Beneath the Canopy: Exploring Amazonian Soils for Nature-based Climate Solutions

Climate change is one of the biggest threats to the health and wellbeing of people worldwide. At Therme, we are proud to support projects that search for solutions to the climate crisis so that, together, we can create a better world for people and planet. 

Last year, Therme proudly sponsored a research expedition to investigate the use of 'terra preta' soils as a carbon store for climate change mitigation. The research also aimed to explore methods to combat illegal logging and support sustainable agriculture by looking into wider questions related to soil, biodiversity and indigenous forms of knowledge. 

The expedition was led by Justus Liebig University Giessen in cooperation with the EMBRAPA Agricultural Research Institute in Manaus. In addition, the project has the support of the International Atomic Energy Agency (IAEA) and the Food and Agriculture Organisation (FAO) in Vienna. 

Therme NAT team member, Jakob Nolte, who was part of the interdisciplinary research team, shares details of the project with us. 

Agriculture is a major contributor to the climate crisis. According to the United Nations’ Food and Agriculture Organisation (FAO), emissions related to farming and land use, crops and livestock, consumption and waste, and energy used in farm and food processing accounted for 21% of all the world's carbon dioxide, 53% of all methane and 78% of all nitrous oxide emissions globally. To help prevent the negative impacts of agriculture, such as greenhouse gas emissions from artificial fertilisation, the FAO advocates for "climate-smart agriculture" which means looking to the natural world to find nature-based solutions. 

Our current agricultural system is trapped in a negative feedback loop: the high emissions from intensive agriculture intensify climate change, negatively impacting production, leading to further intensification of agriculture, and so on. 

Our expedition aimed to find answers to the challenging question of ‘How can we make agriculture climate-neutral?’.

Terra preta, also known as Amazonian dark earth, is a type of soil found throughout the Amazon. It is believed to have been created by ancient civilisations 5 to 7 thousand years ago. Terra preta soil is far more fertile than standard Amazonian soil which lacks essential nutrients, such as phosphorus, as the high level of rainfall washes them away. It is thought that ancient civilisations added charcoal to improve the soil nutrients so that it could feed a large population. 

The soils have been developing over thousands of years in what is called a ‘closed material cycle’. This has resulted in a build-up of nutrient reserves which enables the soil to be used for a long period of time without the need to add additional fertiliser. 

But how does this work? 

The incredibly high level of nutrients in the soil is thanks to its special microbiology. Aggregates of the charcoal and soil organisms make more key nutrients, like phosphorus, available. And, in the case of terra preta soils, their microbial communities have had a long time to optimise and increase efficiency within closed cycles. Because of their unique microbial and nutrient makeup, terra preta soils offer a prime example of how closed material cycles could be used to improve agricultural efficiency and act as carbon stores. It is these characteristics that are the basis of our expedition. 

Currently, there are only two potential ways to remove large quantities of carbon dioxide (CO²) from the atmosphere. The first involves filtering the CO² out of the air and injecting it into deep layers of rock. However, this is an extremely expensive, energy-intensive and questionable process. The alternative is to use the photosynthesis power of plants to concentrate the carbon into organic matter. Once converted into charcoal, this carbon can be stored in the soil for a long time with the added benefit of improving soil fertility, a big win for sustainable agriculture. 

During the expedition, we analysed and compared the material cycles of terra preta and non-terra preta soils at sites in the Amazon region. These balances provided information on the potential of terra preta soil compared to ‘normal’ Amazon soil. 

We found that terra preta soils had significant advantages compared to soils that have not been influenced by humans. 

These include: 

• Higher carbon storage and potentially lower greenhouse gas emissions 

• A high level of phosphorus for plant growth (a key limitation in other Amazonian soils) 

• Higher water holding capacity 

• Higher microbial activity 

• Build-up of reserves for a long time 

From our findings, we believe that terra preta soils could support the development of solutions for climate-smart agriculture that can help reduce greenhouse gas emissions and decrease reliance on synthetic fertilisers.

Our research indicates that we can learn from indigenous, nature-based methods to create sustainable and productive land-use systems that address current ecological crises. 

These solutions thrive in ecosystems with diverse species that support each other. Terra preta soils owe their richness to high soil biodiversity. Monocultures, as is the norm in modern farming, will not be able to achieve the same level of fertility. 

Moreover, the widespread belief that intensive agriculture is the most productive land use is wrong. In the Amazon, it has been shown that the six most fruit-bearing trees cultivated and spread by people thousands of years ago produce six times as much protein as all the cattle kept in the region today (Clement, 2019). If we were to bring these trees back into the landscape in a manageable form of agroforests, in combination with terra preta, this would result in a new system that could combine biodiversity support, climate management and high food production. 

Much of the Amazonian rainforest is characterised by human-nature relationships. Even today, indigenous peoples spread crops and cultivate them in harmony with the natural ecosystem. For nature-based solutions to work, we must realise that humans and biodiversity are not opposites; we are part of nature and can actively promote biodiversity. 

Our research to explore how ecosystem material cycles and terra preta soils can inform the search for nature-based solutions to the climate crisis is ongoing. 

In the future, we would like to explore these solutions further by replacing fertilisers with substances that activate microbes and introducing charcoal to soils (this is already showing success with nitrate retention and higher water-holding capacity). We are also looking to use bioinformatics to analyse soil activity and build a digital model to simulate plants in their environment. These simulations will then be manipulated to test the effect of new solutions on plants and visualise the relationships between each active component.

This is an exciting time for research, and we are optimistic about the potential of nature-based solutions in creating a more sustainable and resilient future. Therme remains committed to contributing to the journey towards a healthier, balanced coexistence with our environment.