Perspectives

180° Shift: What Really Drove the Green Revolution

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  • Drew Purves

    Drew Purves

Speaker

Drew Purves
Head, Computational Ecology and Environmental Science, Microsoft Research


Purves: Hi, I’m Drew Purves from Microsoft Research. It’s because of the green revolution that most of the world is relatively well fed today. We now grow several times more food per acre than we did 60 years ago. But we’re going to need a second green revolution if we’re going to keep a global growing population well fed into the future. Before we get on to that, let’s talk a little bit about what did we did to enable the first one.

Contrary to popular belief, the green revolution wasn’t just about clever scientists developing better plans, nor was it just about throwing extra inputs like fertilizers onto our fields. Rather, the green revolution was a constellation of technologies around a core idea of altering plant behavior, undoing evolution to create pacifist plants that could benefit from the increased inputs made possible by the industrial revolution.

To explain, plants eat sunlight, so when they first arrived on land they were spread out flat on the ground. Makes sense. But they soon evolved stems and trunks to grow tall. Why? You don’t put a solar panel on top of a flimsy wooden pole, right? The reason is that as a plant you have to grow tall because if you don’t your neighbor will and will shade you and kill you. Thus began a billion years of global war for light that culminated in the magnificent trunks of those Redwoods that some of us hiked up to only yesterday. Until the green revolution, when scientists bred out those weapons to create dwarf varieties. Less weight, less productivity wasted on stems, that left more for food. However, even more important than that, we could now put more fertilizer on the field and these short plants could support the extra seed mass that resulted. On the other hand, these newly pacifist fields became vulnerable to invasion by wild plants that were still engaged in the global war for light, hence the need for herbicides to keep down those weeds.

There was another global war with the plants and fungi that evolved to eat the leaves. For this reason plants evolved to put lots of productivity into nasty chemicals in leaves, which, bizarrely, much later led to some terrible wars between us humans. So we bred out those chemicals, but we didn’t tell the pests, so we needed pesticides.

So what next? Well, we can’t just do more of the same. We can’t keep throwing more and more inputs onto our fields and we can’t keep clearing more and more forest for agricultural land. Also, those pests and weeds are regrouping, defeating our artificial chemicals one by one.

The good news is there are many ways that we can undo evolution and change plant behavior to create a second truly green evolution. As it happens, the plants that had evolved to spend lots of their productivity on seeds, annuals, hardwired to commit suicide every autumn, and that means we have to regrow the root systems that support our fields every spring. It’s crazy. It’s like you guys destroying all your buildings every autumn, then having to rebuild all those buildings for monthly profits the next spring. So let’s reprogram that. Our plants are also hugely profligate with water, so let’s make them more efficient.

I had a final point, and I’ve dried up. I thought I was doing okay up to that point. Oh, I know what it was. This time round, the difference this time round is that we have the Internet of things, simulation modeling, and machine learning to work out exactly what it is that we need to reprogram, and we have things like sequencing, new languages, and compilers with which to do the reprogramming. Maybe we’ll be able to create things like plants that we can control remotely through flashes of light. It’ll be things like satellite-driven weather model that says that drought is on its way, let’s grow some more roots, that kind of thing. Thank you very much.

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