all year round. Fires are growing bigger and way more destructive. The absorption of CO₂ has weakened by 30% since the 1990s. 

What will happen to the Amazon when we keep on burning fossil fuels? “Some hope for the CO₂ fertilisation effect”, explains Fuchslueger. In glasshouses for example, with sufficient water and nutrients, the extra carbon causes plants to grow faster. With more leaves and roots, they can absorb more CO₂. “If that would translate to whole forests, their carbon storage capacity would rise, helping to even better mitigate our emissions.”

Over the past ten years, a wealth of preliminary data has been collected onsite in preparation for the large-scale project. For example, scientists measured the effects of CO2 on smaller plants with Open-Top Chambers (OTC): octagonal huts with transparent walls. 

Fuchslueger, expert for biogeochemical cycling at the University of Vienna, was there to investigate the interactions between plants, roots, microorganisms and the soil. Her in-depth knowledge of the project and the people made her an ideal candidate to become one of AmazonFACE’s research coordinators, responsible to oversee the nutrients research area. (The main coordination is with Brazil’s National Institute for Amazon Research (INPA) and the UK Met Office). Brazil and Britain provide most of the funding for the massive installation. In addition, Fuchslueger is part of the Scientific Steering Committee and helped to draft the research plan for the next five years.

To simulate future aerial carbon levels, for the next ten years the trees on the eCO₂ plots will continuously be fumigated with high amounts of CO₂ during daytime. 200 parts per million (ppm) CO₂ will be mixed to the ambient air (ppm is a unit used to measure very small concentrations of a substance - here CO₂ - in a mixture or solution - here the air). This corresponds to about half the amount of CO₂ our atmosphere already contains. 

“A difference of 200 ppm is a lot for a forest to adapt to”, Fuchslueger explains. “But we need a high-enough trigger for a measurable response. And it is a realistic future scenario.” According to the most likely climate scenarios, we will reach 615 ppm CO₂ by 2070 at the latest. In addition, the different FACE experiments use similar amounts of CO₂. The reactions of different types of forest can thus better be compared. 

Throughout the program’s running time, trees on the six plots will be measured meticulously: Will the fumigated trees produce larger leaves, grow taller, store more CO2 than the controls? Is there a limit? How will the soil microbiome - mycorrhizae, bacteria, microorganisms - react to the changes? According to the small-scale OTC experiments, understorey plants seemed to benefit from eCO2. Will the 30- to 45-metre-tall giant trees respond in a similar way? 

“The soil in the Amazon basin is millions of years old, which means, it is weathered and depleted”, states Fuchslueger. Particularly low is phosphor, which plants need to grow. “Getting it out of the soil can be an investment for the plant,” she says. It is called the “C(arbon) cost of P(hosphor) acquisition.”. 

To cope with scarcity, Amazonian trees have developed highly efficient internal nutrient cycles. For example, they are withdrawing nutrients from their leaves before they drop them. The rapid organic matter decomposition on the ground provides additional nutrients. It is not clear if this system can get any better. “Given the lack of phosphor, it might just not be possible for the trees to produce additional biomass”, she points out. The depleted soil might limit or cancel out the CO₂ fertilisation. If that is the case, climate scientists would need to adapt some of the current climate change scenarios that are counting on CO₂ fertilisation. 

AmazonFACE will deal with other questions too. The six defined key research areas are Carbon, Nutrients, Water, the forest’s Biodiversity - a novelty for a FACE project. Equally innovative: Socio-Ecological questions. Local communities heavily rely on ecosystem services of the Amazon: on food, raw materials, medicinal plants, or water (not to mention spiritual and cultural „services“). Social scientists will focus on the changes that are already taking place or can be expected due to climate change; on adaptation strategies; and on advising policymakers. 

Last but not least, any data obtained will be used for modelling. With new data, the scientists hope to reduce uncertainties in existing models and improve their predictions. “The project will look at this most fascinating ecosystem from so many different angles,” raves Fuchslueger. “The broad approach, the diversity of the teams, make it very special.” 

However, she adds, data alone will not be enough to safe the precious biome. Humans also need… connection. “Only by experiencing a place like the Amazon, by seeing and understanding all of its beautiful interdependencies will we know that we want to protect it. That’s why we’re there.”