To start, I learned that this unusual word "syntropy" is more or less the opposite of "entropy". A tendency towards more complexity. It is a natural tendency of living systems, but humans can greatly accelerate it. Scientists say that the forest Götsch grew in Brazil in the past 40 years would have taken 700 years to grow on its own.
And it turns out that accelerating natural processes like this is something humans have evolved to do. It gives us pleasure, and it has become part of many peoples' cultures. Götsch learned his principles by interacting with Amerindian tribes. When colonizers arrived in South America in the 1500s, what they thought were natural forests were actually complex agricultural systems managed by humans.
One principle of syntropic forestry is understanding the succession of plants. Identifying the pioneer plants, that can grow naturally in harsh conditions and prepare the soil for the secondary plants.
Plant very densely, to create an interconnected root system, cover the soil, accumulate organic matter and release hormones that promote even more growth. Then prune heavily, which sends signals for the plants to grow more, and generates more matter to cover the soil. It simulates herbivores eating and stepping on the plants. It's a disturbance that helps the forest grow faster.
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Another principle is creating strata to ensure each plant gets the amount of sunlight it needs. Plants that need more light create shade for plants that need less. When plants find themselves in the wrong stratum, they develop diseases.
This is the part that made me think of what farmers have been doing with solar panels.
Another principle is making the system self-sufficient in water, through plants that can accumulate and distribute it. This part I don't understand as much I think (not that I'm an expert in the other parts). I'll try to read a bit more about it. The presenter said that animals that can be seen as invasive in gardens, such as slugs, are sometimes only coming for the water, and not actually eating anything. It's important to observe and understand what is happening.
Of course, all of this requires a deep understanding of the species of plants, animals, fungi etc that grow in a given place, and how they interact. As well as careful planning accounting for the time, space and other resources available. Ernst Götsch says the main input humans bring to a syntropic forest is knowledge.