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Simulating Nature
to Improve Life on Earth
CHANSHENG LI has spent 22 years building a single, mathematical ecosystem model. So it’s a bit surprising to hear him say that the discipline is just getting underway. “Modeling for ecosystems is really in the very early stages of development because natural ecosystems are so complex and therefore very difficult to simulate,” says Li of the Complex Systems Research Center.

Since 1987 Li has been trying to simulate the soil biogeochemical processes occurring in agricultural systems throughout the world with his DeNitrification-DeComposition or DNDC model. And in order to put all the modeling puzzle pieces together, he has traveled the globe to talk with field researchers and gather the data they have gleaned.

Changsheng Li
Changsheng Li
Photo by Perry Smith, UNH Photographic Services


For this, Li has been honored by UNH with a Faculty Excellence in International Engagement award.

Although the foundation of a mathematical model such as Li’s is constructed on basic physical, chemical, and biological equations to create a virtual ecosystem, without real-world information to run on, a model is virtually useless.

Says Li, “That’s why I’ve had to leave the ivory tower and go out into the field to talk with the field researchers, get them to share their observations and experience, show them how the model works, and let them use the model. Through this kind of feedback and use the model gets calibrated and validated.”

And, eventually, it becomes a tool that can be applied to vastly different regions around the world. Li has collaborated with scientists in Canada, China, Japan, India, Germany, France, Italy, the United Kingdom, Russia, Belgium, Finland, Spain, Australia, and New Zealand.

His globetrotting has been essential because, he notes, researchers are understandably reluctant to share hard-earned data for nothing in return.

“You can’t just email someone asking to use their data, there must be something mutually beneficial, that’s fundamental to international collaboration,” Li says. He adds, “Of course, the basis for offering something is that you want to improve the environmental quality of the planet in collaboration with other scientists.”

Li has dedicated his scientific career in the service of planet Earth’s health. Specifically, after all these years of development and refinement, the DNDC model can precisely simulate greenhouse gas emissions (e.g., nitrous oxide, carbon dioxide, and methane) across a variety of terrestrial ecosystems, under any climatic condition, anywhere in the world – almost.

The DNDC model is currently used only in temperate zone environments. However, Li is hopeful that a proposal currently in the works will be funded and allow the model to be used for the high-latitude Arctic regions where things are changing very rapidly.

Indeed, with the growing possibility that thawing permafrost will release prodigious amounts of methane – a far more potent greenhouse gas compared to carbon dioxide – being able to accurately model emissions in the region would be a significant step forward scientifically.

Recently, researchers in New Zealand who use Li’s model established the DNDC Global Network that links users worldwide and allows them to make modifications to the model to suit their specific needs.

Explains Li, “There are so many users worldwide and they raise lots of questions and suggest modifications. I only have one post-doc working with me and so I simply can’t handle that kind of workload.”

So users make changes to the model’s source code or input parameters to accurately mirror their region’s ecosystem characteristics, and that model becomes their own. There is now a DNDC model for Canada, the UK, Europe, China, and New Zealand.

Just as 1+1=2 is true anywhere in the world, the model is applicable across pasture, forest, wetland, or agricultural ecosystems because it’s built on fundamental, classic principles capable of predicting the biochemical or geochemical reactions of carbon and nitrogen driven by common environmental factors like gravity, temperature, moisture, pH, etc.

While the model lends itself to international use because of its universal foundation, oftimes there are language barriers to overcome when Li travels overseas to confer with field researchers. But, Li says, he’s found that because everyone is working toward the same cause there is a common language that guides discussions.

“I’ve learned that most people living on the planet are looking for a better life and are holding out hope. So we need to improve the atmosphere to let global study advance, because we are dealing with global issues.” Li adds, “If we develop these kinds of mutually beneficial friendships, there is great hope to stop the degradation of our environment. That’s why I think it’s worth spending my life on modeling work in collaboration with worldwide researchers and friends.” -DS


by David Sims, Science Writer, Institute for the Study of Earth, Oceans, and Space. Published in Summer 2009 issue of EOS Spheres.