John W. (Jack)_Williams.jpg

As climate change continues to tick the Earth's temperature upward, we can learn what to expect of a hotter planet by looking at the past. 

In his research, Jack Williams, director of the Nelson Institute Center for Climatic Research, studies the impact climate change had at the end of the last ice age--around 15,000 years ago--when global temperatures rose by 9°F. By analyzing ancient materials trapped in lake beds, he and his colleagues in the field have come to some startling conclusions. For one, small fluctuations in global temperature can cause large-scale biological changes across the planet, including mass migrations and extinctions. 

Here, he talks about what we can learn about current climate change from the historical record, the importance of coalition research, and the process of extracting ancient DNA. 


I study species and community responses to climate change. I'm particularly interested on the responses of tree species and forests to the end of the last ice age, roughly 15,000 to 8,000 years ago. In many ways, this is our best available geological analog to the climate changes expected this century: mean global temperatures rose by about 9°F (5°C), atmospheric CO2 increased by 90 parts per-million, ice sheets melted, and sea level rose. And almost all of the species around today were present then.

So we can use the last deglaciation to ask, and answer, questions such as: How fast can species migrate or otherwise respond to rapid climate change? Where did species find refuges during the last ice age, and how can we best protect these biodiversity hotspots today? How good are our models at predicting the responses of species and communities to climatic conditions wholly outside the range of environments experienced today? This last problem, known as the 'no-analog' problem, is a major theme in my research.

My work combines primary data collection (i.e. I core lakes and then extract fossil pollen, charcoal, and other materials from the lake sediments), continental-scale mapping of climate-driven species range shifts using databases of fossil pollen records, and lots of different kinds of data-model mashups.


The ability to extract DNA from fossils from long-dead organisms ("ancient DNA") is really opening up a new frontier. Ancient DNA of bison bones from Alaska, for example, has shown that even the survivors of the last ice age went through major population bottlenecks, then recoveries. Conversely, many of the hotspots of genetic diversity today are places that were refugia for species during the last ice age. Sustaining genetic diversity today thus requires knowledge of these historical legacies.


For me, the most profound lesson from the past is that even seemingly small climate changes can have major ecological effects. A 5°C global warming, which is at the upper-middle of projected 21st-century scenarios, doesn't sound like a big deal. But 5°C is about the amount of global warming from the last glacial maximum to present. These few degrees triggered massive shifts in species ranges, on the order of hundreds of miles, the reshuffling of species into novel mixtures, and the transfer of hundreds of billions of metric tons of carbon from the oceans to the atmosphere and terrestrial biosphere. And of course, many large animals (mammoths, mastodons) died out, although these extinctions were probably caused by the combination of climate change driving many populations to small sizes and human hunters finishing them off.


I'm keeping a close eye on the bark beetle outbreaks in western North America. These outbreaks have spread amazingly quickly, and are transforming the forests of Canada from a net carbon sink to a net source. And, of course, they are profoundly affecting the timber industry.

What's a sustainability trend that you wish would go away?

Our country's seeming inability to have a rational, national-level discussion about climate change and energy policy. Or just about any other major issue that requires hard decisions and tradeoffs, for that matter.


A big part of my research includes coalition-building -- bringing scientists together into ad-hoc research teams to share ideas, datasets, and models. This sort of thing fails more often than it succeeds, for all the usual reasons -- lack of focus, lack of resources, personality conflicts, etc. But when a good group comes together and starts hitting on all cylinders, it's incredibly exciting and a chance for real creativity applied to problems that no single scientist could tackle alone.


Margaret Davis, Herb Wright, and Colin Prentice. Margaret, who retired about 10 years ago from the University of Minnesota, was a genius at asking the right questions. Many of the questions she posed -- e.g. how fast can tree species migrate as climates change -- we are still chasing today. Herb, also from Minnesota, is the ultimate tough-as-nails field geologist. He's in his 90's now and was a WWII bomber pilot, and has done fieldwork all over the world. His former graduate students have written songs about how hard it is to find lakes that Herb hasn't already cored. Colin is simply one of the smartest people I've ever met. He's made a number of major advances in our development of global-scale vegetation models that incorporate our best available knowledge about plant physiology.

What other field or occupation did you consider going into?

As a teenager, I mostly told people that I was going to be an archaeologist. It sounded like a lot of fun and as a high school student I even did a summer field course with UC Berkeley at a former Maryland plantation called Flowerdew Hundred. I still remember the team's excitement when we rediscovered the plantation cemetery that was mentioned in the historical records, but the physical location had been forgotten for hundreds of years. But when I hit college, I took a geology class, and I was hooked.


I'm part of a research group that's been building a public database called the Neotoma Paleoecology Database ( This is becoming a standard public repository for paleoecological data. I've also become a recent convert to Twitter (@IceAgeEcologist) and my lab is starting to use DokuWiki for an internal knowledge-management and file sharing system. But really, a lot of my day-to-day work uses standard outlets: Thunderbird for email, Microsoft Word for writing, and Powerpoint for presentations.

What song's been stuck in your head lately?

The Ship Titanic has been stuck in my head a lot lately. It's tempting to draw parallels here to the potentially fragile state of our world, but it's mostly because I have 5-year old and 7-year old daughters, and they love this song. It's got a really catchy refrain: It was SAD when that GREAT ship went down.