Amazonian 'dark earth' could speed up forest regeneration
Have a fiddle V natural regen
Every permaculture design has, or should have, a wild area, often referred to by Permaculture designers as a zone 5. Ideally neighbouring projects connect their wild areas together to create a shared wild zone, this can and should continue right across bioregions. I am often confronted with the question “replant with natives or leave the area to naturally regenerate. In virtually all cases the answer is natural regen, there are of course exceptions to this but these don’t necessarily involve replanting but more often the use of a variety of techniques to reduce erosion, reduce the incidence of wildfire and sometimes replanting to stop soil slumping. In the main these ‘zone 5’ areas are left to themselves and areas which need other strategies can be designed as semi-wild/semi managed areas, often referred to as zone 4 areas.
A recent study in Brazil made some headlines recently as some ‘in pot’ experiments seem to shown that growing trees in Terra preta or what is better called Amazonian dark earths (ADE) speeds up tree growth. The idea will probably be actively promoted as the hands-off natural regeneration approach doesn’t make anybody any money, whereas selling ADE and tree seedlings does.
As is so often the case what we are doing isn’t necessarily wrong but how we do it often is. In my part of the world last years wildfires burnt a national park area which was primarily covered with Bracken (Pteridium) with some areas planted to conifers. The whole lot burnt and there are now big panels up announcing proudly that the local authority with the help of some EU grants have the whole thing in hand and that they are going to restore the area. So far this has involved cutting down the standing dead blackened trees. What they have actually done is remove potential wildlife habitat, the blackened and apparently ‘unsightly’ trees and trample/drive over the plants that were starting to grow. The next phase will involve trampling and driving over the regrowth to plant ‘native trees’. An information panel explaining about dead trees being habitats and natural regeneration would have been cheaper, more effective and helped people understand about how ecosystems evolve. But of course it is ‘important to be seen to be doing something and there is a lot of money floating around to be grabbed and misused. For governments who continue to use the utterly flawed gross domestic product metric spending money to buy trees and hire people to replant is a plus plus for the economy, letting natural processes run their course isn’t. Another argument that is used is ‘the impact on tourism’, people won’t come to see burnt out areas so it’s important to make them look nice, actually a lot of people do come to see what has happened so that argument, in the case I’m talking about doesn’t hold.
If we look at the Amazonian forest, people of a certain generation who studied ecology will have been told that this forest was an example of a climax system and ‘pristine’. Subsequent research has shown that this is not the case and that huge areas of what is now forest was cultivated fields, villages and towns, the so-called lost temples were lost when the forest regenerated after the local population was decimated by disease or massacred. Thanks to the local climate natural regen happens very fast. Studies have shown that about one third of the deforested areas in the Amazon basin have regenerated with secondary growth forests. Researchers have estimated that this secondary forest is offsetting around 12% of the total carbon emissions from deforestation. These secondary forests actually absorb more greenhouse gases than mature forest.
Yes, deforestation needs to stop and we need to encourage a new agricultural revolution which doesn’t destroy forests, soils, water sources and all the rest. At the same time it is important not to just jump in and start getting busy without having a good long think first. I’ve lost track of the number of times when we haven’t been able to get a project trundling along because we have had to spend a lot of time mitigating the effects of initiatives done previously by well meaning people or NGO’s. This is one reason the Permaculture designers are so often to heard shouting quietly “analyse and design the thing first and try to consider all the parameters before you start messing around with it!” But as there are saplings and planting machines to be sold and money to be made the response is all too often to destroy natural regen and plant in saplings which often have low survival rates.
Another problem which is cropping up more and more as the climate changes is ‘what trees should be plant’. The knee jerk reaction of planting back the types of trees and bushes that were there before isn’t always appropriate as they are stressed by the changing climate and would have, over a certain period, have been replaced by trees and bushes more adapted to the future or new climate. This is one reason the Permaculture designers prefer natural regen which can allow for such change, the mos adapted tree and bush varieties will be those that thrive the most. This climatic factor is also a difficulty when designing agroforestry systems, for the most part permaculture designs for agricultural systems over the last 40 years have been agroforestry based, either at a domestic scale or as part of holistic land management agricultural systems.
Coming back to Amazon dark earths I would like to mention the convergent evolution between Amazonian peoples and those to be found in West Africa, in the latter part of the world these earth are called ‘the dark earths of West Africa’ which frankly swings less well than terra preta. Over centuries people in West Africa have developed what are, for the most part, very similar strategies to improve the fertility of the native red earths, the age of a village can be assessed by examining the depth of the surrounding dark earths.
There is definitely a place for dark earths but not necessarily for replanting destroyed forests, there is a place for replanting areas but not as the first recourse and not to be done blindly. In the end the Permaculture approach ‘analyse, design, install is still the best. Deep analysis of as many as possible of the different parameters followed by designing the system and making mistakes at the design stage when they can be easily rectified is so much more pragmatic than diving in with knees jerking full of the desire to be seen to be doing something. This is true of all the different reconstructions we have to do from buildings through to economic and agricultural systems.
And of course ‘everything depends on the context’, there is no one size fits all solution, an approach which works well in Brazil will most probably need to be radically adapted to the cool-temperate area where I am. I bought a hat once, the label told me that it was a universal fit, it fitted me ok but was either too small or too big for everyone else around here, this is an advantage as nobody borrows it but the label ‘universal fit’ seems to be …. not true.
https://phys.org/news/2023-05-secret-amazonian-dark-earth-forest.html
https://royalsocietypublishing.org/doi/full/10.1098/rspb.2015.0813
https://news.mongabay.com/2023/05/many-features-of-the-amazon-are-man-made-qa-with-archaeologist-eduardo-neves/
https://news.mongabay.com/2020/12/brazil-scientists-map-forest-regrowth-keeping-amazon-from-collapse-study/