Run it again, with extra goats (Image: Planet Observer/UIG/REX)

We can simulate the climate and we can even simulate babies. Now, we can simulate life on Earth, too – the vast and complex interactions of the living organisms on our planet.

Named Madingley, after the village in Cambridgeshire, UK, where the idea was dreamed up, it’s a mathematical model that could help us predict the future. It could tell us what would happen if all the bees disappeared, the difference it would make if pandas died out, and what the world might have looked like if humans had never invented intensive farming. The work also suggests that the basic structures of all ecosystems can be predicted using a small number of universal ecological principles.

The Madingley model is the first computer model to simulate the way in which all types of organisms interact on a global scale. Researchers attempting to model ecosystems typically take a top-down approach, collecting as much data as they can from a chosen system, such as a forest or an ocean, and cramming it into a model. Instead, Drew Purves of Microsoft’s Computational Science Lab in Cambridge and his colleagues built a mathematical world that obeys the same basic principles as life on Earth.


“It’s a silicon ecosystem. That’s what is really nice about it,” says Georgina Mace of University College London, who was not involved in the project. “It has all these interactions between the physical environment and all the different ecosystem components that exploit it.”

All shapes and sizes

The team first simulated the physical Earth, with continents, oceans and a global climate, and then populated it with digital organisms. As in the world outside your window, life inside Madingley comes in all forms, from plants to herbivores and carnivores, some of which are cold-blooded, others warm-blooded, and all of which come in a range of sizes, down to those as small as aphids. It does not simulate specific species quite yet, but rather types of animals.

“We throw small amounts of every type of animal and plant everywhere and off they go,” says Purves. The team was able to watch as different types of organisms went through periods of boom and bust, some vanishing completely from one environment but thriving in another, others competing for space or finding ways of moving into new niches. But eventually, things settled down into an equilibrium that looks roughly like the real state of play on Earth, with similar proportions of different types of species.

Before they could press play and set their simulated life forms in motion, the team had to give Madingley some basic rules. We know, for instance, that on average predators tend to prey on things that are roughly one-tenth of the mass of their own body, so the animals in Madingley do too. There is also a relationship between body temperature and how large animals can get, so this forms the basis of another rule.

“Out of everything we put in, something emerges that looks about right,” says Purves. “We get a collection of individuals in each place, and patterns of who eats who, how quickly they’re growing and dying. We have a virtual world and it’s incredibly rich.”

Life is predictable

The fact that the model works using a set of basic ecological rules suggests that the fundamental structure of ecosystems is to some degree predictable, and repeatable. “A lot of the broad features of the world’s ecosystems are determined by these ecological laws and if you did it again you would get the same thing,” says Purves.

The model currently predicts the types of organisms expected in each environmental niche – the types, not the actual species it is open source, available to all scientists to play with, and Purves hopes that with extra work the model will be able to simulate precise situations. For instance, if an invasive snake were wreaking havoc on an ecosystem – as happened on the Pacific island of Guam – we could safely test the potential of various solutions. To make such testing possible, the researchers are now building extra parameters, including humans, into the model. At the moment we’re not included – the Earth of Madingley is “pristine”.

“Building ecology first makes sense, but eventually humans in particular will need to be recognised as part of the ecosystem and modelling that part is really hard,” says Beth Folton of the CSIRO Marine and Atmospheric Research in Hobart, Australia, who has led efforts to build several large ocean models.

“At the moment we don’t have any way of looking at how global environmental change – that is, climate change or massive land-use change – is going to affect ecological communities,” says Mace. Now we do. Mace says that with a general ecosystem model like Madingley, it becomes possible to simulate what would happen if top predators like tuna or tigers were hunted to extinction, or if vast swathes of land were turned into a monoculture through farming. “That’s incredibly important,” she says.

Silicon ecosystems may also reveal errors in our understanding of the world around us. Madingley threw a curveball when the team found that its oceans contained ten times more fish than expected. They initially put this down to an error in their model. Then came real world findings from researchers studying fish biomass that best estimates were off by an order of magnitude. Madingley’s “error” may well have been its first prediction.

Journal reference: PLoS Biology, DOI: 10.1371/journal.pbio.1001841