31:19 Indeed and it's interesting and definitely new to me to hear about the engineered savannahs of america i wanted to try to squeeze in a little bit about the amazon is obviously the most complex and. Biodiverse landscape on the planet and i think the wilderness myth might play it as well cuz you told me that its pretty clear, did it was engineered how do we know what are the signs and clues that kinda show us that essentially, when you exclude humans the plant community it's the same exact phenomenon as we're talking about for North America in that when you have humans managing a system for themselves to produce food those are the type of species that are going to persist in your force in your ecosystem whether that's a savannah in the Midwest or the Amazon at the equator and so
32:14 When we look at the species composition, the way it was when we can first have any data on it. There was a lot more species that produce food for humans in that species composition than there is now so as humans are removed and less active in this system It goes to a less diverse state and a state that produces more trees that don't produce food for human So there's obviously wide spectrum of different species some of them are more valuable than others from a human perspective The ratio of non-productive trees has increased over the last hundred years as humans have been less active in the ecosystem. And so what's really interesting is if you read about the indigenous people of the Amazon, we call their practices of agriculture slash and burn which is a very derogatory way
33:06 gaining your existence, slashing and burning sounds so bad. And we look down upon them for it but when you actually go down to the Yucatan which I have not done but I've spoken to several archeologists that have spent a lot of time down there trying to figure out the old ways of growing food and essentially they would go into an area and clear out say an acre of forest and then they would burn that and they would burn the biomass in a very low intensity way like you mentioned biochar it creates a lot of charcoal Down in the Amazon, they don't have the thick topsoils that we have thanks to our grassland ecosystems. Grassland ecosystems create topsoil. That's like one of the byproducts of a grassland with grazers is thick topsoil and so we have that up here down there in a forest all the nutrients that we have in our soils They have locked up in their giant trees and plants And so they really don't have a soil
34:01 all of the potential nutrients are used in a rainforest ecosystem. They're all up above ground, they're not below ground and so it's really hard to grow annual crops so vegetables corn grains it's hard to grow that stuff because there is no soil minerals all the nutrients are locked up in trees so they would cut down trees they would slash and burn But they would do it as a part of this much larger cycle of food production. So you'd come into an area, cut down an acre of forest and burn it in a way that produced a whole bunch of charcoal on the ground then plant your garden say so you're going to have a really diverse garden
34:40 80 to 150 different vegetables and plant species and grains. But at the same time, you're also planting fast growing an slow-growing perennial trees for your vegetables to grow between. And so they would plant their favorite fruit and nut bearing trees in their gardens. So in one year they might slash and burn one acre But then that acre over the next 20 years, for the first two or three years it's producing annual vegetables. But then they would stop that and then they would just let the fruit and nut trees come in. Then they have this one-acre orchard or food forest of breadfruit and avocados and bananas and all the things that they have down there. And then they could go do that again somewhere else. So you kind of zoom out and look at that process. It's like a twenty year process by Year 20 its a closed canopy forest of all food producing trees
35:31 and they had immense diversity down there. So we're talking like hundreds of species, and if that had been let go there would have been like the two dozen plant species that would've been there that they cut and burned but that's fairly low diversity relative to what they would then turn around and plant so you look at that scale, the one acre scale and imagine hundreds or thousands of people over time doing all these little patches What that turns into over time is an Amazon rainforest, that's essentially one giant shifting mosaic of food forest. So they were essentially terraforming the Amazon in order to produce a whole lot of perennial foods like fruit from trees you know they had their annual vegetables in there but that was only small part of the cycle The main point is that they were planting lots of trees Yeah