Life support for the planet: Trees and climate change
01 December 2009
Software tools that help researchers to study the role of forests in climate change could make it easier to understand a wide variety of natural and artificial complex systems.
The notion that it is a bad idea to have your head in the clouds does not apply to trees. As they reach upwards in an attempt to outgrow their neighbours, trees play an important part in the Earth’s climate, soaking up carbon dioxide and returning oxygen to the atmosphere in the process. So, if we really want to understand our changing climate, it is important to know what is going on in the planet’s tree cover.
Forests contain two-thirds of Earth’s biodiversity: trees store as much carbon as is in the atmosphere. Such facts are critical to understanding the ramifications of climate change – and how we can best respond. But unlike other key factors such as ocean dynamics, the effects of forest dynamics – how tree populations interact and impact the environment – remain uncharted territory.
Scientists from Microsoft Research in Cambridge, UK, are working to understand the role of vegetation, especially trees, in the climate. To do this, the researchers collect data on vegetation cover and weather from satellites and build sophisticated computer models.
Drew Purves, one of Microsoft’s research ecologists, works in the Computational Ecology and Environmental Science Group (CEES), which is part of the Computational Science group at Microsoft Research Cambridge. Coming at a time when concern about climate change and carbon dioxide emissions is acutely heightened, the need for such work, Purves says, is obvious. “I’ve realised that we have a real responsibility as ecologists to do whatever we can to address the problems of climate change and biodiversity,” he says. ”This really is an important problem.”
Purves leads the group’s Plant Ecology research unit and some of the work in the Spatial Ecology and Biogeography research unit. “The research undertaken within the Plant Ecology research unit aims to provide – eventually – a quantitative, scientific basis for the management of plant communities,” he says.
Russian birch wood in summer.
Computational skills
CEES is one of many groups around the world that are working on environmental issues. It is bringing Microsoft’s computing skills to the challenge by developing computational tools and methods to predict and mitigate the rapid changes occurring in the Earth’s life support systems.
The research depends heavily on developments in computation. This includes computational modelling of complex systems, integrating models and data, data acquisition and management, and visualisation techniques. And that’s not all. These software tools must also be usable, easily maintained and capable of being adapted in the future.
Working for Microsoft is a return to Cambridge for Purves. He studied ecology at Cambridge University before going on to research for a PhD in ecological modelling at the University of York. He then spent nearly six years in the Department of Ecology and Evolutionary Biology at Princeton University before joining Microsoft Research in Cambridge in 2007.
“My research focuses on the dynamics of populations and communities of plants, especially forests,” says Purves. “Forests are made of trees, and trees are made of carbon. “And we know that forests are processing and storing large amounts of carbon. When trees grow, they remove carbon from the atmosphere and store it in wood. But eventually, every tree dies, and the wood rots or burns, releasing the carbon back into the atmosphere. There’s a potential for a huge effect of that cycling and storage of carbon on the future of the Earth’s climate.”
The research he and his associates are pursuing addresses fundamental scientific questions that could help conservationists and governmental officials to decide how to protect the climate. His work has produced more than 20 scientific papers in such prestigious journals as Science and the Proceedings of the National Academy of Sciences.
Stephen Pascala of the Department of Ecology and Evolutionary Biology at Princeton University co-authored the Science paper “Predictive Models of Forest Dynamics”. “Until now,” he says, “one of the most important pieces of the climate change jigsaw has been missing. We argue that we can significantly further our understanding of forest dynamics if scientists work together to use new computational techniques and data sources. We feel that these discoveries could unlock the climate change mysteries of forests on a global scale in as little as five years.”
A part of the work includes developing accurate predictive models. “Most of the research involves nonlinear models, large amounts of data, and the computational statistics needed to combine the two,” explains Purves.
Models help researchers to take their knowledge of what goes on in individual trees and to extrapolate it to whole forests. For example, the Plant Ecology research unit works on such important topics as tree mortality. Important as this may be, there are still huge gaps in our understanding of the nature or magnitude of variation in tree mortality, how it depends on species, climate, or extreme events, or how best to include it in simulation models.
“An overarching concern is the impact of climate change on plant communities, and what we can do to mitigate these effects,” says Purves. “Depending on the project, the research requires everything from pure theorising to making new discoveries about basic ecological processes.”
The group’s work has implications beyond understanding trees and vegetation. “Hopefully, the new software tools that we are developing for this research will enable others to generate predictive models for a wide variety of natural and artificial complex systems.”
In recent years, a number of nations have invested in assessing their timber stocks, with an eye toward production forestry. For example, Russia has put a lot of effort into collecting data about its forests, which cover vast areas of the country. With more forests than any other country, Russia accounts for more than 20 per cent of global forests, an area larger than the continental USA. Timber is also an important part of the country’s exports. So it is important to understand what is happening in the country’s forests.
"An overarching concern is the impact of climate change on plant communities.”
Drew Purves, research ecologist at Microsoft Research Cambridge.
A trillion trees
Something like a trillion “canopy” trees – trees that when mature have proper crowns – grow around the planet. The fate of all those trees is important when we want to investigate the likely effects of climate change.
This is why researchers want to know where the trees are, along with other vegetation. While we have a reasonable understanding of ocean dynamics, we know much less about forest dynamics, how tree populations interact and affect the environment.
Earth observation satellites are important tools in gathering data for environmental models. They can investigate vegetation cover in places that are inaccessible to people.
Satellites can carry arrays of different sensors that can gather huge amounts of data. The challenge is to process and understand the information in that data torrent.
Satellite monitoring of vegetation for large territories, as well as high-resolution climate modelling, can provide the missing data for the impact studies. The combination of satellite data and massive computer power, along with new mathematical algorithms, makes it possible to develop models of how tree populations interact and affect the environment. With the tools to hand, the researchers hope to be able to predict how trees and forests will develop over the years.
larch forest on the Ural taiga.
Purves and colleagues use such data for more far-reaching purposes. “They’re a hugely underutilised resource,” he says, “some of the largest ecological data sets in the world in terms of sample sizes and potential impact. These are a bit like ecology’s equivalent of the Human Genome Project. They’re just enormous, millions of individual trees. It’s really exciting.”
“We suggest that the convergence of recently developed mathematical models, improved data sources, and new methods in computational data analysis could produce a step change in the realism of these models,” Purves says. “That would give us truly invaluable information to help manage the world’s forests and understand their impact on our climate.”
Michael kenward