“The struggle to defend the trees and forests is above all a struggle against imperialism. Because imperialism is the arsonist setting fire to our forests and our savannas.”

Throughout history, people and communities have built close connections with the land. When we talk about soil — and about trying to “fix” soil —taking action can mean breaking or disrespecting those connections, good intentions or not.

Lessons on environmental cooperation from a Marxist revolutionary, the Great Green Wall, and more.

Presented by Dan Crane
Written by Ian Steadman
Sound design by 
Laura Irving

Made with the support of The Bill & Melinda Gates Foundation

Featured guests

  • Amber Murrey-Ndewa, post-doctoral fellow in sociology at the American University in Cairo
  • Tiziana Ulian, senior research leader for diversity and livelihoods at the Millenium Seed Bank, Kew Gardens
  • Pablo Barreira, seed biology laboratory technician, Millenium Seed Bank, Kew Gardens
  • Ken Giller, professor of plant production systems at Wageningen University

Music & audio credits

Show notes

Some additional information and resources not directly linked to within the transcript (below):

The Sahel. Image credit: Wikimedia Commons
  • This is quite sweet: a journalist remembers interviewing Thomas Sankara when she was 11 years old, on a sponsored trip to Burkina Faso.
  • Sankara’s political legacy is enjoying a revival across Africa, while Mohamed Keita writes for Quartz about the impact of Sankara’s death when he was a child in Dakar, Senegal.
  • You can find out more about the Great Green Wall today—including its origins—on its site.
  • If you want to see what the Great Green Wall looks like on the ground, the BBC’s Newsnight show covered it recently:
  • Not covered in the episode, but Western air pollution is believed to be at least partly responsible for current droughts in the Sahel.
  • Here’s that “gorgeous mansion” where the Millennium Seed Bank is based…

…although the building next door with the actual seed bank is, sorry to break the illusion, more modern:


DAN CRANE: February, 1986, and you’re in Paris — for an international forestry conference. Not the most romantic reason to visit the city of love, sure, but you’re a scientist, and you’ve got work to do. This is a big event, so as well as tree experts there are politicians in attendance. Most of you are in ties and suits, and then you see a man in the among the dignitaries, not dressed like the rest. He’s young, in army fatigues, wearing a red beret. And when it comes to his turn to give a speech to the assembled delegates…

AMBER MURREY-NDEWA: He said, quote, our struggle for the trees and forests is first and foremost a democratic and popular struggle because a handful of forestry engineers and experts getting themselves all worked up in a sterile and costly manner will never accomplish anything. Nor can the worked-up consciouses of a multitude of forums and institutions, sincere and praiseworthy though they may be, make the Sahel green again. The struggle to defend the trees and forests is above all a struggle against imperialism. Because imperialism is the arsonist setting fire to our forests and our savannas.

DAN CRANE: I think that last sentence bears repeating: “The struggle to defend the trees and forests is above all a struggle against imperialism. Because imperialism is the arsonist setting fire to our forests and our savannas.” Who knew a debate about soil could get so heated?

Welcome back to The Thin Layer, the podcast about dirt. We’ve had a couple of episodes now about about life and death in soil — how healthy soil is an ecosystem of its own, and how easily human actions can kill that ecosystem, turning soil to dust. But soil isn’t just something to study as a scientist, or to grow food in. People have deep connections to land. And if someone comes into your town, telling you to farm in a different way, or to stop living the way your family has for generations — why should you listen? What gives them the right? And what if you’re on the other side of that equation? If you’re a scientist, how do you tell people that they need to change their behavior, or else they’ll kill their land? When does “convincing” someone about science become forcing them against their will?

We can start looking for an answer back in 1986, with the man who gave that speech at the International Conference on Forests and Trees: Thomas Sankara.

AMBER MURREY-NDEWA: He’s a Burkinabé, a citizen of the West African country of Burkina Faso, born at the time that Burkina Faso was still occupied by the French, and went by the name of the Upper Volta.

DAN CRANE: This is Dr Amber Murrey-Ndewa, a post-doctoral fellow in sociology at the American University in Cairo. She was reading that translation of Sankara’s speech at the forestry conference just now, too. Sankara was a 33-year-old army captain in 1983 when, in a military coup, he came to power.

AMBER MURREY-NDEWA: You know, by the time Thomas Sankara became president, he was the fourth president in a three year period. The people of Burkina Faso were experiencing widespread levels of hunger, of illness, a lack of access to affordable healthcare and a lack of access to affordable education.

DAN CRANE: He was a revolutionary Marxist — and the first thing he did was change the name from Upper Volta to Burkina Faso, meaning “land of upright people.” It was a statement of intent. His country was one of the smallest in Africa, one of the poorest in the world, with frequent famines and widespread poverty and inequality. It was one of many African countries in the post-colonial period dependent on financial aid from its former European overlord — in this case, France. Sankara wanted to break that dependence because, in his words, “he who feeds you, controls you.”

AMBER MURREY-NDEWA: So Thomas Sankara then, was a leader who emerged out of what was a tumultuous period in the country’s history, with a very staunch and unflinching dedication to ensuring that the 90 percent of the citizenry living in the rural areas had access to clean drinking water and two plates of food a day.

DAN CRANE: He sold off the government fleet of Mercedes sedans, making ministers ride around in tiny Renault 5s, the cheapest car available. His own salary was limited to $450 a month, and he allegedly only owned one fridge — and a broken freezer. He was the first African president in the post-colonial era to make gender equality a priority, outlawing forced marriages and female genital mutilation, and appointing women to positions of influence and power in government and the military. He even created a “National Housewives’ Day,” where men were tasked with chores like going to the market, and looking after children, to give them a taste of what their wives’ lives were like. He redistributed land from landowners to peasants, launched road- and rail-building programs, built schools and medical dispensaries, and generally did exactly the things you’d expect from a 20th century communist dictator who wanted to overhaul his country.

And he was handsome, and charismatic — he played the electric guitar, and wrote Burkina Faso’s new national anthem. He quickly became known as “Africa’s Che Guevara” in the West, a label still used today. It’s a problematic way of describing him — there are some big differences in how the two men operated — but in terms of how his glamor makes people forget his human rights violations, it’s not a totally unfair comparison. The revolutionary councils and show trials that Sankara’s government set up were directly inspired by Cuba’s. Sankara banned the free press and trade unions to consolidate power, and political rivals were imprisoned, tortured, even assassinated. I knew it was all sounding too good to be true with this guy. Amnesty International repeatedly condemned him, and the OECD compared what happened in Burkina Faso while he was in power to “the worst days of the French Revolution.”

There’s a reason he was in Paris in 1986, at the French-speaking world’s first major international conference on forestry in the post-colonial era. He was there to wag his finger at the imperialists for ruining his country’s soil.

AMBER MURREY-NDEWA: Another pillar of his radical education was his awareness and deep and abiding respect for strands of early ecosocialist thought, and a sort of foundational understanding that for the true liberation of Burkinabé people, for the true liberation of the African continent, there needed to be a transformation in the relationship between people and their environment.

DAN CRANE: Thomas Sankara was arguably the world’s first radically environmentalist president. When he was a young army officer, he saw how hard rural farmers had to work to water their crops, or to keep the land from turning to desert. He created a new Ministry of Water, and wanted to increase farm productivity while decreasing soil erosion. There were new regulations for clearing brushland with fires, and cutting down trees for firewood. He tried to stop farmers letting their livestock graze on food that humans could eat. And, most famously of all, he launched a program to see ten million new trees planted across the country to stop the desert advancing southwards.

AMBER MURREY-NDEWA: He would always say trees are life. They are the equivalent equivalent of life for people in Burkina Faso. And that if these policies were only 60 percent successful, then for me, they were successful.

DAN CRANE: And these plans didn’t work perfectly — Burkina Faso’s government was too poor to enforce a lot of the new rural regulations. But when it came to increasing farm productivity, they worked enough. In four years, Burkina Faso went from importing most of its food, to being nearly self-sufficient. And the tree-planting? Well, go to the capital, Ouagadougou, today, and you’ll be able to find shade beneath Sankara’s trees.

Now, all this talk about self-sufficiency can be misleading, because Sankara frequently flew in Western scientists to advise on agricultural and environmental policy. The point was that things were happening on Burkina Faso’s terms, not the West’s — that was why he was at the forestry conference in 1986 to wag his finger. And to understand exactly why land use policy, and soil erosion, was so critical to his political project, we have to go back to those ten million trees that he ordered to be planted. Those trees were meant to hold back the Sahara desert.

The Sahara doesn’t have a clean edge, you see. It’s like an ocean — and the southern edge, the shoreline, is a strip of land called the Sahel. It’s not quite desert, it’s not quite savannah, but a place of transition between the two, with long waves of drought interspersed with brief wet periods. You may remember the Bodélé Depression from episode one, that thin strip of land where dust blows into the air, travels across the Atlantic, and lands in the Amazonian rainforest. That’s in the Sahel. A 3,000-mile-long strip of land running from the Atlantic to the Red Sea. Intensely hot and sunny, it’s nevertheless home to more than a hundred million people — and that’s projected to double within the next 30 years. This is soil that’s often dusty and dry and thin, which can make it a tricky place to grow crops. It’s been the home of merchant empires through history, as nomadic peoples moved with their herds of livestock from place to place, building and maintaining routes for commerce and trade. The migrations of different people, the degradation of the land by grazing animals, and the climatic cycles of drought punctuated by wet periods — it doesn’t take a lot to throw off the balance between these factors in the Sahel.

European countries, when they carved up the continent, didn’t care about that. New borders blocked nomadic migration routes, so many herders became farmers in one place instead. Traditional crops and farming habits were forcibly replaced with European-style annual harvests of crop like wheat. It was a deliberate choice, a way of suppressing native cultures as well as reconfiguring the economy of a colonial possession to produce crops and goods for export to the West instead of for domestic consumption. When many of these countries finally gained independence, in the years after World War Two, nothing about their economies was set up for self-sufficiency. A lot of what Sankara’s government did was try and re-establish older farming practices which had been suppressed during colonialism — practices which suited the land of the Sahel more than European-style farming.

And speaking of climate, the Sahel has also been pretty much constantly in drought since the 1960s, as well. The terrible famines that struck much of the region in the latter half of the 20th century were down to the damaging consequences of colonialism, combined with bad luck. If you can call climate change bad luck, that is.

AMBER MURREY-NDEWA: When he spoke about implementing the tree planting as an exercise of celebrating visitors and celebrating graduations and celebrating births and honoring deaths and that sort of thing, he was actually revalorizing practices that had been curtailed during the colonial period.

DAN CRANE: Sankara lasted four years in power, until he was assassinated in another coup in 1987. As much as he is now remembered for looking ahead of the times when it comes to environmentalism, some of his ideas haven’t aged well. Some of the scientists he flew in to consult on land use reform, for example, had good advice, but others brought western new age-y ideas with them, that had questionable, pseudoscientific backing. And as much as Sankara inspired plenty of tree-planting beyond Burkina Faso, across the Sahel, around 80 percent of the trees planted in the region since the 1980s have since died. For lots of poor farmers, having to plant and look after young trees was extra work that they just couldn’t afford — not to mention a lot of the species that were planted were unsuitable for the Sahel’s climate and soil.

Lessons are still being drawn from his four years in power, though. Not the communism, so much, but his recognition of the power dynamics at work in Burkina Faso, and across Africa. It’s about the difference between a conversation, and an order. You don’t need to be a revolutionary Marxist to see how controlling how land is used can control people. But, what does that look like today?

Back in the early 2000s, eleven countries along the length of the Sahel — including Burkina Faso, as well as Sudan, Senegal, Eritrea, Ethiopia, Mali, Mauritania, Niger, Nigeria, Djibouti, and Chad — got together to discuss desertification. How could they stop the Sahara encroaching further south? How could they hold back the tide? Nigeria’s president, Olusegun Obasanjo, had a suggestion, harking back to the 1980s: planting a Great Green Wall.

Three times as big as Australia’s Great Barrier Reef, a literal wall of trees, ten miles thick and 3,000 miles long, pitched as the “largest living structure on the planet.” The name is a conscious reference to the Great Wall of China — when completed, they hoped it would be visible from space. Sankara’s decades-old ambition to plant ten million trees in Burkina Faso was frequently cited as an inspiration — a plan born in Africa, to solve African environmental problems, on Africa’s terms.

That was more than a decade ago, though. A lot can change in that time.

DAN CRANE: I’m walking up the path towards the Millennium Seed Bank, at Kew Gardens, in the United Kingdom. It’s an incredibly beautiful day here. Nice light breeze, there’s flowers blooming everywhere, it’s a fairly magical place.

DAN CRANE: Uh yeah, that’s me, on my way recently to visit the world’s largest seed bank. It’s part of Kew Gardens, London’s famous botanical research facility, but the actual building housing the seed bank is in the grounds of a gorgeous country mansion to the south of the city, about an hour or so by train. It’s the kind of aristocratic-looking English building that would have a secret laboratory under in a James Bond movie, which is fitting, because it kind of does.

The countries that together planned the Great Green Wall didn’t do so with the same revolutionary fervor that Thomas Sankara had, but there are some inescapable parallels between the two. That includes the fact that the Great Green Wall was a political project first and foremost. Actual science — the kind that could explain that blindly planting trees wherever possible wasn’t a great idea — came later.

Back in our Dust Bowl episode, we talked about how humans made that disaster happen. The Great Plains is a grasslands ecosystem, with soil that’s often thin and fragile — it doesn’t take a lot to over-farm it and turn it into dust. A similar dynamic happens in the Sahel. The Sahara desert isn’t growing further to the south on its own. It’s because human activity along the southern border wears down the life in the soil, the balance that keeps it functioning in spite of its thinness in the extreme heat. But just because desertification happens when plants and trees are cut down, and the land isn’t held together any more so can blow away, it doesn’t mean the remedy is, necessarily, just planting more bushes and trees.

DAN CRANE: Hang tight and, so who’s, all right, so what, what, while we’re here, why don’t you just tell me who you are and where we are and what you do?

TIZIANA ULIAN: OK. So my name is Tiziana Ulian, and I work here at the Millenium Seed Bank as a research leader for diversity and livelihood.

DAN CRANE: Which species of trees is best? This is a 3,000-mile-long corridor we’re talking here, with plenty of different climate and soil conditions — and different people have varying uses for different plants. How can you make sure your new trees aren’t immediately cut down for firewood? Are there crops that farmers can grow which will heal the land, and not suck the life from it?

TIZIANA ULIAN: So we’re now entering the dry room.

DAN CRANE: Alright, so it’s uh, it’s very cool in here. It’s very refreshing.

TIZIANA ULIAN: 15 degrees, 15 percent relative humidity. So it’s not just cool, it’s also dry, and this is one of the conditions that is very important for the conservation of the seeds. We’re talking about seeds that they can tolerate drying, and this is the dry room.

Dan Crane: Gotcha.

TIZIANA ULIAN: As you can see we have lots of bags here, and so these bags are coming from all over the world. So we have for example collections from Mexico, Dominican Republic in Latin America. Also we have collections from Africa. We work with a lot of African countries, in particular at the moment we’re working with Kenya, we’re working with South Africa, and also we’re working with Asia and China is one of our biggest, and most important partners in this collaboration. But also we work with Thailand and we work with Australia, and lots of other countries. So our network is very big worldwide.

DAN CRANE: Researchers from the seed bank travel across the world, gathering seeds, and bringing them under one roof. There, they can study them in controlled conditions.

DAN CRANE: Wow. All right. We’re stepping into the X-ray room. It looks like a, like a giant, like a future oven, yeah, like a microwave. Ultra-focused microwave.

DAN CRANE: By the way, seed banks are one of those things that just really hit you in the face with the possibility of civilization collapse. Places like the one at Kew that I saw, or the one up on the Norwegian island of Svalbard, also act as a way of saving and preserving plants for situations where they might be needed again. Svalbard is built into the permafrost itself, so that even the most dramatic climate changes should see it safe. The Millenium Seed Bank is also extremely secure, just in case you were thinking of breaking in.

DAN CRANE: Ah, the cold room. OK, we’re opening a very thick door, that, whoa, alright, wow. It’s cold in there. Sorry, I can’t go in there. It’s minus 20.


DAN CRANE: Well, I think we can get the idea from here, but it’s basically stacks and it looks like a, a card catalog of a library. And then, uh, on the left here on the wall is just rows and rows and shelves with uh jars of seeds that, I mean, it almost looks like candy. It sort of looks like a candy store in there.

PABLO BARREIRO: Yeah. Well, the seed bank, this part of the seed bank is uh, very protected, it’s earthquake proof, bomb proof, even radiation proof. So it’s, it’s one of the safest places in, in England, and it currently holds a collection of almost 40,000 species. I think that’s more than one billion seeds.

DAN CRANE: That’s Pablo Barreiro, by the way. He’s a lab technician at the seed bank. At the bank, they study how the seeds of different plants germinate under every possible climatic condition. If you’ve got a plant where normally only five percent of seeds ever germinate, how can you bump up that number? Is it humidity? Is it temperature? Is it the kind of soil it’s in?

DAN CRANE: And what do you do with the, what do you do with the sprouts, once they’ve germinated?

PABLO BARREIRO: Uh, we dispose of them.

DAN CRANE: So sad.

PABLO BARREIRO: Sorry about that answer. But the information will help to develop deforestation programs in country. So we, we, we provide that information but sadly we don’t have a space to take care of all the seedlings we are germinating here because we could actually occupy the whole UK just with our seedlings.

DAN CRANE: You could occupy the entire UK…

PABLO BARREIRO: I’m sure about that because it’s not only these, we have more than 80 incubators, and germination happens constantly, so sadly we have to dispose of the seedlings.

DAN CRANE: Plenty of the trees planted along the Sahel in the last few decades, which ended up dying, did so because they weren’t right for the local conditions. Like Australian eucalyptus, which might seem like an ideal hot climate tree — but eucalyptus trees suck up a lot of water, and they crowd out other native species as well.

Instead, the seed bank focuses on trees like the Acacia, each one of which can produce six kilos of gum arabic every year — an important export for many West African nations. Or there’s the African birch, whose leaves and branches are crushed to make a yellow dye, used in traditional Malian textiles. Native plants provide a cultural benefit as much as an economic one. It’s about restoring an ecosystem like the one that existed historically in the Sahel, where plants and land and people were in more self-regulating balance. It’s never going to be perfect — climate change brings plenty of new challenges, for example — but it’s already working to turn the Sahel back from dust.

TIZIANA ULIAN: So it’s very important to understand when you work on this direction of land to see which are the best species to be planted. In the past, a lot of forestry projects, they were really using a lot of exotic species. We focus on native useful species, important for local community. So in one way you are trying to identify which species that are growing better, their survival, being better to the condition and to also the change of condition in the future due to climate change. But at the same time these species are important for local community, for their livelihood, for helping them to have, to increase their income.

DAN CRANE: In the decade or so that the Great Green Wall has existed, it’s been transformed from a top-down project to a bottom-up one. In large part, that’s been thanks to scientists pushing back against political naivety like “just plant trees.” That means western experts, but it also means African experts, too. This isn’t just a case of “locals” and “experts” being mutually exclusive groups.

Now, the Great Green Wall is the biggest land use reform project in the world, with a budget of $8bn, where experts are working hand-in-hand with local communities to learn what works for them, and in places where people have independently rediscovered traditional methods to work with the land, those methods have been documented and shared with the wider project. Sometimes that’s planting trees, but it can also be opening community gardens on the edge of a village where people can grow vegetables, or in planting grasses or bushes to form windbreakers. It’s a far cry from the days of “imperialism is the arsonist,” as Thomas Sankara said.

But to go back to our Dust Bowl episode again, remember that warning that the world has only 60 harvests left until it runs out of soil? It’s a pretty dire warning. I told you a cute story about a guy named Hugh Bennett — the man who saw the Dust Bowl coming, who ended up becoming known as the “father of soil conservation” in the U.S. Well let’s come back to that story for a few minutes here, because it’s relevant to what we’ve been talking about this episode.

Back in 1933, Bennett was setting up sites around the U.S. to test different ways of reducing soil erosion, where he could bring farmers and say, “look, it’s working, told you so!” His first, and biggest, site, was in the Navajo Nation reservation in the southwest. Overgrazing by livestock had destroyed the surface vegetation holding the land together. This wasn’t how they had historically farmed — sheep and cows aren’t even native to the Americas — but since they were stuck in one place, they’d had to adjust from nomadic herding to static grazing. This may be sounding familiar.

Bennett and his men arrived on the reservation in 1933 with a pitch for the tribal council: You’ve got half a million too many animals here, so let us buy them off you and sell them for food out east. Problem was, for the Navajo, livestock weren’t just their main source of income — they were sacred. The very idea that there were “too many” was a kind of sacrilege. The plan ended up crushing the Navajo Nation’s economy, as well as disrespecting and attacking Navajo culture.

And Bennett? Well, he chose the Navajo Nation for a reason. It was easier than negotiating with dozens of farmers elsewhere, each with their own property rights, for as big a test site. Hugh Bennett worked out how to undo the Dust Bowl by listening to farmers talk about their problems, designing bespoke solutions for each specific farm. It’s used to this day as a model of respect and cooperation between scientists and farmers, but the story of the Navajo Nation experiment shows just how easily it can turn into a method of control and coercion.

And it’s worth noting that many of the methods for reducing soil erosion and degradation that are pushed in countries in sub-Saharan Africa today by multinational organizations like the U.N. are based on how the U.S. reacted to the Dust Bowl. Hugh Bennett’s legacy lives on around the world — in the precepts of “conservation agriculture.”

KEN GILLER: Now, those principles of conservation agriculture, of zero till, of mulching and then legume rotation, have been very heavily promoted in Africa with actually very little success. Farmers have tended to reject the technologies.

DAN CRANE: This is Ken Giller, a professor of Plant Production Systems at Wageningen University in the Netherlands. Remember that “60 harvests left” warning? Well, there are plenty of soil scientists who think it’s nonsense. Ken is one of them.

KEN GILLER: But we work in areas where agriculture’s been practiced intensively for over a hundred years and in many of those areas, the soils are indeed, they are infertile, because they’ve been heavily cropped without nutrients being added. But they’re soils where the crops will respond very well if fertilizers are supplied. And I find this idea of 60 harvest left, I find it alarmist and actually not really engaging with the real problems because I think the real problems are giving farmers access to the inputs they need to be able to produce good crops.

DAN CRANE: Ken has spent decades working with smallholder farmers in sub-Saharan Africa, helping to improve soil fertility. The problems that he sees are complex, requiring complex solutions. But he’s also seen the blunt ways in which farmers in sub-Saharan Africa are made to grow crops in certain ways, using methods which are imposed from above without consideration for context.

KEN GILLER: Now obviously there’s concerns about soil erosion, and these concerns have been there all the time that science has been working in Africa. It was a big concern, particularly of the colonial services who used to impose, actually, soil conservation programs often using violence, I mean direct violence, or fines, or locking people up in prison for not imposing the procedures which were being recommended.

DAN CRANE: Ken is currently working on two projects that are about giving farmers access to some of the inputs that they need. The first is on trying to improve cocoa yields in Côte d’Ivoire and Ghana, where 70 percent of the world’s cocoa is grown — on farms that are usually only around two hectares or smaller.

KEN GILLER: Well cocoa’s quite a difficult crop to manage. It’s a tree that came out of the forest in Central and South America, so it’s really a shade-loving plant, and there’s quite a fine balance between managing shades, it’s often grown under shade trees, but also pruning the tree to give you an optimal canopy, but then also if you have too much shade, you get a lot of humidity and fungal diseases and insect pests, so there’s quite a fine balance there, it’s quite a difficult crop to manage.

DAN CRANE: The other is N2Africa, a large-scale program of introducing legumes to smallholder farmers.

KEN GILLER: So these are the beans, common bean, soybean, cowpea, ground nuts, which are major sources of protein for poor farmers, they call them poor man’s meat if you like.

DAN CRANE: These are plants that have a symbiotic relationship with a type of bacteria in the soil. They cling to the plant roots, sucking up things like nitrogen and phosphorus, and putting them back into the dirt. These are the kinds of plants that are perfect as cover crops, not just for their harvest, but also because they breathe life back into the soil.

The plan is to take $50m and give inoculants that can kick-start new colonies of bacteria to half a million farmers, working on small plots of land across 11 different sub-Saharan countries. Different species of pea or bean grow better or worse in different areas of the continent, but, like the seeds studied at Kew, it’s about maximizing efficiency while working within local contexts. The plants repair the soil, they provide food, and they provide an income to the farmer.

KEN GILLER: And we can introduce the inoculants in a powder that goes on to the seed and farmers can sow it, and in northern Ghana where I am at the moment, they call this, this sort of black magic powder because they see the benefits of increase in yield.

DAN CRANE: Even though the powder can as much as double a farmer’s yields, it’s still a challenge because the logistics of gettings materials like inoculants or fertilizers into the field requires a distribution network that just isn’t there yet.

For Ken, the precepts of conservation agriculture — no-till and mulching and organic and all the rest of it — might make sense in some places, but it’s missing the forest for the trees. In western countries, conservation agriculture is a lot easier, with huge tractors that can precisely plant seeds beneath mulch-covered fields that haven’t been tilled.

KEN GILLER: In Africa, it’s very hard to keep a mulch on the soil. Decomposition rates are very fast. When crop residues are produced, farmers prefer to feed them to their livestock. And farmers don’t have access to herbicides, and if you don’t till the soil then you usually ended up with huge weed problems. Now if you have weed problems, that’s actually often a transfer of labor to women. Women are often responsible for hand weeding in the field. And if you have actually, have a situation with zero till, without a mulch, you can actually stimulate erosion, because tillage also gives you a rough soil surface which actually helps with the infiltration of water.

DAN CRANE: So, what works in one place, doesn’t work in every place.

KEN GILLER: So there are very good reasons that farmers tend not to adopt these technologies, and yet there’s been this massive promotion which goes on, particularly by the Food and Agricultural Organization of the United Nations, but also by many NGOs, particularly NGOs attached to church organizations seem to love this concept of conservation agriculture, and many researchers as well seem to have such an ardent belief that this is the way everybody should produce their crops.

DAN CRANE: It’s true — there are religious organizations which talk about “farming god’s way” to convince people that, when they change their practices and see that they’re growing more food, it’s because God approves. It’s another avenue for potential control and exploitation.

KEN GILLER: There is this other component of conservation agriculture which is the rotation with, with other crops, and particularly with the legume crops, and I mean that is one that I strongly endorse — because I think there’s, we could do with a lot more legumes being grown in our farming systems because of the soil fertility benefits they provide. I mean, my biggest concern is that because of the huge diversity of crops and cropping systems and cultures and people, we need to be willing and open to adapt our advice from the science side, very much to local conditions, based on the best principles that we understand, and I just see that there’s no real room for dogma in these approaches. There are no doubt some situations where conservation agriculture could be extremely useful approach for farmers, but let’s find out where they are and let’s not try and just generalize those concepts.

DAN CRANE: Today’s dialogue between the people who study land, and the people who live and work on it, can look a lot like what’s happening along the length of the Great Green Wall. Researchers and locals working hand in hand — and many of the people involved are both researcher and local at the same time. It can look like N2Africa, too, or the Millenium Seed Bank at Kew. Or it can look like Thomas Sankara, telling his people to let ten million trees bloom.

KEN GILLER: I think yes, we need to learn from local knowledge, but again, we shouldn’t over-romanticize that, because it’s often knowledge which was developed under conditions which are not the conditions of today.

DAN CRANE: These are challenges that are facing many different parts of the world, and not just along the Sahel. China is planting ten billion trees along the southern border of the Gobi desert, to push back desertification there. The specific causes of desertification there are different to that of the Sahel, but the dynamics between those ordering the trees and those living with them is similarly charged and contentious. In the Middle East, countries like Saudi Arabia and Iraq and Turkey are trying to turn their deserts green again, to try and turn sand into soil that can be used to grow food — but the water required for that has to come from somewhere, from someone else’s supply. You can’t separate the ground from the politics that it supports.

We’re no longer in the age of colonialism, but soil is still something more than just…dirt. It’s where we build our homes and grow our food, and as long as that’s true, it’s also a potential way to control and influence people. Maybe to get beyond that, we’d have to go beyond soil altogether. In our next, and final episode of this series, we’ll be looking at exactly that — the possibility of going beyond soil and into space. Until then, though, we’re going to be stuck here together on Earth. Let’s look after it together, alright?