Just came back from a seminar with William I. Woods of the University of Kansas about Terra Preta. He has spent a lot of time on this and the seminar was very interesting. William was rather provocative and made a number of bold statements such as
- all the fertile steppes (pampas, the Norh American prairies and the Pontic steppe, i.e. are of man-made origin, having been forests burnt down by people
- composting is very bad as most of the carbon is lost
- the best strategy to deal with climate change is to cut down the Amazon forests and to make bio char from it, let it grow again - and make more bio char etc.
The latter statement is closely linked to his research which states that contrary to what most believe the Amazon was rather populated in the history AND it was to a large extent deforested. He stated that the "little ice age" partly was caused by the return of forests in the Amazon (gulping up the carbon in the atmosphere) as a result of post 1491 decline in population. Interesting thought-I do agree with him to some degree. We tend to overlook how much humans have transformed ecosystems in the past. The fact is that also large scale transformation took place long before "modern" society and industrialism. Ruddiman has also pointed that out in a good way.
I have written before about that the relationship between man and nature is a bit more complex than we mostly beleive:
Climate; doing the things right or doing the right thing?
How fertile are terra preta soils?
When it comes to the power of Bio Char I am less convinced. There is a lot of promotion of BioChar today and like many other techno-fixes it seems somewhat over-promoted in my view. We now have multi-million research programs and (of course) biochar standards and certification.
From the presentation of William Woods, I realise that the terra preta soils of the Amazon are not only a result of charcoal use and making, but perhaps even more of a large scale import of nutrients from a hinterland, not much different from the infield-outfield system of Sweden or Plaggen soils of Germany. It is not difficult to maintain high productivity of soils when there is a constant import of nutrients. Also the soils will improve over the years. For me, it appears as if this aspect is more important to understand the fertility of terra preta soils than charcoal. I might be wrong, but I am still waiting for the evidence of the opposite. In addition, the fertility of the terra preta soils as measured by professor Woods wasn't really too impressive.
As a carbon sequestration technology I am sure it works quite well, having the possibility to sequester carbon as the only parameter for measuring success - but I don't think we can manage our world with such one-dimensional criteria. In general, I am afraid about all messianic ideas of simple solutions to climate change - allowing us to continue with "business as usual" as expressed by professor Woods.
Svensk källa för biokol: http://www.geo.uu.se/biokol/