Ask a scientist to speak in broad general terms about anything and you'll usually hear a long pause, followed by an even longer string of caveats.

Science is a realm of the specific, after all, of precise data and accurate measurements.

Asking Los Alamos National Laboratory scientists about what New Mexico's vegetation and drought situation will look like in 50-100 years has a similar effect, but perhaps not for long, if a new computer model and study pans out.

LANL Scientists Nate McDowell and Todd Ringler are working with experts around the state and the country to develop a tool that could predict what will happen to the landscape as the world tries to manage global warming and other environmental issues.

The tool could help environmental managers test how policies could improve the situation for future generations of New Mexicans, the two said.

"We're trying to learn exactly why trees die," McDowell said. "Everyone knows it gets hot, it gets dry, the bugs show up and trees die. But we can't predict when that will happen because we don't understand the underlying processes."

One of the biggest mysteries is why in any given forest, some trees die and some do well in a drought. That's also true on a larger scale, where in a drought some chunks of forest might die while others seem to survive just fine — even though the types of plants in them are exactly the same, McDowell said.

"You know if you look around Santa Fe you see piñons that are dead next to piñons that are alive," McDowell said. "And that happens at many scales. We can't predict any of that, and we'd like to."

Another poorly understood element is how trees respond internally to drought, such as what mechanisms are shut down by a tree when it becomes water-stressed and for how long.

Insect populations and how insects decide to attack particular trees is another part of the puzzle, McDowell said.

As part of the larger scientific investigation, Christina Tague, a researcher from the University of California, Santa Barbara, plans to study the Santa Fe municipal watershed and model how changes in climate have altered its vegetation.

The scientists, along with Craig Allen from the United States Geological Survey, have also started testing plots of vegetation in the Sevilleta Wildlife Refuge by removing water from some areas to simulate drought, adding water to other areas to simulate flooding and leaving some alone as a baseline, McDowell and Ringler said.

With data from those and other studies, the scientists hope to build a larger model to show how policies, like forest thinning or reductions in the burning of fossil fuels, could change the landscape around us, Ringler said.

"Our knowledge and our models are imperfect right now, but what we're looking at so far is that mean temperatures in 2100 will be the same as the average temperatures we saw in New Mexico during the drought we went through in the 1990s," Ringler said.

In general those big climate predictions also suggest the Southwest will get warmer and drier as a whole, and that will also mean more tree and vegetation death.

But again, the models don't have specific enough data to show which areas and what vegetation will suffer the most from the change, Ringler said.

"The primary use of these models is to test different management strategies," Ringler said. "We could test changes in the global energy portfolio as part of that, but we could also get down to a scale where we could see how policy decisions made by the city of Santa Fe might change the landscape at a watershed level."

And the model could let managers test the results of strategies before they actually begin them, McDowell said.

"Thinning landscapes tends to reduce the risk of fire and also water use, but you have to do that in a sustainable way," McDowell said. "And also, if changing climate causes us to lose trees, that could change the carbon dioxide picture because those trees wouldn't be around to soak up the carbon, which could possibly lead to more global warming."

The study has just started, but the group hopes to have parts of the model up and running later this year.

"The goal is to peek into the future and see if we can determine more specifically what the consequences of our actions will be," McDowell said.

Contact Sue Vorenberg at svorenberg@sfnewmexican.com.