Black walnuts (Juglans nigra) are stately forest trees that are found throughout the central and eastern parts of the U.S. from western Vermont in the east to northern Florida in the south, north to southern Michigan and eastern South Dakota and as far west as Oklahoma, Texas and Kansas. They are usually found scattered among other kinds of trees at the forest's edge rather than in large stands. Black walnut has long been valued for its timber, which is prized for furniture making, as well as its tasty nuts.
But Douglass Jacobs, professor of forestry and natural resources at Perdue University in Indiana is worried about walnuts. Along with his former doctoral student, Martin-Michel Gauthier, he has studied the physiology of these trees and is concerned about their ability to adapt to the warmer, drier summers and the increase in extreme weather events that climate change is likely to bring.
According to Jacobs, it is the droughts that are associated with climate change that will be most difficult for walnuts to weather. Noting that almost all climate change models predict drier conditions, he says, ″Changes in moisture could restrict its [the walnut's] ability to survive.″
Walnuts are also sensitive to damage from spring frosts and are one of the latest trees to leaf out in the spring. Erratic and unseasonable temperatures from the extreme weather events that are predicted to become more common could be another way that climate change affects the viability of walnuts.
Researchers at Purdue's Hardwood Tree Improvement and Regeneration Center are conducting a breeding program that is attempting to identify trees with genetic makeups that allow them adapt to different climatic conditions in the hope that this valuable hardwood tree isn't lost as the climate changes.
For more information on walnuts and climate change, go to: Purdue University News.