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Fifth National Climate Assessment - Read the Report

North American tree migration differs from East to West

The ability of tree species to adapt to a shifting climate will depend strongly on capacity of natural regeneration to produce viable seeds and seedling recruits; this adaptation will be particularly challenging for species such as longleaf pine (Pinus palustris) that are more episodic in their seed production. Credit: Don C. Bragg/USDA-FS.

Suitable habitats for forest trees may be shifting rapidly as the climate changes. These environmental alterations affect important processes in seed production and quality (called fecundity), seedling establishment, and seedling recruitment into larger-sized trees. Previous studies tracking the shift in suitable habitat for forests have been inconclusive, in part because seed production and the subsequent success of the seedlings may have different responses to changes in climate. 

new analysis of these components at a continental scale using long-term seed production datasets and national-scale forest inventories, conducted by a large team of academic, USDA-FS, and USGS researchers, with support from NASA and NSF, reveals an ongoing poleward migration of northern tree species (Sharma et al., 2022). Recruitment and fecundity both contribute to northward spread in the West, while fecundity limits spread in the East. Despite a fecundity hotspot in the Southeast, low fecundity could slow the rate of eastern forest adaptation, which could increase the challenges for managing and conserving forest diversity and structure. Natural resource planning efforts can benefit from knowledge of life-history stages and the species and genetic variants that are best able to tolerate future conditions and sustain mature forests.