Due to historic drought, nearly 700 pines in Pioneers Park, in Lincoln, Nebraska, have died since last July. Although the pines are the first to die, tree such as spruces, white pines, evergreens and red cedars are starting to die out as well. Tree deaths are showing up across the state.

The start of this drought has disproportionately claimed evergreens, which have been especially vulnerable because so few are native to Nebraska. The rapid decline of trees, even species believed to be hardy enough to survive in Nebraska, is worrisome given another hot, dry year may be unfolding. “It's going to be devastating,” said Eric Berg, a community forester with the Nebraska Forest Service.

Deciduous trees, those that shed their leaves seasonally, are struggling too, but they have more ways to adapt. A deciduous tree can drop its leaves when under stress and then bud new ones later. A pine can't drop and later replace needles. Likewise, deciduous trees have a nourishing layer inside their bark that evergreens lack.

As the drought takes its toll, the Nebraska Forest Service is re-evaluating tree recommendations it makes to Nebraskans. “Drought will refine our recommendations, but the greatest challenge is that the climate is changing,” Berg said. It will redefine the trees that can survive the Great Plains' extreme weather.

In the past, foresters have considered winter, not summer, as the limiting factor on tree survival in Nebraska. A tree had to survive a temperature plunge from 70 degrees on one day to 15 degrees the next.

Nebraska is warming at an accelerating pace with a high number of warmer-than-normal nights. In addition to chronic warmth, last year was the hottest and driest on record in Nebraska. This is a problem because trees rest at night and replenish lost moisture. If nights are too warm, trees don't have the chance to recover and instead continue to function as if it were daytime, using up water. In the long term, that weakens the tree and makes it more vulnerable to disease and pests.